[FFmpeg-devel] [Uncompressed MP4] Write uncC Tag

[Devon Sookhoo]

Hello,

This patch is more of a RFC. I'm interested in generating uncompressed MP4
files in FFMPEG according to ISO/IEC 23001-17:2024 and wrote this as a
first step towards implementation. Any feedback or help would be greatly
appreciated.

Thanks

On Tue, Sep 24, 2024 at 2:51 PM Devon Sookhoo <devonsookhoo14 at gmail.com>
wrote:

> From 5767e173414432d6079b1b581121622e874a26cd Mon Sep 17 00:00:00 2001
> From: dukesook <devonsookhoo14 at gmail.com>
> Date: Tue, 24 Sep 2024 12:27:31 -0600
> Subject: [PATCH] mov_write_uncC_tag()
>
> Initial function for writing the uncC, or uncopmressed codec box
> ---
>  libavformat/movenc.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
>
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index d20e45cf81..da40442726 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -2602,6 +2602,58 @@ static int mov_write_aux_tag(AVIOContext *pb, const
> char *aux_type)
>      return update_size(pb, pos);
>  }
>
> +static int mov_write_uncC_component(AVIOContext *pb, uint16_t index,
> uint8_t bit_depth_minus_one, uint8_t format, uint8_t align_size) {
> +    avio_wb16(pb, index);
> +    avio_w8(pb, bit_depth_minus_one);
> +    avio_w8(pb, format);
> +    avio_w8(pb, align_size);
> +    return 0;
> +}
> +
> +static int mov_write_uncC_tag(AVFormatContext *s, AVIOContext *pb,
> MOVMuxContext *mov, MOVTrack *track) {
> +    int64_t pos = avio_tell(pb);
> +    uint8_t version = 0x0;
> +
> +    avio_wb32(pb, 0); /* size */
> +    ffio_wfourcc(pb, "uncC");
> +
> +    //FULL BOX
> +    avio_w8(pb, 0x00);       // Flags
> +    avio_wb24(pb, 0x000000); // Version
> +
> +    avio_wb32(pb, 0x00000000); // profile
> +
> +    if (version == 1) {
> +        return update_size(pb, pos);
> +    }
> +    else if (version == 0) {
> +        avio_wb32(pb, 0x03); // component_count
> +        mov_write_uncC_component(pb, 0x0000, 0x07, 0x00, 0x00); //Red
> +        mov_write_uncC_component(pb, 0x0001, 0x07, 0x00, 0x00); //Green
> +        mov_write_uncC_component(pb, 0x0002, 0x07, 0x00, 0x00); //Blue
> +
> +        avio_w8(pb, 0x00); //sampling_type. 0 = No subsampling
> +        avio_w8(pb, 0x00); //interleave_type. 0 = Planar, 1 = interleaved
> +        avio_w8(pb, 0x00); //block_size;
> +
> +        // Pixel Layout Flags
> +        // bit(1) components_little_endian;
> +        // bit(1) block_pad_last;
> +        // bit(1) block_little_endian;
> +        // bit(1) block_reversed;
> +        // bit(1) pad_unknown;
> +        // bit(3) reserved = 0;
> +        avio_w8(pb, 0X00);
> +
> +        avio_wb32(pb, 0x00000000); // pixel_size;
> +        avio_wb32(pb, 0x00000000); // row_align_size;
> +        avio_wb32(pb, 0x00000000); // tile_align_size;
> +        avio_wb32(pb, 0x00000000); // num_tile_cols_minus_one;
> +        avio_wb32(pb, 0x00000000); // num_tile_rows_minus_one;
> +    }
> +    return update_size(pb, pos);
> +}
> +
>  static int mov_write_video_tag(AVFormatContext *s, AVIOContext *pb,
> MOVMuxContext *mov, MOVTrack *track)
>  {
>      int ret = AVERROR_BUG;
> --
> 2.34.1
>
>
>
> *ISO/IEC 23001-17:2024 Section 5.2.2 Syntax*
> aligned(8) class UncompressedFrameConfigBox extends FullBox('uncC', 0, 0)
> {
>   unsigned int(32) profile;
>   unsigned int(16) component_count;
>   {
>     unsigned int(16) component_index;
>     unsigned int(8) component_bit_depth_minus_one;
>     unsigned int(8) component_format;
>     unsigned int(8) component_align_size;
>   } [component_count];
>   unsigned int(8) sampling_type;
>   unsigned int(8) interleave_type;
>   unsigned int(8) block_size;
>   bit(1) components_little_endian;
>   bit(1) block_pad_lsb;
>   bit(1) block_little_endian;
>   bit(1) block_reversed;
>   bit(1) pad_unknown;
>   bit(3) reserved = 0;
>   unsigned int(8) pixel_size;
>   unsigned int(32) row_align_size;
>   unsigned int(32) tile_align_size;
>   unsigned int(32) num_tile_cols_minus_one;
>   unsigned int(32) num_tile_rows_minus_one;
> }
>
>
>