The VideoLAN Forums

I'd like to add my data-point to those affected by the incorrect surround mapping for LPCM audio with vlc. I recently experienced this bug after a component change, which may or may not help in isolating the cause.

My set-up is as follows:

Mac mini (2018) -> HDMI -> Marantz AV Receiver -> HDMI -> TV

The Mac mini is running macOS Mojave 10.14.6
I'm using the latest version of vlc (3.0.14)
I have a 5.1 audio set-up

The test files were .mkv files with E-AC3 audio. According to vlc, the audio was:

Codec: A/52 B Audio (aka E-AC3) (eac3)
Channels: 3F2M/LFE
Sample Rate: 48000 Hz
Bits per sample: 32

Despite selecting "encoded output" over HDMI for the audio, vlc (or the macos) doesn't bitstream the un-decoded E-AC3 audio (even though my receiver understands and can decode it). Instead, it exports it as multi-channel PCM.

I previously used a 2014 model Marantz AV Receiver and NEVER had any problems with hundreds of mkv files with E-AC3 audio. The audio was always mapped to the correct channels. Other players (such as IINA) similarly outputted multi-channel PCM correctly.

I recently upgraded to a 2017 model Marantz AV Receiver and now the multi-channel PCM playback with vlc is incorrectly mapped, as many others have reported:

https://forum.videolan.org/viewtopic.php?f=14&t=149757
https://forum.videolan.org/viewtopic.php?f=12&t=145451
https://forum.videolan.org/viewtopic.php?f=12&t=157318
https://forum.videolan.org/viewtopic.php?t=152122

That is, the centre channel is mapped to the L-Rear speaker, etc.

Note that nothing else changed. I literally played the same file from the same Mac mini the day after changing the AV Receiver and this incorrect multi-channel PCM mapping occurred.

Note also that the same file plays correctly with IINA, even after changing the AV Receiver. That is, the audio is mapped to the correct channels. It appears that it's only vlc which exhibits this incorrect channel mapping for multi-channel PCM audio.

Is there a ticket for this? There seems to be multiple reports of this bug going back several years.

Summary:

1. Even though the mac claims to natively support E-AC3 since OS X El Capitan (10.11), it apparently cannot output un-decoded E-AC3 as bitstream data (as it can with AC3 and DTS) over HDMI, which would presumably fix this issue:
https://developer.dolby.com/platforms/a ... s-support/

2. Multi-channel PCM audio was always correctly mapped with an older AV receiver but fails on a newer AV receiver.

3. The problem only affects vlc - other players output multi-channel PCM audio correctly mapped.

Thanks,

vlcfaninaus

I'm delighted to report that this mapping error is fixed (for me at least) with vlc 3.0.17.

I assume it's the item listed in the changelog as "macOS: fix some channels ordering for > 5.1 channels"

My thanks to the devs!

vlcfaninaus

I am experiencing LPCM channel mapping issues as well. I'm running VLC 3.0.20 in Windows 11 24H2 Build 26100.2161. My audio device is a Cubilux CA7 7.1 USB audio device configured to 5.1 in the Sound control panel. A good test file to use to verify the LPCM mapping issue is "LPCM 5.1 remuxed.mkv" which can be downloaded from here:

https://drive.google.com/file/d/1yuICqt ... drive_link

That file plays back fine in other players such as MPC-HC. Only VLC shows this LPCM channel mapping issue. Is there a ticket already open for this issue? I found this one, but there aren't enough details in it for me to determine if it's related or not:

https://code.videolan.org/videolan/vlc/-/issues/24752