ac3/divx playback

[señor pantalones]

hello all,

this is my first time posting, so please bare (bear?) with me...

i'd encoded a few movies that i'd ripped with ac3 audio (using the doom9 guide) in the past year. i didn't have any hardware to play it back but was anticipating the day when i did. anyhow, for christmas i got (well i got myself) a set of 4.1 creative speakers and a soundblaster live 5.1 card. i figured this would do the trick.

much to my dismay, when i went to play my movies back i was unable to get discrete channels for the rear speakers. i've tried in both power dvd 4 and with the latest version of bsplayer.

now in either of those programs if i play the ac3 track by itself i do get 4 discrete channels... no problem. as well as with a normal dvd, i get 4 channels. so i know my hardware/software is capable of decoding the signal. what i don't understand is why it won't when it is interlaced with a divx avi file.

i played with all the settings for both players with no encouraging results.

what's the deal?

thanks in advance for any forthcoming advice.

[ChristianHJW]

Have you tried using PowerDivX 3.12 player from Doom9 and setting AC3 out to 'default WAV out' ? BSplayer is very good player, but sometimes PowerDivX works better for AC3 playback ..

[señor pantalones]

thanks for the advice...

i'll try that tonight and keep my fingers crossed...

also - what exactly does the s/pdif option do - i thought that sent the digital signal out for a decoder (external) to deal with and then that sent the processed signal to the speakers... but with my 4.1 speaker set-up, sb live 5.1, and no decoder that i know of, i was able to get some sort of alright results...(what i really need is a test ac3 file that identifies all the channels so i can be dead sure)

another probably numbskull question i wanted to ask is, what is happening with the center speaker signal, and/or the lfe signal (which normally goes to the subwoofer, no?) i've read all the guides, but things are a little unclear sometimes...

the really frustrating thing is how good the ac3 tracks sound without the video interleaved - it sounds perfect, it makes me cry. there should be no reason why it would be so different with video muxed in - but it changes everything. is there room for better software to be developed to remedy this?

thanks again

[Tes]

Hi señor pantalones,

If I am not mistaken the SBLive 5.1 has a built in AC3 decoder, or else it is decoded by your speaker setup. I do not know about the LFE channel in your case but with most of the external AV receivers you can set which speakers you actually have connected and the receiver will take the appropriate steps to make sure you hear all the channels (usually if you are missing the center channel, the sound will instead come from both of your front speakers - similarly if you don't have a subwoofer the LFE channel will be directed to the your largest speakers).

If you want to test if you truly have discrete channels I can email you an AC3 test file (vob format 629KB) if you mail server allows files of this size.

[señor pantalones]

that's a big surprise about sb live 5.1 having a built-in decoder -- i picked up my card for 30 dollars, and figured something that cheap wouldn't include anything so fancy... don't external decoders cost an arm and a leg?

in any case, i would really like that ac3 file you mentioned

stevelawford@hotmail.com

thanks...

[Tes]

Well how did it turn out? Did the test file identify all your channels ok?

i picked up my card for 30 dollars, and figured something that cheap wouldn't include anything so fancy... don't external decoders cost an arm and a leg?

Of course an external decoder is going to sound allot better than the decoder in your soundcard but the price is about 10x as much as you paid for your SB Live 5.1. I have the SPDIF output of my SB Live connected to a Denon AVR 1801 (~$350) and the sound is great :D

[Taric25]

This may sound like a silly question, but did you select Quadrophonic, Surround or 5.1 surround in Advanced Audio Properties Speakers tab?

[señor pantalones]

here is the latest update on my ac3 adventures...

i tried out the ac3 test file (thanks a lot Tes), first as a vob in power dvd 4 - fantastic results, but that wasn't really a surprise. i had 4 discrete channels and (this was a surprise) the ultra-bass lfe signal was dealt with by my subwoofer.

so then i stripped the ac3 and glued it to a divx/avi

shockingly with bsplayer/power dvd/windvd i got pretty crappy results - at best 2 channel output... but at least with the lfe bass going to my subwoofer, which made me a little cheerier about it.

then, by accident, i opened the file in windows media player, and, what do you know, i got my 4 channels...

of course, it isn't a perfect world, and the bass signal was no where to be seen (or heard...)

anyhow -- getting closer all the time.

next move will be to try powerdivx -- i'm in mexico right now, and without my computer hooked up to the internet these things take time...

thanks for all the help.

Taric25: i did have it set to quadraphonic before, but with no results... anything good has come from having it set to s/pdif... you're talking about the intervideo filter, right?

[MaTTeR]

Uhg...the dread SoundBlaster cards with SPDIF issues. How many times have we seen this post? I'll point you the same direction as I've pointed other happy SoundBlaster owners. Visit the HTPC forums (http://www.avsforum.com/avs-vb/forumdisplay.php?s=&forumid=26)

These guys can help get you through the setup woes. Be careful running SPDIF out to an external amp. Apparently, certain SB cards are running out of spec voltage and potentially damage your amp.

[_Vengeance_]

I am running my Playstation2's optical digital out to my computer's digital in (SBLive Platinum 5.1). THEN my computer's digital out is connected to my amplifier. So I may be dealing with multiple AC3 decoders here.

(Why do it this way? My computer runs ALL sound period. My amplifier is NEVER set to anything other than my computer, whether I'm watching AVIs, watching TV via my VCR, listening to music, or [now] playing PlayStation2. Sometimes I want to mix mp3s into the background of my PS2 games...)

So anyway, the THX test on my dvd (the movie Speed) doesn't play the subwoofer channel ... Nor does the AC3TEST file or the SBLive's test.

Very annoying.

I think I'm going to go over to that forum you suggested now.

[killingspree]

i've just gotten a brand new audigy 2 with the fitting 6.1 one speakers and just would be curious to test out the THX sound. unfortunately i haven't got one of the rare THX certified DVDs.
so could somebody please point me to a link where i can download a THX test file?
thanks in advance
steVe