Method add_audio_stream

src/FFmpegWriter.cpp:1012–1143

Add an audio output stream

// Add an audio output stream
AVStream *FFmpegWriter::add_audio_stream() {
	// Find the audio codec
	const AVCodec *codec = avcodec_find_encoder_by_name(info.acodec.c_str());
	if (codec == NULL)
		throw InvalidCodec("A valid audio codec could not be found for this file.", path);

	// Free any previous memory allocations
	if (audio_codec_ctx != nullptr) {
		AV_FREE_CONTEXT(audio_codec_ctx);
	}

	// Create a new audio stream
	AVStream* st = avformat_new_stream(oc, codec);
	if (!st)
		throw OutOfMemory("Could not allocate memory for the audio stream.", path);

	// Allocate a new codec context for the stream
	ALLOC_CODEC_CTX(audio_codec_ctx, codec, st)
#if (LIBAVFORMAT_VERSION_MAJOR >= 58)
	st->codecpar->codec_id = codec->id;
#endif
	AVCodecContext* c = audio_codec_ctx;

	c->codec_id = codec->id;
	c->codec_type = AVMEDIA_TYPE_AUDIO;

	// Set the sample parameters
	c->bit_rate = info.audio_bit_rate;
#if !HAVE_CH_LAYOUT
	c->channels = info.channels;
#endif

	// Set valid sample rate (or throw error)
	if (codec->supported_samplerates) {
		int i;
		for (i = 0; codec->supported_samplerates[i] != 0; i++)
			if (info.sample_rate == codec->supported_samplerates[i]) {
				// Set the valid sample rate
				c->sample_rate = info.sample_rate;
				break;
			}
		if (codec->supported_samplerates[i] == 0)
			throw InvalidSampleRate("An invalid sample rate was detected for this codec.", path);
	} else
		// Set sample rate
		c->sample_rate = info.sample_rate;

	uint64_t channel_layout = info.channel_layout;
#if HAVE_CH_LAYOUT
	// Set a valid number of channels (or throw error)
	AVChannelLayout ch_layout;
	av_channel_layout_from_mask(&ch_layout, info.channel_layout);
	if (codec->ch_layouts) {
		int i;
		for (i = 0; av_channel_layout_check(&codec->ch_layouts[i]); i++)
			if (av_channel_layout_compare(&ch_layout, &codec->ch_layouts[i])) {
				// Set valid channel layout
				av_channel_layout_copy(&c->ch_layout, &ch_layout);