[FFmpeg-devel] FFV1 Specification

Peter B. pb at das-werkstatt.com
Sun Apr 8 22:35:24 CEST 2012

On 04/08/2012 02:45 PM, Michael Niedermayer wrote:
> On Sun, Apr 08, 2012 at 02:36:55PM +0200, Michael Niedermayer wrote:
>> On Sun, Apr 08, 2012 at 02:21:38PM +0200, Peter B. wrote:
>>> I thought that when using an intra-frame-only codec, all frames are
>>> self-contained and there'd be no GOPs. Am I getting something wrong here?
>> they are intra frames in the sense that there is no motion
>> compensation. The previous frame(s) also dont need to be kept as
>> reference frames, but the contexts can be reset once per frame or
>> less often to improve compression performance
>> The ffv1 spec does mention this:
>>     Initial values for the context model
>>     At keyframes all range coder state variables are set to 128
>> this implicates that no keyframe -> no reset
> but reading this again, this should be written in a more direct way
> because as is its easy to miss it.
> maybe you could suggest some text ?
It's difficult for me: I'm used to reading tech-papers, and my math is
not that bad, but I have no hands-on experience in programming audio or
video codecs. So I think I'm able to grasp the rough idea behind FFv1's
compression - but it's too faaaaaaaar from me being really being able to
re-word things like that, I guess :(
Even if I do understand the principle behind range coding and huffman,
the context model is still completely new for me - although exiting to
wrap my brains around the inner workings of something like FFv1, which
I'm using daily :)

So, I hope it's not too cumbersome to answer my questions as they might
seem super-newbie-bla to you. But I'm trying to do my best ;)


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