Attempt decoder fallback if first decode fails

media/filters/decoder_stream.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_FILTERS_DECODER_STREAM_H_
 #define MEDIA_FILTERS_DECODER_STREAM_H_
 
 #include <list>
 
 #include "base/callback.h"
@@ skipping 104 matching lines @@
   typedef base::Closure ConfigChangeObserverCB;
   void set_config_change_observer(
       const ConfigChangeObserverCB& config_change_observer) {
     config_change_observer_cb_ = config_change_observer;
   }
 
   const Decoder* get_previous_decoder_for_testing() const {
     return previous_decoder_.get();
   }
 
+  int get_pending_buffers_size_for_testing() const {
+    return pending_buffers_.size();
+  }
+
+  int get_fallback_buffers_size_for_testing() const {
+    return fallback_buffers_.size();
+  }
+
  private:
   enum State {
     STATE_UNINITIALIZED,
     STATE_INITIALIZING,
     STATE_NORMAL,  // Includes idle, pending decoder decode/reset.
     STATE_FLUSHING_DECODER,
     STATE_PENDING_DEMUXER_READ,
     STATE_REINITIALIZING_DECODER,
     STATE_END_OF_STREAM,  // End of stream reached; returns EOS on all reads.
-    STATE_ERROR
+    STATE_ERROR,
+    // TODO(tguilbert): support config changes during decoder fallback, see
+    // crbug.com/603713
+    STATE_CONFIG_CHANGE_RECEIVED_WHILE_REINITIALIZING_DECODER
   };
 
   void SelectDecoder(CdmContext* cdm_context);
 
   // Called when |decoder_selector| selected the |selected_decoder|.
   // |decrypting_demuxer_stream| was also populated if a DecryptingDemuxerStream
   // is created to help decrypt the encrypted stream.
   void OnDecoderSelected(
       scoped_ptr<Decoder> selected_decoder,
       scoped_ptr<DecryptingDemuxerStream> decrypting_demuxer_stream);
@@ skipping 73 matching lines @@
   // Decoded buffers that haven't been read yet. Used when the decoder supports
   // parallel decoding.
   std::list<scoped_refptr<Output> > ready_outputs_;
 
   // Number of outstanding decode requests sent to the |decoder_|.
   int pending_decode_requests_;
 
   // Tracks the duration of incoming packets over time.
   MovingAverage duration_tracker_;
 
+  // Stores buffers that might be reused if the decoder fails right after
+  // Initialize().
+  std::deque<scoped_refptr<DecoderBuffer>> pending_buffers_;
+
+  // Stores buffers that are garanteed to be fed to the decoder before fetching
+  // more from the demuxer stream. Populated by |pending_buffers_| on decoder
+  // fallback.
+  std::deque<scoped_refptr<DecoderBuffer>> fallback_buffers_;
+
   // NOTE: Weak pointers must be invalidated before all other member variables.
-  base::WeakPtrFactory<DecoderStream<StreamType> > weak_factory_;
+  base::WeakPtrFactory<DecoderStream<StreamType>> weak_factory_;
+  base::WeakPtrFactory<DecoderStream<StreamType>> decode_weak_factory_;

[sandersd (OOO until July 31), 2016/04/14 23:10:30]

This should have a comment, since the usage pattern isn't common in media yet.
Just explain that it will be invalidated each time we fall back to a new
decoder, so that outstanding callbacks will be dropped.

 };
 
 template <>
 bool DecoderStream<DemuxerStream::AUDIO>::CanReadWithoutStalling() const;
 
 template <>
 int DecoderStream<DemuxerStream::AUDIO>::GetMaxDecodeRequests() const;
 
 typedef DecoderStream<DemuxerStream::VIDEO> VideoFrameStream;
 typedef DecoderStream<DemuxerStream::AUDIO> AudioBufferStream;
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_DECODER_STREAM_H_