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* Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include <stddef.h>
#include <map>
#include <string>
#include "absl/strings/string_view.h"
#include "rtc_base/checks.h"
#include "rtc_base/system/rtc_export.h"
namespace webrtc {
// SDP specification for a single audio codec.
struct RTC_EXPORT SdpAudioFormat {
using Parameters = std::map<std::string, std::string>;
SdpAudioFormat(const SdpAudioFormat&);
SdpAudioFormat(absl::string_view name, int clockrate_hz, size_t num_channels);
SdpAudioFormat(absl::string_view name,
int clockrate_hz,
size_t num_channels,
const Parameters& param);
SdpAudioFormat(absl::string_view name,
int clockrate_hz,
size_t num_channels,
Parameters&& param);
// Returns true if this format is compatible with |o|. In SDP terminology:
// would it represent the same codec between an offer and an answer? As
// opposed to operator==, this method disregards codec parameters.
bool Matches(const SdpAudioFormat& o) const;
SdpAudioFormat& operator=(const SdpAudioFormat&);
SdpAudioFormat& operator=(SdpAudioFormat&&);
friend bool operator==(const SdpAudioFormat& a, const SdpAudioFormat& b);
friend bool operator!=(const SdpAudioFormat& a, const SdpAudioFormat& b) {
return !(a == b);
std::string name;
int clockrate_hz;
size_t num_channels;
Parameters parameters;
// Information about how an audio format is treated by the codec implementation.
// Contains basic information, such as sample rate and number of channels, which
// isn't uniformly presented by SDP. Also contains flags indicating support for
// integrating with other parts of WebRTC, like external VAD and comfort noise
// level calculation.
// To avoid API breakage, and make the code clearer, AudioCodecInfo should not
// be directly initializable with any flags indicating optional support. If it
// were, these initializers would break any time a new flag was added. It's also
// more difficult to understand:
// AudioCodecInfo info{16000, 1, 32000, true, false, false, true, true};
// than
// AudioCodecInfo info(16000, 1, 32000);
// info.allow_comfort_noise = true;
// info.future_flag_b = true;
// info.future_flag_c = true;
struct AudioCodecInfo {
AudioCodecInfo(int sample_rate_hz, size_t num_channels, int bitrate_bps);
AudioCodecInfo(int sample_rate_hz,
size_t num_channels,
int default_bitrate_bps,
int min_bitrate_bps,
int max_bitrate_bps);
AudioCodecInfo(const AudioCodecInfo& b) = default;
~AudioCodecInfo() = default;
bool operator==(const AudioCodecInfo& b) const {
return sample_rate_hz == b.sample_rate_hz &&
num_channels == b.num_channels &&
default_bitrate_bps == b.default_bitrate_bps &&
min_bitrate_bps == b.min_bitrate_bps &&
max_bitrate_bps == b.max_bitrate_bps &&
allow_comfort_noise == b.allow_comfort_noise &&
supports_network_adaption == b.supports_network_adaption;
bool operator!=(const AudioCodecInfo& b) const { return !(*this == b); }
bool HasFixedBitrate() const {
RTC_DCHECK_GE(min_bitrate_bps, 0);
RTC_DCHECK_LE(min_bitrate_bps, default_bitrate_bps);
RTC_DCHECK_GE(max_bitrate_bps, default_bitrate_bps);
return min_bitrate_bps == max_bitrate_bps;
int sample_rate_hz;
size_t num_channels;
int default_bitrate_bps;
int min_bitrate_bps;
int max_bitrate_bps;
bool allow_comfort_noise = true; // This codec can be used with an external
// comfort noise generator.
bool supports_network_adaption = false; // This codec can adapt to varying
// network conditions.
// AudioCodecSpec ties an audio format to specific information about the codec
// and its implementation.
struct AudioCodecSpec {
bool operator==(const AudioCodecSpec& b) const {
return format == b.format && info ==;
bool operator!=(const AudioCodecSpec& b) const { return !(*this == b); }
SdpAudioFormat format;
AudioCodecInfo info;
} // namespace webrtc