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

[Hendrik Leppkes]

On Fri, Apr 21, 2017 at 11:52 PM, James Almer <jamrial at gmail.com> wrote:
> 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.
>

Yeah I looked up the FullBox spec and figured the flags of 1 might
mean something I wasn't aware of.

Anyhow, I'll send an amended patch soon that writes an appropriate version numer

- Hendrik