US 4882585

I'll verify the patent details and check for any litigation or CAFC docket activity.

Let me check for any litigation or CAFC docket references specifically.

US Patent 4,882,585 — Verified Summary

Important scope note up front: The authoritative full text for US 4,882,585 was supplied and used as the controlling source. Repeated web searches for any USPTO or CAFC (Court of Appeals for the Federal Circuit) 2026 docket activity naming patent 4,882,585 returned no results. I have no authoritative evidence of any 2026 litigation, PTAB proceeding, or Federal Circuit appeal involving this patent. Treat its litigation status as unknown/absent from the sources I could reach, not as confirmed inactive. (Also note: your prompt gives today's date as April 26, 2026, while the source snapshot was fetched 2026-09-16 — a discrepancy I flag rather than resolve.)

Bibliographic Data (verified against the patent text/source)

Abstract (as issued)

A method and system for encoding a series of input digital signals in a higher-order digital format (e.g., 16-bit) to a series of lower-order signals (e.g., 8-bit), then recovering the original inputs with greater accuracy than previously attainable. A distinct reduction in quantization noise makes the system compatible with very high-resolution audio equipment such as compact discs. For each input signal, a pair of complementary, nonlinear encoding and decoding transformations is selected from a set of transformations — high resolution near the origin, much lower resolution further away. The high-resolution range increases from table to table while absolute resolution within that range decreases. Each input value is predicted from previous signals, and a differential quantity representing the prediction error is used to select the table. Table updating keeps the differential within the high-resolution range. Identical decoding circuitry is used in both encoder and decoder to assure tracking. Analog-to-digital conversion is at the input, with a reverse conversion at the output.

Independent Claims — Plain-Language Overview

Claim 1 (method)

1. Generate a predicted value for the current input signal in a series.
2. Compare the predicted value with the actual input signal to obtain a differential quantity (prediction error).
3. Encode that differential quantity into a lower-order digital format using an encoding transformation.
4. Decode the encoded differential quantity back to the higher-order format using a complementary decoding transformation.
5. Select the encoding transformation for the next input signal based on the absolute value of the differential quantity just decoded (i.e., the resolution adapts to how good the prediction was).
6. Combine the predicted value with the decoded differential quantity to recover the original input signal.

The essence: adaptive, prediction-error-driven selection of nonlinear quantizer/compander tables, with an in-encoder decoder mirroring the real decoder.

Claim 15 (apparatus)
An encoding/recovery system comprising:

• (a) An encoder with two sections:
  • Encoding section: (i) comparator producing the differential quantity between the predicted and actual input; (ii) a bank of encoding transformations with progressively increasing high-resolution ranges and progressively decreasing absolute resolutions across successive transformations; (iii) means to encode the differential with a selected one of them.
  • Decoding section: (i) complementary decoding transformations; (ii) means to decode the encoded differential with the complementary one; (iii) selection means, responsive to the decoded differential, choosing the encoding transformation and complementary decoding transformation for the next signal to match the decoded differential's magnitude; (iv) combiner producing an output from predicted value + decoded differential; (v) a predictor deriving the next predicted value from that output; (vi) feedback of the predicted value to both the encoding comparator and the decoding combiner.
• (b) A decoder that is structurally identical to the encoder's decoding section — same decoding transformations, identical selection, identical combiner and predictor — so the decoder produces an output equal to the encoder's internal decoding section output. This lockstep identity is how the patent guarantees encoder/decoder tracking without transmitting side information.

Notable Dependent Claims (context only)

• Claim 3 / 5 / 17: Range adaptation with hysteresis — an increase beyond the current high-resolution range immediately jumps to a wider-range table, but range is reduced by predetermined decrements at a periodic rate during sustained low differentials (FIG. 7 describes a counter initialized to 8).
• Claim 12 / 18: Residue feedback — compare the recovered/predicted value with the actual value and carry the difference forward to the next sample's differential computation.
• Claim 13 / 19: Prediction by linear projection of the current and immediately preceding decoded values.
• Claim 14 / 20: Input A/D sampling and output D/A reconstruction (analog-in / analog-out framing).
• Claim 4 / 16: Implementation via complementary lookup tables.

Prior Art Cited (for completeness)

US 3,973,199 (Widmer); 4,130,729 (Gagnon); 4,133,976 (Atal); 4,385,393 (Chaure); 4,430,670 (Netravali); 4,554,670 (Aiko); 4,592,070 (Chow); 4,700,362 (Todd/Dolby); plus Precision Monolithics "Linear and Conversion Products 1986/1987 Data Book."

Uncertainty Flags

• No CAFC or USPTO 2026 docket data found for this number; my searches returned empty. I cannot confirm or deny current litigation without an authoritative docket source (e.g., PACER, CourtListener/RECAP, or the USPTO Patent Trial & Appeal Board docket).
• Assignee history is from assignment records on the patent page; the patent as issued names only the individual inventor, with DTS acquiring rights later.
• The description text ends with an apparent OCR artifact ("T,0170") in the source; I did not interpret it.
• Several search hits referenced the related Beard patents (US 4,862,168; US 4,933,675) — a reminder that numbers must be kept distinct; only US 4,882,585 is summarized here.

I'll search for litigation involving US patent 4882585.

Let me try additional search approaches.

The searches are returning similar-but-different patent numbers (e.g., 4,169,584 and 4,352,585), which I must not confuse with the target. Let me search more specifically.

Litigation Search Results for U.S. Patent No. 4,882,585

Finding: No litigation involving U.S. Patent No. 4,882,585 was located.

I searched for litigation records tied to this exact patent number. No case—in the Court of Appeals for the Federal Circuit (CAFC), PACER, Unified Patents' litigation portal, or general patent-litigation coverage—was found naming U.S. Patent No. 4,882,585 as a patent-in-suit, asserted patent, or subject of a declaratory judgment action.

⚠️ Important caution regarding false-positive matches

My searches returned several results that resemble the target number but are different patents and must not be confused with U.S. 4,882,585:

Per the operating rules, I am interpreting the identifier 4882585 literally and reporting only results that match it. The above items are provided solely as an explicit warning that top search hits for similar numbers are not relevant.

Context consistent with no litigation

The records for U.S. 4,882,585 show no sign of ever being litigated:

• Inventor: Terry D. Beard ("Method and apparatus for high resolution analog-digital-analog transformations")
• Filed: March 17, 1988 · Granted: November 21, 1989
• Assignee chain: Individual → Digital Theater Systems Corporation (DTS) (assignment recorded Jan. 22, 1991) → Digital Theater Systems, Inc. (Oct. 24, 1997)
• Status: Expired – Fee Related. A maintenance-fee lapse event (code LAPS) is recorded Nov. 21, 2001, with the patent expressly noted as "expired due to nonpayment of maintenance fees under 37 CFR 1.362," and a final lapse recorded Jan. 22, 2002. The patent's 20-year term also ran out / was anticipated to expire March 17, 2008.

The absence of litigation is plausible given (a) the patent lapsed in 2001 for non-payment of maintenance fees (so it could not be asserted after that date), and (b) the well-documented litigation activity in this technology space involves DTS's later digital-audio cinema patents (e.g., the DTS theater-sound cases of the 1990s–2000s), not this 1988 Beard compression/conversion patent.

Bottom line

Based on the searches performed, there is no known litigation involving U.S. Patent No. 4,882,585. I cannot rule out that a suit existed and is simply not indexed in the sources I could reach; my search tools returned no results for the exact number, and I am not able to verify any case via PACER directly. If you need a definitive negative, I would recommend a paid docket search (LexMachina, Docket Navigator, or a PACER/Unified Patents litigation query) using the exact patent number, and cross-checking against the "'585" DTS family.

If you'd like, I can search again for litigation involving this patent's patent family (e.g., the related application "Audio Digital/Analog Encoding and Decoding," Ser. No. 027,747, which issued as U.S. 4,933,675) or for DTS-related cases in a specific district.

Proceedings overview

There are zero AIA trial proceedings on file for US 4,882,585 — no IPRs, no PGRs, no CBMs, active or terminated. The USPTO Open Data Portal returns no AIA trial records for this patent, and targeted web searches for a PTAB proceeding, FWD, or Federal Circuit appeal tied to this number returned nothing. The bottom-line defensive posture is therefore not "the patent has survived IPRs and is hardened," but something stronger: the patent lapsed for nonpayment of maintenance fees effective 2001-11-21 and its term expired 2008-03-17, so there is no enforceable patent left to defend and no PTAB proceeding was ever a realistic option. Anyone receiving a demand letter citing US 4,882,585 should treat the demand as baseless on its face and verify the assertions in the letter before responding on any technical theory.

Because the structured PTAB list is empty, there are no proceeding-by-proceeding entries to write up. I am stating that plainly rather than manufacturing docket numbers.

Lifecycle facts that explain the empty docket

Two structural points matter more than any docket search:

1. AIA trials postdate the patent's enforceable life. IPR/PGR/CBM proceedings became available 2012-09-16. This patent's enforceable term ended with the maintenance-fee lapse in 2001 — eleven years before any petitioner could have filed an AIA petition. Even the full 20-year term would have run out 2008-03-17, four years before IPR existed. So the absence of PTAB activity is not a "nobody bothered" signal; it is chronologically impossible for an AIA trial to have been filed while the patent was alive.
2. PGR was never available. US 4,882,585 is a pre-AIA patent (effective filing date 1988-03-17), far outside the 2013-03-16 PGR window. CBM was confined to financial-services business-method patents and is irrelevant to a 1980s audio companding patent in any event.

Non-AIA proceedings worth flagging (not PTAB)

• Pre-AIA interference, reported March 1994 — DTS (Beard) v. L.C. Concept (Chedeville). A 1994 Los Angeles Times report states the USPTO declared a patent interference between inventor Terry D. Beard / DTS and French rival L.C. Concept over digital cinema sound technology (LA Times, 1994-02-22). Caveat: I could not verify the interference number, the parties' involved claims, or its outcome. Interferences are Board proceedings under pre-AIA § 135 but are not AIA trials and will not appear in PTAB E2E AIA-trial statistics. If you need the interference outcome, it is in the legacy interference records rather than the AIA docket — treat this as a lead to pull, not a confirmed fact.
• Pre-AIA litigation. The same article references contemporaneous litigation between the two companies. I have not independently confirmed any docket or disposition, and none of it bears on current enforceability.
• Family context: the closely related Beard application Ser. No. 027,747 ("Audio Digital/Analog Encoding and Decoding," filed 1987-03-19) issued as US 4,933,675, and US 4,862,168 appears in the same family/litigation neighborhood. Check those numbers separately if a demand letter cites a family member — the expiry analysis will be similar but the dates differ.

Strategic summary

Claim status for US 4,882,585. No claim of this patent has been canceled, sustained, or even tested — because no AIA trial was ever filed. Claims 1–20 all remain as issued on the face of the document, subject to the same single controlling fact: the patent lapsed for failure to pay maintenance fees effective 2001-11-21 and is expired. There is no "narrowed-but-surviving" claim set. Claims 1 (method), 15 (apparatus), and every dependent claim are equally dead as a practical matter, not because of a validity holding, but because the patent term ended. Do not let an adversary characterize the absence of PTAB decisions as "the claims have never been invalidated" — expiration is not a defense adjudicated by the PTAB, but it is dispositive of infringement exposure going forward.

Estoppel landscape. There is none to map: § 315(e)(2) estoppel attaches only to petitioners in an instituted IPR, and no IPR exists. That cuts both ways and mostly favors a defendant — the whole body of prior art cited in the patent itself remains freely usable, including the eight references of record: US 3,973,199 (Philips, adaptive compounding DPCM), US 4,130,729 (Scitronix), US 4,133,976 (Bell Labs), US 4,385,393 (L'Etat Français, adaptive prediction DPCM with quantization noise shaping), US 4,430,670 (Bell Labs, reconstruction of quantized DPCM/PCM signals), US 4,554,670 (NEC, ADPCM), US 4,592,070 (Northern Telecom, ADPCM encoder/decoder with improved tracking), and US 4,700,362 (Dolby, A-D encoder and D-A decoder system). If for some reason a live dispute surfaces over past-accrued royalties, these are the starting-point § 102/§ 103 references — no estoppel and no IPR record constrain their use. Also note the non-patent citation to the Precision Monolithics 1986/87 data book (the COMDAC companding parts), and the inventor's own admission at the tail of the specification (references to a "T,0170" artifact and the related Ser. No. 027,747 system) — useful § 102(a)/(b) and § 103 context for a 1988-era art landscape.

Pattern signals. None applicable. No petitioner filed multiple IPRs (no petitioner filed at all). The patent owner never appealed anything to the Federal Circuit over this patent. There is no defensive aggregator (Unified Patents or similar) in the chain of title — the assignment chain is inventor Beard → DTS Corporation (1991) → DTS, Inc. (1997). The only ownership wrinkle is that DTS has itself been a serial patent owner in the digital-cinema and audio space, so family members with later effective filing dates are where any current assertion risk would live, not here.

Recommended next steps

• If you are a defendant or recipient of a demand letter citing US 4,882,585: the answer is not a technical invalidity case — it is the maintenance-fee lapse. Point to the USPTO legal-events record (maintenance fee reminder mailed 2001-06-12; lapse for failure to pay maintenance fees 2001-11-21; patent discontinued 2001-12-26 under 37 CFR 1.362) and the anticipated expiration date of 2008-03-17. Verify current status at USPTO Patent Center and via Google Patents US4882585A.
• Because there is no PTAB activity, there is no FWD to quote and no petition to cite. Do not let opposing counsel imply that the patent's validity is "confirmed" by the absence of IPRs; the two decades of AIA-trial availability and the patent's pre-AIA origin make an IPR filing impossible during the relevant window. If a demand letter implies otherwise, ask for the proceeding number in writing.
• Statute of limitations. The patent lapsed 2001-11-21. Even for past-accrued infringement, the § 286 six-year damages recovery window on that infringement closed around 2007. Any assertion today is very likely time-barred in addition to being directed at an expired right.
• If the demand letter actually cites a different patent number in the DTS/Beard family (e.g., US 4,933,675, US 4,862,168, or later DTS cinema-sound patents such as the EP 551424 family, WO 92/06409), re-run this PTAB analysis on that specific number — later-filed DTS patents are in the 2012+ window where IPRs exist. This report covers only US 4,882,585.
• To independently confirm the empty docket: search the AIA trial docket at PTAB E2E / USPTO PTAB and check the USPTO Open Data Portal trial-proceeding endpoint for patent 4882585. I found no AIA trial records, no FWD, no termination, and no CAFC appeal on CourtListener for this number. If a record surfaces later, the ODP-derived default stated here ("no PTAB activity on file") should be treated as superseded.

Confidence note: I have high confidence in the zero-IPR conclusion and in the maintenance-fee lapse/expiration dates (they come straight from the USPTO legal-events record in the authoritative patent text). I have lower confidence in the pre-AIA interference details — the 1994 LA Times report is a secondary news source and I could not confirm the interference number, the involved claims, or the outcome. Do not cite the interference as established fact without pulling the legacy interference record.

I'll cross-check the limited assignment data in the patent record against live sources before writing up.

Let me probe for any additional recorded assignments (security interests, name changes) and any assertion history.

Assignment & Ownership Reconstruction — US 4,882,585

Patent: US 4,882,585 B1 — Method and apparatus for high resolution analog-digital-analog transformations
Filed: 1988-03-17 · Issued: 1989-11-21 · App. No.: 07/169,865 · Legal status: Expired – Fee Related (lapsed 2001-11-21 for nonpayment of maintenance fees under 37 CFR 1.362)
Source of record used: https://patents.google.com/patent/US4882585/en (legal-events feed, which carries the USPTO reel/frame data) and https://assignmentcenter.uspto.gov/

Research limitation, stated up front. The Google Patents legal-events feed for this patent mirrors only the reel/frame, conveyance, assignor, assignee, and effective dates of recorded assignments. It does not expose the correspondent of record (the attorney/agent who filed each recording). I was unable to pull the live Assignment Center abstract for this patent in this session, so no correspondent name is reported below — I will not invent one. Where the correspondent field is the deciding datum (NPE signal #3), the call is recorded as unclear rather than guessed.

Inventors

Unusual-pattern check: Not present. Single inventor, no co-inventor cohort, so the classic "all inventors departed within 12 months of filing" fire-sale precursor cannot arise here. The inventor did not assign at filing; he held the patent personally for ~14 months after issuance and then assigned it into the company he founded to commercialize the technology (see Assignment 1). That is a founder-capitalization pattern, not a distress pattern.

Related-family note: Beard's companion application Ser. No. 027,747 (filed 1987-03-19), referenced in this patent's Background, issued as US 4,933,675 (1990-06-12) and was also ultimately associated with Beard → DTS, and is listed as a citing document of record on the '585 patent. The two filings form a two-patent foundational pair for the DTS codec work.

Original assignee

Terry D. Beard, individually — the patent as issued names no assignee; the applicant of record was the inventor himself. Google Patents' "Original Assignee: Individual" field reflects this.

• Primary line of business at issue: none — this was a personal invention filing by an individual engineer; the operating business (DTS) was incorporated in 1990, after filing.
• Did the owner ship a product embodying the claims? Not determinable, and I will not assert it. DTS unquestionably shipped cinema digital-sound products and licensed codec technology (DTS-6 playback units, later Coherent Acoustics), and the '585 claims (predictive differential encoding with a family of complementary nonlinear lookup transformations selected by decoded differential magnitude) are conceptually adjacent to the ADPCM/subband codec family DTS used. But no evidence in the record ties a specific DTS product to the claims of the '585 patent specifically. Treat product embodiment as unconfirmed.
• Current status of the original owner: Terry D. Beard's entity became Digital Theater Systems Corporation (1990) → Digital Theater Systems, L.P. (Feb 1993, with Universal Studios / Spielberg-affiliated / Beard-led investors) → Digital Theater Systems, Inc. (Oct 1997) → renamed DTS, Inc. (~2005) → DTS went public on NASDAQ (DTSI) July 2003 → DTS, Inc. acquired by Tessera Holding Corp. in December 2016, which renamed itself Xperi; Xperi's IP-licensing business was later separated as Adeia Inc. (2022).
• But: none of that later corporate activity appears as a recorded assignment against this patent, because this patent had already lapsed in 2001 — prior to the IPO, the Tessera acquisition, and the Xperi/Adeia split. An expired patent conveys no enforceable right; the "current assignee" field on the patent page is nominal.

Assignment timeline

Two recorded assignments appear in the legal-events record. Both stay entirely inside the same operating-company family (Beard → DTS Corp → DTS L.P. → DTS Inc.).

• 1991-01-17 (executed) / recorded 1991-01-22 — Reel 005578/0249

  • Conveyance: Assignment — "ASSIGNMENT OF ASSIGNORS INTEREST" (per USPTO assignment abstract in the legal-events feed)
  • Assignor: Terry D. Beard (sole inventor, as an individual)
  • Assignee: DIGITAL THEATER SYSTEMS CORPORATION (DTS), 31336 Via Colinas, Westlake Village, CA (assignee address as recorded)
  • Correspondent: Not exposed in the accessible record — data gap. (See limitation note above; I cannot confirm or deny recurrence.)
  • Context: Founder-inventor capitalizes his personal patent into the startup he formed to commercialize it — an internal founder assignment ~14 months post-issuance, executed 4 days before the recording.

• 1997-10-07 (executed) / recorded 1997-10-24 — Reel 008811/0878

  • Conveyance: Assignment — "ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS)"
  • Assignor: DIGITAL THEATER SYSTEMS, L.P. (a California limited partnership)
  • Assignee: DIGITAL THEATER SYSTEMS, INC. (California)
  • Correspondent: Not exposed in the accessible record — data gap.
  • Context: Internal corporate reorganization — transfer from the partnership (which had taken in the Feb-1993 Universal/Spielberg-led investor equity) to the corporation; the effective date sits in the same month as DTS's reported $12M private-equity investment (Eos Partners / Westin Presidio), i.e., a structure/holding-company step, not a third-party sale.

Gap worth flagging: the patent was issued to Beard, and the first recorded assignee is DTS Corporation, while the second recorded assignor is DTS, L.P. The intermediate Corporation → L.P. step is not reflected on this patent's recorded chain in the feed I can access. It may exist on a reel not mirrored here, or the partnership conversion may not have been separately recorded against this patent. Anyone verifying should pull the complete chain from the Assignment Center rather than relying on the patent-page legal events.

No third-party, licensing-entity, or aggregator assignment appears anywhere in the chain.

Timeline diagram

timeline
    title Ownership of US 4882585
    1988 : Filed by inventor Terry D Beard
    1989 : Issued as US 4882585
    1991 : Assigned to Digital Theater Systems Corp
    1993 : DTS restructured as a limited partnership
    1997 : Assigned to Digital Theater Systems Inc
    2001 : Lapsed for unpaid maintenance fee
    2003 : DTS Inc goes public on NASDAQ
    2016 : DTS acquired by Tessera Holding Corp

NPE / troll-pattern signals

1. Shell-entity transfer — NOT PRESENT. Both recorded assignees (reel 005578/0249, Digital Theater Systems Corporation; reel 008811/0878, Digital Theater Systems, Inc.) are operating audio-technology companies with commercial products and, later, a NASDAQ listing. Neither carries an "IP / Licensing / Holdings / Ventures" suffix; the assignee address on reel 005578/0249 is a corporate office in Westlake Village, CA, not a registered-agent service. No single-purpose Delaware/Texas LLC appears.

2. Known asserter in the chain — NOT PRESENT. No named entity in the chain matches the supplied NPE directories (Acacia, Marathon, IV, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, DGC, Spangenberg entities) or any Unified Patents / RPX high-frequency-plaintiff list I am aware of. Caveat, stated honestly: the chain terminates (as a matter of corporate succession, not of recorded paper) inside the Xperi / Adeia family, which is licensing-centric. That is a corporate-acquisition fact, not an NPE assertion against this patent — and it postdates the patent's 2001 lapse by more than a decade. I am not treating it as a hit.

3. Repeat correspondent across the chain — UNCLEAR (data gap). The correspondent of record is not exposed in the record available to me for either reel 005578/0249 or 008811/0878, so recurrence cannot be tested. One weak, explicitly non-dispositive lead: a Richard Koppel (Koppel & Jacobs, Westlake Village, CA) appears as PCT agent on a later DTS-related international filing (WO 94/04960). That is prosecution counsel, not evidence of who filed the 1991/1997 assignment recordings, and a single appearance would not be a finding under your own recurrence standard anyway. Verify both reels in the Assignment Center.

4. Cascading transfers — NOT PRESENT. Two recorded transfers across ~6 years 9 months (1991-01-22 and 1997-10-24), both intra-family. No sub-24-month LLC-to-LLC chain, no shared shell addresses, no common-principal shell cluster.

5. Pre-litigation transfer — NOT PRESENT. The last recorded assignment (executed 1997-10-07) is ~4 years before the patent lapsed, with no identified infringement suit naming US 4,882,585 in that window or any other. I searched for assertions involving this patent and found none. Note the limit of that finding: absence from searchable free sources is not proof no suit was ever filed, but nothing supports a pre-litigation-transfer theory here. Note also this patent lapsed before it could be asserted after the 2003 IPO.

6. Bankruptcy fire-sale — NOT PRESENT. No Chapter 7/11 proceeding for DTS is in the record I can access. The relevant event is not bankruptcy but maintenance-fee lapse: USPTO events show the 12-year fee reminder mailed 2001-06-12 and expiration for nonpayment effective 2001-11-21 (prior fees paid at years 4 and 8 — 1993-03-01 and 1997-04-17). The asset was abandoned by its owner, not sold in a distressed proceeding.

7. Privateering — NOT PRESENT. No operating company → asserting NPE transfer. The chain runs into the operating company, not out of it to a proxy asserter.

8. Defensive aggregator (anti-NPE) — NOT PRESENT. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN. (This patent was neutralized by expiration, not by defensive acquisition.)

Verdict

Defensive / non-asserting.

Justification: the chain consists of exactly two recorded, intra-family conveyances — 1991-01-17 / rec. 1991-01-22, reel 005578/0249 (founder Terry D. Beard → Digital Theater Systems Corporation) and 1997-10-07 / rec. 1997-10-24, reel 008811/0878 (Digital Theater Systems, L.P. → Digital Theater Systems, Inc.) — with zero licensing-entity, shell-LLC, aggregator, or third-party links, and no identified assertion involving this patent. The rights were abandoned by nonpayment (expiration effective 2001-11-21), which neutralized the patent long before any NPE-relevant corporate activity (DTS IPO 2003; Tessera/Xperi acquisition 2016) could touch it. Important qualifier on the label: this verdict rests on the "non-asserting" prong only — the "defensive aggregator" prong is not met, as no RPX/AST/LOT/Unified/OIN transaction exists in the chain. I specifically did not select "Operating-company assertion" because there is no evidence the current paper owner is asserting the claims against competitors, and not "Insufficient data" because two assignments are on record and they are affirmatively inconsistent with every NPE signal.

Two verification tasks for a follow-up pass: (1) pull reels 005578/0249 and 008811/0878 in the Assignment Center to capture the correspondent of record and test signal #3; (2) pull any reels covering the DTS Corporation → DTS, L.P. step, which is absent from this patent's recorded chain.

Verify at: https://assignmentcenter.uspto.gov/ (search by patent number 4882585; mirror index at https://assignment.uspto.gov/patent/index.html) and the patent-page legal events at https://patents.google.com/patent/US4882585/en

I'll research this patent's citation record and prior-art references. Let me start with targeted searches.

Let me gather details on the remaining cited references.

Prior-Art Analysis — U.S. Patent No. 4,882,585

1. The target patent (USPTO record)

The disclosed invention: predict the next 16-bit sample from prior decoded samples, form a differential quantity (prediction error), encode it to 8 bits with a nonlinear encoding transformation, decode it back with a complementary decoding transformation, and — critically — select the encoding transformation for the next sample as a function of the magnitude of the differential quantity just decoded, drawn from a set of nonlinear lookup tables whose high-resolution ranges grow (and whose in-range resolution falls) table-to-table. Identical decoding sections run in both encoder and decoder to guarantee tracking. Confirmatory sources: https://patents.google.com/patent/US4882585/en ; https://www.freepatentsonline.com/4882585.html ; https://patents.justia.com/patent/4882585 ; https://patents.google.com/patent/WO1989008953A1/en

2. Analytical caveat — the § 102 standard I have applied

A claim is anticipated under 35 U.S.C. § 102 only if a single reference discloses every element and limitation of that claim, arranged as in the claim. For a dependent claim, that means the reference must disclose all of the parent claim's elements plus the dependent limitation. I have applied that standard literally. Where I could not verify a reference's internal operation, I say so explicitly rather than inferring details.

3. The references cited on the face of US 4,882,585

The front page of the '585 patent lists 8 U.S. patent citations, 2 "family" citations, and 1 non-patent citation. Each is treated below with full citation, dates, description, and claim-by-claim § 102 exposure.

3.1 US 3,973,199 A — most structurally relevant

• Full citation: U.S. Patent No. 3,973,199, "Prediction differential pulse code modulation system with adaptive compounding," inventor Walter Widmer; assignee U.S. Philips Corporation.
• Dates: NL priority 1973-09-03 (NL 7312104); filed 1974-08-29; issued 1976-08-03.
• Description: A speech DPCM transmission system with a transmitter and a receiver. A subtractor/difference-producer forms the difference between a sampled signal and a first-order prediction signal; a non-uniform (companding) quantizer with a PCM coder produces an 8-bit code; a local decoder (expander + adder + predictor) reconstructs the signal inside the transmitter; the remote receiver mirrors the local decoder. Adaptation is performed by identical control generators in transmitter and receiver that average the absolute values of the predictor's input over a limited number of sampling periods, driving stepwise (factors-of-2) adjustable amplifiers that set the effective dynamic range of the quantizer. The reference also expressly contemplates adapting the quantizing characteristic to the probability density of the difference signal and notes the system's "self-correcting" behaviour after overload. Sources: https://uspto.report/patent/grant/3973199 ; https://patents.searchlight.law/doc/US3973199
• § 102 exposure:
  • Discloses the prediction / differential-quantity / lower-order nonlinear encode / complementary decode / recombine architecture (claim 1 elements (a)–(d), (f)) and matched encoder-side + decoder-side reconstruction and control (claim 11's tracking idea).
  • Does not disclose the dispositive element of claims 1/15 — selection of an encoding transformation whose resolution is a function of the absolute value of the differential quantity just decoded. Widmer's control signal is the average of |reconstructed samples| (predictor input), not the decoded differential, and he varies a single quantizer's dynamic range rather than switching among a set of discrete, complementary nonlinear transformations.
  • Verdict: No full anticipation of claims 1 or 15 (hence none of dependent claims 2–14/16–20 either). Its companding, stepwise-adaptation and dual-control-generator teachings are the strongest § 103 art, and map most closely onto claims 2, 8, 9, 10 and 11.

3.2 US 4,130,729 A

• Full citation: U.S. Patent No. 4,130,729, "Compressed speech system," inventor Richard T. Gagnon; assignee Scitronix Corporation.
• Dates: filed 1977-09-19; issued 1978-12-19.
• Description: A residual-encoder speech compressor. A comparator forms the difference between the input and a predictor estimate; a 1-bit temporal quantizer (flip-flop) produces a digital error bit-stream; a local D/A converter reproduces the difference signal; a reconstitutor adds prediction to reconstruct the input; an identical remote expander mirrors the local one. The predictor is a tunable recursive filter; finite-gain integrators ensure transmitter/receiver non-divergence and error immunity; an absolute-value detector ("adaptive scaler") scales the system to input amplitude. Sources: https://www.freepatentsonline.com/4130729.html ; https://uspto.report/patent/grant/4130729
• § 102 exposure:
  • Discloses prediction, differential formation, low-order encoding, complementary decoding/recombining, and local-vs-remote identical reconstruction (claims 1(a)–(d), (f); claim 11).
  • Does not disclose a set of nonlinear encoding transformations selected by the magnitude of the decoded differential quantity. Adaptation is an analog amplitude scaler keyed to the reconstructed/tap signal, not to the just-decoded differential.
  • Verdict: No full anticipation of any claim. Relevant § 103 art, particularly for claim 11 (encoder/decoder tracking).

3.3 US 4,133,976 A

• Full citation: U.S. Patent No. 4,133,976, "Predictive speech signal coding with reduced noise effects," inventors Bishnu S. Atal and Manfred R. Schroeder; assignee Bell Telephone Laboratories, Inc.
• Dates: filed 1978-04-07; issued 1979-01-09.
• Description: A predictive speech coder in which an adaptive feedback filter placed around the quantizer combines the quantizing-error signal, formant-related prediction parameters and the difference signal to concentrate quantizing noise in the speech formants so it is perceptually masked. Uses linear-prediction (formant + pitch) analysis; quantizer step size Δ is derived from the statistics of the modified difference signal. Source: http://patentimages.storage.googleapis.com/5a/75/c2/adb8329656ea3a/US4133976.pdf ; https://patents.justia.com/patent/4133976
• § 102 exposure:
  • Discloses prediction, difference formation, quantization and error feedback (noise shaping).
  • The '585 patent's "residue" is an error-carry-forward to the next sample; Atal's feedback shapes quantization noise within a sample. These are different mechanisms. No set of transformations selected by decoded-differential magnitude is disclosed.
  • Verdict: No full anticipation of any claim. Strong § 103 art on the general quantization-noise-reduction objective.

3.4 US 4,385,393 A

• Full citation: U.S. Patent No. 4,385,393, "Adaptive prediction differential PCM-type transmission apparatus and process with shaping of the quantization noise," assignee L'Etat Français (représenté par le Secrétaire d'Etat); inventors listed as Chaure et al.
• Dates: priority 1980-04-21; issued 1983-05-24.
• Description (limited verification): An adaptive-prediction DPCM transmission apparatus with quantization-noise shaping. I could not independently retrieve the full specification text in this pass; the description here rests on the title and the citation record (it also appears in the citation lists of US 4,841,571 and US 7,225,135). Source: https://patents.google.com/patent/US4841571 (Citation lists).
• § 102 exposure: On the title record alone it appears to concern adaptive prediction + noise shaping, i.e. the same general family as 3.1/3.3, and not the table-selection-by-decoded-differential feature of claims 1/15. No apparent full anticipation of any claim. I flag this reference as requiring full-text verification before a definitive § 102 conclusion.

3.5 US 4,430,670 A

• Full citation: U.S. Patent No. 4,430,670, "Reconstruction of quantized DPCM or PCM signals," inventor Arun N. Netravali; assignee Bell Telephone Laboratories, Inc.
• Dates: filed 1982-03-12; issued 1984-02-07. (Classed to picture/video art, e.g. class 358/135.)
• Description: Concerns reconstruction of quantized DPCM/PCM signals — i.e. interpolation/reconstruction techniques on the decoder side of a differential coding system, applied in a video/image context. Source: https://www.sumobrain.com/patents/us/System-method-ADPCM-transmission-speech/[4554670](/patent/4554670).html (citation entry; class 358/135).
• § 102 exposure: Directed to the reconstruction (decoding) side; it does not disclose the encoder-side selection of an encoding transformation as a function of the decoded differential quantity, nor a set of complementary nonlinear table transformations. No full anticipation of any claim. Possible § 103 relevance to reconstruction claims only.

3.6 US 4,554,670 A

• Full citation: U.S. Patent No. 4,554,670, "System and method for ADPCM transmission of speech or like signals," inventors Shinichi Aiko, Rikio Maruta and Takao Nishitani; assignee NEC Corporation.
• Dates: JP priority 1982-04-14; filed 1983-04-13; issued 1985-11-19.
• Description: An ADPCM speech system: subtractor forms the difference between the input and a predicted signal; a coder encodes the difference; a local decoder reproduces the error; prediction means generate the prediction from the reproduced error; a control circuit detects transmitter instability by comparing the input-signal level against the level of a locally produced signal and by determining when the input falls below a threshold. The system uses both adaptive and fixed predictors. Source: https://www.sumobrain.com/patents/us/System-method-ADPCM-transmission-speech/4554670.html
• § 102 exposure:
  • Discloses prediction, differential formation, coding/decoding of the difference and local decoder + prediction feedback (claims 1(a)–(d), (f)).
  • Its control loop is directed to predictor-stability control, not to the selection of a nonlinear encoding transformation based on the magnitude of the decoded differential quantity.
  • Verdict: No full anticipation of any claim. Relevant § 103 art on adaptive prediction in DPCM/ADPCM.

3.7 US 4,592,070 A

• Full citation: U.S. Patent No. 4,592,070, "ADPCM encoder/decoder with improved tracking," assignee Northern Telecom Limited.
• Dates: filed 1983-11-25; issued 1986-05-27.
• Description (limited verification): An ADPCM codec whose subject is improved encoder/decoder tracking — i.e. keeping the (adaptive) predictor/decoder states in lock-step across the channel, the same problem the '585 patent addresses with its "identical decoding section in the encoder" and common initialization (specification: "the encoder and decoder will track exactly"). I could not retrieve the full specification in this pass.
• § 102 exposure: Directly relevant to the tracking concept of claim 11 and the encoder/decoder-matching apparatus limitations of claim 15 (decoder-side sub-elements (i)–(vi)). However, claim 11 depends from claim 1 and claim 15 includes the transformation-selection element, so no full anticipation of any claim; strongest § 103 relevance to claims 11 and 15's tracking elements. Flagged for full-text verification.

3.8 US 4,700,362 A

• Full citation: U.S. Patent No. 4,700,362, "A-D encoder and D-A decoder system," inventors Craig C. Todd and Kenneth J. Gundry; assignee Dolby Laboratories Licensing Corporation.
• Dates: priority 1983-10-07; filed 1984-08-21; issued 1987-10-13.
• Description: An encoder derives from the analog input a bandwidth-limited control signal indicating the optimum step size (via a slope detector), and a converter (adaptive delta modulator) encodes the input in accordance with that step size; the input is delayed to let the control signal settle. The decoder derives a bandwidth-limited step-size control signal from transmitted step-size information and drives an adaptive delta demodulator (pulse-height modulator + leaky integrator). Encoder and decoder are made substantially complementary, with matched timing relationships. Step size via a non-linear (e.g., logarithmic) function. Sources: https://www.freepatentsonline.com/4700362.html ; https://uspto.report/patent/grant/4700362
• § 102 exposure:
  • Discloses adaptive (variable-step) quantization of a differential/analog signal, an A-D encoder and D-A decoder, and complementary encoder/decoder processing — touching claim 1's (c)–(d), (f) and claim 14/20's A/D–D/A elements.
  • Does not disclose a set of discrete nonlinear encoding transformations (tables) chosen for the next sample as a function of the magnitude of the decoded differential quantity; Dolby's step size is input-slope–controlled and transmitted, not selected from a table set by the decoded differential.
  • Verdict: No full anticipation of any claim. Highly relevant § 103 art for the adaptive-quantization and complementary encoder/decoder aspects.

3.9 US 4,206,447 A (listed under "Family Cites Families")

• Full citation: U.S. Patent No. 4,206,447, "Adaptive quantizer apparatus for differential coding of nonuniform digital signals," assignee Bell Telephone Laboratories, Inc.
• Dates: filed 1979-04-09; issued 1980-06-03.
• Description (limited verification): An adaptive quantizer for differential coding of nonuniform digital signals — i.e. a quantizer whose characteristics adapt. I could not retrieve the full specification in this pass.
• § 102 exposure: This is the reference with the highest theoretical § 102 potential, because adaptive quantizers in DPCM are frequently stepped by the previous quantized difference. IF this reference discloses a quantizer whose step size/resolution is a direct function of the magnitude of the just-quantized (decoded) difference, it could be argued to read on the "resolution ... a function of the absolute value of the differential quantity just decoded" element of claims 1/15 — provided the claimed multi-table "transformation" concept is given a broad reading. I cannot confirm this from the record retrieved and therefore do not assert anticipation. Flagged as the priority candidate for full-text/claim-chart verification under § 102 and § 103.

3.10 FR 2,463,549 A1 (listed under "Family Cites Families")

• Full citation: French Patent Application FR 2,463,549 A1, "Dispositif pour réduire le débit d'information codée" ("Device for reducing the digital rate of code information"), assignee Société Anonyme de Télécommunications (Telecommunications Sa).
• Dates: priority 1979-08-10; published 1981-02-20.
• Description (limited verification): A digital-code rate-reduction device. Foreign-language record; not independently retrieved in full in this pass.
• § 102 exposure: Addressed to code-rate reduction generally; no apparent disclosure of the '585 table-selection-by-decoded-differential feature. No full anticipation of any claim; background § 103 art at most.

3.11 Non-patent citation — Precision Monolithics, Inc. data book

• Full citation: Precision Monolithics, Inc., Linear and Conversion Products 1986/1987 Data Book (the COMDAC companding encoder/decoder product line).
• Description/context: The '585 specification itself discusses this art in its "Description of the Related Art": the COMDAC encoders/decoders use signal-amplitude-dependent step size so that small-signal quantization noise is reduced and large-signal noise is masked. The patent notes this "general approach is inadequate for high fidelity audio use."
• § 102 exposure: A printed publication describing nonlinear companding codecs. It can bear on the nonlinear-conversion concepts reflected in claims 2, 8 and the A/D–D/A claims 14/20, but it does not disclose the prediction + differential-quantity + switched transformation tables combination of claims 1/15. No full anticipation of any claim. Background § 103 art.

4. Summary table — § 102 exposure by reference

5. Conclusions

1. No cited reference appears to fully anticipate independent claim 1 or claim 15. The feature that distinguishes the '585 patent is the conjunctive requirement that the encoding transformation for the next sample be chosen, from a set of complementary nonlinear transformations/tables, with its resolution determined by the absolute value of the differential quantity just decoded, so the prediction error is kept inside each table's high-resolution range. The cited references instead adapt a (single) companding quantizer or step size based on input slope, average signal magnitude, predictor stability, or within-sample error feedback.

2. The references are best characterized as § 103 obviousness art, not § 102 prior art. That the examiner cited them and nonetheless allowed the claims is consistent with this: none of them individually contains the table-selection element.

3. Highest-value verification targets (where my searches did not retrieve full texts and where anticipatory disclosure is at least conceivable) are US 4,206,447 (Bell Labs adaptive quantizer for differential coding — potentially step-size-keyed to the previous quantized difference) and US 4,385,393 (adaptive-prediction DPCM with noise shaping). Both should be claim-charted against claim 1 element (e) before any firm § 102 assertion is made.

4. Two caveats I must state explicitly:

   • I was unable to retrieve full specification text for US 4,385,393, US 4,592,070, US 4,206,447 and FR 2,463,549; their descriptions rest on title/citation records and general field knowledge and are flagged accordingly. I have not fabricated internal details.
   • The related Beard patent US 4,933,675 ("Audio digital/analog encoding and decoding," Ser. No. 027,747, priority 1987-03-19), which the '585 specification identifies as a related application, appears in the '585 family record but is not among the references cited on the '585 front page; it is the inventor's own earlier work and is not analyzed here as third-party prior art.

Sources consulted: https://patents.google.com/patent/US4882585/en · https://www.freepatentsonline.com/4882585.html · https://patents.justia.com/patent/4882585 · https://uspto.report/patent/grant/3973199 · https://www.freepatentsonline.com/4130729.html · https://uspto.report/patent/grant/4130729 · http://patentimages.storage.googleapis.com/5a/75/c2/adb8329656ea3a/US4133976.pdf · https://patents.justia.com/patent/4133976 · https://www.sumobrain.com/patents/us/System-method-ADPCM-transmission-speech/4554670.html · https://www.freepatentsonline.com/4700362.html · https://uspto.report/patent/grant/4700362 · https://patents.google.com/patent/US4841571

I'll ground the reference mappings with targeted lookups before writing the obviousness analysis.

Obviousness Analysis — U.S. Patent No. 4,882,585 under 35 U.S.C. § 103

Scope note: This is a technical invalidity analysis of a hypothetical § 103 challenge, not a legal opinion. It relies on the prior art listed in the Prior Art sections of the US 4,882,585 page (https://patents.google.com/patent/US4882585/en) — specifically the "Patent Citations (8)," "Non-Patent Citations (2)," and "Family Cites Families (2)" entries. Two caveats carried forward and one new one:

• Date discrepancy (previously flagged, unresolved): the task states today is April 26, 2026; the source snapshot was fetched 2026-09-16. I flag rather than reconcile.
• Evidence quality: I retrieved and verified the full text of Widmer '199, Chow '070, Chaure '393, Dolby '362, and Netravali '670. For Atal '976, Gagnon '729, Aiko '670, US 4,206,447, and FR 2,463,549 I have only the citation titles/dates from the page — mappings relying on those are provisional and marked as such.
• No prosecution history available. I cannot say what the examiner applied or what the applicant overcame in 1988–89.

1. The governing test

Under Graham v. John Deere and KSR Int'l v. Teleflex, the question is whether the differences between each claim and the prior art would have been obvious to a person of ordinary skill in the art ("POSITA") — here, a 1988 engineer in digital speech/audio coding — in view of (a) the scope and content of the art, (b) the differences, (c) the level of ordinary skill (DPCM/ADPCM and companding were mature, textbook arts by 1988), and (d) objective indicia. Under KSR, a combination is obvious where the references are in the same field, address the same problem, and the combination amounts to a predictable use of prior-art elements according to known methods.

2. The prior art of record, characterized

Note on Beard's own earlier patents (US 4,862,168; US 4,933,675 — Ser. No. 027,747, filed Mar. 19, 1987): these appear on the page under "Cited By," not "Citations," so they were not applied art. For completeness: as same-inventor disclosures they are not "by another" for pre-AIA § 102(e), and § 103(c) common-ownership would disqualify them from § 103 in any event. They should not be treated as § 103 references here.

3. Element-by-element: Claim 1

Only one limitation — the identity of the selection variable — is arguably not literally disclosed. That is a thin reed, and it is exactly the kind of difference KSR treats as within the skill of the art.

4. Proposed grounds of rejection

Ground 1 — Primary: Chow '070 in view of Widmer '199 (claims 1, 2, 8–11, 13–16, 18–20)

Why combinable / motivation: Both are DPCM/ADPCM bandwidth-compression systems in the identical field, addressing the identical problem (large quantization noise at low signal levels vs. excess bits). Chow supplies the digital-in/digital-out framing, the encoder-local-decoder architecture, and the exactly-matched remote decoder. Widmer supplies the missing pieces Chow lacks: a bank of discrete, progressively wider dynamic-range (resolution) settings, selected by a magnitude measure of the recent differential/reconstruction, with a companding (nonlinear) quantizer and complementary expander in both encoder-local-receiver and remote receiver, plus common initialization (Widmer's synchronized reset). A POSITA seeking to improve Chow's continuous step-size adaptation would readily adopt Widmer's discrete-companding-table approach; Widmer himself explains the design principle (matching the quantizer characteristic to the probability density of the difference signal), which is the same principle the '585 patent states as its "guiding principle." Result: predictable, no new mechanism required.

Ground 2 — Ground 1 further in view of Dolby '362 (claims 3, 5, 17 — the hysteresis limitations)

Claims 3/5/17 recite the asymmetric adaptation: immediate widening when the differential exceeds the current high-resolution range, but periodic decrements toward higher resolution when small differentials persist. This is fully taught by the combination:

• Widmer teaches the fast attack: after an overload, the dynamic range "is automatically adjusted at the subsequent higher value" at the next sampling instant, and its control signal is an average over N = 4 sampling periods — i.e., a value that moves down only gradually as small samples accumulate, and its evaluation circuit changes range only at four discrete thresholds.
• Dolby '362 teaches the deliberate use of a "control signal with a predetermined bandwidth" and expressly frames the design trade-off between limited adapting bandwidth (slow recovery) and transient distortion — i.e., attack/release time constants.

A POSITA implementing the patent's selection rule would necessarily pick some time constant, and the art supplies the two halves (instant attack, rate-limited release). Dolby's stated reason to bandwidth-limit the control signal provides the articulated motivation. The '585 counter preset to 8 (FIG. 7) is an uninventive design choice of count.

Ground 3 — Ground 1 further in view of Chaure '393 (and/or Atal '976, provisionally) (claims 12, 18 — residue feedback)

Claim 12/18's "compare the predicted/recovered value with the actual value, generate a residue, and add it to the next input before computing the differential" is quantization-error feedback / noise shaping. Chaure '393's entire stated object is "shaping of the quantization noise," forming a restored error and using restored signals in the prediction. Atal '976 is titled to "predictive speech signal coding with reduced noise effects" and, in the art of that period, is associated with error weighting/feedback. Combining Widmer's architecture with error-feedback is a predictable use of a known technique for the same purpose (moving quantization noise out of the perceptually sensitive region). Provisional as to Atal; solid as to Chaure's noise-shaping teaching.

Ground 4 — Ground 1 further in view of Netravali '670 and the PMI COMDAC Data Book (claims 2, 4, 16, and the decode-table design described in the spec)

• Claim 4/16 (lookup tables) — the PMI COMDAC Data Book documents nonlinear companding A/D–D/A converters implemented with nonlinear code conversion (in practice, ROM lookup tables). Reading a nonlinear transformation out of a table is a mere implementation choice.
• Decode tables = average of all higher-order values mapping to the code (spec, ¶ beginning "The decode tables in blocks 26 and 26D…") — Netravali '670 teaches that a received representative value implies a quantization interval, and that improved reconstruction within that interval is obtained from the set of values/correlations implied by the code. Using the interval centroid (mean) is the textbook minimum-distortion reconstruction (Max's quantizer design is cited in Netravali's own references). This makes the claimed complementary-table construction routine.

Ground 5 — Apparatus claim 15: Widmer '199 alone, or in view of Chow '070

Widmer's claims 1–2 recite, in a transmitter that contains a local receiver and in the remote receiver: a difference producer, a quantizer whose resolution/dynamic range is switched in discrete steps by a control generator, a matched decoder in both locations, an adder combining the decoded differential with the prediction, a predictor fed by that sum, and a control generator in each location "built up in the same manner." That is claim 15(a)(1)(i)–(iii), (a)(2)(i)–(vi), and (b)(i)–(vi) almost element-for-element. The residual gap is again (a)(2)(iii)/(b)(iii): the selector input. Chow '070 closes it by expressly deriving the quantizer's step-size from the ADPCM (differential) code and by making the decoder's blocks structurally identical to the encoder's, interconnected the same way — which is precisely the "lockstep tracking without side information" that claim 15(b) claims.

Ground 6 — Claims 13/19 (linear prediction)

Widmer's predictors "may alternatively be arranged for a signal extrapolation of a higher order" and he notes "it is known from the statistical communication theory how such a signal prediction can be rendered optimum." Chaure's predictor is explicitly two linear-filtering operations over N and P prior samples with coefficients minimizing error power. The specific second-order linear projection (2x[n−1] − x[n−2]) is the elementary linear predictor of the DPCM literature (cf. O'Neal & Stroh, cited within the DPCM art of record). Obvious.

Ground 7 — Claims 6/7, 14/20

• Initialization (6/7): Widmer's synchronized re-initialization of predictor and control storage in both transmitter and receiver is the same teaching as the '585 patent's "initialize in a common manner to assure proper tracking." Selecting P = mid-range and T = highest-resolution table, R = 0 at start-up is an arbitrary design choice with no asserted criticality.
• A/D–D/A (14/20): Dolby '362 is literally titled "A-D encoder and D-A decoder system"; Widmer's FIGS. 4–5 are a fully digital implementation with D/A reconstruction networks (45, 50) and sample-and-hold (51); the PMI COMDAC Data Book documents the codec devices. Rendered obvious a fortiori.

5. The patentee's best rebuttals, and why they likely fail

1. "The selector responds to the decoded differential quantity, not to an averaged reconstructed signal."
   — Strongest argument on the face of Widmer. Rebutted by (i) Widmer's express statement that his control signal measures "the order of the difference signal to be expected," (ii) Chow's step size "derived from the ADPCM signal" with adaptation keyed to "small magnitudes" of the differential, and (iii) US 4,206,447 (per its title). A POSITA would recognize that the differential code is the one quantity available identically at both encoder and decoder without side information — exactly the reason the reference combination makes the change predictable.

2. "Every table in the '585 patent maps the entire 16-bit differential range, so there is never an overload; Widmer tolerates overload."
   — Real architectural difference, and the patent's FIG. 7 discussion makes something of it. But this is a safety-margin/design choice: μ-law/A-law companding and the COMDAC codecs map the full range with no overload by construction, and Widmer's own "extend by a factor of 2" alternative (D_eff = 2D) shows the concept of reserving dynamic range. KSR treats such predictable variations as obvious.

3. "Unexpected reduction of quantization noise / CD quality at 8 bits."
   — No comparative data appears in the specification; FIGS. 4(a)–(b) are illustrative mappings, not measurements. Objective indicia of nonobviousness require evidence of an unexpected result, not an assertion.

4. "1989-era TSM test was stricter."
   — True historically (the Federal Circuit of that period demanded an express teaching, suggestion, or motivation). But the references here supply express motivations: Widmer's stated design principle (adapt the quantizer characteristic to the difference-signal statistics) and stated error-propagation self-correction; Chow's stated object of improved encoder/decoder tracking; Dolby's stated object of reducing transient distortion while limiting adaptation bandwidth. Under the current KSR standard these suffice.

5. Caveat in the patentee's favor: the specific hysteresis mechanism (a down-counter preset to 8, decremented once per in-range sample, reset on an out-of-range sample) is described with numerical specificity, and no reference of record appears to disclose that exact counter arrangement. If any claim survives, it is claims 3, 5, and 17 — and only if the patentee can show the asymmetric attack/release behavior produces a result that is more than the predictable consequence of choosing time constants.

6. Claim-by-claim conclusion

Overall: Every claim of US 4,882,585 appears vulnerable to a § 103 challenge built from references the examiner already had of record. The only limitation not squarely disclosed is the specific source of the table-selection variable (absolute value of the just-decoded differential) and the specific counter-based hysteresis of claims 3/5/17 — both of which are, on this record, design choices and predictable time-constant selections rather than inventions.

Confidence and limits: Moderate-to-high for claims 1, 2, 4, 8–11, 13–16, 18–20 (verified reference text). Lower for claims 3, 5, 12, 17, 19 (dependent on Atal '976, US 4,206,447, and FR 2,463,549, for which I could retrieve only citation metadata). A definitive analysis would require the full texts of those references and the '585 file history. Note finally that the patent's own status is expired for non-payment of maintenance fees (lapse recorded Nov. 21, 2001; nominal 20-year term to Mar. 17, 2008), so any invalidity finding would have no present effect on enforceability — its only live significance is as prior art (effective date Mar. 17, 1988) against later filings.