How to passthrough 2 channel DTS and AC3 files?

[Phat J]

Hey everyone!

So I have my PC hooked up to my home theater receiver via HDMI and TOSLink. I set up the SPIDIFER program to pass through videos with multichannel DTS and AC3 for the receiver to decode, and it shows up either DTS or Dolby Digital on my receiver display.

But when I play back a video with 2 channel DTS or AC3, it appears to be decoded by the PC, then outputted as PCM, as my receiver displays Stereo digital PCM. Why would this be? How do I get the PC to send the undecoded 2 channel DTS or AC3 sound to the receiver?

My system:
Windows XP SP3 OS
Asus Xonar DS soundcard
Denon AVR-1712 receiver

Thanks!

[Baldrick]

Spidifer program?

You can try use another app like ac3filter.

[Phat J]

I've tried both, and FFDShow, both don't fix the problem. But thanks.

[jman98]

Phat J - It doesn't matter that it gets output as PCM. You only have 2 channels. PCM is LOSSLESS. LOSSLESS. Conversion of 2.0 AC3 and 2.0 DTS to 2.0 PCM is LOSSLESS. The PCM file is IDENTICAL to the original audio. Stop worrying about a problem that doesn't actually exist.

[Phat J]

I understand you jman98, I realize PCM is lossless and that the PC converts whatever source file to PCM to send down the cord to the receiver. I would prefer to have my hardware (receiver) decode it entirely rather than the software filters on the PC, since the hardware should produce better quality sound. Multichannel DTS and AC3 allows this, why not dual channel DTS and AC3?

Here's another thing. If I play a movie with 5.1 AAC audio, I understand that the PC's SPIDFER or FFDShow filter converts the AAC as AC3 and sends it to the receiver as Dolby Digital, since the receiver won't natively decode AAC. The receiver shows Dolby Digital while this is being played back. Now if I turn off that feature in SPIDFER, the receiver decodes it as PCM 2 channel, ignoring the other 4 channels. This is leading me to believe that the PC is decoding the 2 channel DTS and AC3 instead of just passing them through, since the receiver display shows the same PCM decoding message. I tried turning on and off all the pass through and encoding options on AC3Filter, SPIDFER, and FFDShow, but it makes no difference.

My question is why is the PC decoding my 2 channel AC3 and DTS files instead of just passing them through untouched so the receiver can decode them? Why is it only doing that with the multichannel files? Maybe my receiver for some reason does not support 2 channel Dolby Digital and DTS? Or maybe the software filters only passthrough multichannel AC3 and DTS and not dual channel ones? Just seems odd to me.

I even tried taking one of these 2 channel AC3 files and converting it to 2 channel stereo, then creating a 6 channel AC3 file, leaving the other 4 channels as blank tracks. I played back this multichannel test file, and yes the receiver recognizes it as Dolby Digital rather than PCM. But I certainly don't want to re-encode all my 2 channel files to 5.1.

Hope this makes my question more clear.