Problems with 5.1 surround sound

[RYORK]

Hi,

I have prepared a video project which is in 5.1 surround sound. When I play the dvd through my cinema sound system it is fine and I get the full surround experience. However, if I play the dvd through my TV speakers, the stereo sound is off balance. It tends to be louder in the right speaker. I have burned the same project with the 5.1 surround sound deselected and the stereo sound is fine on the TV. I noticed also on when playing the soundtrack on the editing software and listening to it through my headphones it does the same thing, however the dvd seems to play alright when I use powerdvd or windows media to play it. I have ruled out any problems with my TV so any help would be greatfully appreciated.

Rob

[sjj1805]

Does this video give the answer?
VS10 CH 06 Dolby Surround Sound

[laidback]

Hi,

I have prepared a video project which is in 5.1 surround sound. When I play the DVD through my cinema sound system it is fine and I get the full surround experience. However, if I play the DVD through my TV speakers, the stereo sound is off balance. It tends to be louder in the right speaker. I have burned the same project with the 5.1 surround sound deselected and the stereo sound is fine on the TV. I noticed also on when playing the soundtrack on the editing software and listening to it through my headphones it does the same thing, however the DVD seems to play alright when I use PowerDVD or windows media to play it. I have ruled out any problems with my TV so any help would be gratefully appreciated.

Rob

The problem stems from how Dolby surround is encoded.. and then played back by some stereo systems that don't have one of the channels Phase correct.. if you are able to swap the wires connected to one of the speakers channel then I would try that first, if that fails, there's not much one can do, other than adjust the balance or if no balance is available I would output the TV through a surround system that uses this extra loud information for correct channel placement..

Below is a link that I hope gives insight as to why one channel is heard louder in some stereo systems, specially in older stereo systems that were designed and assembled around and before surround sound was common..

http://en.wikipedia.org/wiki/Dolby_Pro_Logic

Cheers,

Pete..

[DVDDoug]

....that don't have one of the channels Phase correct...

Ahhh... phase! Maybe that's it! (But, I don't think swapping the phase of a speaker will help.)

Where did the rear-channel audio come from? If it was "derived" from a 2-channel file, phase is the likely problem... If you want to derive surround sound, it's generally best to let Dolby Pro Logic do it at playback time. (But I admit, I have made a 5.1 channel surrround track from a mono file.)

Suppose the the right-front and right-rear are in-phase with each other, but the left-front and left-rear are out-of-phase with each other*... When the surround-sound is downmixed to stereo, the right channel will become louder, and the left channel will become softer. (This will only happen when the front & rear channels are from the same source. If the front & rear are completely different signals, such as different instruments or different voices, the phase relationship will be random.)

You could try inverting the phase of the left-rear channel (with your audio editor before AC3 encoding).

If it is a phase problem, just about anything you do to make the rear channels different from the front channels should help. Try adding some delay to the rear channels (maybe 10-15ms). But, delay & re-mixing will create a "comb filter" effect (also caused by phase) which could be objectional too. Reducing the rear channel volume will reduce the comb filter effect...

The best solution is probably to have a stereo soundtrack and a 5.1 channel soundtrack. But, that requires more-professional DVD authoring software. (Most commercial DVDs are done this way, but most DVDs also have a sourround track that sounds OK when downmixed.)


* This is exactly what will happen if you derive the rear channel information by subtracting the left & right channels.

[laidback]

....that don't have one of the channels Phase correct...

Ahhh... phase! Maybe that's it! (But, I don't think swapping the phase of a speaker will help.)

Where did the rear-channel audio come from? If it was "derived" from a 2-channel file, phase is the likely problem... If you want to derive surround sound, it's generally best to let Dolby Pro Logic do it at playback time. (But I admit, I have made a 5.1 channel surround track from a mono file.)

Suppose the the right-front and right-rear are in-phase with each other, but the left-front and left-rear are out-of-phase with each other*... When the surround-sound is downmixed to stereo, the right channel will become louder, and the left channel will become softer. (This will only happen when the front & rear channels are from the same source. If the front & rear are completely different signals, such as different instruments or different voices, the phase relationship will be random.)

If it is a phase problem, just about anything you do to make the rear channels different from the front channels should help. Try adding some delay to the rear channels (maybe 10-15ms). But, delay & re-mixing will create a "comb filter" effect (also caused by phase) which could be objectionable too. Reducing the rear channel volume will reduce the comb filter effect...

Oh, you could try inverting the phase of the left-rear channel (with your audio editor).

The best solution is probably to have a stereo soundtrack and a 5.1 channel soundtrack. But, that requires more-professional DVD authoring software. (Most commercial DVDs are done this way, but most DVDs also have a surround track that sounds OK when downmixed.)

And as you so elegantly put it - is begot by simply adding an ever so slight delay to one of the channels..

Cheers,

Pete..

[RYORK]

Thanks for your help on this. Looks like I will have to do 2 discs one in stereo and one 5.1 surround sound.

Rob

[laidback]

Thanks for your help on this. Looks like I will have to do 2 discs one in stereo and one 5.1 surround sound.

Rob

Say Rob,
You wouldn't have some other codec pack/s installed in your editing system by chance, would you?

Because if you do, this may also be the reason why you have that extra loud channel err~sound problem..

If you do - Then I would uninstall the pack and try to burn a DVD without it installed, and see what happens, if this post is no help then I am sorry I couldn't help you..

Good luck N cheers,

Pete.