Core i3's ability to pass surround sound over HDMI

Freeco · Post by **Freeco** » Fri Jul 02, 2010 4:33 am

I'm thinking of getting a HTPC to connect to my new flatscreen.
If I'm well informed the Core i3 is able to send surround sound over a HDMI cable thanks to its IGP.

I'm quite new on this niche area of IT, so some (noob) questions came to mind...
Audio coming from a bluray disc shouldn't be processed and can be sent straight to my amplifier over HDMI, so no issue there.
But was about sound that's normally treated by the onboard sound chip, or in my case a discrete Creative X-fi card? Things like simple Windows sounds, music files (mp3 etc), web format movies, etc. Will that sound also pass through the IGP over HDMI to my amplifier, or do I need an extra TOSlink for that?

m1st · Post by **m1st** » Fri Jul 02, 2010 5:30 am

I can't say specifically for the i3, but for other computers that I've built that pass audio through HDMI, it passes both movie stuff and normal windows sounds. So unless there is something broken with the i3's implementation of HDMI (which I doubt), your computer sounds should be sent over HDMI, just like the movie stuff.

Freeco · Post by **Freeco** » Fri Jul 02, 2010 8:45 am

in the meantime I also tried googling on this topic (found quite some topics on problems with HDMI pass through

)

But basically what I found was that you just need to specify in either the BIOS or the software that comes with the motherboard that audio should go through HDMI in stead of SPDIF/analog. This won't work when using a discrete sound card I guess.
Some (older?) motherboard/GPU combos also have a way of linking the SPDIF to the GPU and then passing A/V over HDMI. But as I want to use the IGP, that's not what I'm interested in.

correct me if I've misunderstood

swivelguy2 · Post by **swivelguy2** » Fri Jul 02, 2010 9:24 am

So, all normal sounds can be passed as LPCM via HDMI for up to 7.1 channels (only 5.1 on some older chipsets like AMD 785G). LPCM is decoded audio, the raw data - but it's still digital and still lossless.

However, if you're using bitstreaming to play a blu-ray disc over HDMI, there's no way to add any other sounds to that. Bitstreaming means you're passing the encoded audio stream (DTS-HD-MA or whatever they're calling it now).

So if you wanted to watch a blu-ray in the background while playing a game, you'd have to have your blu-ray player application decode the sound and pass it as LPCM. There's no problem with this, as it's still a lossless decoding whether it's done in your PC or in your receiver.

As for using an extra sound card like an X-Fi, I have no idea how that would work, I've never had one.

Freeco · Post by **Freeco** » Fri Jul 02, 2010 10:23 am

the HTPC would only be used for 1 purpose at a time. Regular HTPC stuff:
* occasionally browse the web
* watch movies
* listen to music
definatelly not doing x while y.

I now have an X-fi Platinum in my desktop (one of the first cards that was released with that chipset), and it doesn't have any digital outputs at the rear. I do have an extra 5.25" panel at the front with all sorts of digital/analog input/output connectors. But being at the front that's not that ideal for permanent cabling. edit: I see newer X-fi cards do have optical in/out at the rear.
Guess the onboard chip would be easier for this.

vortex222 · Post by **vortex222** » Sun Jul 04, 2010 2:12 pm

it does have digital output on the back, The top 1/8" plug (also used as line in/mic) is a flexjack that can be set with the creative software for coaxial digital output (on the right channel when using rca adaptors i think). It is however rather limited in capability and performance. It will send unmodified AC3 And DTS signal from a source movie and will also send stereo output from most games and such, but i do not think it will encode 5.1 or 7.1 sound from any game or other software that does not nativly generate AC3 sound.

Freeco wrote:the HTPC would only be used for 1 purpose at a time. Regular HTPC stuff:
* occasionally browse the web
* watch movies
* listen to music
definatelly not doing x while y.

I now have an X-fi Platinum in my desktop (one of the first cards that was released with that chipset), and it doesn't have any digital outputs at the rear. I do have an extra 5.25" panel at the front with all sorts of digital/analog input/output connectors. But being at the front that's not that ideal for permanent cabling. edit: I see newer X-fi cards do have optical in/out at the rear.
Guess the onboard chip would be easier for this.

Freeco · Post by **Freeco** » Sun Jul 04, 2010 11:17 pm

even more: I'd need an extra module to connect to that flexijack I/O connector.
Think I'll just try the onboard

vortex222 · Post by **vortex222** » Mon Jul 05, 2010 10:49 am

that is to provide optical, i have used an 1/8thinch stereo to rca plug right from that output to my amplifier. However it would not work with any games for 5.1 due to no software encoding of ac3, so i went with descreet analog cords for all 6 channels.... heh.

m1st · Post by **m1st** » Wed Jul 07, 2010 5:41 am

Freeco wrote:even more: I'd need an extra module to connect to that flexijack I/O connector.
Think I'll just try the onboard

Sorry if this is late. What video card are you planning on using to send the HDMI signal? If it is the video card in your signature (Radeon 5750), those have a built-in audio core that will pass the audio over HDMI. The only time that you need a S/PDIF connector plugged into your video card is on older nVidia cards that didn't have this built-in (such as: GTX260). Can someone confirm that you don't need to plug anything into the 5750 in order to send audio over HDMI?

Freeco · Post by **Freeco** » Thu Jul 08, 2010 2:12 am

I'd be simply using the IGP of the Core i3. Should be more than enough for an HTPC that's not used for gaming.
As an alternative I'd buy a budget HD5450. Have that one in my wife's desktop. But don't think it has any advantages for this kind of use.

m1st · Post by **m1st** » Thu Jul 08, 2010 6:04 am

Freeco wrote:I'd be simply using the IGP of the Core i3. Should be more than enough for an HTPC that's not used for gaming.
As an alternative I'd buy a budget HD5450. Have that one in my wife's desktop. But don't think it has any advantages for this kind of use.

Okay. In that case, then the integrated audio core in the i3 or 5450 would pass the audio over HDMI (either as LCPM or as a bit-stream passthrough) perfectly. When you want to play the audio through your regular speakers, you would set your "Default Playback Device" (assuming Windows) as your normal audio card, and when you want it to pass over the HDMI you would set your default playback device as the other option. Should be named HDMI or S/PDIF or something like that. No need to attach any cables from your X-fi or anything like that.