[FFmpeg-devel] [PATCH 1/3] avcodec/h264, videotoolbox: pass SPS changes into the VT decoder

[wm4]

On Thu, 16 Feb 2017 10:29:36 -0800
Aman Gupta <ffmpeg at tmm1.net> wrote:

> From: Aman Gupta <aman at tmm1.net>
> 
> This fixes playback of h264 streams with SPS changes. One such sample
> is available at http://tmm1.s3.amazonaws.com/videotoolbox/spschange.ts.
> It switches mid-stream from level 4.0 to level 3.2.
> 
> Previously, playing this sample with the VT hwaccel on iOS would crash.
> After this patch, it plays back as expected.
> 
> On macOS however, feeding in new SPS into an existing decompression
> session does not always work, so this patch is only a partial fix.
> ---
>  libavcodec/h264dec.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/libavcodec/h264dec.c b/libavcodec/h264dec.c
> index 41c0964..e521c52 100644
> --- a/libavcodec/h264dec.c
> +++ b/libavcodec/h264dec.c
> @@ -740,6 +740,13 @@ FF_ENABLE_DEPRECATION_WARNINGS
>              break;
>          case H264_NAL_SPS: {
>              GetBitContext tmp_gb = nal->gb;
> +            if (avctx->hwaccel && avctx->hwaccel->pix_fmt == AV_PIX_FMT_VIDEOTOOLBOX) {
> +                ret = avctx->hwaccel->decode_slice(avctx,
> +                                                   nal->data,
> +                                                   nal->size);
> +                if (ret < 0)
> +                    goto end;
> +            }
>              if (ff_h264_decode_seq_parameter_set(&tmp_gb, avctx, &h->ps, 0) >= 0)
>                  break;
>              av_log(h->avctx, AV_LOG_DEBUG,

A bit ugly but ok IMHO. Maybe it would be better to add a new hwaccel
callback here, even if it's used by VT only.

You should probably wait for approval by michaelni.