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Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain
From: |
Richard van den Berg |
Subject: |
Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain |
Date: |
Fri, 08 May 2009 16:16:45 +0200 |
User-agent: |
Thunderbird 2.0.0.21 (Macintosh/20090302) |
On 5/8/09 2:26 PM, H. Langos wrote:
Could you send me a sample of an iTunes generated RVA2 tag?
Sure. I'll fire up iTunes later and send it to you privately.
Yeap. And if mp3gain can't be changed to do write RVA2 tags by itself, maybe
there is a way to make mp3gain only do the analysis and pass its result to a
programm that can write those RVA2 tags?
That would be possible using:
$ mp3gain -o -q -s s foo.mp3
File MP3 gain dB gain Max Amplitude Max global_gain Min
global_gain
foo.mp3 -7 -10.500000 38780.534185 255 145
"Album" -7 -10.500000 38780.534185 255 145
Do you know if the author of mp3gain is still active? reachable? alife?
I have no clue.. in the thread from 2004 they mention he was unresponsive.
So how do we get mp3gain's analysis results into RVA2 / XRVA tags?
By changing the mp3gain C code. It's open source after all. I just don't
have the stomach or time for it at the moment. Perhaps using the tagging
code from normalize will make it easier. However, there could be a good
reason not to attempt it. From
http://jwz.livejournal.com/370342.html?thread=4232358#t4232358
Anway, whats not clear to me is if the RVA2 value could be used with
ReplayGain. Both ReplayGain and RVA2 are applied as a constant value
across the complete track, but I'm not sure the units are the same as
the RVA2 tag.
Are you sure about the non desctructivnes of mp3gain?
You can run mp3gain in several modes, either (often reversible) changing
the volume of the file or just tagging it. I use it only for tagging.
From the Debian man page:
mp3gain actually changes your file’s gain only when you use one
of the
options -r, -a, -g, or -l. If none of these options is given,
only a
tag denoting the recommended gain change is written to the file.
If you've got a strong stomach you might want to read the whole
thread: http://jwz.livejournal.com/370342.html
Great read, thanks.
If this is all true, than your patch for gnupod is in vain as the volume
of those files was already changed by mp3gain. Reading the APE tag and
acting on the information would either double the adjustment or cancel
it out, depending on wether mp3gain stores the information on what it
did, or how to undo its action.
Interesting question. Since I only tag my mp3s, and never let anything
change the audio frames, I'm safe no matter what.
The following shows others are too. The ReplayGain APE tags always
contain the dB change needed to get the volume to the reference level.
When mp3gain has altered the file, the RG APE tags will be close(r) to
0. It will also store undo information in the MP3GAIN_UNDO APE tag.
$ cp -p org.mp3 cleaned.mp3
$ mp3gain -s d cleaned.mp3
$ mp3gain -s c cleaned.mp3
cleaned.mp3
$ cp -p cleaned.mp3 altered.mp3
$ mp3gain -r altered.mp3
altered.mp3
Applying mp3 gain change of -7 to altered.mp3...
$ mp3gain -s c altered.mp3
altered.mp3
Recommended "Track" dB change: 0.035000
Recommended "Track" mp3 gain change: 0
Max PCM sample at current gain: 11529.519104
Max mp3 global gain field: 248
Min mp3 global gain field: 138
$ mp3gain tagged.mp3
tagged.mp3
Recommended "Track" dB change: -10.500000
Recommended "Track" mp3 gain change: -7
Max PCM sample at current gain: 38780.534185
Max mp3 global gain field: 255
Min mp3 global gain field: 145
Recommended "Album" dB change for all files: -10.500000
Recommended "Album" mp3 gain change for all files: -7
$ cp -p cleaned.mp3 tagged.mp3
$ mp3gain -s c tagged.mp3
tagged.mp3
Recommended "Track" dB change: -10.500000
Recommended "Track" mp3 gain change: -7
Max PCM sample at current gain: 38780.534784
Max mp3 global gain field: 255
Min mp3 global gain field: 145
$ cp -p altered.mp3 undo.mp3
$ mp3gain -u undo.mp3
Undoing mp3gain changes (7,7) to undo.mp3...
$ mp3gain -s d undo.mp3
$ cmp -l cleaned.mp3 undo.mp3
$
Cheers,
Richard
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, (continued)
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, Richard van den Berg, 2009/05/09
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, H. Langos, 2009/05/09
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, Richard van den Berg, 2009/05/09
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, H. Langos, 2009/05/09
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, H. Langos, 2009/05/12
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, H. Langos, 2009/05/08
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain,
Richard van den Berg <=
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, H. Langos, 2009/05/09
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, Richard van den Berg, 2009/05/09
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, H. Langos, 2009/05/09
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, Richard van den Berg, 2009/05/09
- Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain, H. Langos, 2009/05/09