Implement WebKitClientImpl::loadAudioResource() to decode in-memory audio fil...

media/filters/audio_file_reader.cc

+// Copyright (c) 2010 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 "media/filters/audio_file_reader.h"
+
+#include <string>
+#include "base/basictypes.h"
+#include "base/string_util.h"
+#include "media/base/filters.h"
+#include "media/ffmpeg/ffmpeg_common.h"
+#include "media/ffmpeg/ffmpeg_util.h"
+#include "media/filters/ffmpeg_glue.h"
+
+namespace media {
+
+AudioFileReader::AudioFileReader(FFmpegURLProtocol* protocol)
+  : protocol_(protocol),
+    format_context_(NULL),
+    codec_context_(NULL),
+    codec_(NULL) {
+}
+
+AudioFileReader::~AudioFileReader() {
+  Close();
+}
+
+size_t AudioFileReader::NumberOfChannels() const {

[scherkus (not reviewing), 2010/12/09 17:35:40]

I think it'd be best to not do type conversion here but rather in the glue layer

this means more or less copying FFmpeg's types for these accessors:
channels -> int
sample_rate -> int
duration -> int64
length -> int64

[Chris Rogers, 2010/12/10 23:34:00]

Done.

+  return codec_context_->channels;
+}
+
+double AudioFileReader::GetSampleRate() const {
+  return codec_context_->sample_rate;
+}
+
+double AudioFileReader::GetDuration() const {
+  return 1e-6 * format_context_->duration;

[scherkus (not reviewing), 2010/12/09 17:35:40]

what are we converting here to/from?  what are the units of time duration is
specified in?

in general when working with FFmpeg durations and time units you should use
av_rescale_q

const AVRational av_time_base = {1, AV_TIME_BASE};

take a look at ConvertTimestamp() in src/media/ffmpeg/ffmpeg_util.cc

general best practice is to use TimeDelta which is a self-documenting unit of
time, then in the glue layer simply call InSecondsF()

[fbarchard, 2010/12/09 21:11:02]

1e-6 is obscure.

[Chris Rogers, 2010/12/10 23:34:00]

Thanks for the tip - I've switched the code over to use ConvertTimestamp()

On 2010/12/09 17:35:40, scherkus wrote:

[Chris Rogers, 2010/12/10 23:34:00]

This is addressed by switching the code over to use CovertTimestamp()
On 2010/12/09 21:11:02, fbarchard wrote:

+}
+
+size_t AudioFileReader::Length() const {
+  return GetDuration() * GetSampleRate();
+}
+
+int AudioFileReader::Open() {
+  // Add our data reader to the protocol list and get our unique key.
+  std::string key = FFmpegGlue::get()->AddProtocol(protocol_);
+
+  // Open FFmpeg AVFormatContext.
+  DCHECK(!format_context_);
+  AVFormatContext* context = NULL;
+
+  int result = av_open_input_file(&context, key.c_str(), NULL, 0, NULL);
+
+  // Remove our data reader from protocol list since av_open_input_file() setup
+  // the AVFormatContext with the data reader.
+  FFmpegGlue::get()->RemoveProtocol(protocol_);
+
+  if (result) {
+      DLOG(WARNING)
+          << "AudioFileReader::Open() : error in av_open_input_file() -"
+          << " result: " << result;
+      return result;
+  }
+
+  DCHECK(context);
+  format_context_ = context;
+
+  // Get the codec context.
+  codec_context_ = NULL;
+  for (unsigned i = 0; i < format_context_->nb_streams; ++i) {
+    AVCodecContext* c = format_context_->streams[i]->codec;
+    if (c->codec_type == CODEC_TYPE_AUDIO) {
+      codec_context_ = c;
+      break;
+    }
+  }
+
+  // Get the codec.
+  if (codec_context_) {
+    av_find_stream_info(format_context_);
+    codec_ = avcodec_find_decoder(codec_context_->codec_id);
+    if (codec_) {
+      if ((result = avcodec_open(codec_context_, codec_)) < 0) {
+        DLOG(WARNING) << "AudioFileReader::Open() : could not open codec -"
+            << " result: " << result;
+        return result;
+      }
+
+      result = av_seek_frame(format_context_, 0, 0, 0);
+    }
+  } else {
+    result = -1;
+  }
+
+  return result;
+}
+
+void AudioFileReader::Close() {
+  if (codec_context_ && codec_) {
+    avcodec_close(codec_context_);
+  }
+  codec_context_ = NULL;
+  codec_ = NULL;
+
+  if (format_context_) {
+      av_close_input_file(format_context_);
+      format_context_ = NULL;
+  }
+}
+
+int AudioFileReader::Read(const std::vector<float*>& audio_data,
+                          size_t number_of_frames) {
+  DCHECK_EQ(audio_data.size(), NumberOfChannels());
+  if (audio_data.size() != NumberOfChannels())
+    return -1;
+
+  DCHECK(format_context_ && codec_context_);
+  if (!format_context_ || !codec_context_) {
+    DLOG(WARNING) << "AudioFileReader::Read() : reader is not opened!";
+    return -1;
+  }
+
+  int16* output_buffer =
+    static_cast<int16*>(malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE));
+
+  unsigned number_of_channels = NumberOfChannels();
+
+  // Read until we hit EOF or we've read the requested number of frames.
+  AVPacket avpkt;
+  av_init_packet(&avpkt);
+
+  int result = 0;
+  unsigned current_frame = 0;
+
+  while (current_frame < number_of_frames
+      && (result = av_read_frame(format_context_, &avpkt)) >= 0) {
+    int out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
+    result = avcodec_decode_audio3(codec_context_,
+                                   output_buffer,
+                                   &out_size,
+                                   &avpkt);
+
+    if (result < 0) {
+      DLOG(WARNING)
+          << "AudioFileReader::Read() : error in avcodec_decode_audio3() -"
+          << result;
+      free(output_buffer);
+      return result;
+    }
+
+    // Determine the number of sample-frames we just decoded.
+    size_t sample_byte_size = codec_context_->sample_fmt == AV_SAMPLE_FMT_S32

[scherkus (not reviewing), 2010/12/09 17:35:40]

use av_get_bits_per_sample_fmt() and divide by 8 -- or right shift by 3 :)

[fbarchard, 2010/12/09 21:11:02]

You missed 8 bit.

[Chris Rogers, 2010/12/10 23:34:00]

Done.

[Chris Rogers, 2010/12/10 23:34:00]

Done.

+      ? sizeof(int32) : sizeof(int16);
+
+    unsigned frames_read = out_size / (number_of_channels * sample_byte_size);
+
+    // Truncate, if necessary, if the destination isn't big enough.
+    if (current_frame + frames_read > number_of_frames) {
+      frames_read = static_cast<int>(number_of_frames) - current_frame;
+    }
+
+    // Convert to Float32 with nominal range -1.0 -> +1.0
+    for (unsigned channelIndex = 0; channelIndex < number_of_channels;

[scherkus (not reviewing), 2010/12/09 17:35:40]

I can't remember if FFmpeg offers any sort of utility function like this, but in
any case I'd recommend extracting this and putting it under
src/media/audio/audio_util.h/cc

[Chris Rogers, 2010/12/10 23:34:00]

I've created a utility function called DeinterleaveAudioChannel() and put it in
audio_util.h/cc

On 2010/12/09 17:35:40, scherkus wrote:

+         ++channelIndex) {
+      float* destination = audio_data[channelIndex];
+      destination += current_frame;
+
+      switch (codec_context_->sample_fmt) {
+        case AV_SAMPLE_FMT_S16:
+        {
+          const float kScale = 1.0f / 32768.0f;
+          for (unsigned i = 0; i < frames_read; ++i) {
+            destination[i] =
+              kScale * output_buffer[i * number_of_channels + channelIndex];
+          }
+          break;
+        }
+
+        case AV_SAMPLE_FMT_S32:
+        {
+          const float kScale = 1.0f / (1L << 31);
+          int32* output_buffer32 = reinterpret_cast<int32*>(output_buffer);
+          for (unsigned i = 0; i < frames_read; ++i) {
+            destination[i] =
+              kScale * output_buffer32[i * number_of_channels + channelIndex];
+          }
+          break;
+        }
+
+        default:
+          DLOG(WARNING)
+              << "AudioFileReader::Read() : Unsupported sample format : "
+              << codec_context_->sample_fmt
+              << " codec_->id : " << codec_->id;
+          return -1;
+      }
+    }
+
+    current_frame += frames_read;
+  }
+
+  free(output_buffer);
+  return 0;  // success
+}
+
+InMemoryDataReader::InMemoryDataReader(const char* data, int64 size)
+  : data_(data),
+    size_(size),
+    position_(0) {
+}
+
+int InMemoryDataReader::Read(int size, uint8* data) {
+  if (size < 0)
+    return -1;
+
+  int64 available_bytes = size_ - position_;
+  if (size > available_bytes)
+    size = available_bytes;
+
+  memcpy(data, data_ + position_, size);
+  position_ += size;
+  return size;
+}
+
+bool InMemoryDataReader::GetPosition(int64* position_out) {
+  if (position_out)
+    *position_out = position_;
+  return true;
+}
+
+bool InMemoryDataReader::SetPosition(int64 position) {
+  if (position >= size_)
+    return false;
+  position_ = position;
+  return true;
+}
+
+bool InMemoryDataReader::GetSize(int64* size_out) {
+  if (size_out)
+    *size_out = size_;
+  return true;
+}
+
+bool InMemoryDataReader::IsStreaming() {
+  return false;
+}
+
+}  // namespace media