Re: [FFmpeg-devel] [PATCH] avfilter/src_movie: activate & dr

[James Almer <jamrial@gmail.com>]

On 5/18/2023 7:22 AM, Paul B Mahol wrote:
> From af73b69a0be9033fddf222b6e9ac60799de85691 Mon Sep 17 00:00:00 2001
> From: Paul B Mahol <onemda@gmail.com>
> Date: Mon, 15 May 2023 21:54:25 +0200
> Subject: [PATCH 26/27] avfilter/src_movie: dr support
> 
> Signed-off-by: Paul B Mahol <onemda@gmail.com>
> ---
>  libavfilter/src_movie.c | 44 +++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 42 insertions(+), 2 deletions(-)
> 
> diff --git a/libavfilter/src_movie.c b/libavfilter/src_movie.c
> index 5937613d13..a2ecc5a625 100644
> --- a/libavfilter/src_movie.c
> +++ b/libavfilter/src_movie.c
> @@ -23,7 +23,6 @@
>   * @file
>   * movie video source
>   *
> - * @todo use direct rendering (no allocation of a new frame)
>   * @todo support a PTS correction mechanism
>   */
>  
> @@ -156,6 +155,43 @@ static AVStream *find_stream(void *log, AVFormatContext *avf, const char *spec)
>      return found;
>  }
>  
> +static int get_buffer(AVCodecContext *avctx, AVFrame *frame, int flags)
> +{
> +    int linesize_align[AV_NUM_DATA_POINTERS];
> +    AVFilterLink *outlink = frame->opaque;
> +    int w, h, ow, oh;
> +    AVFrame *new;
> +
> +    h = oh = frame->height;
> +    w = ow = frame->width;
> +
> +    if (!(avctx->codec->capabilities & AV_CODEC_CAP_DR1))
> +        return avcodec_default_get_buffer2(avctx, frame, flags);
> +
> +    switch (avctx->codec_type) {
> +    case AVMEDIA_TYPE_VIDEO:
> +        avcodec_align_dimensions2(avctx, &w, &h, linesize_align);
> +        new = ff_default_get_video_buffer(outlink, w, h);
> +        break;
> +    case AVMEDIA_TYPE_AUDIO:
> +        new = ff_default_get_audio_buffer(outlink, frame->nb_samples);

I wonder, are these two functions thread safe?
AVCodecContext.get_buffer2() no longer supports non-thread safe 
callbacks, and these seem to allocate and replace the pool inside 
outlink as required. If called from more than one thread with different 
frame parameters, wouldn't there be a race?

> +        break;
> +    default:
> +        return -1;
> +    }
> +
> +    av_frame_copy_props(new, frame);
> +    av_frame_unref(frame);
> +    av_frame_move_ref(frame, new);
> +    av_frame_free(&new);
> +
> +    frame->opaque = outlink;
> +    frame->width  = ow;
> +    frame->height = oh;
> +
> +    return 0;
> +}
> +
>  static int open_stream(AVFilterContext *ctx, MovieStream *st, int dec_threads)
>  {
>      const AVCodec *codec;
> @@ -171,6 +207,8 @@ static int open_stream(AVFilterContext *ctx, MovieStream *st, int dec_threads)
>      if (!st->codec_ctx)
>          return AVERROR(ENOMEM);
>  
> +    st->codec_ctx->flags |= AV_CODEC_FLAG_COPY_OPAQUE;
> +    st->codec_ctx->get_buffer2 = get_buffer;
>      ret = avcodec_parameters_to_context(st->codec_ctx, st->st->codecpar);
>      if (ret < 0)
>          return ret;
> @@ -479,8 +517,10 @@ static int movie_decode_packet(AVFilterContext *ctx)
>      /* send the packet to its decoder, if any */
>      pkt_out_id = pkt.stream_index > movie->max_stream_index ? -1 :
>                   movie->out_index[pkt.stream_index];
> -    if (pkt_out_id >= 0)
> +    if (pkt_out_id >= 0) {
> +        pkt.opaque = ctx->outputs[pkt_out_id];
>          ret = avcodec_send_packet(movie->st[pkt_out_id].codec_ctx, &pkt);
> +    }
>      av_packet_unref(&pkt);
>  
>      return ret;
> -- 
> 2.39.1
> 
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