media: Support better decoder switching

media/filters/decoder_selector.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_SELECTOR_H_
 #define MEDIA_FILTERS_DECODER_SELECTOR_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 21 matching lines @@
 // encrypted, a DecryptingDemuxerStream may also be created.
 // The template parameter |StreamType| is the type of stream we will be
 // selecting a decoder for.
 template<DemuxerStream::Type StreamType>
 class MEDIA_EXPORT DecoderSelector {
  public:
   typedef DecoderStreamTraits<StreamType> StreamTraits;
   typedef typename StreamTraits::DecoderType Decoder;
   typedef typename StreamTraits::DecoderConfigType DecoderConfig;
 
+  // Callback to create a list of decoders to select from.
+  // TODO(xhwang): Use a DecoderFactory to create decoders one by one as needed,
+  // instead of creating a list of decoders all at once.
+  using CreateDecodersCB = base::RepeatingCallback<ScopedVector<Decoder>()>;
+
   // Indicates completion of Decoder selection.
   // - First parameter: The initialized Decoder. If it's set to NULL, then
   // Decoder initialization failed.
   // - Second parameter: The initialized DecryptingDemuxerStream. If it's not
   // NULL, then a DecryptingDemuxerStream is created and initialized to do
   // decryption for the initialized Decoder.
   // Note: The caller owns selected Decoder and DecryptingDemuxerStream.
   // The caller should call DecryptingDemuxerStream::Reset() before
   // calling Decoder::Reset() to release any pending decryption or read.
-  typedef base::Callback<void(std::unique_ptr<Decoder>,
-                              std::unique_ptr<DecryptingDemuxerStream>)>
-      SelectDecoderCB;
+  using SelectDecoderCB =
+      base::Callback<void(std::unique_ptr<Decoder>,
+                          std::unique_ptr<DecryptingDemuxerStream>)>;
 
-  // |decoders| contains the Decoders to use when initializing.
   DecoderSelector(
-      const scoped_refptr<base::SingleThreadTaskRunner>& message_loop,
-      ScopedVector<Decoder> decoders,
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+      CreateDecodersCB create_decoders_cb,
       MediaLog* media_log);
 
   // Aborts pending Decoder selection and fires |select_decoder_cb| with
-  // NULL and NULL immediately if it's pending.
+  // null and null immediately if it's pending.
   ~DecoderSelector();
 
   // Initializes and selects the first Decoder that can decode the |stream|.
   // The selected Decoder (and DecryptingDemuxerStream) is returned via
   // the |select_decoder_cb|.
   // Notes:
   // 1. This must not be called again before |select_decoder_cb| is run.
-  // 2. Decoders that fail to initialize will be deleted. Future calls will
-  //    select from the decoders following the decoder that was last returned.
-  // 3. |cdm_context| is optional. If |cdm_context| is
-  //    null, no CDM will be available to perform decryption.
+  // 2. |create_decoders_cb| will be called to create a list of candidate
+  //    decoders to select from.
+  // 3. The |blacklisted_decoder| will be skipped in the decoder selection
+  //    process, unless DecryptingDemuxerStream is chosen. This is because
+  //    DecryptingDemuxerStream updates the |config_|, and the blacklist should
+  //    only be applied to the original |stream| config.
+  // 4. All decoders that are not selected will be deleted upon returning
+  //    |select_decoder_cb|.
+  // 5. |cdm_context| is optional. If |cdm_context| is null, no CDM will be
+  //    available to perform decryption.
   void SelectDecoder(StreamTraits* traits,
                      DemuxerStream* stream,
                      CdmContext* cdm_context,
+                     const std::string& blacklisted_decoder,
                      const SelectDecoderCB& select_decoder_cb,
                      const typename Decoder::OutputCB& output_cb,
                      const base::Closure& waiting_for_decryption_key_cb);
 
  private:
 #if !defined(OS_ANDROID)
   void InitializeDecryptingDecoder();
   void DecryptingDecoderInitDone(bool success);
 #endif
   void InitializeDecryptingDemuxerStream();
   void DecryptingDemuxerStreamInitDone(PipelineStatus status);
   void InitializeDecoder();
   void DecoderInitDone(bool success);
   void ReturnNullDecoder();
 
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-  ScopedVector<Decoder> decoders_;
+  CreateDecodersCB create_decoders_cb_;
   MediaLog* media_log_;
 
   StreamTraits* traits_;
 
   // Could be the |stream| passed in SelectDecoder, or |decrypted_stream_| when
   // a DecryptingDemuxerStream is selected.
   DemuxerStream* input_stream_;
 
   CdmContext* cdm_context_;
+  std::string blacklisted_decoder_;
   SelectDecoderCB select_decoder_cb_;
   typename Decoder::OutputCB output_cb_;
   base::Closure waiting_for_decryption_key_cb_;
 
+  ScopedVector<Decoder> decoders_;
+
   std::unique_ptr<Decoder> decoder_;
   std::unique_ptr<DecryptingDemuxerStream> decrypted_stream_;
 
   // Config of the |input_stream| used to initialize decoders.
   DecoderConfig config_;
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<DecoderSelector> weak_ptr_factory_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(DecoderSelector);
 };
 
 typedef DecoderSelector<DemuxerStream::VIDEO> VideoDecoderSelector;
 typedef DecoderSelector<DemuxerStream::AUDIO> AudioDecoderSelector;
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_DECODER_SELECTOR_H_