Decode entire in-memory file for WebAudio

media/filters/audio_file_reader.h

 // Copyright (c) 2011 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_AUDIO_FILE_READER_H_
 #define MEDIA_FILTERS_AUDIO_FILE_READER_H_
 
 #include <memory>
+#include <vector>
 
 #include "base/macros.h"
 #include "media/base/audio_codecs.h"
 #include "media/base/media_export.h"
 #include "media/ffmpeg/ffmpeg_deleters.h"
 #include "media/filters/ffmpeg_glue.h"
 
 struct AVCodecContext;
 struct AVPacket;
 struct AVStream;
@@ skipping 12 matching lines @@
   // simply maintains a weak reference to it.
   explicit AudioFileReader(FFmpegURLProtocol* protocol);
   virtual ~AudioFileReader();
 
   // Open() reads the audio data format so that the sample_rate(),
   // channels(), GetDuration(), and GetNumberOfFrames() methods can be called.
   // It returns |true| on success.
   bool Open();
   void Close();
 
-  // After a call to Open(), attempts to fully fill |audio_bus| with decoded
-  // audio data.  Any unfilled frames will be zeroed out.
-  // |audio_data| must be of the same size as channels().
-  // The audio data will be decoded as floating-point linear PCM with
-  // a nominal range of -1.0 -> +1.0.
-  // Returns the number of sample-frames actually read which will always be
-  // <= audio_bus->frames()
-  int Read(AudioBus* audio_bus);
+  // Returns true if (an estimated) duration of the audio data is
+  // known.  Must be called after Open();
+  bool HasKnownDuration() const;
+
+  // After a call to Open(), attempts to decode the entire data,
+  // updating |decodedAudioPackets| with each decoded packet in order.
+  // The caller must convert these packets into one complete set of
+  // decoded audio data.  The audio data will be decoded as
+  // floating-point linear PCM with a nominal range of -1.0 -> +1.0.
+  // Returns the number of sample-frames actually read which will
+  // always be the total size of all the frames in
+  // |decodedAudioPackets|.
+  int Read(std::vector<std::unique_ptr<AudioBus>>& decodedAudioPackets);

[DaleCurtis, 2017/02/09 18:47:36]

Pass by pointer instead of ref. decoded_audio_packets. I think using a list here
might be better to avoid doubling behavior that comes with the vector. I don't
think there's any benefit for the colocation of elements that the vector
provides in this case.

Don't have any data to back that last statement up though, so up to you.

[Raymond Toy, 2017/02/09 18:56:12]

Good point. I expect the size of this vector to be quite small compared to the
actual decoded audio data.

[Raymond Toy, 2017/02/09 21:45:06]

Passing by pointer.

Decided to keep a vector because it's pretty simple.  I think a vector of 1000
elements would hold about a million audio frames, so it's pretty small in
comparison.

 
   // These methods can be called once Open() has been called.
   int channels() const { return channels_; }
   int sample_rate() const { return sample_rate_; }
 
   // Please note that GetDuration() and GetNumberOfFrames() attempt to be
   // accurate, but are only estimates.  For some encoded formats, the actual
   // duration of the file can only be determined once all the file data has been
   // read. The Read() method returns the actual number of sample-frames it has
   // read.
@@ skipping 37 matching lines @@
 
   // AVSampleFormat initially requested; not Chrome's SampleFormat.
   int av_sample_format_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioFileReader);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_AUDIO_FILE_READER_H_