FIXUP: Fix building with system ffmpeg 4.4 or 5.1

Revert the change made in ffmpeg_demuxer.cc as it messing up
timestamp calculations that makes some mp4s unplayable.
This fix breaks the compatibility with system ffmpeg 5.0 and above
as chromium tries to use the 'first_dts' value, that has been moved
out from public api and it is only available from bundled ffmpeg.
See: https://github.com/FFmpeg/FFmpeg/commit/591b88e6787c

Fixes: QTBUG-110749
Change-Id: I5786b1a40939d7c9e490ad51ae2e910b8498c71c
Reviewed-on: https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/457644
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
(cherry picked from commit 0efb774616745b2e103efbca814b45fa1da0626c)
Reviewed-on: https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/460039
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 7 insertions, 16 deletions

diff --git a/chromium/media/filters/ffmpeg_demuxer.cc b/chromium/media/filters/ffmpeg_demuxer.cc
index 1a478f713fe..7b709d70d78 100644
--- a/chromium/media/filters/ffmpeg_demuxer.cc
+++ b/chromium/media/filters/ffmpeg_demuxer.cc
@@ -58,7 +58,7 @@ namespace media {
 
 namespace {
 
-constexpr int64_t kRelativeTsBase = static_cast<int64_t>(0x7ffeffffffffffff);
+constexpr int64_t kInvalidPTSMarker = static_cast<int64_t>(0x8000000000000000);
 
 void SetAVStreamDiscard(AVStream* stream, AVDiscard discard) {
   DCHECK(stream);
@@ -101,7 +101,7 @@ static base::TimeDelta FramesToTimeDelta(int frames, double sample_rate) {
                             sample_rate);
 }
 
-static base::TimeDelta ExtractStartTime(AVStream* stream, int64_t first_dts) {
+static base::TimeDelta ExtractStartTime(AVStream* stream) {
   // The default start time is zero.
   base::TimeDelta start_time;
 
@@ -111,12 +111,12 @@ static base::TimeDelta ExtractStartTime(AVStream* stream, int64_t first_dts) {
 
   // Next try to use the first DTS value, for codecs where we know PTS == DTS
   // (excludes all H26x codecs). The start time must be returned in PTS.
-  if (first_dts != AV_NOPTS_VALUE &&
+  if (av_stream_get_first_dts(stream) != kInvalidPTSMarker &&
       stream->codecpar->codec_id != AV_CODEC_ID_HEVC &&
       stream->codecpar->codec_id != AV_CODEC_ID_H264 &&
       stream->codecpar->codec_id != AV_CODEC_ID_MPEG4) {
     const base::TimeDelta first_pts =
-        ConvertFromTimeBase(stream->time_base, first_dts);
+        ConvertFromTimeBase(stream->time_base, av_stream_get_first_dts(stream));
     if (first_pts < start_time)
       start_time = first_pts;
   }
@@ -285,7 +285,6 @@ FFmpegDemuxerStream::FFmpegDemuxerStream(
       fixup_negative_timestamps_(false),
       fixup_chained_ogg_(false),
       num_discarded_packet_warnings_(0),
-      first_dts_(AV_NOPTS_VALUE),
       last_packet_pos_(AV_NOPTS_VALUE),
       last_packet_dts_(AV_NOPTS_VALUE) {
   DCHECK(demuxer_);
@@ -352,11 +351,6 @@ void FFmpegDemuxerStream::EnqueuePacket(ScopedAVPacket packet) {
   int64_t packet_dts =
       packet->dts == AV_NOPTS_VALUE ? packet->pts : packet->dts;
 
-  if (first_dts_ == AV_NOPTS_VALUE && packet->dts != AV_NOPTS_VALUE &&
-      last_packet_dts_ != AV_NOPTS_VALUE) {
-    first_dts_ = packet->dts - (last_packet_dts_ + kRelativeTsBase);
-  }
-
   // Chained ogg files have non-monotonically increasing position and time stamp
   // values, which prevents us from using them to determine if a packet should
   // be dropped. Since chained ogg is only allowed on single track audio only
@@ -1455,7 +1449,7 @@ void FFmpegDemuxer::OnFindStreamInfoDone(int result) {
 
     max_duration = std::max(max_duration, streams_[i]->duration());
 
-    base::TimeDelta start_time = ExtractStartTime(stream, streams_[i]->first_dts());
+    base::TimeDelta start_time = ExtractStartTime(stream);
 
     // Note: This value is used for seeking, so we must take the true value and
     // not the one possibly clamped to zero below.
@@ -1612,7 +1606,7 @@ FFmpegDemuxerStream* FFmpegDemuxer::FindStreamWithLowestStartTimestamp(
   for (const auto& stream : streams_) {
     if (!stream || stream->IsEnabled() != enabled)
       continue;
-    if (stream->first_dts() == AV_NOPTS_VALUE)
+    if (av_stream_get_first_dts(stream->av_stream()) == kInvalidPTSMarker)
       continue;
     if (!lowest_start_time_stream ||
         stream->start_time() < lowest_start_time_stream->start_time()) {
@@ -1633,7 +1627,7 @@ FFmpegDemuxerStream* FFmpegDemuxer::FindPreferredStreamForSeeking(
     if (stream->type() != DemuxerStream::VIDEO)
       continue;
 
-    if (stream->first_dts() == AV_NOPTS_VALUE)
+    if (av_stream_get_first_dts(stream->av_stream()) == kInvalidPTSMarker)
       continue;
 
     if (!stream->IsEnabled())
diff --git a/chromium/media/filters/ffmpeg_demuxer.h b/chromium/media/filters/ffmpeg_demuxer.h
index 6b093318f36..45ab0f348ad 100644
--- a/chromium/media/filters/ffmpeg_demuxer.h
+++ b/chromium/media/filters/ffmpeg_demuxer.h
@@ -152,8 +152,6 @@ class MEDIA_EXPORT FFmpegDemuxerStream : public DemuxerStream {
   base::TimeDelta start_time() const { return start_time_; }
   void set_start_time(base::TimeDelta time) { start_time_ = time; }
 
-  int64_t first_dts() const { return first_dts_; }
-
  private:
   friend class FFmpegDemuxerTest;
 
@@ -211,7 +209,6 @@ class MEDIA_EXPORT FFmpegDemuxerStream : public DemuxerStream {
   bool fixup_chained_ogg_;
 
   int num_discarded_packet_warnings_;
-  int64_t first_dts_;
   int64_t last_packet_pos_;
   int64_t last_packet_dts_;
 };