Re: [Bug-gnupod] Patch to support ReplayGain / mp3gain

[H. Langos]

On Sat, May 09, 2009 at 12:13:01PM +0200, Richard van den Berg wrote:
> On 5/9/09 9:14 AM, Frank Blendinger wrote:
>> I'll talk to the mpd developers to see if they are willing to support
>> RVA2/RGAD and/or APE tags.
>
> I used mpd before switching to a Squeezebox. IIRC it is written in perl.  
> If they are using MP3::Info adding APE support is easy; just add an  
> extra option to the get_mp3tag() call.

mpd is written in C.
It already has APE tag support but I don't know if that support is 
limited to certain file formats.

>> Do I understand you correctly that this could lead to have two gain
>> values added on top of each other? I don't think you'd want that...
>>   
...
>
>> I think this would destroy the whole "have all songs at the same average
>> volume level" concept, when you apply something else on top of the
>> ReplayGain data.
>>   
>
> I agree, and I think Apple implemented it this way because Sound Check  
> uses a crappy algorithm. When you use Replay Gain there is really no  
> need for manual adjustments or combining the values.

I guess we should go this way:

1. Use RVA2/XRVA or (if the former is missing) REPLAY_GAIN_x to compute a
   new "soundcheck" value. 

If the first step didn't yield any information: 
2. Use iTunNORM's "soundcheck" value and RVA "volume" adjustment.

This would probably work for most people.

>> At least according to the mpd guys, those TXXX tags are quite common, so
>> it might help some people if those are supported in gnupod. Personally,
>> I'm going to keep the APE tags on my files, so I don't care that much.
>>   
>
> I just checked and MP3::Info returns each TXXX tag as an individual  
> value (not a hash). So TXXX:replaygain_track_gain="-2 dB" becomes  
> $hs{REPLAYGAIN_TRACK_GAIN}="-2 dB". This means the TXXX tags overwrite  
> the APE ReplayGain tags by default. I just tested this, and it works;  
> when ReplayGain data is set differently in the APE tag and TXXX tag, the  
> TXXX is used by gnupod. Sweet.

Great. Did you check if that works with the parameters that FileMagic.pm uses
for its get_mp3tag() call?

cheers
-henrik