Obviousness

As a senior US patent analyst, I am tasked with analyzing the obviousness of US patent US7391791B2 under 35 U.S.C. § 103, including identifying combinations of prior art references and explaining the motivation for combining them.

However, a critical prerequisite for performing an obviousness analysis is the identification of specific prior art references. The authoritative patent text provided for US7391791B2 does not contain a "References Cited" section, nor does it list any specific prior art documents that were considered during its prosecution or are otherwise acknowledged as prior art to this patent. While there is a "Prior art keywords" section, these are descriptive terms and not patent or publication references. The "Cited By" section lists patents that cite US7391791B2, meaning they are generally published after its priority date of December 17, 2001, and are therefore not prior art to US7391791B2.

To address this absence of information, I performed a live web search for "US7391791B2 references cited" and "prior art synchronization content rendering before 2001" to locate the official list of prior art documents. While the search results provided general information about what constitutes prior art and how it's used in obviousness determinations (e.g., MPEP 2141.01, 2120), they did not yield a direct, specific list of prior art references cited against US7391791B2 itself.

Therefore, without specific prior art references that predate the priority date of US7391791B2 (December 17, 2001), it is not possible to:

1. Identify combinations of prior art references that would render the claims obvious.
2. Explain why a person having ordinary skill in the art would have been motivated to combine such references.

I cannot fabricate or assume prior art references, as doing so would violate the operating rules, which state: "If you do not know something with high confidence, say so explicitly rather than fabricating."

General Principles of Obviousness (35 U.S.C. § 103):

In a hypothetical scenario where relevant prior art were available, an obviousness analysis under 35 U.S.C. § 103 would involve the following steps as laid out by Graham v. John Deere Co.:

1. Determining the scope and content of the prior art: This involves identifying relevant publications, patents, or public knowledge existing before the patent's priority date.
2. Ascertaining the differences between the claimed invention and the prior art: This step compares each claim of US7391791B2 to the identified prior art to pinpoint what distinguishes the invention.
3. Resolving the level of ordinary skill in the pertinent art: This establishes the baseline knowledge and capabilities of a typical practitioner in the field of synchronized content rendering at the time the invention was made.
4. Evaluating secondary considerations (if applicable): Factors such as commercial success, long-felt but unsolved needs, failure of others, and unexpected results can provide objective evidence of non-obviousness.

For US7391791B2, given its claims pertaining to master-slave synchronization of content rendering across devices with different time domains, and its method for calculating time domain differentials to factor out transmission latency, the obviousness analysis would likely investigate whether:

• The general concept of master-slave synchronization for distributed systems was known.
• The idea of synchronizing multimedia content (e.g., video and audio) across different devices was known.
• Methods for detecting and correcting clock drift or time domain differences between networked devices were known, particularly those accounting for network latency (e.g., using send and receive timestamps).
• It would have been obvious for a person of ordinary skill in the art to combine these known elements to create a system that specifically synchronizes content rendering by adjusting for both content rendering time and underlying device time domain differences, including mechanisms to account for transmission delays and user-specified offsets.

However, without the actual prior art references, this theoretical discussion cannot be concretely applied to the patent's claims.