Discrepancy between different tools

[239]

While I was looking for a suitable tool for Linux, I made a small comparison with 4 flac/opus files. This resulted in some very different values, which I would like to share here. Could it be that I've overlooked something?

[239]

FTVEP-flac	Ex Falso	foobar2000	loudgain	metaflac	r128gain	rsgain
AG	-5.71 dB	-8.19 dB	-8.19 dB	-5.71 dB	-8.20 dB	-8.19 dB
AP	0.9923	0.992279	1.133981	0.99227905	1.00000000	0.992279
TG1	-4.67 dB	-7.08 dB	-7.08 dB	-4.68 dB	-7.10 dB	-7.08 dB
TP1	0.9877	0.987732	0.989932	0.98773193	0.98922700	0.987732
TG2	-6.61 dB	-9.29 dB	-9.29 dB	-6.61 dB	-9.30 dB	-9.29 dB
TP2	0.9883	0.988342	1.075565	0.98834229	1.00000000	0.988342
TG3	-5.46 dB	-7.55 dB	-7.55 dB	-5.46 dB	-7.50 dB	-7.55 dB
TP3	0.9923	0.992279	1.133981	0.99227905	1.00000000	0.992279
TG4	-2.57 dB	-8.82 dB	-8.82 dB	-2.57 dB	-8.80 dB	-8.82 dB
TP4	0.9844	0.984375	1.056995	0.98437500	1.00000000	0.984375

[239]

FTVEP-opus	Ex Falso	foobar2000	loudgain	opusenc	r128gain	rsgain
AG	-5.62 dB	-3375	-3375		-3379	-3375
TG1	-4.62 dB	-3091	-3090	264	-3098	-3090
TG2	-6.48 dB	-3658	-3658	-230	-3661	-3658
TG3	-5.39 dB	-3212	-3212	64	-3200	-3212
TG4	-2.51 dB	-3536	-3535	804	-3533	-3535

[desbma]

Yes this is expected.

r128gain has a bug because it systematically resamples audio to 48 KHz before analysis, which leads to small offset from the correct value, see also #44.

Ex falso and metaflac probably use the Replay Gain original algorithm which has a different weighting curve, that leads to the ~4 dB difference.

I don't have much time to fix and interest to maintain r128gain nowadays, when I first wrote it there was no alternative, now, as your comparison confirms, I can only recommend rsgain. loudgain's behavior to use true peak instead of sample peak is wrong in my opinion, because it breaks compatibility with previous Replay Gain implementations, and can lead to very important loudness difference if the playback software is set to avoid clipping.