[FFmpeg-devel] [PATCH 01/17] avformat/mxfenc: Auto-insert h264_mp4toannexb BSF if needed

[James Almer]

On 11/9/2021 2:34 PM, Andreas Rheinhardt wrote:
> The mxf and mxf_opatom muxer expect H.264 in Annex B format.

Amazing that nobody noticed this until now. Guess remuxing from mp4/mkv 
to mxf is not a common scenario.

LGTM, just tested a quick remux and without the bsf it just fails.

> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> ---
> The check here is taken from mpegtsenc.
> 
>   libavformat/mxfenc.c | 18 ++++++++++++++++++
>   1 file changed, 18 insertions(+)
> 
> diff --git a/libavformat/mxfenc.c b/libavformat/mxfenc.c
> index c36ebef932..d1c4d43a50 100644
> --- a/libavformat/mxfenc.c
> +++ b/libavformat/mxfenc.c
> @@ -3174,6 +3174,22 @@ static int mxf_interleave(AVFormatContext *s, AVPacket *pkt,
>       return mxf_interleave_get_packet(s, pkt, flush);
>   }
>   
> +static int mxf_check_bitstream(AVFormatContext *s, const AVPacket *pkt)
> +{
> +    AVStream *const st = s->streams[pkt->stream_index];
> +
> +    switch (st->codecpar->codec_id) {
> +    case AV_CODEC_ID_H264:
> +        if (pkt->size >= 5 && AV_RB32(pkt->data) != 0x0000001 &&
> +                             (AV_RB24(pkt->data) != 0x000001 ||
> +                              (st->codecpar->extradata_size > 0 &&
> +                               st->codecpar->extradata[0] == 1)))
> +            return ff_stream_add_bitstream_filter(st, "h264_mp4toannexb", NULL);
> +        break;
> +    }
> +    return 1;
> +}
> +
>   #define MXF_COMMON_OPTIONS \
>       { "signal_standard", "Force/set Signal Standard",\
>         offsetof(MXFContext, signal_standard), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 7, AV_OPT_FLAG_ENCODING_PARAM, "signal_standard"},\
> @@ -3249,6 +3265,7 @@ const AVOutputFormat ff_mxf_muxer = {
>       .audio_codec       = AV_CODEC_ID_PCM_S16LE,
>       .video_codec       = AV_CODEC_ID_MPEG2VIDEO,
>       .write_header      = mxf_write_header,
> +    .check_bitstream   = mxf_check_bitstream,
>       .write_packet      = mxf_write_packet,
>       .write_trailer     = mxf_write_footer,
>       .deinit            = mxf_deinit,
> @@ -3282,6 +3299,7 @@ const AVOutputFormat ff_mxf_opatom_muxer = {
>       .audio_codec       = AV_CODEC_ID_PCM_S16LE,
>       .video_codec       = AV_CODEC_ID_DNXHD,
>       .write_header      = mxf_write_header,
> +    .check_bitstream   = mxf_check_bitstream,
>       .write_packet      = mxf_write_packet,
>       .write_trailer     = mxf_write_footer,
>       .deinit            = mxf_deinit,
>