[FFmpeg-devel] [PATCH v4 4/8] avformat/mux: add proper support for full N:M bitstream filtering

[Andreas Rheinhardt]

Marton Balint:
> Previously only 1:1 bitstream filters were supported, the end of the stream was
> not signalled to the bitstream filters and time base changes were ignored.
> 
> This change also allows muxers to set up bitstream filters regardless of the
> autobsf flag during write_header instead of during check_bitstream and those
> bitstream filters will always be executed.

Ignoring the autobsf flag is not ok IMO. The muxer should not add a bsf
when the user explicitly didn't want this.

- Andreas

> 
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
>  libavformat/mux.c | 87 +++++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 56 insertions(+), 31 deletions(-)
> 
> diff --git a/libavformat/mux.c b/libavformat/mux.c
> index 33aed9da90..d3a98499ce 100644
> --- a/libavformat/mux.c
> +++ b/libavformat/mux.c
> @@ -1077,8 +1077,8 @@ static int interleave_packet(AVFormatContext *s, AVPacket *out, AVPacket *in, in
>          return ff_interleave_packet_per_dts(s, out, in, flush);
>  }
>  
> -static int do_packet_auto_bsf(AVFormatContext *s, AVPacket *pkt) {
> -    AVStream *st = s->streams[pkt->stream_index];
> +static int check_bitstream(AVFormatContext *s, AVStream *st, AVPacket *pkt)
> +{
>      int ret;
>  
>      if (!(s->flags & AVFMT_FLAG_AUTO_BSF))
> @@ -1093,30 +1093,6 @@ static int do_packet_auto_bsf(AVFormatContext *s, AVPacket *pkt) {
>          }
>      }
>  
> -    if (st->internal->bsfc) {
> -        AVBSFContext *ctx = st->internal->bsfc;
> -        // TODO: when any bitstream filter requires flushing at EOF, we'll need to
> -        // flush each stream's BSF chain on write_trailer.
> -        if ((ret = av_bsf_send_packet(ctx, pkt)) < 0) {
> -            av_log(ctx, AV_LOG_ERROR,
> -                    "Failed to send packet to filter %s for stream %d\n",
> -                    ctx->filter->name, pkt->stream_index);
> -            return ret;
> -        }
> -        // TODO: when any automatically-added bitstream filter is generating multiple
> -        // output packets for a single input one, we'll need to call this in a loop
> -        // and write each output packet.
> -        if ((ret = av_bsf_receive_packet(ctx, pkt)) < 0) {
> -            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
> -                return 0;
> -            av_log(ctx, AV_LOG_ERROR,
> -                    "Failed to receive packet from filter %s for stream %d\n",
> -                    ctx->filter->name, pkt->stream_index);
> -            if (s->error_recognition & AV_EF_EXPLODE)
> -                return ret;
> -            return 0;
> -        }
> -    }
>      return 1;
>  }
>  
> @@ -1161,17 +1137,53 @@ static int write_packet_common(AVFormatContext *s, AVStream *st, AVPacket *pkt,
>      }
>  }
>  
> +static int write_packets_from_bsfs(AVFormatContext *s, AVStream *st, AVPacket *pkt, int interleaved)
> +{
> +    AVBSFContext *bsfc = st->internal->bsfc;
> +    int ret;
> +
> +    if ((ret = av_bsf_send_packet(bsfc, pkt)) < 0) {
> +        av_log(s, AV_LOG_ERROR,
> +                "Failed to send packet to filter %s for stream %d\n",
> +                bsfc->filter->name, st->index);
> +        return ret;
> +    }
> +
> +    do {
> +        ret = av_bsf_receive_packet(bsfc, pkt);
> +        if (ret < 0) {
> +            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
> +                return 0;
> +            av_log(s, AV_LOG_ERROR, "Error applying bitstream filters to an output "
> +                   "packet for stream #%d: %s\n", st->index, av_err2str(ret));
> +            if (!(s->error_recognition & AV_EF_EXPLODE) && ret != AVERROR(ENOMEM))
> +                continue;
> +            return ret;
> +        }
> +        av_packet_rescale_ts(pkt, bsfc->time_base_out, st->time_base);
> +        ret = write_packet_common(s, st, pkt, interleaved);
> +        if (ret >= 0 && !interleaved) // a successful write_packet_common already unrefed pkt for interleaved
> +            av_packet_unref(pkt);
> +    } while (ret >= 0);
> +
> +    return ret;
> +}
> +
>  static int write_packets_common(AVFormatContext *s, AVStream *st, AVPacket *pkt, int interleaved)
>  {
>      int ret = prepare_input_packet(s, pkt);
>      if (ret < 0)
>          return ret;
>  
> -    ret = do_packet_auto_bsf(s, pkt);
> -    if (ret <= 0)
> +    ret = check_bitstream(s, st, pkt);
> +    if (ret < 0)
>          return ret;
>  
> -    return write_packet_common(s, st, pkt, interleaved);
> +    if (st->internal->bsfc) {
> +        return write_packets_from_bsfs(s, st, pkt, interleaved);
> +    } else {
> +        return write_packet_common(s, st, pkt, interleaved);
> +    }
>  }
>  
>  int av_write_frame(AVFormatContext *s, AVPacket *in)
> @@ -1238,9 +1250,22 @@ int av_interleaved_write_frame(AVFormatContext *s, AVPacket *pkt)
>  
>  int av_write_trailer(AVFormatContext *s)
>  {
> -    int ret, i;
> +    int i, ret1, ret = 0;
> +    AVPacket pkt = {0};
> +    av_init_packet(&pkt);
>  
> -    ret = interleaved_write_packet(s, NULL, 1);
> +    for (i = 0; i < s->nb_streams; i++) {
> +        if (s->streams[i]->internal->bsfc) {
> +            ret1 = write_packets_from_bsfs(s, s->streams[i], &pkt, 1/*interleaved*/);
> +            if (ret1 < 0)
> +                av_packet_unref(&pkt);
> +            if (ret >= 0)
> +                ret = ret1;
> +        }
> +    }
> +    ret1 = interleaved_write_packet(s, NULL, 1);
> +    if (ret >= 0)
> +        ret = ret1;
>  
>      if (s->oformat->write_trailer) {
>          if (!(s->oformat->flags & AVFMT_NOFILE) && s->pb)
>