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Topic: Replay Gain tagging (Read 29180 times) previous topic - next topic
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Replay Gain tagging

Reply #50 –
Quote from: Lear on
But RGAD is obsolete, as it doesn't contain peak album amplitude.

This was also the case with the original Vorbis comment format. This situation prompts a question for me. What are players supposed to do with album peak amplitude information?

Clearly, peak level allows you to predict whether clipping will occur. The Replay Gain proposal suggests that you use that information to either activate a limiter or lower the gain below target. The proposal doesn't say whether you do this on an album basis or a track basis. The new specification needs to address this.

When in album playback mode, do we always want to do clipping prevention based on album peak level? If we're actually playing the album, ideally we might want to. What if we're only playing a portion of the album? What if we're playing several albums back-to-back?

Does anyone bother to switch modes dependent on how they're using the player? Is there a way players could automatically choose the best mode? I personally use album playback mode full time. I find it works well even in shuffle play - a track that was intended to be quieter in the context of an album usually sounds better played more quietly in the context of a playlist. With the way I use album playback mode, I would prefer that clipping prevention be based on track peak levels, not on album peak levels.

Replay Gain tagging

Reply #51 –
Quote from: singlethread on
Example: I have in the past tried to use mp3gain to add ReplayGain tags to audio files, naively expecting that ReplayGain-enabled players would automatically use that information. That did not work, of course, because mp3gain created APE tags which were not supported by Quod Libet.


QL includes a plugin for converting APE tags to id3v2.4 tags (RVA2 in this case).

Replay Gain tagging

Reply #52 –
Quote from: Notat on
What are players supposed to do with album peak amplitude information?


I'd say not confuse users. Default: album gain => album peak, track gain => track peak. Optionally allow all combinations through advanced options.

Replay Gain tagging

Reply #53 –
In my opinion, the available options for tagging containers should be evaluated with respect to how well they would support future extensions of the standard. I'm thinking about more advanced, especially gated, scanning methods, which shouldn't break legacy devices, but could improve results for modern players. Any methods for which such future extension would be a PITA should be marked as deprecated. There should also not be more than one recommended method per file format. Existing files can always be rescanned and tagged. That's not nice, but in the long term the price of carrying the ballast of multiple formats forever would be higher.

Replay Gain tagging

Reply #54 –
Quote from: googlebot on
I'd say not confuse users. Default: album gain => album peak, track gain => track peak. Optionally allow all combinations through advanced options.

I don't see this as a user issue. It is a player developer issue. Even advanced users should not be confronted with these design decisions. Are we concerned about confusing developers?

It seems like there's nothing preventing us from choosing the best technical solution and documenting it carefully. I should reiterate that the RG proposal doesn't include a concept of album peak. I don't know if this was an intentional or unintentional omission. In any case, album peak is in use and the new RG specification probably needs to describe how to calculate it and what a player do with it.

Replay Gain tagging

Reply #55 –
Album peak is required if you want to guarantee both during album gain playback: 1. Neither clipping nor limiting 2. 100% correct relative loudness. Without album peak information you either have to sacrifice 1 or 2.

So if album peak information is available AND playback is set to album mode AND clipping prevention is set to "audiophile", then album peak should be used to lower the gain of any track relative to the whole album. In all other cases limiting and track gain should be the best trade-off, respectively track peak based scaling during "audiophile" track mode playback.

Replay Gain tagging

Reply #56 –
That's an accurate but incomplete summary. There are two adverse effects of using album peak: 1/ Greater chance of inconsistent loudness album to album. 2/ Unnecessary gain reductions when using album mode for general playlist or shuffle playback.

Replay Gain tagging

Reply #57 –
Quote from: Notat on
Quote from: Lear on
But RGAD is obsolete, as it doesn't contain peak album amplitude.

This was also the case with the original Vorbis comment format. This situation prompts a question for me. What are players supposed to do with album peak amplitude information?

Some history: Album peak was first discussed here. Then 2Bdecided mentioned some things to improve in the ReplayGain spec, and one thing was the addition of album peak.

Quote
Does anyone bother to switch modes dependent on how they're using the player?

I do, sort of. I've set Rockbox to use track gain when shuffle is on, album gain otherwise. When shuffling, album gain can make the volume a bit low for my taste on some tracks (from loud rock albums).

Replay Gain tagging

Reply #58 –
I've put some more work into the Metadata and Metadata format sections of the specification draft.

I'm not yet happy with the quality of the Metadata section. I'll have another look at it later with fresh eyes. If anyone else wants to try and help me untangle this section, I'd appreciate it.

I've added a comprehensive list of audio file formats to the Metadata format section. Each file type then supports zero one or more metadata formats. Please have a look at this list and heple ne fill in any missing information, let me know if I've missed any important formats or if any that I have included are not worthy of mention. It's a zoo out there!

Finally, I've concluded that three metadata formats are worthy of recommendation by new ReplayGain implementations: ID3v2, Vorbis comments and APEv2. Actually I'm not entirely convinced of that last one because it seems that every file format I found that supports APEv2 also supports ID3v2. So, convince me...

I have not yet composed descriptions of how ReplayGain uses the three metadata formats. I plan to document the TXXX method for IDv3. The RGAD method will be documented as historical in an appendix. Vorbis comments use "REPLAYGAIN_" tags. Former "RG_" tags will be in the appendix.

Replay Gain tagging

Reply #59 –
Quote from: Notat on
Finally, I've concluded that three metadata formats are worthy of recommendation by new ReplayGain implementations: ID3v2, Vorbis comments and APEv2. Actually I'm not entirely convinced of that last one because it seems that every file format I found that supports APEv2 also supports ID3v2. So, convince me...


WavPack only supports ID3v1 and APEv2 (according to wavpack.com). Does APE really support ID3v2? Rockbox only supports APEv2 for APE... So yes, APEv2 is needed.

And ID3v2 isn't used for MP4, it has its own format.

Replay Gain tagging

Reply #60 –
I have completed editing the metadata section of the specification. Please have a look and see if you can suggest or make any improvements.

One question I had was about various flag values for APEv2. I could not find any explanation for how the header and footer related tage are to be used. I'm also unsure whether to recommend that the tags be written with read-only or read-write attribute.