Speex encoding/decoding.

remoting/codec/audio_encoder_speex.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 "remoting/codec/audio_encoder_speex.h"
+
+#include <string>
+#include <sstream>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/stl_util.h"
+#include "remoting/proto/audio.pb.h"
+#include "third_party/speex/speex.h"
+
+namespace {
+const int kSpeexQuality = 8;
+const int kEncodedDataBufferSize = 0xFF;
+}  // namespace
+
+namespace remoting {
+
+AudioEncoderSpeex::AudioEncoderSpeex() {
+  // Create and initialize the Speex structures.
+  speex_bits_.reset(new SpeexBits());
+  speex_bits_init(speex_bits_.get());
+  speex_state_ = speex_encoder_init(&speex_wb_mode);
+
+  // Set the encoding quality.
+  int quality = kSpeexQuality;
+  speex_encoder_ctl(speex_state_, SPEEX_SET_QUALITY, &quality);
+
+  // Get the frame size and construct the input buffer accordingly.
+  speex_encoder_ctl(speex_state_, SPEEX_GET_FRAME_SIZE, &speex_frame_size_);
+  raw_data_buffer_.reset(new int16[speex_frame_size_]);
+
+  encoded_data_buffer_.reset(new char[kEncodedDataBufferSize]);
+}
+
+AudioEncoderSpeex::~AudioEncoderSpeex() {
+  speex_encoder_destroy(speex_state_);
+  speex_bits_destroy(speex_bits_.get());
+}
+
+scoped_ptr<AudioPacket> AudioEncoderSpeex::Encode(
+    scoped_ptr<AudioPacket> packet) {
+  DCHECK_EQ(AudioPacket::ENCODING_RAW, packet->encoding());
+  DCHECK_EQ(AudioPacket::BYTES_PER_SAMPLE_2, packet->bytes_per_sample());
+
+  // Put the samples onto the queue.
+  int number_of_samples = packet->data().size() / sizeof(spx_int16_t);

[Sergey Ulanov, 2012/08/14 00:54:32]

nit: divide by packet->bytes_per_sample(). It's the same value, but more
readable.

[kxing, 2012/08/16 13:57:54]

Done.

+  const int16* sample = reinterpret_cast<const int16*>(packet->data().data());
+
+  for (int i = 0; i < number_of_samples; i++) {
+    queued_samples_.push_back(*sample);

[Sergey Ulanov, 2012/08/14 00:54:32]

The data we store between Encode() calls is always smaller than a single frame.
So maybe store the leftovers from the previous call in speex_bits_ and reset the
bits struct after speex_encode_int()?

[kxing, 2012/08/16 13:57:54]

Done.

+    sample++;
+  }
+
+  // Create a new packet of encoded data.
+  scoped_ptr<AudioPacket> encoded_packet(new AudioPacket());
+  encoded_packet->set_data(std::string());

[Sergey Ulanov, 2012/08/14 00:54:32]

don't need this line.

[kxing, 2012/08/16 13:57:54]

Done.

+  encoded_packet->set_encoding(AudioPacket::ENCODING_SPEEX);
+  encoded_packet->set_sampling_rate(packet->sampling_rate());
+  encoded_packet->set_bytes_per_sample(packet->bytes_per_sample());
+  encoded_packet->set_channels(packet->channels());
+
+  while (static_cast<int>(queued_samples_.size()) >= speex_frame_size_) {
+    // Copy the bytes from the sample queue.
+    for (int i = 0; i < speex_frame_size_; i++) {
+      raw_data_buffer_[i] = queued_samples_.front();

[Sergey Ulanov, 2012/08/14 00:54:32]

ouch. we just copied data to queued_samples, now we are copying it again to
raw_data_buffer_. That's slow because you will need malloc/free for each sample.

[kxing, 2012/08/16 13:57:54]

Done.

+      queued_samples_.pop_front();
+    }
+
+    // Reset the bits structure for this frame.
+    speex_bits_reset(speex_bits_.get());

[Sergey Ulanov, 2012/08/14 00:54:32]

why do we need to reset it here?

[kxing, 2012/08/16 13:57:54]

Done.

+
+    // Encode the frame, treating all samples as integers.
+    speex_encode_int(speex_state_, raw_data_buffer_.get(), speex_bits_.get());
+
+    DCHECK_LE(speex_bits_nbytes(speex_bits_.get()), kEncodedDataBufferSize);
+
+    // Copy the encoded data from the bits structure into the buffer.
+    int bytes_written = speex_bits_write(speex_bits_.get(),
+                                         encoded_data_buffer_.get(),

[Sergey Ulanov, 2012/08/14 00:54:32]

pass a buffer inside encoded_packet->mutable_data() instead? 

[kxing, 2012/08/16 13:57:54]

Done.

+                                         kEncodedDataBufferSize);
+    DCHECK_LE(bytes_written, kEncodedDataBufferSize);
+
+    // Write out the data as the data size followed by the encoded data.
+    // The data size is an unsigned int8 so we can support sizes up to 255
+    // bytes.
+    uint8 bytes_written_as_byte = static_cast<uint8>(bytes_written);

[Sergey Ulanov, 2012/08/14 00:54:32]

can we be sure that each encoded frame is smaller than 255?

[kxing, 2012/08/16 13:57:54]

Done.

+    encoded_packet->mutable_data()->append(

[Sergey Ulanov, 2012/08/14 00:54:32]

Would it be better to make data field in AudioPacket repeated? Alternately you
can keep data field as as, but add repeated field speex_frame and use it for
speex-encoded frames?

[kxing, 2012/08/16 13:57:54]

Done.

+        reinterpret_cast<char*>(&bytes_written_as_byte), sizeof(uint8));
+    encoded_packet->mutable_data()->append(
+        encoded_data_buffer_.get(), bytes_written);
+  }
+
+  return encoded_packet.Pass();

[Sergey Ulanov, 2012/08/14 00:54:32]

we may return an empty packet that will be wasting the bandwidth. return NULL
instead?

[kxing, 2012/08/16 13:57:54]

The empty packet filtering happens at the capturer level, so it should not reach
the encoder.

+}
+
+}  // namespace remoting