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

[Frank Blendinger]

Hello Richard.

On Fri 2009-05-08 13:30, Richard van den Berg <address@hidden>
proclaimed:
> On 5/8/09 12:14 PM, Frank Blendinger wrote:
>> You might want to take a look at this python script:
>> http://mpd.wikia.com/wiki/Hack:ape2id3.py
>>
>> It will read the ReplayGain settings from APE tags and add it to ID3v2
>> tags. It has worked without any problems for me so far.
>
> That script seems to create custom TXXX tags. This is not a standard and  
> it surprises me that players support it. I know rockbox (alternative  
> iPod firmware) does as well.

Indeed, it does. I somehow assumed that RVA2/RGAD were used, sorry for
the confusion. The mpd guys actually chose those TXXX tags because
rockbox and some common software player support/create them.

> Besides, I don't need to store the data I already have in APE tags in
> yet another format. This would require me to always run a conversion
> script after I run mp3gain, and I would have to add the script to
> abcde (the ripper script I use) as well.

While the thought of having that data stored redundantly in different
tags really annoys me, I guess this is just what I will have to do, as I
want have RG support on both mpd and my iPod.

I'll talk to the mpd developers to see if they are willing to support
RVA2/RGAD and/or APE tags. There was a feature request for APE tags, but
IIRC that was pretty much ignored. I sort of can understand that, it
personally don't see the point in having a different tagging system when
there is already ID3v2 which has all tags one could every want. People
just would have to support those.


>> So how will gnupod handle this? I suppose the iPod will just use
>> iTunNORM and ignore anything else. Will gnupod use a present iTunNORM
>> comment or will it always create one from ID3v2/APE information?
>
> The patch I created will favor ReplayGain info found in an APE tag over  
> iTunNORM since RG is a superior algorithm. RVA2 tags are converted to  
> the iTunesDB volume value when "--max-vol-adj" is used with  
> gnupod_addsong.pl. It is combined with normalization info (if also  
> present) when Sound Check is enabled on the iPod.
> [...]
> One of the problems is that normalization data like RG APE tags and
> iTunNORM comments is sometimes combined with RVA2 volume information.
> iTunes is one of the software that does this, and SqueezeCenter also
> combines the tags (but there is some debate to change that). So
> favoring RVA2 over RG info should really be selectable by the user.
> As explained above, iPods will combine the two when both are present
> in the iTunesDB and Sound Check is enabled.

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.

To have only ReplayGain and nothing else applied in the iPod, I will
have to not use the --max-vol-adj parameter and not use Sound Check,
right?


>> What will be used if both ID3v2 and APE is present? I read about a
>> (possible?) --ignore-ape option, but I didn't really get what the
>> default behaviour will be. 
>
> The new default behavior will be to read APE tags, including ReplayGain  
> information. ID3 tags with the same name of APE tags will overwrite the  
> APE tags. ID3v2 tags are favored over ID3v1 tags.  Perhaps we should  
> also read TXXX:replaygain_album_gain and TXXX:replaygain_track_gain from  
> ID3v2 tags to replace the respective APE tags.

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.


> [...]
> gnupod_convert_OGG.pl uses Ogg::Vorbis::Header which may or may not  
> support the RG tags. If you send me an ogg file (privately) that  
> contains RG info I can check (and patch gnupod_convert_OGG.pl).

I've sent you a private mail on this, it should be easy to do.


Greetings,
Frank

-- 
Frank Blendinger | fb(at)intoxicatedmind.net | GPG: 0x0BF2FE7A
Fingerprint: BB64 F2B8 DFD8 BF90 0F2E 892B 72CF 7A41 0BF2 FE7A

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