README.md

BASS_REPLAY_GAIN

A replay gain calculator for BASS which uses IIR stereo filters similar to libavfilter.

bass.dll is required for native projects. ManagedBass is required for .NET projects.

A simple example;

int Main()
{
	//Load as a plugin if you like, or use Loader.Load("bass_replay_gain")
	BassReplayGain.Load();

	var handle = Bass.CreateStream("test.mp3", Flags: BassFlags.Decode | BassFlags.Float);

	var info = new ReplayGainInfo();
	if (!BassReplayGain.Process(handle, out info))
	{
		Console.WriteLine("Failed to process stream: {0}", Bass.LastError);
		return 1;
	}

	Console.WriteLine("Gain: {0}", info.gain);
	Console.WriteLine("Peak: {0}", info.peak);
}

#include <stdio.h>
#include "../bass_replay_gain/bass_replay_gain.h"

int main(int argc, char** argv) {
	DWORD handle;
	REPLAY_GAIN_INFO info;

	if (!BASS_Init(0, 44100, 0, 0, NULL)) {
		printf("Failed to initialize BASS: %d\n", BASS_ErrorGetCode());
		return 1;
	}

	handle = BASS_StreamCreateFile(FALSE, "test.mp3", 0, 0, BASS_STREAM_DECODE | BASS_SAMPLE_FLOAT);

	if (!BASS_REPLAY_GAIN_Process(handle, &info)) {
		printf("Failed to process stream: %d\n", BASS_ErrorGetCode());
		return 1;
	}

	printf("Gain: %f\n", info.gain);
	printf("Peak: %f\n", info.peak);

	BASS_Free();
}

Using BASS_SAMPLE_FLOAT is recommended but not required.

BASS_REPLAY_GAIN_Process is quite fast, less than a second for a 30MB track. It could be used for playback on the fly (just reset the stream position).

If you wish to apply a volume effect with BASS_FX the calculation is pow(10, gain / 20).

A batch mode is also available to calculating album gain: BASS_REPLAY_GAIN_ProcessBatch. It accepts set of channel handles (up to 256) and returns a REPLAY_GAIN_BATCH_INFO containing information for both individual tracks and the entire batch.

BASS_REPLAY_GAIN_Process and BASS_REPLAY_GAIN_ProcessBatch are thread safe.