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X-FI, digital out and AVI's with 5.1 AC3, can it be done.

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June 3, 2006 7:33:36 PM

When I set AC3 Filter to SPDIF passthrough, the X-Fi drivers won't leave the AC3 stream alone. It decodes it then reencodes it and since it doesn't support 5.1 AC3 encoding (as is the case for nearly every sound card) it downsamples to 2.0

None of this effects DVD playback, just avi's with 5.1 AC3 sound tracks.

On older SB cards you had to uncheck AC3 decoding to get AC3 Filter to work properly.

This isn't an option for the X-FI, at least not for non-DVD sources.

It turns out disabling AC3 passthrough was worked better anyway as the X-FI's DAC renders the audio better than my $350+ home theater reciever. (I have an 2nd PC with working SPDIF passthrough for side by side comparision with the same DVD).

But I am still curious if anyone has managed to get digital output of 5.1 AC3 from a non-DVD source using the X-Fi.

More about : digital avi ac3

June 4, 2006 4:47:44 AM

You really need a digital solution to a HT receiver, you need a soundcard with hardware DDL or DTS-Connect.

And, hey, it sounds like you prefer the analog way anyway.
June 4, 2006 9:29:50 PM

So you manged to get all 6 channels for a 5.1 ch AC3 avi file from an XFi using digital output?

What settings/Ac3 filter's were used?
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June 5, 2006 1:55:13 AM

Quote:
So you manged to get all 6 channels for a 5.1 ch AC3 avi file from an XFi using digital output?

What settings/Ac3 filter's were used?


I think you need to reread my post again.
June 5, 2006 4:05:21 PM

I didn't ask for what was required in gernal for digital output.

All I asked and all I am interested in is whether anyone was able to get the XFi to output digital 5.1 AC3 from an .avi source.

Anyway you definately don't need Hardware DD or DTS support to get 5.1 from your .avi files.

In fact you need the exact opposite. You need to be able to tell the card to do nothing to the AC3 track and just send it out bit for bit via the digital port. The best cards for digital passthrough of AC3 and DTS happen to be the CMedia cards which don't have any hardware AC3 and DTS decoding to get in the way of a simply bitstream passthrough.

With the older Sound Blasters you just had to set them to digital out and uncheck AC3 decode and then you can passthrough an AC3 stream without any processing from a Direct Show filter such as AC3 filter.

I haven't been able to get the X-Fi to do the same. When AC3 filter tries to passthrough the AC3/DTS track directly to the digital output the X-FI steps in and decodes and rencodes the signal.
June 5, 2006 10:07:49 PM

This is the wrong forum to ask anyway, in my opinion.

I would try arstechnica or avsforum.
June 5, 2006 10:50:59 PM

I might do that.

I have a friend who has a $1000+ Home Theater Reciever and is thinking of building a home theater PC. (Don't ask what his TV or Speakers Cost).

I am guessing the X-FI's DAC doesn't sound as good as his reciever, so he would definately want to use Digital out for movie and analog out for games.

The X-FI's digital port is shared with the mic, and the mode switcher lets you save settings for games vs enterainment.

So the X-FI would be perfect for him, if I can solve the .avi digital passthrough problem.

But he isn't building for a few months. By then new drivers may be out, or a new version of AC3 Filter that is more compatible with the X-FI. So I am not trying too hard yet.
June 6, 2006 4:23:37 AM

DACs are one of the least things you need to worry about in the noise chain, but in this situation, using the analog outs would put the signal through the X-FIs DAC process, then it would run through the receiver's ADC and DAC, then a filter would send parts to the speakers and sub, then finally it would be seperated amplified.

If he is gaming with a home theater setup, it would be preferential to go all digital with a dolby digital live or DTSC-based

Staying digital before amplification means less DAC-ADC processes, less distortion, less floor noise (generally the tweeter). Also avoiding Creative's resampling process is always a plus for waveform accuracy.

But of course, electronics is a sliding hill of diminishing returns. The difference between digital and analog (X-Fi) aren't a huge factor in the final output, just as the X-Fi is hardly any different than a shielded onboard sound card. The actual audio output, depends heavily on the quality of the amplifier and the loudspeakers.
June 6, 2006 6:14:17 AM

Heh, actually I don't know why the X-Fi's AC3 decoding sounds better than the reciever's AC3 decoding.

I do know that I had to use a DVD to test it because Creative seems to write their drivers with the assumptions that DVD's are the only source of AC3 or DTS soundtracks.

Again I am just assuming that with a $1000+ Receiver you are better off using external AC3 and DTS decoding. Maybe its so expensive because of the insane number of connections. Analog output might end up sounding just as good or even better.

Really I am just annoyed that I cannot enable AC3/DTS digital passthrough from .avi sources with the X-FI.

I got SPDIF passthrough to work correctly with every other Creative Card supporting Digital Output.

Honestly, once I got it working I would just turn it off.

But I am still going to give it a try everytime Creative releases a new driver or if and when a new AC3 filter version is released.

The Russian who codes AC3 Filter answers most comptiblity problems with the offer that if you send him the hardware he will see if he can tweak his code to work with it. I guess no one has sent him an X-Fi yet. :) 
June 6, 2006 8:55:06 AM

Quote:
Heh, actually I don't know why the X-Fi's AC3 decoding sounds better than the reciever's AC3 decoding.


I don't know either. Some more anal blind testing types might point out a lack of level-matching, differences in the setup, measurements to show the output is different etc. I personally believe if something sounds better to you, go with it because trying to prove it with measurements does require a bit of a dedicated hobby that most people don't have the time or drive for.

Quote:
I do know that I had to use a DVD to test it because Creative seems to write their drivers with the assumptions that DVD's are the only source of AC3 or DTS soundtracks.


Interesting. Perhaps you should try the Creative forums and ask the tech support, perhaps they could confirm your beliefs or help you reach a solution to your problem.

Quote:
Again I am just assuming that with a $1000+ Receiver you are better off using external AC3 and DTS decoding. Maybe its so expensive because of the insane number of connections. Analog output might end up sounding just as good or even better.


Analog output might sound better for any number of reasons; could be objective (measurement's neglibly different in noise level, but for some reason volume is higher, and louder = better to the ears) or subjective (personal preference to a certain type of distortion).

However, analog output objectively cannot measure better if the volume is level-matched, because even if you have a better external DAC than the receiver's DAC, and the noise differential between ADC+DAC and DAC only processes is neglible, you still go through both the receivers DAC and the external DAC. So even with 0 conversion loss, the use external DAC logically couldn't result in a better real measureable output.

This isn't to challenge your assertions, these are simply what I've come to believe from what I've read about audio theory. So, there certainly could be holes (or additional problems) that somehow could lead to analog > digital.

The whole concept of digital isn't who has the better DAC, but to minimize the totally digital to analog processes. Your receiver could have the crappiest DAC in the whole chain, but using it alone instead of in conjunction with all the others should give you the least noise level. If you go analog, aka going with a seperate DAC other than a receiver's DAC, then you need a seperate amplifier as well.

From what I understand, alot of people use seperates for this reason: they wan't a better DAC than the receiver offers (audio purists with alot of money?), and so they use the pre-outs (effectively regulating the receiver to just a dolby digital/DTS decoder) and feed it directly to seperates amps from an external DAC, to avoid the whole receiver DAC-ADC process.

Quote:
Really I am just annoyed that I cannot enable AC3/DTS digital passthrough from .avi sources with the X-FI.

I got SPDIF passthrough to work correctly with every other Creative Card supporting Digital Output.

Honestly, once I got it working I would just turn it off.

But I am still going to give it a try everytime Creative releases a new driver or if and when a new AC3 filter version is released.

The Russian who codes AC3 Filter answers most comptiblity problems with the offer that if you send him the hardware he will see if he can tweak his code to work with it. I guess no one has sent him an X-Fi yet. :) 


Freelancers do need a bit of nudge to work on something, perhaps a donation ;) 
June 6, 2006 9:48:44 AM

Quote:
When I set AC3 Filter to SPDIF passthrough, the X-Fi drivers won't leave the AC3 stream alone. It decodes it then reencodes it and since it doesn't support 5.1 AC3 encoding (as is the case for nearly every sound card) it downsamples to 2.0

None of this effects DVD playback, just avi's with 5.1 AC3 sound tracks.

On older SB cards you had to uncheck AC3 decoding to get AC3 Filter to work properly.

This isn't an option for the X-FI, at least not for non-DVD sources.

It turns out disabling AC3 passthrough was worked better anyway as the X-FI's DAC renders the audio better than my $350+ home theater reciever. (I have an 2nd PC with working SPDIF passthrough for side by side comparision with the same DVD).

But I am still curious if anyone has managed to get digital output of 5.1 AC3 from a non-DVD source using the X-Fi.


I have made it work... I bought SoundBlaster X-Fi Elite Pro. It has:
- Digital-out / Line-in / Mic-in
- Aux-in 2 / Phono-in
- DIN
- Midi-in / Midi-out
- Optical-in (Toslink)
- Optical-out (Toslink)
- SPDIF-in (Coax)
- SPDIF-out (Coax)
- Headphone connection
- Line-in 2 / Mic-in 2
- Line-in 3 / HI-Z

In Audio Console I have these settings too play with:
- SPDIF Input Settings
- Digital Output (PCM) Sampling Rate Settings
- Dolby Digital/DTS Bitstream Out (Note: External Decoder required)
- Use Built-in Decoder and settings for Dolby Digital-EX and DTS-ES-something...
- Bit-Matched Recording...

If you run an AVI-movie with AC3 5.1 sound with VLC media player, then it will work perfectly, but it will be decoded in the computer...
June 7, 2006 3:14:40 AM

Quote:
]If you run an AVI-movie with AC3 5.1 sound with VLC media player, then it will work perfectly, but it will be decoded in the computer...


I can get perfect 5.1 from avi files usind AC3 filter with X-FI's analog 5.1 output.

I just can't get AC3 Filter's SPDIF passthrough to actually passthrough the X-Fi's digital out unmolested.

PowerDVD's SPDIF passthrough works perfectly, but only when playing DVD's.

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