commit 62274859104bd828373ae406aa9309e610449ac5
Author: Ted Meyer <tmathmeyer@chromium.org>
Date:   Fri Mar 22 19:56:55 2024 +0000

    Replace deprecated use of AVCodecContext::reordered_opaque
    
    We can use the AV_CODEC_FLAG_COPY_OPAQUE flag on the codec context
    now to trigger timestamp propagation.
    
    Bug: 330573128
    Change-Id: I6bc57241a35ab5283742aad8d42acb4dc5e85858
    Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5384308
    Commit-Queue: Ted (Chromium) Meyer <tmathmeyer@chromium.org>
    Reviewed-by: Dan Sanders <sandersd@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#1277051}

diff --git a/media/filters/ffmpeg_video_decoder.cc b/media/filters/ffmpeg_video_decoder.cc
index bd75477feeabb..8a658a58caac5 100644
--- a/media/filters/ffmpeg_video_decoder.cc
+++ b/media/filters/ffmpeg_video_decoder.cc
@@ -134,7 +134,7 @@ bool FFmpegVideoDecoder::IsCodecSupported(VideoCodec codec) {
 }
 
 FFmpegVideoDecoder::FFmpegVideoDecoder(MediaLog* media_log)
-    : media_log_(media_log) {
+    : media_log_(media_log), timestamp_map_(128) {
   DVLOG(1) << __func__;
   DETACH_FROM_SEQUENCE(sequence_checker_);
 }
@@ -363,8 +363,10 @@ bool FFmpegVideoDecoder::FFmpegDecode(const DecoderBuffer& buffer) {
     DCHECK(packet->data);
     DCHECK_GT(packet->size, 0);
 
-    // Let FFmpeg handle presentation timestamp reordering.
-    codec_context_->reordered_opaque = buffer.timestamp().InMicroseconds();
+    const int64_t timestamp = buffer.timestamp().InMicroseconds();
+    const TimestampId timestamp_id = timestamp_id_generator_.GenerateNextId();
+    timestamp_map_.Put(std::make_pair(timestamp_id, timestamp));
+    packet->opaque = reinterpret_cast<void*>(timestamp_id.GetUnsafeValue());
   }
   FFmpegDecodingLoop::DecodeStatus decode_status = decoding_loop_->DecodePacket(
       packet, base::BindRepeating(&FFmpegVideoDecoder::OnNewFrame,
@@ -423,7 +425,12 @@ bool FFmpegVideoDecoder::OnNewFrame(AVFrame* frame) {
   }
   gfx::Size natural_size = aspect_ratio.GetNaturalSize(visible_rect);
 
-  const auto pts = base::Microseconds(frame->reordered_opaque);
+  const auto ts_id = TimestampId(reinterpret_cast<size_t>(frame->opaque));
+  const auto ts_lookup = timestamp_map_.Get(ts_id);
+  if (ts_lookup == timestamp_map_.end()) {
+    return false;
+  }
+  const auto pts = base::Microseconds(std::get<1>(*ts_lookup));
   auto video_frame = VideoFrame::WrapExternalDataWithLayout(
       opaque->layout, visible_rect, natural_size, opaque->data, opaque->size,
       pts);
@@ -498,8 +505,10 @@ bool FFmpegVideoDecoder::ConfigureDecoder(const VideoDecoderConfig& config,
   codec_context_->thread_count = GetFFmpegVideoDecoderThreadCount(config);
   codec_context_->thread_type =
       FF_THREAD_SLICE | (low_delay ? 0 : FF_THREAD_FRAME);
+
   codec_context_->opaque = this;
   codec_context_->get_buffer2 = GetVideoBufferImpl;
+  codec_context_->flags |= AV_CODEC_FLAG_COPY_OPAQUE;
 
   if (base::FeatureList::IsEnabled(kFFmpegAllowLists)) {
     // Note: FFmpeg will try to free this string, so we must duplicate it.
diff --git a/media/filters/ffmpeg_video_decoder.h b/media/filters/ffmpeg_video_decoder.h
index d02cb89c3ddf7..0a2de1c623fff 100644
--- a/media/filters/ffmpeg_video_decoder.h
+++ b/media/filters/ffmpeg_video_decoder.h
@@ -7,10 +7,12 @@
 
 #include <memory>
 
+#include "base/containers/lru_cache.h"
 #include "base/functional/callback.h"
 #include "base/memory/raw_ptr.h"
 #include "base/memory/scoped_refptr.h"
 #include "base/sequence_checker.h"
+#include "base/types/id_type.h"
 #include "media/base/frame_buffer_pool.h"
 #include "media/base/supported_video_decoder_config.h"
 #include "media/base/video_decoder.h"
@@ -87,6 +89,20 @@ class MEDIA_EXPORT FFmpegVideoDecoder : public VideoDecoder {
   // FFmpeg structures owned by this object.
   std::unique_ptr<AVCodecContext, ScopedPtrAVFreeContext> codec_context_;
 
+  // The gist here is that timestamps need to be 64 bits to store microsecond
+  // precision. A 32 bit integer would overflow at ~35 minutes at this level of
+  // precision. We can't cast the timestamp to the void ptr object used by the
+  // opaque field in ffmpeg then, because it would lose data on a 32 bit build.
+  // However, we don't actually have 2^31 timestamped frames in a single
+  // playback, so it's fine to use the 32 bit value as a key in a map which
+  // contains the actual timestamps. Additionally, we've in the past set 128
+  // outstanding frames for re-ordering as a limit for cross-thread decoding
+  // tasks, so we'll do that here too with the LRU cache.
+  using TimestampId = base::IdType<int64_t, size_t, 0>;
+
+  TimestampId::Generator timestamp_id_generator_;
+  base::LRUCache<TimestampId, int64_t> timestamp_map_;
+
   VideoDecoderConfig config_;
 
   scoped_refptr<FrameBufferPool> frame_pool_;