Source repositoryaudio.cpp File Reference

Definitions for audio capture and encoding. More...

#include <algorithm>
#include <array>
#include <thread>
#include <libavcodec/avcodec.h>
#include <libavutil/avutil.h>
#include <libavutil/channel_layout.h>
#include <libavutil/frame.h>
#include <opus/opus_multistream.h>
#include "audio.h"
#include "config.h"
#include "globals.h"
#include "logging.h"
#include "platform/common.h"
#include "thread_safe.h"
#include "utility.h"

Include dependency graph for audio.cpp:

Classes
class	audio::ffmpeg_audio_encoder_t
	Encode one interleaved stereo or 5.1 float PCM frame as an AC-3-family access unit. More...

Typedefs
using	audio::opus_t = util::safe_ptr<OpusMSEncoder, opus_multistream_encoder_destroy>
	Owning pointer for an Opus multistream encoder.
using	audio::sample_queue_t = std::shared_ptr<safe::queue_t<std::vector<float>>>
	Shared queue carrying captured PCM sample buffers to the encoder thread.

Functions
bool	audio::ac3_available ()
	Check whether the linked FFmpeg build provides the AC-3 encoder.
void	audio::capture (safe::mail_t mail, config_t config, stream::session_t *channel_data)
	Run the capture loop for this backend.
dolby_codec_e	audio::configure_dolby_audio (config_t &config, std::string_view offered, std::string_view accepted, bool ac3_encoder_available, bool eac3_encoder_available, bool high_quality)
	Configure a Dolby stream only for an exact, supported client acceptance.
int	audio::dolby_bitrate_kbps (bool eac3, bool high_quality, int channels)
	Select a channel-aware bitrate for Dolby audio encoding.
std::string_view	audio::dolby_codec_name (dolby_codec_e codec)
	Return the codec label for the RTSP audio-codec response header.
bool	audio::eac3_available ()
	Check whether the linked FFmpeg build provides the E-AC-3 encoder.
void	audio::encodeThread (sample_queue_t samples, config_t config, stream::session_t *channel_data)
	Encode captured PCM samples into Opus packets on the audio worker thread.
audio_ctx_ref_t	audio::get_audio_ctx_ref ()
	Get the reference to the audio context.
bool	audio::is_audio_ctx_sink_available (const audio_ctx_t &ctx)
	Check if the audio sink held by audio context is available.
int	audio::map_stream (int channels, bool quality)
	Select the Opus stream configuration for a channel count and quality tier.

Variables
constexpr auto	audio::SAMPLE_RATE = 48000
	Audio sample rate in hertz required by Opus.
const std::array< opus_stream_config_t, MAX_STREAM_CONFIG >	audio::stream_configs
	Opus stream layouts and bitrates advertised to clients.

Detailed Description

Definitions for audio capture and encoding.

Function Documentation

ac3_available()

bool audio::ac3_available

(

)

Check whether the linked FFmpeg build provides the AC-3 encoder.

Check whether a compatible optional FFmpeg AC-3 encoder is available.

Returns

True when the AC-3 encoder is available in this build.

True when the required FFmpeg DLLs and AC-3 encoder are available.

capture()

void audio::capture	(	safe::mail_t	mail,
		config_t	config,
		stream::session_t *	channel_data )

Run the capture loop for this backend.

Capture, encode, and publish audio packets for a stream.

Parameters

mail	Mailbox used to publish encoded audio packets.
config	Audio capture and encoder settings.
channel_data	Stream session that receives the encoded packets.

configure_dolby_audio()

dolby_codec_e audio::configure_dolby_audio	(	config_t &	config,
		std::string_view	offered,
		std::string_view	accepted,
		bool	ac3_encoder_available,
		bool	eac3_encoder_available,
		bool	high_quality )

Configure a Dolby stream only for an exact, supported client acceptance.

Parameters

config	Audio configuration to update for the negotiated stream.
offered	Codec offered by Sunshine, or empty when using Opus.
accepted	Codec explicitly accepted by the client.
ac3_encoder_available	Whether the AC-3 encoder is available.
eac3_encoder_available	Whether the E-AC-3 encoder is available.
high_quality	Whether the higher Dolby bitrate was requested.

Returns

Selected codec, falling back to Opus when negotiation is unsupported.

dolby_bitrate_kbps()

int audio::dolby_bitrate_kbps	(	bool	eac3,
		bool	high_quality,
		int	channels )

Select a channel-aware bitrate for Dolby audio encoding.

Parameters

eac3	True to select E-AC-3; false to select AC-3.
high_quality	Whether to use the higher Dolby bitrate.
channels	Number of output audio channels (stereo or 5.1).

Returns

The selected bitrate in kbit/s, or 0 for unsupported channel layouts.

dolby_codec_name()

std::string_view audio::dolby_codec_name

(

dolby_codec_e

codec

)

Return the codec label for the RTSP audio-codec response header.

Parameters

codec

Selected audio codec.

Returns

RTSP codec label.

eac3_available()

bool audio::eac3_available

(

)

Check whether the linked FFmpeg build provides the E-AC-3 encoder.

Check whether a compatible optional FFmpeg E-AC-3 encoder is available.

Returns

True when the E-AC-3 encoder is available in this build.

True when the required FFmpeg DLLs and E-AC-3 encoder are available.

encodeThread()

void audio::encodeThread	(	sample_queue_t	samples,
		config_t	config,
		stream::session_t *	channel_data )

Encode captured PCM samples into Opus packets on the audio worker thread.

Parameters

samples	Queue of captured PCM sample buffers to encode.
config	Audio stream settings negotiated with the client.
channel_data	Stream session carried with each encoded packet.

get_audio_ctx_ref()

audio_ctx_ref_t audio::get_audio_ctx_ref

(

)

Get the reference to the audio context.

Returns

A shared pointer reference to audio context.

Note

Aside from the configuration purposes, it can be used to extend the audio sink lifetime to capture sink earlier and restore it later.

Examples

audio_ctx_ref_t audio = get_audio_ctx_ref()

is_audio_ctx_sink_available()

bool audio::is_audio_ctx_sink_available

(

const audio_ctx_t &

ctx

)

Check if the audio sink held by audio context is available.

Returns

True if available (and can probably be restored), false otherwise.

Note

Useful for delaying the release of audio context shared pointer (which tries to restore original sink).

Examples

audio_ctx_ref_t audio = get_audio_ctx_ref()
if (audio.get()) {
    return is_audio_ctx_sink_available(*audio.get());
}
return false;

Parameters

ctx	Native context object used by the operation or callback.

map_stream()

int audio::map_stream	(	int	channels,
		bool	quality )

Select the Opus stream configuration for a channel count and quality tier.

Parameters

channels	Number of audio channels in the stream.
quality	Whether the high-quality Opus layout should be selected.

Returns

Index into stream_configs for the requested layout.

Variable Documentation

stream_configs

const std::array< opus_stream_config_t, MAX_STREAM_CONFIG > audio::stream_configs

Opus stream layouts and bitrates advertised to clients.

Opus layouts and bitrates advertised for each supported stream mode.