ac3 sound

[johnmckee]

Hi, I have a video with 5 channel ac3 sound that I'm trying to pipe to my stereo with an spdif optical cable. It only seems to work properly when I set the ac3 filter to 2/0 stereo mode. When I set it to 3/2+sw the playback gets all slow and when I set it to spdif I just get a chittering noise...
I'm using winamp 5 + ac3 filter + windows me + via sound card built into motherboard + athlon 1800 cpu + yamaha home theatre receiver with 5.1 sound

It seems like it should be possible to send all 5 channels because I know my dvd player does it, right?

[Center]

I play ac3/dts files through spdif.
Are you able to watch DVD movies with the audio output to through your optical? I had to setup my soundcard to send audio out the spdif unencoded so that my receiver does all the decoding. It could have to do with the setting on your soundcard.

[KpeX]

Try switching to WaveOut instead of DirectSound output, for this and many more SPDIF playback tips see the link in my sig.

[Codesmith]

When you turn off SPDIF passthrough your sound card has to create digital signal.

Only 1 sound card does real time Dolby Digital (5.1) encoding and that's the SoundStorm which is only availiable on certain NF2 motherboards. Most can only create 2 channel Dolby Pro Logic digital signals. Some like my SB Live output 4 channel ProLogic.

The slowdown is probably form AC3 filter having to decode to 5.1, then your soundcard having to downmix to stereo and then encode that to ProLogic.

Play an surround sound test avi and see how many channels your sound card is actually sendin digitally. If its just 2, then its best to have AC3 Filter downmix as it decodes.

BTW I get the same chittering noise when I set AC3 Filter to SPDIF and play an AC3 encoded DivX with Media Player Classic!

I gave up and just use Windows Media Player which works great.

Don't give up. It took me a week, but now the sound I get from DivX movies is 100% identical to the output from my DVD player!

(Well for non DTS movies anyway)