[FFmpeg-devel] Adding ICC profile support to MOV decode/encode

[Hello Vectronic]

> On 18 Sep 2019, at 11:09, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
> 
> On Wed, Sep 18, 2019 at 11:37 AM Hello Vectronic
> <hello.vectronic at gmail.com> wrote:
>> 
>> Hello,
>> 
>> I need to implement support for reading and writing ICC profiles which can be stored in MOV/MP4 sample descriptor colour information.
>> 
>> The relevant extract from the ISO standard is:
>> 
>> class ColourInformationBox extends Box('colr'){
>>    unsigned int(32) colour_type;
>>    if (colour_type == 'nclx')  /* on-screen colours */
>>    {
>>        unsigned int(16) colour_primaries;
>>        unsigned int(16) transfer_characteristics;
>>        unsigned int(16) matrix_coefficients;
>>        unsigned int(1)  full_range_flag;
>>        unsigned int(7)  reserved = 0;
>>    }
>>    else if (colour_type == 'rICC')
>>    {
>>        ICC_profile;    // restricted ICC profile
>>    }
>>    else if (colour_type == 'prof')
>>    {
>>        ICC_profile;    // unrestricted ICC profile
>>    }
>> }
>> 
>> At the moment the code only supports nclc/nclx colour type in:
>> 
>> libavformat/mov.c  => mov_read_colr()
>> libavformat/moveenc.c =>  mov_write_colr_tag()
>> 
>> Support for ICC profile is implemented on a per frame basis in AVFrameSideDataType.AV_FRAME_DATA_ICC_PROFILE. This is used by the PNG, WEBP and MJPEG codec implementations. The ICC profile in this scenario is treated as an opaque octet buffer. I don't believe this is relevant to my use case as the colour information within the MOV/MP4 sample descriptor relates to the entire stream and is not used on a per-frame basis.
>> 
>> My thinking is to implement support for ICC profile in a similar way that color_range, color_primaries etc. are currently handled:
>> 
>> 1. Store the ICC profile as an opaque octet buffer stored in an AVCodecParameters struct value:
>> 
>> uint8_t *icc_profile_data;
>> int     icc_profile_size;
>> 
> 
> Something like this has no place in AVCodecParameters, which is
> intentionally kept simple and easy. It should be stream-global
> side-data, similar to the frame side data, just on a stream level,
> which is already a concept we have, so it should be easy to fit it in
> there.
> 
> - Hendrik
> 



Thanks for the advice. 

So it seems I would:

1. add a new enum value AVPacketSideDataType.AV_PKT_DATA_ICC_PROFILE

2. use av_stream_add_side_data() when reading from the MOV/MP4 in libavformat/mov.c => mov_read_colr()

3. use av_stream_get_side_data() when writing to the MOV/MP4 in libavformat/moveenc.c => mov_write_colr_tag()

And I think that is it..?