Method write_audio_packets

src/FFmpegWriter.cpp:1575–2032

write all queued frames' audio to the video file

// write all queued frames' audio to the video file
void FFmpegWriter::write_audio_packets(bool is_final, std::shared_ptr<openshot::Frame> frame) {
	if (!frame && !is_final)
		return;

	// Init audio buffers / variables
	int total_frame_samples = 0;
	int frame_position = 0;
	int channels_in_frame = 0;
	int sample_rate_in_frame = 0;
	int samples_in_frame = 0;
	ChannelLayout channel_layout_in_frame = LAYOUT_MONO; // default channel layout

	// Create a new array (to hold all S16 audio samples, for the current queued frames
	unsigned int all_queued_samples_size = sizeof(int16_t) * AVCODEC_MAX_AUDIO_FRAME_SIZE;
	int16_t *all_queued_samples = (int16_t *) av_malloc(all_queued_samples_size);
	int16_t *all_resampled_samples = NULL;
	int16_t *final_samples_planar = NULL;
	int16_t *final_samples = NULL;

	// Get audio sample array
	float *frame_samples_float = NULL;

	// Get the audio details from this frame
	if (frame) {
		sample_rate_in_frame = frame->SampleRate();
		samples_in_frame = frame->GetAudioSamplesCount();
		channels_in_frame = frame->GetAudioChannelsCount();
		channel_layout_in_frame = frame->ChannelsLayout();

		// Get samples interleaved together (c1 c2 c1 c2 c1 c2)
		frame_samples_float = frame->GetInterleavedAudioSamples(&samples_in_frame);
	}

	// Calculate total samples
	total_frame_samples = samples_in_frame * channels_in_frame;

	// Translate audio sample values back to 16 bit integers with saturation
	const int16_t max16 = 32767;
	const int16_t min16 = -32768;
	for (int s = 0; s < total_frame_samples; s++, frame_position++) {
		float valF = frame_samples_float[s] * (1 << 15);
		int16_t conv;
		if (valF > max16) {
			conv = max16;
		} else if (valF < min16) {
			conv = min16;
		} else {
			conv = int(valF + 32768.5) - 32768; // +0.5 is for rounding
		}

		// Copy into buffer
		all_queued_samples[frame_position] = conv;
	}

	// Deallocate float array
	delete[] frame_samples_float;