avcodec/videotoolbox: use decode_params to propagate H264 PPS changes and restart on SPS changes

This fixes decoding of H264 video samples with SPS and PPS changes.

See for example https://s3.amazonaws.com/tmm1/videotoolbox/spschange.ts,
which previously stalled the decoder and failed to produce any new frames
after the SPS change.

Also see https://s3.amazonaws.com/tmm1/videotoolbox/ppschange.ts, which
uses multiple PPS and would previously cause VT decode failures.

If the VideoToolbox session needs to be restarted, and
videotoolbox_start() fails for some reason (for instance, if the video
is interlaced and the decoder is running on iOS), avcodec will return
AVERROR_EXTERNAL. This can be used by the API user to switch to another
decoder.

Signed-off-by: Aman Gupta <aman@tmm1.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/libavcodec/vt_internal.h b/libavcodec/vt_internal.h
index 607dd7a6d0..fc27dad9f9 100644
--- a/libavcodec/vt_internal.h
+++ b/libavcodec/vt_internal.h
@@ -38,6 +38,12 @@ typedef struct VTContext {
     // Non-NULL if the new hwaccel API is used. This is only a separate struct
     // to ease compatibility with the old API.
     struct AVVideotoolboxContext *vt_ctx;
+
+    // Current H264 parameters (used to trigger decoder restart on SPS changes).
+    uint8_t                     *sps;
+    uint32_t                    sps_len;
+    unsigned int                sps_capa;
+    bool                        reconfig_needed;
 } VTContext;
 
 int ff_videotoolbox_alloc_frame(AVCodecContext *avctx, AVFrame *frame);