Method ResampleMappedAudio

src/FrameMapper.cpp:878–1094

Resample audio and map channels (if needed)

// Resample audio and map channels (if needed)
void FrameMapper::ResampleMappedAudio(std::shared_ptr<Frame> frame, int64_t original_frame_number)
{
	// Check if mappings are dirty (and need to be recalculated)
	if (is_dirty)
		// Recalculate mappings
		Init();

	// Init audio buffers / variables
	int total_frame_samples = 0;
	int channels_in_frame = frame->GetAudioChannelsCount();
	int sample_rate_in_frame = frame->SampleRate();
	int samples_in_frame = frame->GetAudioSamplesCount();
	ChannelLayout channel_layout_in_frame = frame->ChannelsLayout();

	ZmqLogger::Instance()->AppendDebugMethod(
		"FrameMapper::ResampleMappedAudio",
		"frame->number", frame->number,
		"original_frame_number", original_frame_number,
		"channels_in_frame", channels_in_frame,
		"samples_in_frame", samples_in_frame,
		"sample_rate_in_frame", sample_rate_in_frame);

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

	// Create a new array (to hold all S16 audio samples for the current queued frames)
 	int16_t* frame_samples = (int16_t*) av_malloc(sizeof(int16_t)*total_frame_samples);

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

	// Deallocate float array
	delete[] frame_samples_float;
	frame_samples_float = NULL;

	// Create input frame (and allocate arrays)
	AVFrame *audio_frame = AV_ALLOCATE_FRAME();
	AV_RESET_FRAME(audio_frame);