[Libav-user] Problems with ffvhuff and huvvyuv

[Bruce Wheaton]

On Oct 16, 2013, at 8:56 AM, Bruce Wheaton <bruce at spearmorgan.com> wrote:

> 
>> On Oct 16, 2013, at 8:46, Paul B Mahol <onemda at gmail.com> wrote:
>>> The only workaround is to use intra-frame only compression, so all frames
>>> are independent. Some codecs you listed always work that way.
>> 
>> ffvhuff is intra only.
> 
> I don't know that codec. I just knew it was lossless. So I guess (unless there's a bug) the rule has an exception. Maybe the 'adaptive tables' that google says it has adapt every 24 or so frames. Don't have the source in front of me right now. 
> 
> But it's an FOSS project - anyone look at the code and see what's going on. 

I can't pick it out of the code, and the codec info says it is intra-frame only... but this paper seems to indicate that ffvhuff isn't always intra-frame only:

"FFv1 [16] was also developed by the FFmpeg project and is derived from HuffYUV. The main difference is that the intra-frame coding model is limited to the median model as described above"

From COMPARISON OF LOSSLESS VIDEO CODECS FOR CROWD-BASED QUALITY ASSESSMENT ON TABLETS

Christian Keimel, Christopher Pangerl and Klaus Diepold

https://mediatum.ub.tum.de/doc/1128908/1128908.pdf

So - as I mentioned - videos that aren't encoded as intra-frame often have to decode a number of frames in order to get to your desired frame. As far as I know, the only way ffmpeg deals with that is by decoding all the frames from a known safe search point up until your desired frame.

Bruce

> 
>>>> Does this have anything to do with cached frames, or is that another
>>>> issue?
>>>> 
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