The VideoLAN Forums

Suggestion: Support speaker mapping for multichannel audio content, as Quicktime 7 does.

I have a 7.1 home theater and recently got myself a new MacBook Pro, so naturally I want to see them play nice together. I found some LPCM 7.1 "calibration" or "demonstration" files on a commercial blu-ray disk. These .m2ts test files play in VLC 2.0.6 but the audio channels do not map properly. Audio Midi Setup correctly mapped my system with no action from me, so I figured the problem with VLC (and every other player I tried) is "just" software.

To get the files to play properly I had to stream out the audio as uncompressed, integer, 192kb/s. This created a .wav file that I could edit in Quicktime 7, to reassign the channels. I pasted this audio back into the test video so that I would have an on-screen indication of which speaker was supposed to be firing at any particular moment.

One thing I noted was that the two rear surround channels were identified in Quicktime 7 as "Left Surround Direct" and "Right Surround Direct". Neither would play on any speaker until I reset them to "Rear Surround Left" and "Rear Surround Right". Then I had to make some reassignments to get each channel to play with its respective on-screen indication. I can let you know the correct order if you're interested.

After renaming the "Direct" channels to "Rear" as noted, I was also able to use Audio Midi Setup to map the channels to the right speakers instead of doing the mapping in QT. That was with QT7 as the player of the file withe the channels in the original order. I tried VLC as the player with the same Audio Midi Setup mapping, but those two rear surround channels wouldn't play and I don't think VLC used the mapping I had done in Audio Midi Setup.

Anyway my little experiment was a success! I eventually was able to get very nice 7.1 playback. So I know VLC should be able to do this.

I am aware that this won't help with TrueHD 7.1 or DTS-HD MA 7.1 playback on Macs, in Mountain Lion, but there are a few movies out there with LPCM 7.1 soundtracks, and I gather there are tools in Windows that can decompress the HD codecs into LPCM. We could play these on Macs if we could map the channels properly. I'm guessing there must be a standard for blu-ray content, so that we shouldn't really even need to do mapping ourselves. It just needs to be done once and built-in to VLC.

Try to use 2.1.0

I need to try re-mapping, but I can tell already with 2.1.0 (latest nightly build) that all channels play somewhere, and that was not the case before. So I'm optimistic.

Should I choose the audio device as "System Sound Output Device" instead of HDMI, in order to gain control over the mapping with Audio Midi Setup?

Maybe No idea.

Ok, I've tried both and didn't see any difference between choosing HDMI or System for the audio device, with or without changing Audio Midi settings. In both cases, the settings applied in Audio Midi Setup had no effect and I could not re-map the speakers.

All 8 channels play! Front Left, Right and LFE are mapping fine by default, as are the rear left and rear right surrounds. The Center signal (as indicated on screen by the commercial test file) plays in my left surround speaker. Right surround plays in the Center, and left surround plays in the right surround speaker.

So re-mapping just 3 channels would fix this for LPCM 7.1.

BUT !! For fun I opened up the TrueHD test files I also have and they play PERFECTLY into 7.1 !! Well done. Wasn't expecting such a pleasant surprise.

The DTS-HD MA demo file I have plays and seems to sound fine also. Downloading a speaker assignment file right now.

No surprise I guess - the DTS-HD MA file did not map properly and all channels did not play (no rear surrounds). I guess I was just hearing the core portion of the audio, not the lossless.

Yes, VLC does only decode DTS-core.

TrueHD should be 7.1 and so is LPCM.

Did you need the same remapping for both LPCM and TrueHD?

TrueHD 7.1 is perfect as is. So happy!

The LPCM 7.1 has the remapping issue I mentioned above; the center and two surrounds (not rears) are scrambled.

Please share the LPCM 7.1 file.

I've sent a PM regarding the file.

For the two LPCM 7.1 files I've uploaded, after streaming out of VLC and renaming the rear surround channels, here is the remapping in QT that worked for me. The original assignment in QT is in parentheses.

1 Left (no change)
2 Right (no change)
3 Right Surround (was Center)
4 LFE Screen (no change)
5 Rear Surround Left (was Left Surround)
6 Rear Surround Right (was Right Surround)
7 Center (was Rear Surround Left after renaming)
8 Left Surround (was Rear Surround Right after renaming)

Downloaded latest Mac 64-bit nightly, VLC 2.2.0-git, to test. I noticed that ticket 8526 had been closed as completed.

I initially thought the mapping was not fixed but when I went to check it "one last time", it worked. It seemed to take a while for the channels to set themselves properly. Was finally working with VLC's Audio menu setting set to "HDMI".

I confirm that the speaker mapping is now correct for both LPCM 7.1 and TrueHD 7.1. Yay! Now we just need DTS HD ; )

Yay! Now we just need DTS HD ; )

Yeah...

Using 2.2.0-git; LPCM 7.1 is working, but ACC 5.1 is not. Centre, Surrounds, and ¿LFE? are scrambled.

It would be cool if you can try this test build and report back if channel mapping is better now: https://www.dropbox.com/s/otemq85otkt88 ... g-test.zip

I have hit this problem before, and resolved it, but couldn't remember exactly how. But when the absolute latest VLC 2.1.4 sent audio to the wrong channels on my new MacPro, I went digging again. First I found this thread, which I don't believe has the answer or has even diagnosed the problem correctly. Fortunately, I also found the solution. I don't know why Macs ship this way or why some software still seems to work, but the problem is in the Mac's audio setup, and once you know how, it is quite easy to fix. See the instructions in the top post here: http://forums.macrumors.com/showthread.php?t=1314744. Particularly the "Instructions" section. In fact, in case that ever goes away, here are the most salient bits excerpted:

INSTRUCTIONS
The key to getting dialog to play (indeed, all channels of the source file to play via the correct speakers in your surround system) correctly, i.e., as it was meant to be heard, is to configure the speaker map on your Mac properly. Follow these instructions, as tested on Mac OS X 10.7.2 (earlier versions may be slightly different):
1. You need to enable AC3/DTS passthrough. Go to Applications>Utilities>Terminal. When the application opens, copy and paste the following, without the quotes, then press enter: “defaults write com.cod3r.a52codec attemptPassthrough 1” and “defaults write org.perian.Perian attemptDTSPassthrough 1”. q.v. FOOTNOTE 1
2. Connect the HDMI cable from your AVR to your Mac. Make sure you select the proper mode on your AVR so your computer is recognized. Make sure your audio output device in OS X is changed to, e.g., "DENON-AVAMP" (other AVRs will show something else) from the default "Internal Speakers", otherwise, your audio will play through your internal computer speakers. You can quickly switch the audio output device by clicking on the sound icon in the top menu bar, whilst holding option on the keyboard. If you don't see the sound/volume icon in your menu bar, go to the apple icon in the top left, click System Preferences>Sound. Then click the box for "Show volume in menu bar". This will make your life easier.
3. Go to Applications>Utilities>Audio MIDI Setup
4. On the left side of the "Audio Devices" window that appears, click "HDMI".
5. Change Format to 48000.0 Hz and in the dropdown to the right, select “8ch-24bit Integer”. q.v. FOOTNOTE 2
6. Now click “Configure Speakers”. In the top right, select the surround system you have. I have 5 speakers (no subwoofer), but I selected “5.1 Surround”. Click each speaker name to make sure sound comes out of the speaker name you just clicked. Adjust as necessary.

Perhaps because I had set all this up on the older Mac I imported my settings from (using Migration Assistant), all but the last step (6) were already in place on my system. (Note, you can see the state of the defaults you are told to change in step 1 by typing "defaults read com.cod3r.a52codec attemptPassthrough” and “defaults read org.perian.Perian attemptDTSPassthrough” if you want to check them before you change them.) Once I selected "Multichannel" and "5.1 Surround" in step 6, all was well, and VLC works as intended.

Keep up the great work, VLC contributors, and don't waste time on this non-bug.

I have hit this problem before, and resolved it, but couldn't remember exactly how. But when the absolute latest VLC 2.1.4 sent audio to the wrong channels on my new MacPro, I went digging again. First I found this thread, which I don't believe has the answer or has even diagnosed the problem correctly. Fortunately, I also found the solution. I don't know why Macs ship this way or why some software still seems to work, but the problem is in the Mac's audio setup, and once you know how, it is quite easy to fix. See the instructions in the top post here: http://forums.macrumors.com/showthread.php?t=1314744. Particularly the "Instructions" section. In fact, in case that ever goes away, here are the most salient bits excerpted:

INSTRUCTIONS
The key to getting dialog to play (indeed, all channels of the source file to play via the correct speakers in your surround system) correctly, i.e., as it was meant to be heard, is to configure the speaker map on your Mac properly. Follow these instructions, as tested on Mac OS X 10.7.2 (earlier versions may be slightly different):
1. You need to enable AC3/DTS passthrough. Go to Applications>Utilities>Terminal. When the application opens, copy and paste the following, without the quotes, then press enter: “defaults write com.cod3r.a52codec attemptPassthrough 1” and “defaults write org.perian.Perian attemptDTSPassthrough 1”. q.v. FOOTNOTE 1
2. Connect the HDMI cable from your AVR to your Mac. Make sure you select the proper mode on your AVR so your computer is recognized. Make sure your audio output device in OS X is changed to, e.g., "DENON-AVAMP" (other AVRs will show something else) from the default "Internal Speakers", otherwise, your audio will play through your internal computer speakers. You can quickly switch the audio output device by clicking on the sound icon in the top menu bar, whilst holding option on the keyboard. If you don't see the sound/volume icon in your menu bar, go to the apple icon in the top left, click System Preferences>Sound. Then click the box for "Show volume in menu bar". This will make your life easier.
3. Go to Applications>Utilities>Audio MIDI Setup
4. On the left side of the "Audio Devices" window that appears, click "HDMI".
5. Change Format to 48000.0 Hz and in the dropdown to the right, select “8ch-24bit Integer”. q.v. FOOTNOTE 2
6. Now click “Configure Speakers”. In the top right, select the surround system you have. I have 5 speakers (no subwoofer), but I selected “5.1 Surround”. Click each speaker name to make sure sound comes out of the speaker name you just clicked. Adjust as necessary.

Perhaps because I had set all this up on the older Mac I imported my settings from (using Migration Assistant), all but the last step (6) were already in place on my system. (Note, you can see the state of the defaults you are told to change in step 1 by typing "defaults read com.cod3r.a52codec attemptPassthrough” and “defaults read org.perian.Perian attemptDTSPassthrough” if you want to check them before you change them.) Once I selected "Multichannel" and "5.1 Surround" in step 6, all was well, and VLC works as intended.

Keep up the great work, VLC contributors, and don't waste time on this non-bug.

I wouldn't call this a non-bug.

The problem is even if you can remap the channels in Audio MIDI Setup, then your channels are mapped wrong for any other app. It's not practical to have to remap all your channels every time you switch apps.

Other apps have the channel mapping right, like XMBC and others.

VLC needs to fix the software so that it uses standard channel mapping like all other apps. I think channel mapping is pretty standard. Not sure why this problem has been noted starting in 2011, yet nothing has been done. I think it would be a simple fix to change the channel mapping.

(Where are the nightly builds? is the nightly site down?)

We already fixed that. Why do you bring this up again?

We already fixed that. Why do you bring this up again?

When was it fixed?

I have version 2.2.0 nightly from 5/20/2014 installed and it behaves exactly the same as all the previous versions of VLC. I tried the release version 2.1.1 too which works the same.

The channels are mapped wrong as described in the previous posts.

However, I can play the exact same file on VLC in Windows and all the audio channels are mapped correctly.

I STILL have this problem. Using OS Sierra and version 3.0.8 and I have channel issues continually. Sometimes switching back and forth with the HDMI encoded and not encoded sorts out the channel problem but mostly I either get no center channel or the center plays through the rear speakers. Horribly frustrating. I'd say not fixed.

I also do have this problem...

Mac OS Catalina 10.15.4
VLC 3.0.8