Don't use DVD2AVI to extract dolby PRO LOGIC tracks

[solvalou]

After several tests I just came to the conclusion that DVD2AVI (any version) don't mantain the DOLBY PRO LOGIC information os the audio track. Extracting that kind of track with DVD2AVI will generate a normal 2 ch ac3 file and your receiver wont detect it as DOLBY PRO LOGIC.

The only solution I found to this problem is to use Smart ripper to extract the audio track. It works perfectly.

[digitalman]

Audio settings for demuxing AC3 in DVD2AVI:

Channel format should be set to Dolby Digital.
Dolby Digital should be set to demux or demux all tracks.
Dynamic Range Control should be set to off.
Dolby Surround Downmix should be unchecked.
48->44.1khz should be set to off.

I have used all of these settings and never had an issue with the AC3 audio playing correctly on my Dolby Pro Logic receiver. I have not bought a 5.1 yet so I can not comment on that.
According to PowerDVD XP, while playing the mpeg and AC3 file muxed together, the information screen shows that the audio is 5.1. Also, DVDLab reports the AC3 as 5.1 audio.

[hakko504]

Dynamic Range Control should be set to off.
Dolby Surround Downmix should be unchecked.
48->44.1khz should be set to off.These settings are ignored in demux-mode.

And while I'm not sure why, the only thing missing is a flag somewhere that say's Dolby Pro Logic in the extracted file. If you manually force your receiver to DPL mode, you'll hear the full prologic surround sound. My receiver cannot detect pro logic at all, unless you force it to use Dolby Pro Logic mode.

[solvalou]

Believe me I tried all possible settings.. searched the net for info etc etc etc. Maybe we are not talking about the same thing because I am sure that DVD2AVI doesnt maintain the PRO LOGIC info of the file. I'm not talking about 5.1 ch, im talking about 2ch which uses all 6 speakers simulating a 5.1 with voices being reproduced on central speaker and music/audio effects on the other speakers. When my receiver detects PRO LOGIC it activate these featurs and the PRO LOGIC led lights on. My receiver never detected PRO LOGIC with DVD2AVI extracted audio tracks.

Oh, and about forcing a PRO LOGIC, my receiver doesnt activate PRO LOGIC if it doesnt detect it :((. Thats why I tried everything possible to fix this issue.

[hakko504]

Sounds strange, as DPL is an analoge technique for encoding surround sound. There shouldn't be anything in the signal that identifies it as DPL except the extra channels encoded into the Right/Left stereo channels. It just isn't possible for DVD2AVI to remove the actual sound of the extra channels by just demuxing the file.Rp = R + 0.5 C + 0.5 S
Lp = L + 0.5 C - 0.5 S
where:
R = Right channel, Rp = Prologic encoded right channel
L = Left channel, Lp = Prologic encoded left channel
C = Center channel
S = Surround channel (phase shifted)

How does your receiver react to a regular TV transmission in Pro Logic? Or a CD like Metallica's S&M?

The more I think of it, the more I think there is something else behind this. How do you send the data from the file to your receiver? As .ac3 data, as decoded wav (genuine SPDIF) or in analogue form? Have you made a binary compare between the files you get from smartripper and DVD2AVI? Are the files the same size?`I just checked the source code to DVD2AVI and the only thing it does at all in demux mode is to read the data from the .ac3 track of the dvd and write it in a new file. It does not create a specific header, but relies on the data that already exists in the stream.

[solvalou]

Ok. I just found out some interesting information :). Actually there must be a header that indicates PRO LOGIC. Why am I saying this ? Look what happened:

1 - I wanted to test with a very small ac3 file so I extracted the preview chapter of the episode (30 sec) with smartripper to a vob on the HD.
2 - I used DVD2AVI to demux de ac3 track.
3 - I extracted the chpater again using smartripper but now I enabled stream processing and demuxed the ac3 track.
4 - I got 2 files AC3 on the HD with exact same size (725k). Both were playing perfectly in media player.

Now comes the interesting thing.

5 - When trying to correct the audio delay, I couldnt open the AC3 file from smartripper because the program showed an error message saying that it didn't have the HEADER information. The DVD2AVI AC3 file opened with no problem. I was like ugh ?? Whys that happening. Then I thought.. hmmm.. maybe theres a header info on the beggining of the audio track and the reason DVD2AVI AC3 was working was that it simply ignores this kind of header and as smartripper dopesnt ignores it im having problems.
6 - I extracted the first chapter (opening sequence) of the episode. Guess what ? now both AC3 files opened with no problem.
7 - I used dvdmaestro to author the dvd (1:30 min dvd) :) with 2 audio tracks, 1 from smartripper and the other from DVD2AVI.
8 - Played back the DVD on my standalone player connected to the receiver by optical cable.
9 - Only the smartripper track was detected as PRO LOGIC. :)

[Nic]

Hmmm, This is quite interesting...I can't believe dvd2avi is changing any flags. Were the files "exactly" the same size (i.e. if you wen't to properties was the filesize in bytes exactly the same)

Also, if you know how to use DOS, could you do a fc /b smart.ac3 d2a.ac3 (or whatever the ac3 files are called) and then see the file differences, if you could give us the first few differences that might help.

Cheers,
-Nic

[solvalou]

I downloaded the ac3filter and now when playing back both ac3 files i get this.

ac3 extracted with dvd2avi = 0/2 stereo
ac3 extracted with smartripper = DOLBY SURROUND

so dvd2avi really screws with the ac3 header.

[Matthew]

Disclaimer: I'm rather ignorant when it comes to the different audio types, I don't think I've mistaken the terminology though.

On my HD I happen to have a DVD with 2 channel dolby surround audio.

The audio extracted by DVD2AVI (1.76) is exactly the same as that extracted by VobEdit (byte for byte comparison says so).

I used the clock.avi provided by windows and muxed in the audio using nandub. Result was 2 avis, one with DVD2AVI audio, 1 with VobEdit audio. The audio tracks produced by DVD2AVI and VobEdit are both reported as "dolby surround" in AC3filter. Not that I really needed to create 2 avis as the audio files are exactly the same :P