Dolby Surround = Pro Logic I ??

[lilhobo]

i have seen this setting in many GUI.....is dolby surround, pro logic I ???

as opposed to dolby digital surround?

[FlimsyFeet]

"Dolby Surround" describes a 2-channel soundtrack which is created by matrix-encoding four channels of audio information - Left, Centre, Right, and a mono surround channel.

"Dolby Pro Logic" describes the decoding process by which the original four channels are recreated from a Dolby Surround soundtrack.

"Dolby Digital" can transmit up to 6 discrete channels of surround sound - Left, Centre, Right, Rear Left, Rear Right and Low Frequency Effects.

[tebasuna51]

And "Dolby ProLogic II" is 2-channel soundtrack which is created by matrix-encoding five channels of audio: Left, Center, Right, Left Surround and Right Surround.

[Crono141]

And how does Dolby Pro Logic II compare to its source AC3 track? For instance, if I Rip a DVD with AC3 5.1 into 2 channel AAC as Dolby Pro Logic II, how will its output compare with the DVDs?

[tebasuna51]

If we compare in size the aac track can be the 25% than the ac3 track. In quality, of course, the aac track is worse.;)

[Crono141]

Worse is a given, but how much worse? For instance if I have a test ac3 file that calls out each channel (Left front, left surround, etc) and encode to DPLII, how much separation will be lost? Hardly noticeable? Almost total loss? Has anyone even done any testing on this, just to see?

[tebasuna51]

The channel separation is very good with test channels like you say.
Maybe you are interested in my tests decoding dpl II with PowerDVD and a free plugin for Foobar2000 in this thread (http://www.hydrogenaudio.org/forums/index.php?showtopic=52235#)

The problem is with real audio tracks with channels dependencies. The mix sometimes dup/cancel signals

[Crono141]

I just ran the channel test. Surround channels weren't so good though. Left rear was louder in the left rear speaker, but could be heard pretty good out of the RR speaker as well. Also center channel comes out of all front speakers, but mostly the center channel. I ran the test file through my PS3 to make sure my PC wasn't introducing the problem, and it was the same. Makes me have second thoughts about using DPLII AAC in my H264 encodes (for x360 playback). I also wonder if the encoding on that MP3 is the best you can get, or if a better DPLII encode is possible.

Funny thing, I discovered I had my RR and FR speakers backwards, thanks to this. :)

[burfadel]

Also Dolby Prologic IIx is an extension of Prologic II to support 7.1. I assume it works much like DTS Neo:6 (which I prefer) that essentially mirrors the 2 rear channels on the two side channels.

[tebasuna51]

I just ran the channel test. Surround channels weren't so good though. Left rear was louder in the left rear speaker, but could be heard pretty good out of the RR speaker as well. Also center channel comes out of all front speakers, but mostly the center channel. I ran the test file through my PS3 to make sure my PC wasn't introducing the problem, and it was the same. Makes me have second thoughts about using DPLII AAC in my H264 encodes (for x360 playback). I also wonder if the encoding on that MP3 is the best you can get, or if a better DPLII encode is possible.

Funny thing, I discovered I had my RR and FR speakers backwards, thanks to this. :)

Seems your test dpl II sample is bad codified.
Try with this DplII_samples.7z (http://www.sendspace.com/file/0rhevs)

Don't forget put the dpl II decoder in your receiver for mp3 or mp4 sample, if the ac3 is sended by SPDIF/HDMI must activate automatically the dpl II decoder.

[Crono141]

Thanks, those samples were better. Now if I could just get my ac3 to properly encode to DPLII I'd be in business.