Re: [FFmpeg-devel] [PATCH 2/4 v6] avformat: add a Tile Grid stream group type

[James Almer <jamrial@gmail.com>]

On 1/31/2024 3:33 PM, Andreas Rheinhardt wrote:
> James Almer:
>> On 1/31/2024 3:08 PM, Andreas Rheinhardt wrote:
>>> James Almer:
>>>> This will be used to support tiled image formats like HEIF.
>>>>
>>>> Signed-off-by: James Almer<jamrial@gmail.com>
>>>> ---
>>>>    libavformat/avformat.c |   5 +++
>>>>    libavformat/avformat.h | 100 +++++++++++++++++++++++++++++++++++++++++
>>>>    libavformat/dump.c     |  29 ++++++++++++
>>>>    libavformat/options.c  |  32 +++++++++++++
>>>>    4 files changed, 166 insertions(+)
>>>>
>>>> diff --git a/libavformat/avformat.c b/libavformat/avformat.c
>>>> index 8e8c6fbe55..32ef440207 100644
>>>> --- a/libavformat/avformat.c
>>>> +++ b/libavformat/avformat.c
>>>> @@ -100,6 +100,11 @@ void ff_free_stream_group(AVStreamGroup **pstg)
>>>>           
>>>> av_iamf_mix_presentation_free(&stg->params.iamf_mix_presentation);
>>>>            break;
>>>>        }
>>>> +    case AV_STREAM_GROUP_PARAMS_TILE_GRID:
>>>> +        av_opt_free(stg->params.tile_grid);
>>>> +        av_freep(&stg->params.tile_grid->offsets);
>>>> +        av_freep(&stg->params.tile_grid);
>>>> +        break;
>>>>        default:
>>>>            break;
>>>>        }
>>>> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
>>>> index 5d0fe82250..6577f13ef1 100644
>>>> --- a/libavformat/avformat.h
>>>> +++ b/libavformat/avformat.h
>>>> @@ -1018,10 +1018,109 @@ typedef struct AVStream {
>>>>        int pts_wrap_bits;
>>>>    } AVStream;
>>>>    +/**
>>>> + * AVStreamGroupTileGrid holds information on how to combine several
>>>> + * independent images on a single grid for presentation. None of the
>>>> tiles may
>>>> + * overlap inside the grid.
>>>> + *
>>>> + * The following is an example of a simple grid with 3 rows and 4
>>>> columns:
>>>> + *
>>>> + * +---+---+---+---+
>>>> + * | 0 | 1 | 2 | 3 |
>>>> + * +---+---+---+---+
>>>> + * | 4 | 5 | 6 | 7 |
>>>> + * +---+---+---+---+
>>>> + * | 8 | 9 |10 |11 |
>>>> + * +---+---+---+---+
>>>> + *
>>>> + * Assuming all tiles have a dimension of 512x512, the
>>>> + * @ref AVStreamGroupTileGrid.offsets "offset" of the topleft pixel of
>>>> + * the first @ref AVStreamGroup.streams "stream" in the group is
>>>> "0,0", the
>>>> + * @ref AVStreamGroupTileGrid.offsets "offset" of the topleft pixel of
>>>> + * the second @ref AVStreamGroup.streams "stream" in the group is
>>>> "512,0", the
>>>> + * @ref AVStreamGroupTileGrid.offsets "offset" of the topleft pixel of
>>>> + * the fifth @ref AVStreamGroup.streams "stream" in the group is
>>>> "0,512", the
>>>> + * @ref AVStreamGroupTileGrid.offsets "offset", of the topleft pixel of
>>>> + * the sixth @ref AVStreamGroup.streams "stream" in the group is
>>>> "512,512",
>>>> + * etc.
>>>> + *
>>>> + * sizeof(AVStreamGroupTileGrid) is not a part of the ABI. No new
>>>> fields may be
>>>> + * added to this struct without a major version bump.
>>> This is inconsistent. I think you mean that sizeof is part of the ABI.
>>
>> No? It's not a part of the ABI because AVStreamGroupTileGrid must not be
>> ever used on stack, or allocated by anything other than AVStreamGroup.
>> That way we can add fields to it without waiting for a major bump.
> 
> "No new fields may be added to this struct without a major version bump"

Ah, i see. Copy paste fail. Will remove that part.
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