Request: Replaygain preamp change

[rangi_chip]

iPod 5.5G 80GB - Rockbox 3.13

The current ReplayGain preamp gains any files with ReplayGain info tags.
This is fine when all you files are simply ReplayGained.

I also have MP3 files that have been MP3Gained, which adds ReplayGain info to the tags, but also changes the global gain field in each frame header. I set MP3Gain to 95db (which is +6db above the default 89db).
Now I also have FLAC files that are ReplayGained (89db). I want these FLACs to play at the same level as the MP3s. To do this I adjust the preamp to +6db. But of course the MP3s contain ReplayGain info, they actually get gained a second time; once from the global gain field in each frame header and again from the preamp.

I am requesting that there be three preamps available, like the following, if possible:
Preamp
For MP3Gained MP3's:
<-----------------------|----------------------->
For ReplayGained files (excluding MP3Gained MP3's):
<-----------------------|----------------------->
For all other files:
<-----------------------|----------------------->

See here for a lot more information: http://www.hydrogenaudio.org/forums/index.php?showtopic=101182&st=0&gopid=836460&#entry836460


Cheers.

[saratoga]

Its not obvious from our documentation, but you could do this using the EQ preamp.  Set the EQ to -3dB, the replaygain preamp to +3dB.  In that case all files without replaygain get -3dB, while those with it get 0dB (that is, the normal replaygain adjustments in their tags).

We should probably make this more obvious though. 

[rangi_chip]

But that means that MP3s that have been gained by MP3Gain, say from 89db (+6db) to 95db, will then be gained again by the ReplayGain preamp by (+3db) to 98db, but the FLACs will only be at (+3db) 92db...
The EQ preamp wouldn't help in this case because they both have ReplayGain tags.

Maybe just the addition of one more preamp for MP3Gained MP3s only, and the original ReplayGain preamp does all files containing ReplayGain tags, except for MP3Gained MP3s?

[saratoga]

But that means that MP3s that have been gained by MP3Gain, say from 89db (+6db) to 95db, will then be gained again by the ReplayGain preamp by (+3db) to 98db, but the FLACs will only be at (+3db) 92db...

If you alter the volume permanently using mp3gain, the file does not actually get a replaygain adjustment, and thus is ignored by our replaygain code. 

Actually, if you're using mp3gain, then you don't care about what rockbox does at all, since mp3gain is handling it and rockbox doesn't do anything.

[rangi_chip]

If you alter the volume permanently using mp3gain, the file does not actually get a replaygain adjustment, and thus is ignored by our replaygain code.

If you look at the discussion http://www.hydrogenaudio.org/forums/index.php?showtopic=101182&st=0&gopid=836460&#entry836460, it shows that when MP3Gain does it's adjustment, it does actually store ReplayGain info in the APE tag, as well as changes the global gain field in each frame header.

These fields are stored in APE tag after being MP3Gained:

• MP3GAIN_ALBUM_MINMAX
• MP3GAIN_MINMAX
• MP3GAIN_UNDO
• REPLAYGAIN_ALBUM_GAIN
• REPLAYGAIN_ALBUM_PEAK
• REPLAYGAIN_TRACK_GAIN
• REPLAYGAIN_TRACK_PEAK

So I'm assuming that Rockbox behaves the same as foobar2000, and gains the MP3 twice, as it does actually contain ReplayGain info.

[saratoga]

If you alter the volume permanently using mp3gain, the file does not actually get a replaygain adjustment, and thus is ignored by our replaygain code.

If you look at the discussion http://www.hydrogenaudio.org/forums/index.php?showtopic=101182&st=0&gopid=836460&#entry836460, it shows that when MP3Gain does it's adjustment, it does actually store ReplayGain info in the APE tag, as well as changes the global gain field in each frame header.

We don't even parse APE tags. 

[rangi_chip]

So where do you read the ReplayGain info from then??

[saratoga]

So where do you read the ReplayGain info from then??

In the case of MP3, we use ID3v2.  Its different for each format though, and some do support APEv2:

http://download.rockbox.org/daily/manual/rockbox-sansaclipv2/rockbox-buildap2.html#x18-341000B

[rangi_chip]

Thanks for your help.
So if those APE fields appeared in the ID3 tag with the same field names, then Rockbox would use this as the ReplayGain for that MP3, regardless of whether or not it has been gained by MP3Gain?

[saratoga]

Thanks for your help.
So if those APE fields appeared in the ID3 tag with the same field names, then Rockbox would use this as the ReplayGain for that MP3, regardless of whether or not it has been gained by MP3Gain?

APE anything on MP3 is always ignored.  Replaygain tags in ID3v2 are used if you've enabled replaygain.  Simple as that.