Multi-audio output and LPCM wrapping

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Multi-audio output and LPCM wrapping

Postby mario595 » Fri Oct 05, 2012 7:05 am

Can somebody help me understand something...

I am using the optical output of the PS3. It is going to my AV reciever.
I also have connected the analog outputs of the PS3 to the receiver and turned the multiple audio output feature on.

My receiver has a zone2 feature that runs a couple speakers from an analog source while simultaneously playing Dolby digital or DTS 5.1 from a digital input source.

If I stream a file to the PS3 from the PS3 media server with AC3 (dolby digital) or transcode an audio file to AC3 everything works as expected.

The way I understand it the PS3 downscales the AC3 signal to two channel analog stereo and output that via the red and white RCA cables.

If I turn on the LPCM 2.0 wrapping option in the media server and transcode using tsMuxer the receiver gets the DTS signal and playes that 5.1 ok but zone 2 gets crazy static.

What is going on here exactly?

My guess is that with the wrapping option the PS3 is assuming that the audio track is LPCM 2.0 (since that is what is in the header). It then converts that LPCM 2.0 audio stream to two channel analog stereo. However since what is in there is actually a DTS track the conversion results into the static mess I hear. If an AC3 track were in there the same thing would occur.

Am I right? Is there a way to get the multiple audio to work properly when wrapping? What about converting to LPCM 5.1 and sending that audio? Is there something different in the latest releases of the media server that would have an affect on this?
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Re: Multi-audio output and LPCM wrapping

Postby meskibob » Fri Oct 05, 2012 12:06 pm

Yes, the PS3 can't do the DAC on the fake 2ch LPCM stream (in this case it's not even trying to downmix like it normally would for a 5.1 AC3). Since you're playing from the same PS3, there's no way for PMS to send two different audio tracks, one as 5.1 AC3 for the analog out and one as fake 2.0 LPCM for the digital out. You need to disable the "Keep DTS track..." setting in PMS so the DTS audio will get transcoded, and I'm not sure if 5.1 LPCM will work since you're not using an HDMI connection on the PS3 (I don't remember what it can handle as input when you're using the optical out).
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Re: Multi-audio output and LPCM wrapping

Postby mario595 » Fri Oct 05, 2012 7:49 pm

I believe PS3 only does 5.1 LPCM on HDMI.
It will do LPCM 2.1 on optical. I assume that if a blu-ray has 5.1 LPCM and you are using the optical cable that it will downconvert (if that is the correct term) to 2.1

The only thing I don't like about transcoding it wil not just transcode audio and mux into .m2ts which streams natively. It goes to the trouble of re-encoding the x264 to MPEG2. Is there a customizable way to have the media server not re-encode the video when transcoding and presenting it in a m2ts container with the AC3 track (reencoded DTS).
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