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stormy
2007-06-10, 03:06
Hi,

I notice the SB3 has lots of options for Volume Adjustment which rely on the data supplying "gain" infomation.

The trouble is I have bolted my SB3 onto an existing collection of music in MP3, OGG, and Flac.

The collection for me is large (about 6000 tracks) which maybe to others here isnt huge. What I am asking is probably impossible but is there anyway to post-ripping add this information. When playing a random playlist some tracks are blowing the house apart and then others are fairly quiet.

I think its probabaly a no go without manual interaction or having to mess about greatly is it?

I just thought I would ask.

ta

Mike

badbob
2007-06-10, 03:21
Foobar, import collection. Select all, right click, replygain, scan as albums, update. Enable replygain in SS, smart mode.

Mark Lanctot
2007-06-10, 07:15
MP3Gain can also do this and I found the UI to be simpler. Use the analysis button only, do not use the gain button or it will modify the file's volume.

MelonMonkey
2007-06-10, 08:13
Anyone know of a tool that will do this (analyze and modify only gain metadata) for Mac OS?

stormy
2007-06-10, 10:16
Foobar, import collection. Select all, right click, replygain, scan as albums, update. Enable replygain in SS, smart mode.

Thanks, I will give it ago. I have foobar somewhere.. Is there an "import collection" option or just a case of selecting my music directory that I use for SB/SS? :) Does this damage the quality in anyway by transcoding or sth? What does it actually do?

edit, awesome! Works a treat! Thanks :)


MP3Gain can also do this and I found the UI to be simpler. Use the analysis button only, do not use the gain button or it will modify the file's volume.

Will check this out too, thanks.

ta,

Mike

MelonMonkey
2007-06-10, 12:18
Here's a good source for information on Replay Gain, including links to a number of programs for various operating systems that can generate the metadata.

http://en.wikipedia.org/wiki/Replay_Gain

For Mac OS, iVolume can be used to create track or album-based Replay Gain data inside the iTunes-proprietary "Sound Check" tag, "ITUNNORM" - SlimServer will read this tag to apply the volume adjustments.

http://www.mani.de/en/software/macosx/ivolume/ (download and try for free, full license $15)

Hercules
2007-06-10, 13:57
Foobar, import collection. Select all, right click, replygain, scan as albums, update. Enable replygain in SS, smart mode.

I've found that if I do that I don't get a consistent album gain value for things like mix albums when there will (usually) be a different artist for each track.

Or maybe I just have my tags wrong!

badbob
2007-06-10, 14:21
I've found that if I do that I don't get a consistent album gain value for things like mix albums when there will (usually) be a different artist for each track.

Or maybe I just have my tags wrong!

If you mean "live" albums or those like Enigma, I have no such problems. If you replaygain to "album" then it'll keep each album to a specific gain, so it won't differ in volume per track. You then use smart mode in slimserver. If you use track it'll change per track, which you don't want.


Does this damage the quality in anyway by transcoding or sth? What does it actually do?

Nope it doesn't alter the actual gain of the track, it just adds a replygain comment in the file, so if you have a compatible player (winamp, slimserver) it'll then apply a gain or cut. I'm not sure what replygain "calibrates all files" to, but it works. If you disable replaygain in slimserver/player, it'll just ignore the replaygain tag level and it'll just play as normal (different levels per album)

slimkid
2007-06-10, 16:42
What puzzled me always is how does SB apply positive gain, assuming that the volume is already at its max?

Club1820
2007-06-10, 19:22
Foobar, import collection. Select all, right click, replygain, scan as albums, update. Enable replygain in SS, smart mode.

There are two options when you right-click: "Scan selection as single album" or "Scan selection as Albums (by tags)". Which should I use?

Thanks!

badbob
2007-06-11, 02:32
There are two options when you right-click: "Scan selection as single album" or "Scan selection as Albums (by tags)". Which should I use?

Thanks!

Depends. If you're got a single album in Foobar, select "Scan selection as single album"

If you've got 2 or more albums select "Scan selection as Albums (by tags)"

And remember if you select the wrong one, it doesn't matter! Just re-scan/re-update the files. Replygain is non destructive to the actual file.

Mark Lanctot
2007-06-11, 06:56
What puzzled me always is how does SB apply positive gain, assuming that the volume is already at its max?

Apparently it sends a scaling factor to the processor.

It doesn't matter much - you won't see positive gain on 99% of CDs made in the past 15 years because of the loudness wars.

Skittler
2007-06-11, 12:33
How long should Foobar2000 take to analyse and apply Replay Gain to a typical length album (in FLAC format)?

slimkid
2007-06-11, 12:44
Apparently it sends a scaling factor to the processor.

It doesn't matter much - you won't see positive gain on 99% of CDs made in the past 15 years because of the loudness wars.

Well, it does matter to me. I'd like to know how does SB process positive gain if the digital voulme is at its max already. Boosting analog output?

Mark Lanctot
2007-06-11, 13:03
Well, it does matter to me. I'd like to know how does SB process positive gain if the digital voulme is at its max already. Boosting analog output?

I'm not sure - again, the only response I got was that it uses a "scaling factor". There is actually a lot of room here - the RG standard is 89 dB. If you have a positive RG value, that indicates the CD is less than that. However most CDs these days have -10 dB RG values, so a raw CD without any ReplayGain applied to it will be ~99 dB. A Squeezebox can play such CDs just fine, although there will be clipping but that's been applied right at the master.

Take a look at your ReplayGain values. Probably less than 5% are positive.

Club1820
2007-06-11, 14:16
Depends. If you're got a single album in Foobar, select "Scan selection as single album"

If you've got 2 or more albums select "Scan selection as Albums (by tags)"

And remember if you select the wrong one, it doesn't matter! Just re-scan/re-update the files. Replygain is non destructive to the actual file.

Well, I have some of my library set up as Album Folders, but the majority of folders are set up by Genre. With most of those tunes not having the Album field in the Tag populated.

Before I read your response, I went ahead and selected "scan selection as one album" after highlighting the main music folder.

So what will do end up doing? Will I have to redo it?

badbob
2007-06-11, 15:49
hmm if the tag comment for "album" is missing then it won't correctly scan each album for a set amount of gain. I think you're going to have to correctly tag your albums.

Club1820
2007-06-11, 17:56
Well, unfortunately I dont know the albums for most of my tunes. I don't really have "whole" albums, but mostly singles and remixes of songs.

slimkid
2007-06-11, 18:04
Take a look at your ReplayGain values. Probably less than 5% are positive.

Actually, I don't care for RG itself - I don't use it. However, I was hoping to use RG for level matching of different sources to be able to do DBT with equal levels. That's why I need to know if increasing RG will influence the sound in any negative way, other increasing the 'loudness'.

MelonMonkey
2007-06-11, 20:55
I need to know if increasing RG will influence the sound in any negative way, other increasing the 'loudness'.

Sure it "can." You gain up too much and you're going to clip. Some of the programs linked on the Wikipedia page I mentioned allow manual input of the reference level. And iVolume (which I mentioned for the Mac) starts with a setting of 92db.

cliveb
2007-06-12, 00:27
Well, it does matter to me. I'd like to know how does SB process positive gain if the digital voulme is at its max already. Boosting analog output?
Replaygain includes "peak" tags as well as "gain" tags. The peak tag simply defines what the peak level in the file is. When a Replaygain capable playback device plays a file with a positive gain tag, it may (should?) take notice of the peak tag and scale back the volume increase if that would cause clipping. But I don't know whether the Squeezebox does this - I'll try an experiment and report back.

cliveb
2007-06-12, 02:35
... But I don't know whether the Squeezebox does this - I'll try an experiment and report back.
OK, I've done a quick experiment. I prepared a short FLAC file with a deliberately low average volume and with a short section that peaks at 0dB. (The Replaygain value for this file is +20.18dB, and it includes the necessary peak tags as well). Playing this file through Foobar2000 (with the appropriate options active) demonstrated that the gain is scaled back to avoid clipping.

Playing it through an SB2 (firmware version 69) resulted in clipping. I therefore downloaded the latest Slimserver (6.5.2-12047) to check this had not changed. The clipping still happens with firmware version 81. Therefore we can conclude that the Squeezebox does NOT take notice of the Replaygain peak tags. I also tried reducing the SB2 volume to 2 (out of 100, which means it is at about -49dB). The clipping still occured. Therefore we can also conclude that the Replaygain adjustment is applied to the raw data stream before the digital volume control is applied.

(I did not try the test on my Transporter, as I didn't want to risk the possible consequences of extreme clipping on my main speakers).

I think that the way it should work is as follows:

1. Certainly, the peak tag should be honoured so that clipping cannot be introduced. The fact that it is not should be considered a bug.

2. A "nice to have" would be for the digital volume control setting to be considered in the calculation. For example, suppose the Replaygain value for a track is +6dB and the peak value is 0dB. A simplistic honouring of the peak tag would result in no gain being applied. But if the Squeezebox's digital volume control is currently set to -6dB, then the overall volume could be set to 0dB, thus achieving the desired loudness equalisation. (And if the SB volume is set to -9dB, the overall volume should be -3dB, etc). Of course, this refinement should only happen if the digital output is set as variable.

I've searched Bugzilla looking to see if this has already been reported, and couldn't find it. But before I do add a bug report, I'd like to hear the views of others.