Recoding Dolby Digital 5.1 bitstream from Xbox360 [Archive]

View Full Version : Recoding Dolby Digital 5.1 bitstream from Xbox360

Seraphic-

2nd April 2009, 19:15

I've been doing extensive research trying to find a way to record Dolby Digital 5.1 from Xbox 360 over Toslink or HDMI.
At first I was looking for hardware that would be able to decode Dolby Digital 5.1 to LPCM 5.1 over HDMI.
Found a few devices as seen below (but can't confirm if they would be able to do the decoding):

http://www.gefen.com/gefentv/gtvproduct.jsp?prod_id=5277
http://www.lektropacks.com/view_product_standard.php?product=1001185&sub1=&show=
http://www.tmfsolutions.co.uk/Octava_HDMIto71.htm

Since I haven't been able to get confirmation on the above hardware, I next moved on to researching direct Dolby Digital 5.1 recoding over Toslink or Coax. Found several interesting reads:

http://www.videohelp.com/forum/archive/how-to-capture-ac3-t347474.html
http://forum.doom9.org/showthread.php?t=70024
http://forum.doom9.org/showthread.php?s=&threadid=25650
http://forum.doom9.org/showthread.php?s=&threadid=65549
http://forum.doom9.org/showthread.php?t=56795

From what I can gather, you need a few things to do this.
1. A soundcard with Toslink or Coax input
2. Bit-matched recording
3. 48khz - 16bit recoding option
4. BeSplit software
5. Even with all of the above, some soundcards still might not work

My Auzentech Prelude 7.1 (not sure it it works) soundcard supports one through three and using BeSplit I've done a several tests.

Set Xbox 360 to output Dolby Digital 5.1
Started up a game and let it run
Set soundcard software to record Digita-In (toslink) bitmatched

http://www.seraphicgate.com/test/scdi.jpg
http://www.seraphicgate.com/test/scdbi.jpg

Viewing the above topics I'm told you should have a wave
that has white noise. Below is what I see viewed with Adobe Audition (peaked out).

http://www.seraphicgate.com/test/aav.jpg

Next using BeSplit I ran the following script. It runs, but does not read any track time during creation and creates an .ac3 file with no file size.

BeSplit -core( -input live.wav -prefix e:\track -type ac3 -fix )

The following script runs, reads track time and creates file with a file size. But doesn't seem to be correct as when you play it, there is no audio.

BeSplit -core( -input live.wav -prefix e:\track -type ddwav -fix )

I also learned that this could be done doing capture with VirtualDub, but I haven't had much luck since I have no bit-matched option when recording the audio.

Is anyone able to offer some more thoughts? Thanks

ACrowley

4th April 2009, 09:33

You can record it with Sony Vegas and capture it dirctly in 6 (mono)CH when you record it in a 5.1 channel recording Project

http://forum.doom9.org/showthread.php?t=118759&highlight=Vegas

-Open the 5.1 record project /get it here: http://www.badongo.net/file/1786817
-Setup your input Bus in Options (Asio/SPDIF... )
-Press record and then Playback your DD Track from SPDIF in

Now you should have proper 6 Ch record with 6 discrete Channel ( R L C LFE SL SR)
-You can export it to Dolby Digital with the Vegas Dolby Digital Encoder.
-Export the 6 mono waves and encode with Aften when you dont have the DD Pro Encoder Plugin

Seraphic-

4th April 2009, 18:47

Thanks, I'll give this a try. Are any other modifications needed for the bus in options (seen below)?

Edit: I'm not getting any audio at all when set to digital in l/r (which is what I'm using).
Does the sound card need to be able to decode Dolby Digital 5.1 (ac-3)? Soon as I switch Xbox360 from Digital Stereo to Dolby Digital 5.1 all audio cuts out.

http://www.seraphicgate.com/test/svas.jpg

Seraphic-

5th April 2009, 20:28

Did some more research and the Prelude 7.1 seems to have no decoding features at all. Just encoding features for Dolby/DTS.
It only accepts two channel PCM over toslink/coax. Seems Like I would have to find an old Audigy 2 ZS Platinum Pro for this to work.

http://www.seraphicgate.com/test/sol.jpg

ACrowley

8th April 2009, 12:50

yes, you dont have the DD 5.1 Decoder. All X-fi PCI_E dont have 5.1 Input via toslink/SPDIF in. Only Stereo

It should work with a Audigy2 ZS (no Platinum required)

Seraphic-

8th April 2009, 19:23

yes, you dont have the DD 5.1 Decoder. All X-fi PCI_E dont have 5.1 Input via toslink/SPDIF in. Only Stereo

It should work with a Audigy2 ZS (no Platinum required)

The Prelude 7.1 is just normal PCI, but not like it makes a difference since it still only supports stereo in.

And I think you do need the Audigy2 ZS Platinum as the card itself has no toslink/spdif input.
The Platinum comes with the add-on drive bay with toslink/spdif input.

http://jimmyauw.com/wp-datajim/audio/19_sc/audigy2zs.jpg

http://h10025.www1.hp.com/ewfrf-JAVA/Doc/images/c00059778.jpg

ACrowley

9th April 2009, 10:06

Seraphic-

9th April 2009, 20:41

yes, youre right....the audigy2zs has only coax and no toslink.

You can use a SPDIF 2 COAX Changer, this is what i have done. Because a Platimun is more expensive compared to a audigy2zs + SPDIF to Coax changer
http://www.svideo.com/coaxtoslink1.html

Also the Audigy2 has has a internal SPDIF connector. You can connect a little SPDIF Slot Panel to it.
http://www.twam.info/elektronik/spdif-audigy2

Don't you mean this?:
http://www.svideo.com/toslinkcoax1.html
Xbox 360 already has toslink output (no coax).

Also, where do you see Coax in? The port on the far/top left is Digital Out.
http://upload.wikimedia.org/wikipedia/commons/1/1f/Soundblaster_Audigy2_ZS.jpg
http://www.mat2057.info/wp-content/uploads/2008/06/audigy2zs.png

You can use a SPDIF 2 COAX Changer, this is what i have done. Because a Platimun is more expensive compared to a audigy2zs + SPDIF to Coax changer

So you have a Audigy 2 ZS for recording Dolby Digital 5.1 input?

ACrowley

10th April 2009, 10:21

No, i have a Xfi Titanium PCI_E Now..

The Audigy2zs ha s a 3,5mm Jack SPDIF (electrical) That means you must have a Adapter to mono chinch( =coax)
http://www.andoo.de/details_Shop_Verzeichnis.Computer_Shops,SPDIF-Adapter-3-5%20mm%20Jack%20auf%20SPDIF-Cinch,453090.html

Or you can take a standard stereo Cable with 3,5mm Headphone and stereo chinch. Just use one of the Chinch Connectors.
This works for SPDIF Out. Im not 100% sure if the Audigy 2sz has a SAPDIF In. Maybe you search in the Creative Forum

Maybe you better by a Platinum...no need to for those Adapters.

Seraphic-

17th April 2009, 17:53

It's alive!!! AC-3 Dolby Digital 5.1 internal decoding input and AC-3 passthru working from Xbox 360 in Audigy2 ZS Platinum.
Going to try and do AC-3 bit-matched recording now and see how it goes.

EDIT: Does Sony Vegas have bit accurate recording? Not having much luck yet.

Seraphic-

18th April 2009, 20:31

Well, I have still not been able to do a direct recoding of the AC-3 bitstream.
But I think that is because I'm still just unsure how to do it correctly.

However, after some trial and error, I was able to let the soundcard do the decoding and record its streams and it worked.
But I would be interested to know which would be better quality, recording the direct ac-3 stream or letting the soundcard do the decoding and recording that stream.

Seraphic-

19th April 2009, 20:36

Should all Dolby Digital 5.1 streams contain an LFE stream or is it up to the speakers/receiver to handle it?
Tested a PS3 games and two Xbox 360 games, PS3 game had all channels plus an LFE stream as did one of the Xbox 360 games.
However, one of the Xbox 360 had all streams but LFE. Is that normal or...?