Guide: 2- to 5-channel upmix using Dolby Pro Logic II

[PDU]

You mentioned that you've encoded some files using V.I. <as ursamtl gleefully dons his "shameless self-promotion" hat >I think I missed that the thread was originally posted by you. Thank's for the V.I. bidule anyway :)
Yeah, reading might not be as fun as actually doing the stuff, but it's been my experience that you can gain a much more thorough appreciation of the whole surround process if you get some idea of what's going on.You're right. I have a lot to learn and reading is what I'll be doing for a while.

Regarding V.I.
The files I have encoded so far (1 actually) worked like a charm as soon as I muxed the resulting AC-3 file with som DivX video. My MPEG4 enabled DVD player was happy - and I was happy (Damn Audio DVD Creator). However I noticed that the levels of the rear channels are higher than the front channels. This is actually "spottable" just by looking at the channels in Soft Encode - and by listening to the file. Is this intentional? I mean is the 6 channels generated by the V.I. bidule correct in regards to levels or is some kind of leveladjustment in Soft Encode necessary? Also the LFE track level seems very low.

Before I forget. I changed the pin connections in V.I. to the following:

V.I. 1 -> Rec 1
V.I. 2 -> Rec 3
V.I. 3 -> Rec 2
V.I. 4 -> Rec 6
V.I. 5 -> Rec 4
V.I. 6 -> Rec 5

By doing this the resulting 6-track wavefile can be opened in Soft Encode without rearringing the channel assignments at all.

Now gonna play with the Spatdecoder and Bidule. Have some MPA files (Dolby Surround encoded) that has to be converted to AC-3.

Cheers,
Peter

[ursamtl]

Originally posted by PDU
You're right. I have a lot to learn and reading is what I'll be doing for a while.Reading is good, but experiment a bit too. This will give you a better understanding of what you're reading.

Originally posted by PDU
The files I have encoded so far (1 actually) worked like a charm as soon as I muxed the resulting AC-3 file with som DivX video. My MPEG4 enabled DVD player was happy - and I was happy (Damn Audio DVD Creator). However I noticed that the levels of the rear channels are higher than the front channels. This is actually "spottable" just by looking at the channels in Soft Encode - and by listening to the file. Is this intentional? I mean is the 6 channels generated by the V.I. bidule correct in regards to levels or is some kind of leveladjustment in Soft Encode necessary? Also the LFE track level seems very low.

Before I forget. I changed the pin connections in V.I. to the following:

V.I. 1 -> Rec 1
V.I. 2 -> Rec 3
V.I. 3 -> Rec 2
V.I. 4 -> Rec 6
V.I. 5 -> Rec 4
V.I. 6 -> Rec 5

By doing this the resulting 6-track wavefile can be opened in Soft Encode without rearringing the channel assignments at all.

Now gonna play with the Spatdecoder and Bidule. Have some MPA files (Dolby Surround encoded) that has to be converted to AC-3.

Cheers,
Peter

The pinout changes you describe will work with SoftEncode. The order I used in V.I is the ITU 5.1 spec, which is pretty much the standard these days. I'm curious about your surrounds being louder than your fronts. This happens to me on perhaps one song out of 20 and only because of the way the song is recorded. That's why I put the level controls on the outputs. Try backing off on the rear level to about 0.6 or 0.7 and see what that gives you. 0.7 corresponds to approx. -3dB which is often recommended for surround level attenuation. However, this comes from processing movies, which have their surround level boosted by 3dB to compensate for the size of most cinema rooms. For upmixing music, the attenuation is normally not necessary.

Yes, the LFE level is low. This shouldn't matter if your playback system has bass management. It will direct bass from the main channels to the subwoofer. Some pros insist that one should never use the LFE on music, whereas others do use it. I set the LFE channel in V.I below 60Hz, which moves it out of the way of bass management crossovers and still uses the channel to give that extra bit of oomph to bass note fundamentals and drum transients for music, and all the low-frequency effects in movie soundtracks. The wave may look really small and at a low volume in Softencode but on a decent playback system, it's all you need. The option is also available in V.I to shut the LFE channel off completely.

In the end, go with what works for you and enjoy it.
Steve.

[joshbm]

Originally posted by ursamtl
Yes, you're right. I forgot about ssrc (I don't know about the "hp_" prefix. I've never heard of it and Google turns up nothing). r8brain is better for those who like a GUI, but SSRC seems fine otherwise. I don't know if anyone has test data or anything otherwise scientific for a comparison of the two. I haven't done much work at all converting to 48kHz because my interest so far has been music. I do have some video footage with soundtracks I eventually plan to upmix to 5.1, so one of these days I'll have to get to the 48kHz stuff.

As per the AC3 bit depth, I'm not really sure. I've seen varying discussions on this but no solid answer. For sure 16-bit files should work on all playback devices but obviously 24- or 32-bit files will give better quality. From what I've read the difference between the latter two is virtually inaudible so if the software you're using only support 24-bit, don't sweat it. As a result, you don't really need dithering when reducing from 32 to 24 bits.

Steve.
Sorry I meant ssrc_hp.exe.

:p
Josh

[joshbm]

Guide was updated :)

http://forum.doom9.org/showthread.php?s=&threadid=83384

Suggestions/Comments welcomed!

Regards,
Josh