Getting DD 5.1 and DD+ out of external generic USB sound card

[ken h]

I want to get Dolby Digital 5.1 and/or Dolby Digital Plus (either spdif optical or coax) from Windows Media Center via an external USB sound card. I've already used HDMI from the same system and it has DD output, so I know it's available in the PC, somewhere.

The unit I bought is only outputting 2 channel PCM. In the Control Panel, Sound, Speaker Properties, there is no option for AC3 or E-AC3; only three 16 bit options (FM quality, CD quality, DVD quality) which I tried; the configuration only 'sees' 2 speakers.

I also tried using a 'Windows 7 Codec Pack' from CNET.com that says it has DD & DD+. When I installed it and set it up, it would not save the settings that select AC3, etc.

The chip used on the USB card is a PCM2704. All I can figure is that it's only capable of PCM, but I've been told that any USB card with SPDIF out should be able to pass DD from a source that has it, like live HDTV from Windows Media Center. In other words, no encoding is necessary by the card.

Here's a link from ebay to the product: http://www.ebay.com/itm/PCM2704-USB-to-DAC-Optical-S-PDIF-USB-Sound-Card-Decoder-Board-Aluminum-case-/262001131967?hash=item3d007c01bf

Help.

 

[Rogue Leader]

This is never going to work. You need to still have hardware that can provide a Dolby Digital signal, and that simple PCM decoder you have does not do that. They even have an alternate version of it I saw which will give you 5.1 but only via analog outputs, the digital output is only 2 channel.

You need a real 5.1 USB sound card such as:

http://www.soundblaster.com/products/Sound-Blaster-X-Fi-Surround-5-1-Pro.aspx

Purchase link:

http://smile.amazon.com/Creative-Blaster-Surround-System-SB1095/dp/B0044DEDCA/ref=sr_1_2?ie=UTF8&qid=1443645665&sr=8-2&keywords=sound+blaster+usb

 

[ken h]

This is never going to work. You need to still have hardware that can provide a Dolby Digital signal, and that simple PCM decoder you have does not do that.

Not sure you understand. The WMC audio output (from HDTV) is providing an encoded Dolby Digital signal; all the sound card needs to do is pass that native signal; no encoding or decoding is necessary. The decoding is done downstream in a conventional AV receiver.

The Dolby Digital Live function for the linked product, is to do real time encoding for audio sources that are not already encoded, like many video games.

But, you might be right, which is why I'm asking.

 

[Rogue Leader]

This is never going to work. You need to still have hardware that can provide a Dolby Digital signal, and that simple PCM decoder you have does not do that.

Not sure you understand. The WMC audio output (from HDTV) is providing an encoded Dolby Digital signal; all the sound card needs to do is pass that native signal; no encoding or decoding is necessary. The decoding is done downstream in a conventional AV receiver.

The Dolby Digital Live function the linked product has is for audio sources that are not already encoded, like many video games.

But, you might be right, which is why I'm asking.

No DD Live doesn't matter, while WMC has the software codec for DD, and is providing DD DATA, you still need hardware that can output a DD Signal. There is no such thing as a native signal, the DD sound data needs to be transmitted by hardware that can provide a DD encoded signal. The box you're trying to use cannot. Your HDMI output can, as can the Sound Blaster I linked.

 

[ken h]

There is no such thing as a native signal, the DD sound data needs to be transmitted by hardware that can provide a DD encoded signal.

I beg to differ. By native, I mean that each program with audio has a native format. For most Windows programs, that format is 2 channel stereo. The native audio format for Windows Media Center is Dolby Digital Plus.

All the hardware should have to do is pass what it gets when WMC is running.

 

[Rogue Leader]

There is no such thing as a native signal, the DD sound data needs to be transmitted by hardware that can provide a DD encoded signal.

I beg to differ. By native, I mean that each program with audio has a native format. For most Windows programs, that format is 2 channel stereo. The native audio format for Windows Media Center is Dolby Digital Plus.

All the hardware should have to do is pass what it gets when WMC is running.

Right and you need a chipset that can pass a dolby encoded signal. The only way to do that is to use something like what I linked. The device you have will not do that, it passes PCM audio only. Maybe I worded it wrong saying ther eis no such thing as a DD native signal, there is, but that signal requires the proper hardware to output it.

 

[ken h]

Right and you need a chipset that can pass a dolby encoded signal. The only way to do that is to use something like what I linked. The device you have will not do that, it passes PCM audio only. Maybe I worded it wrong saying ther eis no such thing as a DD native signal, there is, but that signal requires the proper hardware to output it.

That appears to be what is happening.

Like I said though, I was told elsewhere that a USB device with SPDIF output, optical or coax, should pass DD regardless.

What I have found is the PCM audio is quite good, much better than analog. Still, I miss Dolby Digital.

Thanks for your input.

 

[Rogue Leader]

Right and you need a chipset that can pass a dolby encoded signal. The only way to do that is to use something like what I linked. The device you have will not do that, it passes PCM audio only. Maybe I worded it wrong saying ther eis no such thing as a DD native signal, there is, but that signal requires the proper hardware to output it.

That appears to be what is happening.

Like I said though, I was told elsewhere that a USB device with SPDIF output, optical or coax, should pass DD regardless.

What I have found though is the PCM audio is quite good, much better than analog. Still, I miss Dolby Digital.

Thanks for your input.

Yeah whoever told you that is definitely wrong. Barring the technical reasons, the #1 reason it works like that is because Dolby Laboratories makes money from every device that can output its signal, so it needs their encode/decode chipset process to work. Part of the cost of the Sound Blaster is the license costs for DD/DTS.

 

[ken h]

I just found this. It should do the job for much less.

http://www.turtlebeach.com/product-detail/sound-cards-accessories/audio-advantage-micro-ii/31

 

[Rogue Leader]

I just found this. It should do the job for much less.

http://www.turtlebeach.com/product-detail/sound-cards-accessories/audio-advantage-micro-ii/31

Yes that will definitely work. Good find.

 

[ken h]

It's on ebay from Newegg for $30.48, including shipping, so about 1/2 price.

 

[ken h]

I did get one of these (Turtle Beach Micro II) locally from Microcenter, they had it for $25.

It works quite well but first you have to download and install the specific driver from the Turtle Beach website.