Need suggestions for a sound card with toslink output for audio passthrough

For discussion of topics specific to MythTV on linux
Post Reply
kdx7214
Junior
Posts: 17
Joined: Sat Nov 23, 2019 10:47 pm
United States of America

Need suggestions for a sound card with toslink output for audio passthrough

Post by kdx7214 »

I've got a cheap RCA stereo that I want to use for audio from mythtv. It's a 5.1 receiver, but it *only* has stereo rca inputs and toslink optical for 5.1. Can anyone recommend an inexpensive sound card that works on ubuntu and can be used for pass through support?
blm-ubunet
Senior
Posts: 265
Joined: Sun Jun 15, 2014 1:08 am
Cambodia

Re: Need suggestions for a sound card with toslink output for audio passthrough

Post by blm-ubunet »

You shouldn't need a soundcard.
I'm still using the SPDIF bracket plugged into the mobo internal headers (12 yrs+).
So just an old Core2Duo P45 chipset audio codec.
It can output 192KHz 24bit stereo & pass-thru DTS/AC3.

Coaxial SPDIF is actually superior to TosLink optical if you have golden ears.
kdx7214
Junior
Posts: 17
Joined: Sat Nov 23, 2019 10:47 pm
United States of America

Re: Need suggestions for a sound card with toslink output for audio passthrough

Post by kdx7214 »

Well, this mobo was a cheapie and doesn't have an spdif header (I just checked), so I'm sort of stuck. I'm not looking for anything fancy, just something supported by ubuntu and mythtv to do pass through.
blm-ubunet
Senior
Posts: 265
Joined: Sun Jun 15, 2014 1:08 am
Cambodia

Re: Need suggestions for a sound card with toslink output for audio passthrough

Post by blm-ubunet »

My Asus P5 mobo has been cheap amortized over 12+ years of use..
2 PSUs & 3 videocards & 2 tunercards later..

Could try cheat & use the audio output from HDMI TV or monitor. I think some TVs can pass thru' AC3/DTS but they can not transcode.. only pass thru or 2 ch PCM stereo.
I'm fairly sure HDMI (& DVI-D sometimes) can still carry SPDIF encoded bitstream AC3/DTS. But whether the TV will pass this thru' is another matter..


Or there are some very cheap HDMI adaptors US$10 with SPDIF audio output..
kdx7214
Junior
Posts: 17
Joined: Sat Nov 23, 2019 10:47 pm
United States of America

Re: Need suggestions for a sound card with toslink output for audio passthrough

Post by kdx7214 »

I've considered that. The problem is, from what I understand, MythTV doesn't output 5.1 or 7.1 through the HDMI on the graphics card (a GTX-1060). I already have an optical from my tv to the stereo and it works just fine, but it's only stereo. My guess is that MythTV is downmixing to stereo or some such as it shows the video.

Thanks for the input!
blm-ubunet
Senior
Posts: 265
Joined: Sun Jun 15, 2014 1:08 am
Cambodia

Re: Need suggestions for a sound card with toslink output for audio passthrough

Post by blm-ubunet »

I fairly (very) sure MythTV can be setup to output discrete multi-channel PCM or bitstream encoded (AC3/DTS) over HDMI.

I believe most mobos can be setup to output HDA over some of the analog headers.

MythTV by default uses the highest quality audio format over a connection/codec.
That information for HDMI/DVI etc is contained in ELD of the EDID information.
But I think that bitstream encoded formats may not be included / supported in it.

Best source of information could easily be Nvidia's write up on Intel HDA Azalia
https://download.nvidia.com/XFree86/gpu ... -document/
Nvidia's documentation is just the best but still there is no useful mention of SPDIF.

Your TV will be very likely reporting discrete multi-channel or just 2 ch PCM.
Because almost all TVs have support for AC3 (in OTA dvb & atsc), it is very likely you can force AC3 5.1 into it.

Your TV is not licenced to be able/allowed to encode discrete PCM into AC3, it can only pass AC3 thru. Edit: Or just output 2 ch stereo PCM.
Post Reply