Method GetFrame

src/audio_effects/Echo.cpp:63–105

This method is required for all derived classes of EffectBase, and returns a modified openshot::Frame object

// This method is required for all derived classes of EffectBase, and returns a
// modified openshot::Frame object
std::shared_ptr<openshot::Frame> Echo::GetFrame(std::shared_ptr<openshot::Frame> frame, int64_t frame_number)
{
	const float echo_time_value = (float)echo_time.GetValue(frame_number)*(float)frame->SampleRate();
	const float feedback_value = feedback.GetValue(frame_number);
	const float mix_value = mix.GetValue(frame_number);
	int local_write_position;

	setup(frame);

	for (int channel = 0; channel < frame->audio->getNumChannels(); channel++)
	{
		float *channel_data = frame->audio->getWritePointer(channel);
		float *echo_data = echo_buffer.getWritePointer(channel);
		local_write_position = echo_write_position;

		for (auto sample = 0; sample < frame->audio->getNumSamples(); ++sample)
		{
			const float in = (float)(channel_data[sample]);
			float out = 0.0f;

			float read_position = fmodf((float)local_write_position - echo_time_value + (float)echo_buffer_samples, echo_buffer_samples);
			int local_read_position = floorf(read_position);

			if (local_read_position != local_write_position)
			{
				float fraction = read_position - (float)local_read_position;
				float echoed1 = echo_data[(local_read_position + 0)];
				float echoed2 = echo_data[(local_read_position + 1) % echo_buffer_samples];
				out = (float)(echoed1 + fraction * (echoed2 - echoed1));
				channel_data[sample] = in + mix_value*(out - in);
				echo_data[local_write_position] = in + out*feedback_value;
			}

			if (++local_write_position >= echo_buffer_samples)
				local_write_position -= echo_buffer_samples;
		}
	}

	echo_write_position = local_write_position;

	// return the modified frame
	return frame;
}

// Generate JSON string of this object
std::string Echo::Json() const {