Wednesday, January 24, 2007

More Qualcomm/Broadcomm: how different must transforms be?

Of the Qualcomm/Broadcomm patent litigation, the San Diego Union-Tribune wrote:

At the heart of the case is whether an "integer transform" is just another type of "discrete cosine transform" [DCT] or they are fundamentally different.

A transform is an algorithm used in video compression. Qualcomm's patented technology describes a method of video compression that calls for a discrete cosine transform. The H.264 standard and its products use an integer transform.

IPBiz notes a paper from MERL (Mitsubishi) which describes a method to convert DCT coefficients into IT coefficients. If there are a variety of ways to interconvert the coding schemes yielding different results, then the two coding schemes probably are not identical. The abstract of the MERL paper notes that MPEG-2 uses a DCT, but that H.264 uses an integer transform, itself suggesting the two are different. Separately, if Qualcomm is taking the position that "all schemes are the same," then is there invalidating prior art from a different scheme?


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