[FFmpeg-devel] [PATCH] avformat/mxfenc: support XAVC long gop

[Thomas Mundt]

Hi Baptiste,

Am Fr., 10. Mai 2019 um 17:51 Uhr schrieb Baptiste Coudurier <
baptiste.coudurier at gmail.com>:

> ---
>  libavformat/Makefile |   2 +-
>  libavformat/avc.c    | 188 ++++++++++++++++++++++++++++++++++++++
>  libavformat/avc.h    |  15 +++
>  libavformat/hevc.c   |  36 +-------
>  libavformat/mxf.h    |   1 +
>  libavformat/mxfenc.c | 213 ++++++++++++++++++++++++++++++++++---------
>  6 files changed, 374 insertions(+), 81 deletions(-)
> [...]

+static const MXFLocalTagPair mxf_avc_subdescriptor_local_tags[] = {
> +    { 0x8100,
> {0x06,0x0E,0x2B,0x34,0x01,0x01,0x01,0x09,0x06,0x01,0x01,0x04,0x06,0x10,0x00,0x00}},
> /* SubDescriptors */
> +    { 0x8200,
> {0x06,0x0E,0x2B,0x34,0x01,0x01,0x01,0x0E,0x04,0x01,0x06,0x06,0x01,0x0E,0x00,0x00}},
> /* AVC Decoding Delay */
> +    { 0x8201,
> {0x06,0x0E,0x2B,0x34,0x01,0x01,0x01,0x0E,0x04,0x01,0x06,0x06,0x01,0x0A,0x00,0x00}},
> /* AVC Profile */
> +    { 0x8202,
> {0x06,0x0E,0x2B,0x34,0x01,0x01,0x01,0x0E,0x04,0x01,0x06,0x06,0x01,0x0D,0x00,0x00}},
> /* AVC Level */
> +};
> +
> [...]
> +static void mxf_write_avc_subdesc(AVFormatContext *s, AVStream *st)
> +{
> +    AVIOContext *pb = s->pb;
> +    int64_t pos;
> +
> +    avio_write(pb, mxf_avc_subdescriptor_key, 16);
> +    klv_encode_ber4_length(pb, 0);
> +    pos = avio_tell(pb);
> +
> +    mxf_write_local_tag(pb, 16, 0x3C0A);
> +    mxf_write_uuid(pb, AVCSubDescriptor, 0);
> +
> +    mxf_write_local_tag(pb, 1, 0x8200);
> +    avio_w8(pb, 0xFF); // AVC Decoding Delay, unknown
> +
> +    mxf_write_local_tag(pb, 1, 0x8201);
> +    avio_w8(pb, st->codecpar->profile); // AVC Profile
> +
> +    mxf_write_local_tag(pb, 1, 0x8202);
> +    avio_w8(pb, st->codecpar->level); // AVC Level
> +
> +    mxf_update_klv_size(s->pb, pos);
> +}
>

Other MXF muxers, e.g. bmxlib, also write the avc profile constraint tag
when the avc subdescriptor is used. At least MediaInfo detects intra coded
files as long gop otherwise.

FFmpeg crashes with this patch when I try to remux AVC Intra files without
SPS/PPS header.
Tested on Windows 7. Compiled with msys2/gcc7.3.0 x86-32bit.
Command: ffmpeg -i AVCI100_Test.mxf -c:v copy out.mxf
Test file:
https://www.mediafire.com/file/n0oi50u39yi3qpr/AVCI100_Test.mxf/file

Regards,
Thomas