ReplayGain writes bad Opus Header Gain

2021-01-01 22:28:54

Original file:

File name : 18. Van Halen - Can't Stop Lovin' You (2004 Remaster).ogg
File size : 4.31 MB (4 523 992 bytes)
Last modified : 2020-12-30 22:45:34
Duration : 4:08.200 (11 913 600 samples)
Sample rate : 48000 Hz
Opus header gain : 0.00 dB
Original sample rate : 48000
Channels : 2
Bitrate : 127 kbps
Codec : Opus
Track Gain: -10.99 dB
Track Peak: 1.169031

When I use FB2K 1.6.2 per-file track gain it changes Opus Header Gain to -15.99 dB and the song is so quiet that it's difficult to hear even at 100% volume. When I scan the whole album as an album the Opus Header Gain is changed to -15.16 dB, which is still absurdly quiet. Audacity measures the RMS volume of the track after ReplayGain at -26.432 dB.

I noticed it because I'm trying to put together a USB thumb drive for the car and want everything to be the same volume, but some tracks are so insanely quiet after ReplayGain that it's unusable.

Re: ReplayGain writes bad Opus Header Gain

Reply #1 – 2021-01-01 22:46:02

After more investigation it looks to be a problem with using RMS. Normalizing this track to -18 dB RMS in Audactiy only requires -7 dB.

Re: ReplayGain writes bad Opus Header Gain

Reply #2 – 2021-01-02 03:08:43

Opus gain headers are supposed to target -23 LUFS. foobar2000 uses R128, but uses ReplayGain relative levels, which target -18 LUFS. So the Opus header and tag fields will be written with a -5 offset, and played with a +5 offset to whatever is already in the headers. If your software is applying the headers as-is, blame that software for not offering a different volume target than -23 LUFS.

Re: ReplayGain writes bad Opus Header Gain

Reply #3 – 2021-01-17 15:24:53

That would be foobar2k.

However, the -15.99 dB tag being written by foobar is causing the RMS volume to be -26.437.

Re: ReplayGain writes bad Opus Header Gain

Reply #4 – 2021-01-17 23:08:26

R128 is not RMS.