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audio_decoder_opus.cc (3101B)

      1 /*
      2 *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
      3 *
      4 *  Use of this source code is governed by a BSD-style license
      5 *  that can be found in the LICENSE file in the root of the source
      6 *  tree. An additional intellectual property rights grant can be found
      7 *  in the file PATENTS.  All contributing project authors may
      8 *  be found in the AUTHORS file in the root of the source tree.
      9 */
     10 
     11 #include "api/audio_codecs/opus/audio_decoder_opus.h"
     12 
     13 #include <map>
     14 #include <memory>
     15 #include <optional>
     16 #include <string>
     17 #include <utility>
     18 #include <vector>
     19 
     20 #include "absl/strings/match.h"
     21 #include "api/audio_codecs/audio_decoder.h"
     22 #include "api/audio_codecs/audio_format.h"
     23 #include "api/environment/environment.h"
     24 #include "api/field_trials_view.h"
     25 #include "modules/audio_coding/codecs/opus/audio_decoder_opus.h"
     26 #include "rtc_base/checks.h"
     27 
     28 namespace webrtc {
     29 namespace {
     30 
     31 int GetDefaultNumChannels(const FieldTrialsView& field_trials) {
     32  return field_trials.IsEnabled("WebRTC-Audio-OpusDecodeStereoByDefault") ? 2
     33                                                                          : 1;
     34 }
     35 
     36 }  // namespace
     37 
     38 bool AudioDecoderOpus::Config::IsOk() const {
     39  if (sample_rate_hz != 16000 && sample_rate_hz != 48000) {
     40    // Unsupported sample rate. (libopus supports a few other rates as
     41    // well; we can add support for them when needed.)
     42    return false;
     43  }
     44  return !num_channels.has_value() || *num_channels == 1 || *num_channels == 2;
     45 }
     46 
     47 std::optional<AudioDecoderOpus::Config> AudioDecoderOpus::SdpToConfig(
     48    const SdpAudioFormat& format) {
     49  if (!absl::EqualsIgnoreCase(format.name, "opus") ||
     50      format.clockrate_hz != 48000 || format.num_channels != 2) {
     51    return std::nullopt;
     52  }
     53 
     54  Config config;
     55 
     56  // Parse the "stereo" codec parameter. If set, it overrides the default number
     57  // of channels.
     58  const auto stereo_param = format.parameters.find("stereo");
     59  if (stereo_param != format.parameters.end()) {
     60    if (stereo_param->second == "0") {
     61      config.num_channels = 1;
     62    } else if (stereo_param->second == "1") {
     63      config.num_channels = 2;
     64    } else {
     65      // Malformed stereo parameter.
     66      return std::nullopt;
     67    }
     68  }
     69 
     70  if (!config.IsOk()) {
     71    RTC_DCHECK_NOTREACHED();
     72    return std::nullopt;
     73  }
     74  return config;
     75 }
     76 
     77 void AudioDecoderOpus::AppendSupportedDecoders(
     78    std::vector<AudioCodecSpec>* specs) {
     79  AudioCodecInfo opus_info{48000, 1, 64000, 6000, 510000};
     80  opus_info.allow_comfort_noise = false;
     81  opus_info.supports_network_adaption = true;
     82  SdpAudioFormat opus_format(
     83      {"opus", 48000, 2, {{"minptime", "10"}, {"useinbandfec", "1"}}});
     84  specs->push_back({std::move(opus_format), opus_info});
     85 }
     86 
     87 std::unique_ptr<AudioDecoder> AudioDecoderOpus::MakeAudioDecoder(
     88    const Environment& env,
     89    Config config) {
     90  if (!config.IsOk()) {
     91    RTC_DCHECK_NOTREACHED();
     92    return nullptr;
     93  }
     94  return std::make_unique<AudioDecoderOpusImpl>(
     95      env.field_trials(),
     96      config.num_channels.value_or(GetDefaultNumChannels(env.field_trials())),
     97      config.sample_rate_hz);
     98 }
     99 
    100 }  // namespace webrtc