Creating 5.1 FLAC from multiple .wavs

Audacity Help Forum Windows
1

I’m a newbie Audacity user, though I have used other audio editors extensively, and am wanting to use Audacity to create a 5.1 flac from a set of wavs that I have been sent by an audio engineer for play testing prior to release.
It’s absolutely essential that I get as close to possible, preferably identical to what he’s hearing in his audio workstation (differing hardware aside, of course.)

I think I have figured it out but as I couldn’t find any tutorials or manual contents on multi-channel and being new to Audacity I thought I would come here and ask for advice. The procedure below describes what I’m doing. What I’m looking for is for someone who knows how Audacity works with multi-channel flac to “peer-review” what I’m doing and tell me if it’s right, if there are any “gotchas” or problems to look out for that could result in my flac not being the same as his original audio in the studio.

• I have four audio (.wav) files from the engineer. A front stereo pair(LR), centre, LFE and a rear stereo pair (LR.)
• I’m using the import menu to import each in turn so that I end up with six channels across four tracks in Audacity – a stereo Front L/R pair, mono Centre, mono LFE, a stereo Rear L/R pair. Audacity telly me they are all 48k 32-bit float files.
• In preferences I have set Import/Export to allow custom mixes (I read about this in another forum post.)
• I’m then using the export dialogue, type “FLAC Files”, level 5 compression, 24 bit.
• This brings up the Advanced Mixing Options which allows me to check my channel mapping, which I have checked against the flac standard for multi-channel and once I have checked and continue it produces a flac.

The flac looks and sounds right when I stream it to my player for play testing but as I said earlier it’s essential that I do this right avoiding any problems such as channel mapping errors, phase issues, track offsets and anything else that could invalidate the play testing.

Also, are there any other settings that could impact the import or export adversely that I should be looking at?

Any comments or suggestions gratefully received, even if it’s only a “yes, that all okay.”

Many thanks in advance!

btw I’m using Audacity 2.1.1 on Windows 7 64bit.

2

You might obtain “MediaInfo” from http://mediainfo.sourceforge.net/en/Download/Windows and compare the channel mapping in the exported FLAC with a 5.1 FLAC that plays correctly on your client’s hardware or with some other known correct 5.1 FLAC. Get the MediaInfo version without installer, because the installer may have malware or adware.

Note that Audacity does not tell you that the WAV’s are 32-bit float. That is just the resolution Audacity imported them at. MediaInfo will tell you what bit depth the WAV files are.

Note also that when exporting, dither will be added. Dither is beneficial when downconverting from 32-bit float to 24-bit export. If this worries you, you could find out the bit depth of the WAV files in MediaInfo, set Default Sample Format in Quality Preferences to that depth, then turn off “High-quality” (export) dither off in those same preferences. This is fine given you are not running effects on the audio before export.

Yes 5.1 FLAC where defined should be: front left, front right, front center, rear surround left, rear surround right.

In the event the target hardware or player software uses some other mapping, then the results will still sound wrong.


Gale

3

Excellent info Gale, many thanks. Since I posted the engineer had confirmed to me that his exports are 24 bit so then assumed it was Audacity doing the upconversion to 32 bit float as you have confirmed, thanks! Mediainfo sounds like a useful tool as well, so thanks for that suggestion too!

I’m not worried about dither from 32 to 24 as I expect that’s well below the level of being able to hear it, but I will try an export without just for comparisons sake.

Thanks again.