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Old 1st December 2014, 17:53   #21  |  Link
hello_hello
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Quote:
Originally Posted by manolito View Post
@ hello_hello
I think you are confusing ReplayGain with EBU R128 a little bit...
Not too much.....

Quote:
Originally Posted by manolito View Post
When you are talking abut the foobar2000 ReplayGain using the EBU R128 method for scanning, I believe this is the wrong term. If loudness scanning is done using EBU R128, then it is NOT ReplayGain any more. I would call it EBU R128 with a different reference level (e.g. -18 LUFS instead of the standard -23 LUFS).
Foobar2000 definitely uses the EBU R128 method for ReplayGain scanning, but the result isn't a lot different most of the time, so in that respect how you describe it is probably semantics. It's the target volume of 89dB or -18 LUFS which makes it ReplayGain, in my opinion. If the two scanning methods always produced dramatically difference loudness results, that'd be a different story, but mostly they don't seem to. Apparently EBU R128 is supposed to be a little more accurate. I don't know, so I won't argue with that.

http://www.foobar2000.org/changelog
1.1.6
ReplayGain scanner now uses libebur128 for improved accuracy.

https://github.com/jiixyj/libebur128
libebur128 is a library that implements the EBU R 128 standard for loudness normalisation.

https://github.com/jiixyj/loudness-scanner
Usage
The scanner also supports ReplayGain tagging.
The reference volume is -18 LUFS (5 dB louder than the EBU R128 reference level of -23 LUFS).


http://en.wikipedia.org/wiki/ReplayGain#Scanners
foobar2000: Generates metadata through included plugin using EBU R128 (but at old 89dB levels) for all supported tag formats.

Quote:
Originally Posted by manolito View Post
Both ReplayGain and EBU R128 establish a method for loudness scanning, plus they establish a reference loudness level. These two things are independent of each other. You can use ReplayGain scanning and set a reference level different from the standard 89 dB, and you can use EBU R128 scanning and also set a different reference level.
Well.....
If you scan with ReplayGain the tags saved will (should) always specify any volume change required to achieve the 89dB target volume. It couldn't work any other way. ReplayGain tagging can only work if the reference level is always the same.
Yes, some programs let you change the ReplayGain target volume and they'll use that target volume when converting etc, but they'll always write a tag relative to 89dB. Take a file that's already at the 89dB target volume. Scan it with ReplayGain while changing the target volume to 83dB, then convert it using the 83dB target volume. Any ReplayGain tag written will be +6dB. If there's no ReplayGain tag, well it's no longer ReplayGain, you've just used it's scanning to adjust the volume to some indiscriminate level.
Even if the playback device lets you change the target playback level it still needs ReplayGain tags relative to 89dB as a point of reference. If a program writes tags relative to some other reference level I can't see how that'd be anything but silly.

In respect to the discussion in this thread, ReplayGain and EBU R128 both have the same goal. ie to determine how loud the audio sounds. They mostly don't seem to disagree by much.
As an experiment I tried some movie audio (Jurassic Park). I downmixed to stereo, normalised and converted to MP3 so I could scan with MP3Gain. I also scanned the MP3 with foobar2000.
Mp3Gain/ReplayGain said it's "Track Gain" is +5.33dB (so it's level would need to be increased by 5.33dB on playback to achieve the 89dB target volume). Foobar2000/EBU R128 says it's +5.62dB.

Quote:
Originally Posted by manolito View Post
For my plugin which covers only DVD creation it makes total sense to use the EBU R128 scanning method, but employ a higher reference level like -18 LUFS. Most people seem to agree hat the EBU scanning method delivers more consistent results than the ReplayGain method, and it handles 6-ch audio which ReplayGain does not.
I'd agree in respect to scanning 6ch audio, but probably not when it comes to using a higher reference level such as -18 LUFS, assuming you're referring to adjusting the audio to that level. Unless I'm completely misunderstanding what the change in reference level would achieve.
That Jurassic Park audio I mentioned earlier.... to hit a target volume of 89dB (-18 LUFS) it needs to be increased by 5.33dB, which can't be done because it's already been normalised. Peaks at maximum, as loud as it gets. In fact after the MP3 was decoded while scanning it, both ReplayGain and EBU R128 agreed the peak level was already just a tad greater than maximum (1.003232 and 1.003263 respectively.... percentage, not dB).

89 - 5.33 = 83.67
The SMPTE reference level of 83dB or R128's -23 LUFS are looking pretty good (assuming 83dB and -23 LUFS are the same target volume).

Quote:
Originally Posted by manolito View Post
For FFmpeg the EBU R128 scanning is totally separate from the following loudness adjustment. You have to do the scanning pass, note the LUFS value, calculate the difference to the desired reference value, and then do a second pass for the loudness correction. The R128Gain software can do it all in one step, using FFmpeg for scanning and either SoX or FFmpeg for the loudness adjustment.
I've never used R128Gain. I assume this is it?
http://r128gain.sourceforge.net
I assume it's one step scan/convert process is really an automated two step process?

A look around the R128Gain site would indicate its kinda ReplayGain with a different name. Same principle, the same sort of tagging, just a different scanning method. Although it appears it does ReplayGain scanning too. I'll definitely have a play with it soon.
I assume it always writes ReplayGain tags relative to -18 LUFS, but what happens in EBU R128 mode in respect to the tags it writes when you change the reference level? Anyway, I'll have a play with it myself tomorrow. I'm keen to check it's EUR128 scan will produce the same result as foobar2000's ReplayGain scan. I assume it will....

Cheers.

Last edited by hello_hello; 1st December 2014 at 18:51.
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