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ReplayGain track-modification forensics, How can you tell which level (Album or Track) was used to modify data?
mcow
post Jul 5 2011, 17:42
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The majority of my collection is in FLAC. However, I find some older CDs to be mixed so low that I want ReplayGain adjustment. It seems that MediaMonkey doesn't apply ReplayGain to FLAC playback, and I'm fine converting these to MP3 anyway since I feel the adjustment overpowers the benefit of lossless playback. For purposes of syncing to a portable, I'd just as soon these MP3s had the track data altered, rather than hoping the player supports ReplayGain.

In MM, when you convert FLAC to MP3, you can opt to apply ReplayGain in the conversion, and that's what I've been doing. However, the options for this are unclear as to whether the Album or Track Gain values are used in the conversion (I prefer Album). I've asked on the forums there, and gotten no satisfactory response; a developer stated that Album Gain was used if the field was available, but that was for automatic conversion when syncing to a device, and my followup request for clarification was ignored.

I tried analyzing the albums, then deleting the Track Gain tag, but during subsequent conversion MM re-filled in the Track Gain fields track by track. This implies to me that it's converting using Track Gain.

I would like to know if there's a way to tell for sure which level was used?

One thought I had was to re-analyze the converted MP3s, to see what gain levels were suggested. My expectation was that either the Album Gain field or the Track Gain field would consistently read 0.0dB, but neither did; instead, each set of levels on the re-analysis came out somewhat lower; not by a particular offset or ratio, however: both the deltas and the ratios of the new levels compared to the old levels were inconsistent at the track level. (I'm not claiming that either deltas or ratios should be identical, but the details of the math are beyond me.)
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2Bdecided
post Jul 27 2011, 11:32
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ReplayGain developer


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You can always apply RG to FLAC if you want. In fb2k you to a FLAC>FLAC transcode (which would be lossless by itself) and apply ReplayGain as a DSP while you're doing it. Not sure about media monkey.

If you apply RG to mp3s, the result is only correct to the nearest 1.5dB - that's the granularity of the globalgain field in the mp3 format. That's why neither ReplayGain value is 0dB when you try to re-calculate.

Hope this helps.

Cheers,
David.
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