[FFmpeg-devel] [PATCH] movenc/isom: update vpcC box to the latest draft specification

[James Almer]

On 4/21/2017 6:47 PM, James Almer wrote:
> On 4/21/2017 6:34 PM, Hendrik Leppkes wrote:
>> On Fri, Apr 21, 2017 at 11:25 PM, KongQun Yang
>> <kqyang-at-google.com at ffmpeg.org> wrote:
>>> Hi Hendrik,
>>>
>>> Thanks for working on it. Version needs to be updated as well:
>>> https://github.com/FFmpeg/FFmpeg/blob/b905ba5bc18c89c7fccd8621795755644442ef19/libavformat/movenc.c#L1115. 
>>>
>>> Suggest moving it into ff_isom_write_vpcc function too.
>>>
>>
>> The actual value of the version field doesn't seem to be mentioned in
>> the specification anywhere.
>> https://github.com/webmproject/vp9-dash/blob/master/VPCodecISOMediaFileFormatBinding.md 
>>
>>
>> The only version info I can see is the v1.0 at the top, but thats
>> hardly a direct correlation to single integer version field in the mp4
>> box.
>>
>> Or did I miss it somewhere?
>>
>> - Hendrik
> 
> https://github.com/webmproject/vp9-dash/commit/7961d0feb5bd879c84aa71d208d5df30bd5d5192 

In fact, i think that commit is wrong. It changed the flags field from 0 
to 1. As per the spec:

aligned(8) class FullBox(unsigned int(32) boxtype, unsigned int(8) v,
                          bit(24) f)
    extends Box(boxtype) {
    unsigned int(8)   version = v;
    bit(24)     flags = f;
}

So they are defining the version number as "version" in 
VPCodecISOMediaFileFormatBinding.md

in any case, version is now 1 instead of 0.