mono DVD sources always come out center channel

[Jeremy Davidson]

A problem I've noticed with several DVD projects I've produced is that when my original source is mono, my home theatre receiver maps that sound to the center channel speaker. For dialogue this is fine, but music (say from a mono mixer feed) would benefit from the better front L/R speakers.

There is a mode that forces it into two-channel stereo mode, but I'm hoping there's a more elegant solution. Is there some kind of post-processing that can be done to "trick" the receiver?

I'm currently using the TMPGEnc AC-3 plugin to convert from a 48K 16bit stereo WAV to a 384kbit 2/0 AC-3 file. I've heard about tricks for creating a Dolby ProLogic signal (haven't tried that yet), but I'm open to any comments or suggestions.

What works for you?

[Rob Lohman]

The obvious trick (I would think) is to make the mono channel
stereo. In other words, duplicate the audio track to get the same
signal in the left and right channel and encode that.

The idea with the dolby digital encoders is that they can decide
how to play a stream and you have zero control over it. I usually
force my receiver into 5 channel stereo mode if I have a stereo
track (on a movie, TV broadcast or music). However, I would
think that if you put a stereo track on the disc it will default be
played either through the left and right speaker and might even
include the center speaker (but that is probably different per
decoder).

[Jeremy Davidson]

I'm currently using the mono-to-stereo trick (the output from Premiere is automatically a 48K 16bit stereo file) by taking my input sources and using the "duplicate left/right" option to place the same audio on both tracks. My home theatre system (Yamaha) sees the identical audio tracks and sends it to the center channel. I suppose encoding to 5.1 would give complete control over which speaker gets what audio, but for now I can only encode two-channel AC-3 files.

If there's no workaround for this, do you see any problem with using the one-channel encoding with AC-3? As long as there are no compatibility problems, this could be a good way to save bandwidth (i.e. more space for better video).

Thanks!

Jeremy

[Rob Lohman]

Yes, AC3 mono is supported in the DVD spec, so that is no issue.
However, I think your receiver is actually the problem here, not
your encode. I find it strange that your receiver would decide to
play a stereo file as mono.

Would it be possible to put up a minute of AC3 (stereo!) audio
somewhere? It would be interesting to see what my receiver
here does with it (I have a Yamaha RX-V620RDS DD/dts AV receiver)

You can also e-mail it to me at visuar@gmail.com
(do leave a note here in the thread if you e-mail it)

[Jeremy Davidson]

Rob, yes, I'll see if I can whip up a couple AC3 files for you to test. I've been frantically trying to finish another video this week (animated this time), so I haven't been able to do this yet. I'll try the test files on my receiver as well, just to make sure I'm not leading anyone astray here.

'Will post again when I have them ready.

Thanks!

[Rob Lohman]

Okay, good luck with that!