'Capturing' AC3

[video]

Hi there. Just an idea i may play with, bit i'm failed atm. i've got an an asus A7n8xdlx, equipped with nVIDIA's real time DD encoder. What i would achieve is to send any 6-ch wave thorugh soundstorm and record the AC-3 output of the audio chip. is it possible to do in some way?

[Rockaria]

It's a quite interesting issue.

If you right-click-open any 6chwav with Graph Editor, you will see the preferred components linked together to decode.

If you can replace the 'default wavout device' with 'nVidia nForce Audio' in the WDM Streaming System Devices and capture from it(maybe spdif), I think you can get the SoundStorm encoded AC3.

But the reality can be very much different. Instead, you can try ac3filter and WAVDEST+file writer(or dump ds filter) to capture the ac3filter encoded AC3 stream(the source must be 48K), which plays directly to the spdif by wav renderer but not a correct AC3 file I believe.

[KpeX]

Check out this thread (http://forum.doom9.org/showthread.php?s=&postid=338286#post338286) (mentioned in the FAQ ;))

[Rockaria]

Yeah, it's an (another) proven way to capture the soundstorm ddlive encoded AC3 using additional bit-accurate (professional) sound card.
The internal(TTL) or external(toslink) connection(soundstorm spdif-out-> audigy(or m-audio) spdif-in) captured ac3 stream can be stripped to ac3 file using besplit(ddwav correction) I suppose.

And the initial 'quest' was capturing the ddlive encoded ac3 directly?

[Rockaria]

I did a further test based on the spdif-in capture with my AN7(nForce Audio driver 3.75).

I connected spdif-out & spdif-in front panel pins using a jumper(sorta TTL connection)

Capturing a dts music(ac3 ecoded by ac3filter or soundstorm DICE) using sound recoder from spdif-in was successful at first.
The output played well with vlc as 5.1ch ddwav.
Converted to ac3 using besplit commandline(no drop fix) and played well.
BeSplit -core( -input d:\a.wav -output d:\a.ac3 -type ddwav -fix )
To make the capturing consistent I tried graph edit :

Wdm streaming capture device(nVidia nForce(tm) Audio))-recodingcontrol->Wav Dest->File Writer
It captured the ddwav flawlessly and played well with vlc.

[edit]
The final AC3(through besplit) was 48K as encoded by sound storm, so can be played directly(passthrough) using AC3 Filter or VLC.
...
SPDIF/AC3
speakers: 3/2.1 (5.1)
sample rate: 48000Hz
stream: 8bit
frame size: 2560 bytes
nsamples: 1536