[jimfisheye]

First, only 5.1 files play back correctly. 4.0 and 4.1 settings do nor route the outputs correctly.
Second, it only seems to like running at 96k.

Most surround program is in fact 5.1 files at 96k, 24 bit so this is not a show stopper. If you try to play a 44.1k file you need to leave your system set up for 96k and let core audio upsample the program. This is not ideal for those who are picky about their sample rate conversion or those who strictly forbid that for their sensibilities.
The best workaround is to convert 4.0 or 4.1 to the 5.1 container and to upsample to 96k with your favorite sample rate conversion app. If you use flac encoding, the extra blank tracks will not use much extra space.

5.1 24/96 wav or flac files simply just work. You can send the audio to a firewire or usb audio interface or a surround receiver via HDMI with no issues.

It appears that XBMC is 'hard wired' at 96k regardless of what sample rate you are running your interface and core audio at. When you set everything to 96k, core audio handles the upsample without error. I cannot find any control panel in XBMC to do anything about this.

[garyi]

I think they are working on the audio part to make it bit perfect

[davilla]

First, only 5.1 files play back correctly. 4.0 and 4.1 settings do nor route the outputs correctly.
Second, it only seems to like running at 96k.

Most surround program is in fact 5.1 files at 96k, 24 bit so this is not a show stopper. If you try to play a 44.1k file you need to leave your system set up for 96k and let core audio upsample the program. This is not ideal for those who are picky about their sample rate conversion or those who strictly forbid that for their sensibilities.
The best workaround is to convert 4.0 or 4.1 to the 5.1 container and to upsample to 96k with your favorite sample rate conversion app. If you use flac encoding, the extra blank tracks will not use much extra space.

5.1 24/96 wav or flac files simply just work. You can send the audio to a firewire or usb audio interface or a surround receiver via HDMI with no issues.

It appears that XBMC is 'hard wired' at 96k regardless of what sample rate you are running your interface and core audio at. When you set everything to 96k, core audio handles the upsample without error. I cannot find any control panel in XBMC to do anything about this.

Go play with Audio MIDI Setup.app, it has the final say on how audio is output.

[jimfisheye]

Go play with Audio MIDI Setup.app, it has the final say on how audio is output.

Doesn't matter. The point is XBMC will only run and play audio at 96k.
If I set my system to run at 44.1k you get this chopped up audio effect (like what some hardware DVD players sound like on fast forward). I had a 24/44.1 4.0 flac file I tried to play. First I just suspected trouble with channel assignments. It seemed to be downmixing everything to the front L,R. Changing from 5.1 to 4.0 or 4.1 made no difference. Not sure why I just happened to try playing the 24/44.1 file after setting the system back to 96k (to make sure everything was still working that way) but I did and here I am talking about it. Then I put it into 5.1 format (added blank C & Lf tracks) and channel assignments worked properly again. The bottom line is the only way to play this 24/44.1 4.0 file is to 1st make it 5.1 and then run the system at 96k and make core audio sample rate convert the audio. Not good.

Just to reiterate - I have 24/96 5.1 flac files playing with no issues.

[jimfisheye]

I just verified all this again.
The issue is with the 'analog' audio output option. There is no bug when using the HDMI audio output option. All file formats and sample rates seem to work with HDMI.
With the analog audio output selected:
Files MUST be 5.1. Anything else (eg. 4.0, 4.1) will be downmixed to stereo. Different speaker configuration settings have no effect.
XBMC will only output in 96k regardless of the sample rate of the file. If you use an external audio interface that requires you to set the sample rate manually, you will find you need to set the system at 96k to play anything.

[jimfisheye]

I spoke too soon. This bug can affect HDMI output as well. It looks like this depends on the receiving end of the HDMI cable. I just had a friend with a Harmon Kardon surround receiver verify the bug with HDMI output. Again, the workaround is to only use 5.1 files (not 5.0, 4.0, 4.1, etc).

For example, to play 4.0 program from a DVDA disc:
1. Rip to wav files as normal (XBMC doesn't play from disc yet).
2. Create blank tracks for C & Lf (use any free DAW for this simple operation)
3. Save as a 5.1 wav (the blank tracks are 'placeholders') with an app like WaveAgent.
4. Convert to flac for convenience - the blank tracks do not use up extra space after converting to flac.
5. Your 4.0 program now plays correctly in a 5.1 container. Enjoy!

[phi2039]

1. Enable debug logging.
2. Post log.

When last I checked (when I wrote the CoreAudio code for XBMC), there was no code that forced any particular bitrate (with the exception of 48k for S/PDIF pass-through).

Also, how exactly are you driving 5.1 channel analog output on OSX? Aftermarket DAC?

[jimfisheye]

1. Enable debug logging.
2. Post log.

When last I checked (when I wrote the CoreAudio code for XBMC), there was no code that forced any particular bitrate (with the exception of 48k for S/PDIF pass-through).

Also, how exactly are you driving 5.1 channel analog output on OSX? Aftermarket DAC?

Yes, an aftermarket DAC. MOTU 828mk3. This all works seamlessly right out of the box. I can select analog/5.1/MOTU828 in XBMC and it just works. What I actually do is select analog/5.1/Soundflower(16) and pickup the outputs in a DAW to control bass management. This is all solid and convenient.

I posted the bug report with the debug log.

The 96k only operation is only for 5.1 files. Stereo files operate at the expected sample rate.

[ArnoldLayne]

I am also having an issue with xbmc playing 4.0 (quadraphonic) flac files. I get a stereo mixdown. Foobar plays the same flac file properly with four channel sound.

System:
Windows 7 64bit SP1
Asus Sabertooth X58
Intel i7 920
12GB DDR3 1066 Ramm
GTX 460 with hdmi
Sony Bravia 1080p TV hdmi
Yamaha RX-V2065 hdmi

A_L

[jimfisheye]

I just discovered that the lowly Songbird playes 5.1 flac files! Not only that, it plays 4.0 files (and 4.1 and 5.0...) and at any sample rate. In other words the XBMC bug described in this thread does not plague Songbird.
XBMC is still the only choice for mixed audio/video program but it's going to be Songbird for audio only until this gets fixed.