Speex encoding/decoding.

remoting/codec/audio_decoder_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_decoder_speex.h"
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/logging.h"
+#include "base/stl_util.h"
+#include "remoting/proto/audio.pb.h"
+#include "third_party/speex/speex.h"
+
+namespace remoting {
+
+AudioDecoderSpeex::AudioDecoderSpeex() {
+  // Create and initialize the Speex structures.
+  speex_bits_.reset(new SpeexBits());
+  speex_bits_init(speex_bits_.get());
+  speex_state_ = speex_decoder_init(&speex_wb_mode);
+
+  // Turn perceptual enhancer.
+  int enhancer = 1;
+  speex_decoder_ctl(speex_state_, SPEEX_SET_ENH, &enhancer);
+
+  // Get the frame size and construct the output buffer acccordingly.
+  speex_decoder_ctl(speex_state_, SPEEX_GET_FRAME_SIZE, &speex_frame_size_);
+  buffer_.reset(new int16[speex_frame_size_]);
+}
+
+AudioDecoderSpeex::~AudioDecoderSpeex() {
+  speex_decoder_destroy(speex_state_);
+  speex_bits_destroy(speex_bits_.get());
+}
+
+scoped_ptr<AudioPacket> AudioDecoderSpeex::Decode(
+    scoped_ptr<AudioPacket> packet) {
+  DCHECK_EQ(AudioPacket::ENCODING_SPEEX, packet->encoding());
+  DCHECK_EQ(AudioPacket::BYTES_PER_SAMPLE_2, packet->bytes_per_sample());
+
+  int bytes_left = packet->data().size();
+  // Either because the Speex decoder modifies the input data buffer,
+  // or the API is not const-correct, we have to convert the packet

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

looking at the speex code it's the latter. speex_bits_read_from() just copies
data to internal buffer. So you can just const_cast<> the packet to avoid
copying it twice.

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

Done.

+  // payload into a non-const pointer.
+  std::string* data = const_cast<std::string*>(&(packet->data()));
+  char* ptr = string_as_array(data);
+
+  // Create a new packet of decoded data.
+  scoped_ptr<AudioPacket> decoded_packet(new AudioPacket());
+  decoded_packet->set_data(std::string());

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

don't need this. mutable_data() will do it for you the first time you call that
method.

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

Done.

+  decoded_packet->set_encoding(AudioPacket::ENCODING_RAW);
+  decoded_packet->set_sampling_rate(packet->sampling_rate());
+  decoded_packet->set_bytes_per_sample(packet->bytes_per_sample());
+  decoded_packet->set_channels(packet->channels());
+
+  while (bytes_left > 0) {
+    // Fetch the number of bytes in the frame.
+    int32 bytes_to_read = *(reinterpret_cast<uint8*>(ptr));
+    ptr++;

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

nit: in remoting code it's more common to use prefix increment: ++ptr.

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

Done.

+    bytes_left--;

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

nit: same here

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

Done.

+
+    DCHECK_GT(bytes_to_read, 0);
+    DCHECK_GE(bytes_left, bytes_to_read);
+
+    // Read the bytes into the bits structure.
+    speex_bits_read_from(speex_bits_.get(), ptr, bytes_to_read);
+
+    // Decode the frame and store it in the buffer.
+    int status =
+        speex_decode_int(speex_state_, speex_bits_.get(), buffer_.get());
+    if (status < 0)
+      LOG(ERROR) << "Error in decoding Speex data.";

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

Do you need to return or break here?

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

Done.

+
+    ptr += bytes_to_read;
+    bytes_left -= bytes_to_read;
+
+    DCHECK_GE(bytes_left, 0);
+
+    decoded_packet->mutable_data()->append(

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

instead of appending data here can you specify mutable_data()->data() when
calling speex_decode_int() (provided you resize it appropriately first).

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

Done.

+        reinterpret_cast<char*>(buffer_.get()),
+        speex_frame_size_ * sizeof(int16));
+  }
+
+  return decoded_packet.Pass();
+}
+
+}  // namespace remoting