media: Support better decoder switching

media/filters/decoder_stream.cc

Index: media/filters/decoder_stream.cc
diff --git a/media/filters/decoder_stream.cc b/media/filters/decoder_stream.cc
index 53cf47c18a725f3eb11ef310c195cf50dbc016aa..6722a2326dba469ae0fe9694d6b3a55b44f5a0a4 100644
--- a/media/filters/decoder_stream.cc
+++ b/media/filters/decoder_stream.cc
@@ -45,7 +45,7 @@ const char* GetTraceString<DemuxerStream::AUDIO>() {
 template <DemuxerStream::Type StreamType>
 DecoderStream<StreamType>::DecoderStream(
     const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
-    ScopedVector<Decoder> decoders,
+    CreateDecodersCB create_decoders_cb,
     MediaLog* media_log)
     : traits_(media_log),
       task_runner_(task_runner),
@@ -53,10 +53,12 @@ DecoderStream<StreamType>::DecoderStream(
       state_(STATE_UNINITIALIZED),
       stream_(NULL),
       cdm_context_(nullptr),
-      decoder_selector_(new DecoderSelector<StreamType>(task_runner,
-                                                        std::move(decoders),
-                                                        media_log)),
+      decoder_selector_(
+          new DecoderSelector<StreamType>(task_runner,
+                                          std::move(create_decoders_cb),
+                                          media_log)),
       decoder_produced_a_frame_(false),
+      is_on_fallback_decoder_(false),
       decoding_eos_(false),
       pending_decode_requests_(0),
       duration_tracker_(8),
@@ -256,9 +258,10 @@ void DecoderStream<StreamType>::SelectDecoder() {
   // the |cdm_context_|. This will also help prevent creating a new DDS on top
   // of the current DDS.
   CdmContext* cdm_context = decrypting_demuxer_stream_ ? nullptr : cdm_context_;
+  std::string blacklisted_decoder = decoder_ ? decoder_->GetDisplayName() : "";
 
   decoder_selector_->SelectDecoder(
-      &traits_, stream_, cdm_context,
+      &traits_, stream_, cdm_context, blacklisted_decoder,
       base::Bind(&DecoderStream<StreamType>::OnDecoderSelected,
                  weak_factory_.GetWeakPtr()),
       base::Bind(&DecoderStream<StreamType>::OnDecodeOutputReady,
@@ -431,7 +434,10 @@ void DecoderStream<StreamType>::OnDecodeDone(int buffer_size,
 
   switch (status) {
     case DecodeStatus::DECODE_ERROR:
-      if (!decoder_produced_a_frame_) {
+      // Only fall back to a new decoder after failing to decode the first
+      // buffer, and we have not falled back before.

[watk, 2017/05/04 21:35:33]

s/and we have not falled/and if we have not fallen/

[xhwang, 2017/05/04 23:53:14]

Done.

+      if (!decoder_produced_a_frame_ && !is_on_fallback_decoder_) {

[watk, 2017/05/04 21:35:33]

I'm not sure why we can't fall back again? Maybe a comment would help. I
expected it to work like this:

The blacklist is a list (more than one) and its lifetime is the same as the
config: config changes imply the blacklist should be reset.

[xhwang, 2017/05/04 23:53:13]

Added comment in the .h file.

+        is_on_fallback_decoder_ = true;
         pending_decode_requests_ = 0;
 
         // Prevent all pending decode requests and outputs from those requests
@@ -501,6 +507,7 @@ void DecoderStream<StreamType>::OnDecodeOutputReady(
     return;
 
   decoder_produced_a_frame_ = true;
+  is_on_fallback_decoder_ = false;
   traits_.OnDecodeDone(output);
 
   // |decoder_| sucessfully decoded a frame. No need to keep buffers for a