How to decode Dolby Digital from SPDIF input?

[Try4ce]

I had absolutely no idea this was a problem.

I have a Creative X-Fi Titanium sound card with SPDIF input. It decodes Pro Logic II just fine, but it took me much longer than it should've to realize that the reason I didn't get PS3 game audio to my computer was because PS3 games output Dolby Digital when I have my console set to output Dolby Digital. Any game that does not support Dolby Digital (such as PS1 or PS2) is fine.

I have my PS3 going into my audio receiver by TOSLINK, and out to my computer's sound card by TOSLINK. From all the research I have done while working on this issue, it appears as though sound cards, for all the Dolby Digital logos slapped on their boxes, don't decode Dolby Digital through SPDIF input. But I'm hoping I'm wrong on that!

The purpose of getting PS3 audio to my computer is to do a weekly show with live video streaming, while not being detrimental to my actual A/V setup. I've decided I'm not going to get all up tight over using Pro Logic II for one night a week, especially when I'll have a headset on anyway to talk on Skype and I wouldn't be able to really hear all of the detailed surround effects coming from my speakers as well as I would without my ears covered.

So. It's no biggie, but I'd still like to solve the problem, if only so I don't have to mess with my PS3 audio settings to turn Dolby Digital on and off every time.

Oh, I also have access to a Sound Blaster Audity with a separate digital I/O module, if that helps. If there's another card that could do this, I suppose I could consider that as well.

Does anyone know anything about this?

[RickA]

Greets,

Hopefully someone will offer you better ideas than I am able to. I know more on outputting DD to a receiver than inputting it to the computer via SPDIF.

Sounds like you want more to be able to just hear the DD output of your receiver on your computer. Not that you want to broadcast your show as DD. I would think DD would eat up a chunk of your transmitting bandwidth. Don't know if Skype handles DD. Those hapless users without DD decoders would not be able to hear you. Given that, I figure you just want the audio input from receiver to be heard by your listeners as wav, mp3, Line In /Stereo Mix kinda thing, etc.

If you have them installed. Possibly there could be some settings you can tweak in ffdshow audio decoder/ mixer section, or in AC3Filter the SPDIF area. I have them both set to Same as Input for my output of DD to receiver via SPDIF.

Does the input from your receiver / PS3 have to be live? Can you pre-record the DD input as wav / mp3 and play it back on your computer as you need it? An extra step of hassle, I know. I take it you have already dug around in the Creative Audio HQ settings? I know my Audigy 2 ZS has an SPDIF area.

Cheers,
Rick

[Try4ce]

Well, the "problem" for the viewers is solved already. I simply go into my PS3 audio settings, turn off Dolby Digital, and the games will output Pro Logic II. Nothing could make it sound any better to the viewers, because they are actually getting a mono mix in the end. The "problem" for me is simply for my own convenience (not having to turn Dolby Digital on and off between broadcasts) and my own listening experience. If I can solve this problem, the viewers shouldn't have any greater or any lesser of an experience. It's just for me.

I actually use Justin.tv to broadcast, and Skype is used for me to speak with my co-hosts and to get their voices flowing through my computer so I can broadcast their audio to Justin.tv. So really, Skype has nothing to do with it.

I've only had my PS3 for a couple of months, and have only done two shows with it so far. The first I gave up on game audio entirely, and the second I had to settle for trying to pick up some game audio over a mic. My other consoles don't cause problems because they are all hooked up with RCA cables and do Pro Logic II at best.

By the way, I'm fairly ignorant on the subject of audio. Doing all these tests last night, I think I only truly felt the difference between Pro Logic II and Dolby Digital last night. It's pretty nice. But most any deep technical speak or abbreviations will be lost on me.

[yoda313]

@try4ce - I am just going to be getting into realtime 5.1 capturing as you are trying. I just ordered the sound blaster i/o module that allows spdif recording via fiber optic and coax.

My goals are to record 5.1 off the ps3, xbox 360, and my cable hddvr box.

Another poster in a seperate thread said you need to record in "bit accurate" recording mode. Also it needs to be a 24bit recording sound card and I believe the other poster said the creative xfi series fits that bill.

You should scan your recording software for any terms that relate to bit for bit or digital stream recording. For true 5.1 audio capturing your goal is to get the ac3 stream off the outputting device.

I have a soundblaster live 24bit external device. I am hoping this will be adequate for recording - if not I plan on upgrading to an internal creative xfi card.

Please let me know how your experiments go. Also have you tried burning a dvd with video and the new audio you are recording? What file types is it recording in? Wav, mp3, .ac3?

[Try4ce]

While our ultimate goals are a bit different, it sounds like we will be using basically the same hardware in hopes of decoding Dolby Digital 5.1. Let's stick together on this one!

I haven't tried actually recording anything, and audio bit rates aren't my specialty (I'm more of a video guy, but I get by with what audio I have to do). Obviously, actually recording in 5.1 isn't my top concern, but I do wonder if I would have to be properly set up to record 5.1 to actually hear 5.1. There's more I could do to mess around with the audio settings... but I got too tired last night to spend any more time on it! I may look into it a bit this weekend if I get the time.

Meanwhile, maybe we can get some more helpful information in this thread.

[Nelson37]

Well, it think it might be possible to do what you are trying to do, but there is both an easier and better way.

To pass along the AC-3 bitstream would be worse than useless unless your users had a DD decoder, which many do not. The hi-volume ac-3 bitstream could damage speakers or rupture eardrums for headphone users, and the bandwidth usage for the audio alone can exceed that of some streaming video sites.

What you really want, if I understand you correctly, is simple stereo at the PC end while maintaining 5.1 output at the console. You could configure AC3Filter to do this at the PC end, also I think the Creative software can do this, or others. 6 waves I know can be done.

Instead of changing the audio at the game console, do it at the amp. Continue with Spdif-in at the amp but use simple stereo RCA line out from the amp for the PC feed. You could also see if the stereo outputs are live at the same time as the optical at the console end, my sat box did this.

[Try4ce]

The PS3 will not output RCA at the same time it outputs Optical if you modify your sound settings (which includes turning on Dolby Digital). Also, my receiver will only output optical audio through the optical output.

I'm hearing all this talk about AC3Filter, but don't understand exactly it's supposed to do, how I can make it work with my sound card, and what I should configure to get the result I'm looking for. Could I get some clarification?

And yes, of course you're right that it doesn't need to be 5.1 on the PC end, but it still has to be decoded at some point. I'm pretty sure no matter what though, that my broadcast will be plain old mono, so no worries for viewers who can't decode 5.1 I'm not sending that signal over the Internet.

[yoda313]

You might want to see if they make fiber optic dual splitters. I'm not talking about switchers but ones that would take one fiber optic signal and DUPLICATE it so you would take 1 signal and send it to 2 devices.

I don't know if they make those nor do I know how expensive they'd be.

You're only other option would be to go strictly analog on audio. Then you could easily split analog audio so it would go to two sources from one output. Those y adpaters are dirt cheap.

Of course you'd be limited to analog audio during playing but that would be a "quicker and cheaper" route.

[Try4ce]

Well there's really no problem with the setup I'm using other than that if I turn off Dolby Digital on my PS3, then I get Pro Logic II on my speaker system. This appears to allow any game's audio to be used by my computer. The digital cable has nothing to do with it, so there's no reason to go analog.

[RickA]

Misspost. Basically said the same thing as Nelson - use RCA analog out from receiver to PC Line in letting receiver decode the DD for you.

Rick

[Try4ce]

Unfortunately I'm pretty much very very certain (and just tried again) that there is no way to output RCA audio from my receiver when the input source was optical. That's the entire reason I needed SPDIF input on a soundcard.

It would make my setup very very easy if I could output RCA but believe me, I tried that long ago. I wouldn't rule out the fact that I just don't understand how to make that work, but it doesn't seem to work.

[x2srj]

I have a similar problem and need help!

I have my PS3 with optical out to my PC SPDIF in... I can hear the main menu click's as I move around the menu system.. but as soon as I load a game or play music I don't hear anymore sound? The sound output it through Logitech X-530.

I've got ffshow and AC3 filter installed on my PC

thanks in advance..

[dadudster]

I have created a new thread on the AVS Forum to compile all of my knowledge about SPDIF related issues.
http://www.avsforum.com/avs-vb/showthread.php?p=15846010#post15846010

It provides a really detailed compiling of everything I have discovered about this issue, and lists the limitations in detail.

Lets move all further discussion related to this issue to that thread.

Also, please circulate the thread. I would like it to become a sticky in that forum subsection (so that people wont waste the hours I have wasted on this issue).