Dolby Pro-Logic II processing of a signal from Line In

Dimensio · May 4, 2006, 08:28 PM

I've been searching on this forum, and I've actually found information that suggests that the answer is no, but I wanted to ask about my situation explicitly in case anyone knows differently.

I have an analog stereo signal coming into my SB Audigy 2 on Line-In. I am seeking a means of obtaining real-time Dolby Pro-Logic II processing of this signal for 5-channel speaker output. Overhead is only an issue in that I need the processing to incur a minimal (as in, not human-detectable) delay -- if there is a method that sucks up 99% of my CPU resources while it runs, that's okay. I don't need it for anything else while while I'm processing the signal.

Thus far I've found a means of getting Pro-Logic processing via the KX drivers. This is what I use currently, but DPLII would be far superior if it is possible. I've also found a means of processing a line-in signal with GraphEdit and using a filter for DPLII processing, but GraphEdit gives me a buffer latency that I can't change (approximately 500ms IIRC), and I need the processing to be as close to real-time as possible.

I will also note -- though I do not know if anyone would be able to provide assistance on this angle -- that I am open to solutions that involve using Linux (with the ALSA emu10k1 driver), as I dual-boot on the target computer.

Is there any feasable solution, or am I simply out of luck?

Russ · May 5, 2006, 06:04 AM

It does not seem that there is any real options there. I do not think that it can be done in the DSP, and there does not seem to be much in the way of software solutions, that would allow real-time DPL II decoding of an external source connected to the sound card (i.e. a VST plugin). The only *possible* options I have seen are imho, too expensive. I think you would be better off just buying an old hardware DPL II decoder and doing it that way, if you need real DPL II decoding. One thing you might check out is V.I STEREO TO 5.1 CONVERTER VST PLUGIN SUITE. It does not claim to do DPL I or II or anything, but maybe it will give you decent results (and it is free).

ROBSCIX · May 5, 2006, 12:42 PM

NOw the trick would be routing the line_in through a VST..you might be able to do it with Winamp, but you will definatley need to do some work setting up the buffers..but I think you will probably get near realtime..BUT if you route a Line_in signal through winamp there are quite a few plugins that would change the 2.0 to surround..I don't knwo if it would be PLII though. Mayeb somebody should code some new surround plugins..Russ your a DSP guy, is it possible to code a PLII DSP module? Isn't surrounder just a upmix?

Russ · May 5, 2006, 03:08 PM

Quote:

Originally Posted by ROBSCIX

Russ your a DSP guy, is it possible to code a PLII DSP module?

The necessary info really is not available (it is a licensed technology after all). Additonally, it would likely require more resources than is available in the DSP.

ROBSCIX · May 5, 2006, 04:43 PM

Well isn't PLII similar to Dolby Digital, in that the Rears are considered two seperate channels, where as in Pro-logic the Rears are just a surround channel with no balance...Isn't there already a Prologic module? I was just curious and it seems like a good point for conversation..

Russ · May 5, 2006, 05:10 PM

Yes there is the Prologica plugin, and I think Surrounder might do Prologic I encoding/decoding as well, under certain presets, but afaik that is a lot different from DPL II.

See the following:
Dolby Surround Pro Logic II Decoder Principles of Operation

I am no expert on it, so I would suggest doing some research on it yourself.

Maddogg6 · May 5, 2006, 07:43 PM

Heres some programming info about the 2 (DPL & DPLII)
http://forum.doom9.org/showthread.php?s=&threadid=27936

Russ · May 5, 2006, 08:25 PM

Quote:

Originally Posted by Maddogg6

Heres some programming info about the 2 (DPL & DPLII)
http://forum.doom9.org/showthread.php?s=&threadid=27936

Yeah, I have seen that info before too, but it is more about doing the encoding, rather than decoding.

As far as decoding goes:

Quote:

DPL2:
Forget it. Too much complicated and not published.

http://forum.doom9.org/showthread.php?s=&threadid=35209

Dimensio · May 6, 2006, 03:21 AM

Quote:

Originally Posted by ROBSCIX

Well isn't PLII similar to Dolby Digital, in that the Rears are considered two seperate channels, where as in Pro-logic the Rears are just a surround channel with no balance...Isn't there already a Prologic module? I was just curious and it seems like a good point for conversation..

I'm using Prologica right now. Looks like that's all I'll have until I can find an easy-to-implement hardware solution for my current setup. Thanks for the info everyone.

kurian2z5 · Dec 16, 2006, 07:29 PM

Aud-X can decode DPL II from line-in..
just keep some video editing tool that uses ffdshow running the the background so that the line in is activated using ffdshow...cos Aud-X is a ffdshow decoder

kurian2z5 · Jan 12, 2007, 11:47 PM

Cyberlink's PowerDVD 7 DPL IIx filter doesnt have any latency for me. Its only some 1ms.