output in stereo over digital coax

[JonTom]

Hi, not sure if this is possible...

My HTPC is connected to my receiver via digital coax. TV shows are detected by the receiver and 'upmixed' to Dolby Surround. DVDs are passed through and the 5.1 is detected and decoded.

When I play MP3s, they are treated like a tv show and are upmixed by the receiver, which then attempts to play them in surround sound. I have to push a button on the receiver so that it turns off surround and plays them in stereo.

Is there a way to set up Sage so that it sends the signal, over the digital coax, and the receiver does not attempt to surround-soundify it?

[malore]

There is no way to differentiate a stereo TV signal from a stereo music signal, how it's played is controlled by your amp, like you are currently doing. Some amps are smart enough to have different settings for pure stereo, dobly pro logic surround, dolby digital, etc.

[JonTom]

Originally Posted by malore

There is no way to differentiate a stereo TV signal from a stereo music signal, how it's played is controlled by your amp, like you are currently doing.

I think I knew this, but i was hoping that I could specify a different decoder or something for MP3 audio, and have it send stereo over the coax. DVDs use different decoders than TV; I hoped this may be possible here too. In my head, perhaps the only way would be mix the MP3 audio into dd5.1, with all but the 2 front channels blank...

Some amps are smart enough to have different settings for pure stereo, dobly pro logic surround, dolby digital, etc.

Mine does, but as the HTPC is setup primarily as a video source, the audio is assumed to want to be in surround, so the amp tries to help. I can override it, but I'd like to automate that. Maybe a USB-UIRT is needed...

[stanger89]

Originally Posted by JonTom

I think I knew this, but i was hoping that I could specify a different decoder or something for MP3 audio, and have it send stereo over the coax.

No, they're both 2 channel PCM audio, there's no way to tell if that 2 channel PCM audio supposed to be matrix decoded (Pro Logic) or not (Music)

DVDs use different decoders than TV;

DVDs (usually) contain an AC3 bitsream with 5.1 channels of discrete-encoded/compressed audio. That AC3 bitstream is passed, as data (not PCM audio) to the processor. That's how that is distinguished from "normal" audio, it's a different data format.

Mine does, but as the HTPC is setup primarily as a video source, the audio is assumed to want to be in surround, so the amp tries to help. I can override it, but I'd like to automate that. Maybe a USB-UIRT is needed...

The only thing I can think of, is to use AC3Filter or ffdshow in Sage to "pre"-upmix TV to 5.1 AC3 and send everything out as AC3. However that may cause music in Sage to be upmixed as well.

If you want to try, set AC3Filter as the audio decoder (not for DVDs) and then find the AC3Filter config panel. Set it to "3/2+SW 5.1 channel" output and check the "S/PDIF (disabled)" box.

I don't know that AC3 filter does as good of a job as DPL or DPL II at upmixing though.

[JonTom]

Originally Posted by stanger89

The only thing I can think of, is to use AC3Filter or ffdshow in Sage to "pre"-upmix TV to 5.1 AC3 and send everything out as AC3. However that may cause music in Sage to be upmixed as well.

Okay, so audio from TV and MP3 is always treated the same way by Sage? This may be along the lines of the kludge that I may have to use to get this to work.

The other thought I had was to connect analog wires for MP3, but how would I tell Sage to use the analog connection for MP3s? Would I have use an external player?

[stanger89]

Originally Posted by JonTom

Okay, so audio from TV and MP3 is always treated the same way by Sage? This may be along the lines of the kludge that I may have to use to get this to work.

Not exactly the same, but I'm not entirely sure how audio is rendered, depending on what you change where, you may end up affecting both. I don't think AC3Filter would affect music, but I'm not sure.

The other thought I had was to connect analog wires for MP3, but how would I tell Sage to use the analog connection for MP3s? Would I have use an external player?

Wouldn't you have to change inputs on your reciever then? Is that better than changing the surround mode?

[JonTom]

Wouldn't you have to change inputs on your reciever then? Is that better than changing the surround mode?

You may have a point there...