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Topic: Multichannel ALAC encoding channel order bug (Read 1970 times) previous topic - next topic
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Multichannel ALAC encoding channel order bug

Hi everyone,
I am getting wrong channels when converting to ALAC, other formats (WAV, FLAC) are correct. I am only having issues with ALAC. Any fix?
P.S. No i dont have any reverse channel processing activated, I have also tested on my second computer and received the same incorrect results.
Pictures

Re: Multichannel ALAC encoding channel order bug

Reply #1 –
Can't replicate. I converted a 6 channel audio file to ALAC with the command line refalac tool manually and with foobar2000 converter and decoded the files with the command line tool and with foobar2000. Each file had the channels in correct order matching the source.

Perhaps provide a sample file and/or exact steps how to produce the incorrect results.

Re: Multichannel ALAC encoding channel order bug

Reply #3 –
Quote from: Case on
Can't replicate. I converted a 6 channel audio file to ALAC with the command line refalac tool manually and with foobar2000 converter and decoded the files with the command line tool and with foobar2000. Each file had the channels in correct order matching the source.

Perhaps provide a sample file and/or exact steps how to produce the incorrect results.

It doesnt matter, you can take any audio file, i have tested with multiple ones.
MediaInfo shows ChannelLayout for FLAC: L R C LFE Lb Rb and for ALAC: C L R Ls Rs LFE, however when i convert back ALAC to FLAC the order is correct. I assume it is only displayed incorrectly, but will be played back correctly ?
The thing is that Audition doesnt display channels it only shows numbers, but WAV format shows the channel names, thus when I was converting from FLAC to WAV the order was correct I havent looked at channel names, but when I converted from FLAC to ALAC the order was mixed.
 

Re: Multichannel ALAC encoding channel order bug

Reply #4 –
don't use audition
    or
don't use alac
    or
qaac/refalac --chanmap

Re: Multichannel ALAC encoding channel order bug

Reply #6 –
Quote from: E.G. on
MediaInfo shows ChannelLayout for FLAC: L R C LFE Lb Rb and for ALAC: C L R Ls Rs LFE, however when i convert back ALAC to FLAC the order is correct. I assume it is only displayed incorrectly, but will be played back correctly ?
No, it displayed correctly; ALAC channel order  is not the same as channel order in FLAC/WAV. Apparently Audition cannot properly handle multichannel files.

Re: Multichannel ALAC encoding channel order bug

Reply #7 –
Quote from: lvqcl on
Quote from: E.G. on
MediaInfo shows ChannelLayout for FLAC: L R C LFE Lb Rb and for ALAC: C L R Ls Rs LFE, however when i convert back ALAC to FLAC the order is correct. I assume it is only displayed incorrectly, but will be played back correctly ?
No, it displayed correctly; ALAC channel order  is not the same as channel order in FLAC/WAV. Apparently Audition cannot properly handle multichannel files.
But MediaInfo also gives the same layout results. Here are some images from FLAC to WAV and ALAC with channels and MediaInfo. Im not sure but, I assume this is because Apple doesnt support multichannel ALAC normally. I have tried to import 5.1 ALAC to iTunes and seems like it wont read it at all.

Re: Multichannel ALAC encoding channel order bug

Reply #10 –
Some time last year, the way MediaInfo displays audio changed. Channels were renamed and it appears MediaInfo now displays the order the channels are encoded in, rather than the same channel order for (almost) everything.
The current "stable" MPC-HC uses a much older version of MediaInfo, which made it easy to compare the current MediaInfo with an older version.

Attached are comparison screenshots for AC3, ALAC and DTS, along with a screenshot of fb2k's peak meter displaying the channels while decoding the ALAC audio, which appear to be in the correct. They are correct, if you're happy to take my word for it.

You could try importing the ALAC audio into Audacity. It'd require ffmpeg to import it, but the audio should be imported using the wave file channel order, regardless of the order the channels are encoded. There's a screenshot attached of Audacity importing the ALAC audio too.

The audio in the screenshots were encoded using fb2k, including the AC3, although my source file was also AC3.