Volume too quiet playing 24-bit FLAC (VLC 0.8.5, OSX)

[jt]

Volume of playing 24-bit flac is much lower (barely audible) relative to playing other files, including 16-bit flacs, 16 or 24-bit wavs, mp3, etc.

I first noticed the problem with 24/96 flacs. Cross testing to 16/96 and 24/48 flacs (of an identical sound) shows the problem to be specific to 24-bit (ie. the 16/96 flac plays at correct volume, the 24/48 flac is barely audible like the 24/96).

This is on (VLC 0.8.5, OS X 10.4.6) using 24/96 sound hardware for output.

In sum: playing flacs from a 16-bit source sounds great; from a 24-bit source they are barely audible.

-jt

[Peter keller]

I'm finding the same with 24/96 flac's (originally showed up in Songbird, but turns out to be a VLC problem). Was a bug ever filed for this? I had a quick look on Trac but couldn't find anything.

Regards,
P.

[Jean-Baptiste Kempf]

I don't think there has been a bug filled with this one. But have you tried the development version (NB)?

[Peter keller]

OK - I've tried trunk-intel-20070730-2013.dmg, and the problem is still there (this is on a MacBook Pro running OS X 10.4.10).

A bit more digging in Trac has turned up this: https://trac.videolan.org/vlc/ticket/600 . If I have understood this ticket correctly, the problem with playing 24-bit flac's has been known about for ages, but has got mixed up with an issue over ordering multiple channels in the flac format. I'm a bit puzzled about why problems with 5.1 channel flacs should stop 24-bit, 2-channel audio from being supported. In any case, the channel order does seem to me to be defined in the flac frame header now (see http://flac.sourceforge.net/format.html#frame_header):

Channel assignment
0000-0111 : (number of independent channels)-1. Where defined, the channel order follows SMPTE/ITU-R recommendations. The assignments are as follows:
1 channel: mono
2 channels: left, right
3 channels: left, right, center
4 channels: left, right, back left, back right
5 channels: left, right, center, back/surround left, back/surround right
6 channels: left, right, center, LFE, back/surround left, back/surround right
7 channels: not defined
8 channels: not defined
1000 : left/side stereo: channel 0 is the left channel, channel 1 is the side(difference) channel
1001 : right/side stereo: channel 0 is the side(difference) channel, channel 1 is the right channel
1010 : mid/side stereo: channel 0 is the mid(average) channel, channel 1 is the side(difference) channel
1011-1111 : reserved

What is the best way to raise the priority of fixing the 24-bit flac issue, and attach it to an earlier milestone than bugs paradize? Shall I submit a new ticket and upload some samples, or could the development team re-prioritise ticket 600?

Regards,
P.

[Jean-Baptiste Kempf]

samples and description of the problem would help, yes. ftp://streams.videolan.org

[CloudStalker]

I'll file the bug if necessary. I've had the same problem as well, also with the latest nightly build. I do a lot of audio encoding and want to be able to use 24bit FLAC. I've also noticed this behavior awhile ago but that was before I knew how to file tickets.

[Peter keller]

@CloudStalker: thanks, if you could that would be an enormous help (I've registered on the VLC Trac, but haven't managed to get my account validated to create tickets yet). I've uploaded some samples at ftp://streams.videolan.org/incoming/FlacAttenuation (24-bit/96kHz and 16-bit/44.1kHz in both Wave and FLAC, all created by exporting from Audacity 1.3.3).

I have tested this with VLC versions 0.8.6c and trunk-intel-20070730-2013.dmg under OS X 10.4.10, and also with Ubuntu Linux 7.0.4 with the current repository version (0.8.6 I think) running under VMWare Fusion. In all cases, only the 24-bit FLAC plays quietly, the other three samples are fine.

Regards,
P.

[CloudStalker]

if you could that would be an enormous help (I've registered on the VLC Trac, but haven't managed to get my account validated to create tickets yet).

Done. ticket

Btw, PM j-b your username and he'll active you account.

[DGMurdockIII]

has this been fixed i still see the problem when playing 24bit flac