[Ffmpeg-devel] [PATCH] Snow multiple reference frames

Loren Merritt lorenm
Fri May 26 11:24:03 CEST 2006

On Fri, 26 May 2006, Oded Shimon wrote:
> On Fri, May 26, 2006 at 01:53:20AM -0700, Loren Merritt wrote:
>> $subject.
>> notes:
>> * Reduces bitrate by anywhere from 0 to 15%. Very content dependent.
>> * Doesn't modify mv prediction. It still takes a median of neighbors,
>> regardless of which ref they used.
>> * Doesn't work very well at low bitrate or with 8x8 partitions. Maybe
>> I'm underestimating the cost of specifying refs, or maybe due to the
>> above prediction? (but an exact rangecoder cost didn't help either.)
>> * Slow encoding. Does a naive search over all available refs. A possible
>> optimization that helped muchly in x264, would be to stop a motion search
>> after fullpel or halfpel if the residual so far is much worse than some
>> previously searched ref.
>> +#define MAX_REF_FRAMES 8
> Does this mean it stores the entire last 8 frames always? isn't this
> extremely memory intensive?

No, it stores 8 AVFrame structs, which are all of 192 bytes each. Only the 
ones currently in use have pictures allocated to them.

--Loren Merritt

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