Android implementation of WebAudio audio file decoder

webkit/media/android/audio_decoder_android.cc

 // Copyright (c) 2012 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.
 
 #include "webkit/media/audio_decoder.h"
 
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/file_descriptor_posix.h"
 #include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
+#include "base/shared_memory.h"
+#include "media/base/audio_bus.h"
+#include "media/base/limits.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebAudioBus.h"
 
 namespace webkit_media {
 
+class AudioDecoderIO {
+ public:
+  AudioDecoderIO(const char* data, size_t data_size);
+  ~AudioDecoderIO();
+  bool ShareEncodedToProcess(base::SharedMemoryHandle* handle);
+
+  // Returns true if AudioDecoderIO was successfully created.
+  bool IsValid() const;
+
+  int read_fd() const { return read_fd_; }
+  int write_fd() const { return write_fd_; }
+
+ private:
+  // Shared memory that will hold the encoded audio data.  This is
+  // used by MediaCodec for decoding.
+  base::SharedMemory encoded_shared_memory_;
+
+  // A pipe used to communicate with MediaCodec.  MediaCodec owns
+  // write_fd_ and writes to it.
+  int read_fd_;
+  int write_fd_;

[DaleCurtis, 2013/04/12 21:47:45]

Needs DISALLOW_COPY_ASSIGN, etc.

+};
+
+AudioDecoderIO::AudioDecoderIO(const char* data, size_t data_size)
+    : read_fd_(-1),
+      write_fd_(-1) {
+
+  if (!data || !data_size || data_size > 0x80000000)
+    return;
+
+  // Create the shared memory and copy our data to it so that
+  // MediaCodec can access it.
+  encoded_shared_memory_.CreateAndMapAnonymous(data_size);
+
+  if (!encoded_shared_memory_.memory())
+    return;
+
+  memcpy(encoded_shared_memory_.memory(), data, data_size);
+
+  // Create a pipe for reading/writing the decoded PCM data
+  int pipefd[2];
+
+  if (pipe(pipefd))
+    return;
+
+  read_fd_ = pipefd[0];
+  write_fd_ = pipefd[1];
+}
+
+AudioDecoderIO::~AudioDecoderIO() {
+  // Close the read end of the pipe.  The write end should have been
+  // closed by MediaCodec.
+  if (read_fd_ >= 0) {

[DaleCurtis, 2013/04/12 21:47:45]

&& close(read_fd_) ?

+    if (close(read_fd_)) {
+      DVLOG(0) << "Cannot close read fd " << read_fd_
+               << ": " << strerror(errno);
+    }
+  }
+}
+
+bool AudioDecoderIO::IsValid() const {
+  return read_fd_ >= 0 && write_fd_ >= 0 &&
+    encoded_shared_memory_.memory() ;

[DaleCurtis, 2013/04/12 21:47:45]

spaces at end?

+}
+
+bool AudioDecoderIO::ShareEncodedToProcess(base::SharedMemoryHandle* handle) {
+  return encoded_shared_memory_.ShareToProcess(
+      base::Process::Current().handle(),
+      handle);
+}
+
+// To decode audio data, we want to use the Android MediaCodec class.
+// But this can't run in a sandboxed process so we need initiate the
+// request to MediaCodec in the browser.  To do this, we create a
+// shared memory buffer that holds the audio data.  We send a message
+// to the browser to start the decoder using this buffer and one end
+// of a pipe.  The MediaCodec class will decode the data from the
+// shared memory and write the PCM samples back to us over a pipe.
 bool DecodeAudioFileData(WebKit::WebAudioBus* destination_bus, const char* data,
-                         size_t data_size, double sample_rate) {
-  NOTIMPLEMENTED();
-  return false;
+                         size_t data_size, double sample_rate,
+                         const WebAudioMediaCodecRunner& runner) {
+  AudioDecoderIO audio_decoder(data, data_size);
+
+  if (!audio_decoder.IsValid())
+    return false;
+
+  base::SharedMemoryHandle encoded_data_handle;
+  audio_decoder.ShareEncodedToProcess(&encoded_data_handle);
+  base::FileDescriptor fd(audio_decoder.write_fd(), true);
+
+  DVLOG(0) << "DecodeAudioFileData: Starting MediaCodec";
+
+  // Start MediaCodec processing in the browser which will read from
+  // encoded_data_handle for our shared memory and write the decoded
+  // PCM samples (16-bit integer) to our pipe.
+
+  runner.Run(encoded_data_handle, fd);
+
+  // First, read the number of channels, the sample rate, and the
+  // number of frames and a flag indicating if the file is an
+  // ogg/vorbis file.  This must be coordinated with
+  // WebAudioMediaCodecBridge!
+  //
+  // TODO(rtoy): If we know the number of samples, we can create the
+  // destination bus directly and do the conversion directly to the
+  // bus instead of buffering up everything before saving the data to
+  // the bus.
+
+  int input_fd = audio_decoder.read_fd();
+  unsigned long info[4];
+
+  DVLOG(0) << "Reading audio file info from fd " << input_fd;
+  ssize_t nread = HANDLE_EINTR(read(input_fd, info, sizeof(info)));
+  DVLOG(0) << "read:  " << nread << " bytes:\n"
+           << " 0: number of channels = " << info[0] << "\n"
+           << " 1: sample rate        = " << info[1] << "\n"
+           << " 2: number of frames   = " << info[2] << "\n"
+           << " 3: is vorbis          = " << info[3];
+
+  if (nread != sizeof(info))
+    return false;
+
+  unsigned number_of_channels = info[0];
+  double file_sample_rate = static_cast<double>(info[1]);
+
+  // Sanity checks
+  if (!number_of_channels ||
+      number_of_channels > media::limits::kMaxChannels ||
+      file_sample_rate < media::limits::kMinSampleRate ||
+      file_sample_rate > media::limits::kMaxSampleRate) {
+    return false;
+  }
+
+  int16_t pipe_data[PIPE_BUF / sizeof(int16_t)];
+  std::vector<int16_t> decoded_samples;

[DaleCurtis, 2013/04/12 21:47:45]

should probably pre allocate this to the expected size at least?

[Raymond Toy (Google), 2013/04/12 22:12:47]

Can't do this right now because some audio files return a duration of 0 even
though the file is not empty.  MediaCodec will still continue to decode the
entire file.  High on my TODO list is to do the preallocation when the duration
(number of samples) is not 0.

+
+  // Keep reading from the pipe until it's closed.
+  while ((nread =
+          HANDLE_EINTR(read(input_fd, pipe_data, sizeof(pipe_data)))) > 0) {
+    size_t nsamples = nread / sizeof(int16_t);
+    decoded_samples.reserve(decoded_samples.size() + nsamples);
+    for (size_t k = 0; k < nsamples; ++k) {
+      decoded_samples.push_back(pipe_data[k]);
+    }
+  }
+
+  DVLOG(0) << "Total samples read = " << decoded_samples.size();
+
+  // Convert the samples and save them in the audio bus.
+  size_t number_of_samples = decoded_samples.size();
+  size_t number_of_frames = number_of_samples / number_of_channels;
+
+  destination_bus->initialize(number_of_channels,
+                              number_of_frames,
+                              file_sample_rate);
+
+  size_t decoded_frames = 0;
+  for (size_t m = 0; m < number_of_samples; m += number_of_channels) {
+    for (size_t k = 0; k < number_of_channels; ++k) {
+      destination_bus->channelData(k)[decoded_frames] =
+          decoded_samples[m + k] / 32768.0;
+    }
+    ++decoded_frames;
+  }
+
+  return true;
 }
 
 }  // namespace webkit_media