Multi channel audio problem

[hELLO wORLD]

Hi,

I am using VLC 0.8.2 on Mac OS X, but I think the problem is not platform specific.

I have encoded a movie in H264, and sound is in AAC 5.1. All of that is inside a .mov file container.

In Quictime, audio channels are correctly setup (L R SL SR LFE SUB channels), but when I am playing the file with VLC, channels are not sent to their right places, center is sent to right, etc…
Is there a way to have VLC sending correct channels using QT info ?

If not, the suggestion would be to add an audio filter to VLC to manually assign audio channels to audio channels outputs. It should not be too hard, is it ?

I have a M-Audio Sonica Theater as audio device, but the problem does not come from this I think.


I have an other probem, but not related to audio : this H264 file was produced by ffmpegX (mencoder engine) and was originally a .h264 file. This file is unreadable in Quicktime (blank), but readable by VLC. However, if I try to change manually the position in the movie, or if I try to fast forward, VLC is crashing. Any idea on what is this problem, and how to fix this ?

[The DJ]

Please read the README.MacOSX.rtf of the 0.8.2 release.

[hELLO wORLD]

Please read the README.MacOSX.rtf of the 0.8.2 release.

Well, thank you for that trick, but it does not change my problem.
With your trick, now Quicktime plays in 5.1 with the correct channels, but VLC still send channels to the wrong place.

I can temporarily correct the problem by allocation wrong channels to wrong speakers to restablish the correct setup, but only VLC is affected… Quicktime sends right channels to right speakers.
I have tried both Coreaudio output and HAL audiounit output in VLC…

VLC sends 5.1 to 6 channels, but wrong places

Si I renew my demand :
I suppose it is a bug in VLC that is not allocating the right channel to the right coreaudio channel with AAC 5.1 (I have tried other AAC 5.1 files).
In Quicktime pro, if I change the channels into the movie properties by assigning Left to LFE for exemple, it changes nothing in VLC playback.

So… could you correct this for futures releases, or at least add a way to manually dispatch channels for the VLC audio output ?

An other thing, when I play a DVD with VLC, channels are on the right place, so this confirms it is not a general VLC-Coreaudio bug, but more still a multichannelAAC-VLC bug.

Thanks

[The DJ]

I missed the .aac part.
Could you make a file with a multichannel aac sample available online, or upload it to:

ftp://streams.videolan.org/incoming


Thank you.

[hELLO wORLD]

I missed the .aac part.
Could you make a file with a multichannel aac sample available online, or upload it to:

ftp://streams.videolan.org/incoming


Thank you.

I have made a test file.
I have uploaded it, file name is "AAC51 PROBLEM UPLOAD.zip"

Hope you will be able to fix this easily. Please send news on your progress in this topic if you have the time

[hELLO wORLD]

Well, any new on the problem ?

Is the file I have uploaded useful for you ?


Regards.

[The DJ]

Basically, the file contains a "channel order" atom, which is something we currently don' support yet. If you put the channels in the default AAC order, instead of a custom QT defined order, then it should work just fine.

[hELLO wORLD]

Basically, the file contains a "channel order" atom, which is something we currently don' support yet. If you put the channels in the default AAC order, instead of a custom QT defined order, then it should work just fine.

Well, thank you, but… how can I reorder the channels ?

I cannot choose how the channels are stored in the file in Quicktime, I can only assign a channel to a track…

[hELLO wORLD]

Hi,

Nobody knows an easy way to reorder AAC channels in .mov file ?
What DJ says is that in QT Pro, when we reorder channels, it does not physically reorder channels in the file, but only a "channel order" atom.

Is there a software to edit how channels are stored in such a file ? ffmpegX seems unable to read multichannel AAC in a .mov file.

Will VLC be able to read the "channel order atom" in a future release ? Could it be soon, or is this too complex to implement it in next releases ?

And as I said in my firsts posts, as an idea, could it be possible for someone to develop an audio filter that could permit to reorder VLC audio channels outputs, for exemple a sort of mixer that could also be able solo or mute, assign audio channels from the input (the file or an input stream) to the output (local computer A/V devices, output stream or file). This sort of feature could be useful for multiple purposes and would offer a lot of flexibility.

[larryy]

A bit late in coming, but apparently this multichannel audio problem has been around for a long time. I have successfully got VLC 1.1.12 to 2.0.5 multi-channel audio to work correctly using the instructions written up here:
http://forums.macrumors.com/showthread.php?t=1314744
HTH

- larryy