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

[Hendrik Leppkes]

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