[FFmpeg-devel] [PATCH] lavc/ffv1: Properly check that the 4th and 5th quant tables are zeroes

[Michael Niedermayer]

On Thu, Jan 02, 2020 at 03:22:25PM +0000, Derek Buitenhuis wrote:
> Currently, the decoder checks the 128th value of the 4th quant table during
> while deriving the context on each sample, in order to speed itself up. This
> is due to relying on the behavior of FFmpeg's FFV1 encoder, in which if that
> value is zero, the entire 4th and 5th quant tables are assumed to be entirely
> zero.

I think if entry 128 is 0 then the whole table must be 0.
If that is the case, checking the entry 128 of table 4 and 5 would be enough
and caching the entry comparission is maybe not needed.

thx

[...]
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