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// 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 "content/browser/speech/audio_encoder.h"
#include <stddef.h>
#include <memory>
#include "base/logging.h"
#include "base/strings/string_number_conversions.h"
#include "content/browser/speech/audio_buffer.h"
namespace content {
namespace {
const char kContentTypeFLAC[] = "audio/x-flac; rate=";
const int kFLACCompressionLevel = 0; // 0 for speed
FLAC__StreamEncoderWriteStatus WriteCallback(
const FLAC__StreamEncoder* encoder,
const FLAC__byte buffer[],
size_t bytes,
unsigned samples,
unsigned current_frame,
void* client_data) {
AudioBuffer* encoded_audio_buffer = static_cast<AudioBuffer*>(client_data);
encoded_audio_buffer->Enqueue(buffer, bytes);
return FLAC__STREAM_ENCODER_WRITE_STATUS_OK;
}
} // namespace
AudioEncoder::AudioEncoder(int sampling_rate, int bits_per_sample)
: encoded_audio_buffer_(1), /* Byte granularity of encoded samples. */
encoder_(FLAC__stream_encoder_new()),
is_encoder_initialized_(false) {
FLAC__stream_encoder_set_channels(encoder_, 1);
FLAC__stream_encoder_set_bits_per_sample(encoder_, bits_per_sample);
FLAC__stream_encoder_set_sample_rate(encoder_, sampling_rate);
FLAC__stream_encoder_set_compression_level(encoder_, kFLACCompressionLevel);
// Initializing the encoder will cause sync bytes to be written to
// its output stream, so we wait until the first call to Encode()
// before doing so.
}
AudioEncoder::~AudioEncoder() {
FLAC__stream_encoder_delete(encoder_);
}
void AudioEncoder::Encode(const AudioChunk& raw_audio) {
DCHECK_EQ(raw_audio.bytes_per_sample(), 2);
if (!is_encoder_initialized_) {
const FLAC__StreamEncoderInitStatus encoder_status =
FLAC__stream_encoder_init_stream(encoder_, WriteCallback, nullptr,
nullptr, nullptr,
&encoded_audio_buffer_);
DCHECK_EQ(encoder_status, FLAC__STREAM_ENCODER_INIT_STATUS_OK);
is_encoder_initialized_ = true;
}
// FLAC encoder wants samples as int32s.
const int num_samples = raw_audio.NumSamples();
std::unique_ptr<FLAC__int32[]> flac_samples(new FLAC__int32[num_samples]);
FLAC__int32* flac_samples_ptr = flac_samples.get();
for (int i = 0; i < num_samples; ++i)
flac_samples_ptr[i] = static_cast<FLAC__int32>(raw_audio.GetSample16(i));
FLAC__stream_encoder_process(encoder_, &flac_samples_ptr, num_samples);
}
void AudioEncoder::Flush() {
FLAC__stream_encoder_finish(encoder_);
}
scoped_refptr<AudioChunk> AudioEncoder::GetEncodedDataAndClear() {
return encoded_audio_buffer_.DequeueAll();
}
std::string AudioEncoder::GetMimeType() {
return std::string(kContentTypeFLAC) +
base::NumberToString(FLAC__stream_encoder_get_sample_rate(encoder_));
}
int AudioEncoder::GetBitsPerSample() {
return FLAC__stream_encoder_get_bits_per_sample(encoder_);
}
} // namespace content
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