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Author Topic: Longstanding ReplayGain tag issue during handheld conversion  (Read 2359 times)

BryanC

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Longstanding ReplayGain tag issue during handheld conversion
« on: April 15, 2014, 05:04:54 pm »

I've had this problem for about 4 or 5 years now, but today was the first day I procrastinated long enough to figure out what was going on.

I occasionally noticed that certain songs on my rockbox'd Sansa Clip Zip with track-level replaygain enabled would be significantly quieter than the rest.

To sum up a long story, the replaygain tags are not added correctly to tracks that are converted (in my case, from FLAC) to mp3 during handheld sync. After I sync the Clip Zip and open the tracks on the player using foobar2000's tag editor, all of the songs that have been converted during the sync process are missing the replaygain_track_gain tag that foobar2000 (and I assume Rockbox) uses to grab replaygain info. However, all of the metadata volume tags that MC writes, such as VOLUME LEVEL (REPLAYGAIN) are present in all of the files. So it seems that the following tags are not copied to the converted track during handheld sync even though they are created correctly for the original files via MC's audio analysis:

replaygain_track_gain
replaygain_track_peak
replaygain_album_gain
replaygain_album_peak

It appears that rockbox uses these tags for replaygain info and not the:

VOLUME LEVEL (REPLAYGAIN)

tag that is correctly written to the converted file.

You can see in the attached photo the tag properties of two songs on my Sansa Clip. The song on the left was synced as an mp3 and the song on the right was converted from flac to mp3 during the handheld sync. The replaygain tags are not present in the converted song.
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mwillems

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Re: Longstanding ReplayGain tag issue during handheld conversion
« Reply #1 on: April 18, 2014, 06:16:39 pm »

I've had this problem for about 4 or 5 years now, but today was the first day I procrastinated long enough to figure out what was going on.

I occasionally noticed that certain songs on my rockbox'd Sansa Clip Zip with track-level replaygain enabled would be significantly quieter than the rest.

To sum up a long story, the replaygain tags are not added correctly to tracks that are converted (in my case, from FLAC) to mp3 during handheld sync. After I sync the Clip Zip and open the tracks on the player using foobar2000's tag editor, all of the songs that have been converted during the sync process are missing the replaygain_track_gain tag that foobar2000 (and I assume Rockbox) uses to grab replaygain info. However, all of the metadata volume tags that MC writes, such as VOLUME LEVEL (REPLAYGAIN) are present in all of the files. So it seems that the following tags are not copied to the converted track during handheld sync even though they are created correctly for the original files via MC's audio analysis:

replaygain_track_gain
replaygain_track_peak
replaygain_album_gain
replaygain_album_peak

It appears that rockbox uses these tags for replaygain info and not the:

VOLUME LEVEL (REPLAYGAIN)

tag that is correctly written to the converted file.

You can see in the attached photo the tag properties of two songs on my Sansa Clip. The song on the left was synced as an mp3 and the song on the right was converted from flac to mp3 during the handheld sync. The replaygain tags are not present in the converted song.


+1

I just spent most of the afternoon trying to figure out why album-based replay gain wasn't working on my android device, and just happened across this thread, and sure enough, when I checked the converted files I synced to my device the four "regular" replaygain tags were blank.  Most 3rd party software (in my case the poweramp app for android) uses those tags to pick up the replaygain values, rather than volume level (replay gain).

At least I'm not going crazy   ;)

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Hendrik

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Re: Longstanding ReplayGain tag issue during handheld conversion
« Reply #2 on: April 22, 2014, 02:15:21 am »

In a future build:
Fixed: ReplayGain tags were not properly written to MP3 files during audio conversion.

One limitation though, right now we only have track gain and peak, since MC doesn't have a field for album gain (its computed on the fly).
Maybe we can add that back in the future some day.
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BryanC

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Re: Longstanding ReplayGain tag issue during handheld conversion
« Reply #3 on: April 22, 2014, 10:03:25 am »

In a future build:
Fixed: ReplayGain tags were not properly written to MP3 files during audio conversion.

One limitation though, right now we only have track gain and peak, since MC doesn't have a field for album gain (its computed on the fly).
Maybe we can add that back in the future some day.

Excellent! Thank you!
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6233638

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Re: Longstanding ReplayGain tag issue during handheld conversion
« Reply #4 on: April 22, 2014, 10:45:50 am »

Something else which needs to be considered:
 
Does Media Center reduce the gain when encoding to lossy files? This is usually required to prevent clipping.
 
Whether it does or not, don't the converted files need to be re-analyzed for accurate information anyway?
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Hendrik

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Re: Longstanding ReplayGain tag issue during handheld conversion
« Reply #5 on: April 22, 2014, 11:06:27 am »

On-the-fly conversions for Handhelps simply copy the tags from the original, and while lossy compressions can slightly modify the value, it will generally stay in the same area, so that these values are accurate enough for a low-quality encode of the audio.
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yonkiman

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Re: Longstanding ReplayGain tag issue during handheld conversion
« Reply #6 on: May 29, 2014, 07:11:11 am »

In a future build:
Fixed: ReplayGain tags were not properly written to MP3 files during audio conversion.

One limitation though, right now we only have track gain and peak, since MC doesn't have a field for album gain (its computed on the fly).
Maybe we can add that back in the future some day.

Would be nice - I've been asking for this for years now, for the same reason the OP asked...  It's the only audio feature MC is missing as far as my usage goes, but it's a big one.  If it gets addressed I'll upgrade from MC16 in a heartbeat.

-Fred
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