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5.1 FLAC decoding
Grrr Grrr Grrril...
post Mar 11 2009, 02:41
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I have received a FLAC file containing 5.1 audio data in six discrete channels.
FLAC Front-End successfully decodes this to a .wav file.
WMP will not play either the FLAC original or the decoded .wav file.
Winamp will play the .wav file - apparently in 2-channel stereo

My old version of Cool Edit 2.1 will import the wav file as a multi-channel file and shows six separate waveforms when imported. In multichannel mode, I can play any one or several of these channels, but these are all panned by default as Centre and are labelled 1 to 6 with no indication which is which.

It is of course very easy to tell which of the six channels is the LFE (or sub-woofer) track; surprisingly, this shows up as Channel 4 of 6 (I would have thought 6 of 6 would be normal).
It is not so easy to tell which of the other five channels is which.
I am not familiar with the material, but by listening carefully to the Winamp playing, I can more or less tell which is Left and which is Right, but I am not really sure which is front and rear and even less certain which is Centre channel.
Is there a standard methodology for the channel arrangement?
If not, what other detection methods work reliably.
What I hope to do eventually is to upsample the bitrate and resolution to 96/24, edit the material in Cool Edit then encode and burn the six channels to DVD-A using Disc Welder.

Any tips?
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jcoalson
post Mar 11 2009, 05:53
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if the 4th channel is lfe, it's probably the standard 6ch assignment (fl, fr, fc, lfe, sl, sr)
see channel assignment: http://flac.sourceforge.net/format.html#frame_header
if it has a WAVEFORMATEXTENSIBLE_CHANNEL_MASK tag you can figure it out from that
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Grrr Grrr Grrril...
post Mar 11 2009, 13:22
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Thanks Josh,
I guess I'll take it that the file is standard and work from there.
Thanks for the link.
I tried a couple of things to discover whether the file has the tag you mention and what it contains if it exists, but I don't know how to do this.
I can't find any reference in the "explain" feature for FLAC and none of the references on a web search helps.
Still, I am fairly confident I won't need to know.
Presumably, if I want a 2-channel stereo mix of this, I pan the Left front channel 100% Left, pan the Right front channel Right and leave LFE in the centre. I am guessing I won't need the Centre channel as this is usually derived from LF and RF anyway. The rear channels are essentially echo from the front channels, so I would not want to try to mix those in at all. Is that Correct, Nearly correct, or Close enough for government work?

Regards
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jcoalson
post Mar 12 2009, 05:45
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you can use
CODE
metaflac.exe --list --block-type=VORBIS_COMMENT

to show all the tags, or just
CODE
metaflac.exe --show-tag=WAVEFORMATEXTENSIBLE_CHANNEL_MASK

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Grrr Grrr Grrril...
post Mar 12 2009, 14:58
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Thanks again, Josh.
As it happens, I think the WAVEFORMATEXTENSIBLE_CHANNEL_MASK tag is missing from the file.
The only tag data types are Streaminfo, Vorbis_Comment and Padding and the only Vorbis tags are Length, Vendor string and (5) Comments containing text details of the recording.
A Streaminfo tag confirms the data is 6-channel but that's it.
Anyway DVD-R blanks are 35, so if it doesn't come out right I'll re-do it.

Regards
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