Need Clarification on HTPC Audio

[quanta15]

Hi everyone. I've recently become interested in the HTPC concept, and after browsing the forums and looking at a fair amount of threads in detail, the audio portion is still a bit confusing for me... I think. I've been building PCs for about 15 years now, and I've always just thrown a decent sound card into the system, plugged in my $100-$200 5.1 PC speaker system, positioned them accordingly, and called it a day. But, in the middle part of next year, I'll be moving into a more permanent residence for the first time, and I want to create a home theater with an HTPC at its heart. I also have an obsession with minimalism, so reducing the number of components and wires is key.

So here's what I THINK I know, and I'm just looking for a confirmation before I press forward:

-I don't need a sound card, just the SPDIF capability on the motherboard. I'd connect it to an external receiver, and all of my system sounds, movies, music, etc will be audible via the speakers I connect to the receiver.

-When I play DVD's, movies, or play games that provide an option to output 5.1/7.1 DD, DTS, etc, as long as my receiver supports the format, I'll get surround sound. Can SPDIF handle 7.1 LPCM?

-I will only hear 2.0 PCM sound for playing MP3s, watching Youtube, hulu, etc, unless I get one of those fancy sound cards that encodes everything into some type of surround sound format regardless of the source. I think there are also some newer motherboards that do this encoding for me eliminating the need for a soundcard.

-I can also get a video card that supports bit-streaming audio over HDMI. This part is murky to me; do I need audio over HDMI if I'm using SPDIF? Will the video card also pass system sounds, web-browsing, you tube, etc over HDMI as stereo, or does this bit-streaming just apply to compressed digital streams like DD and DTS?

Thanks in advance for your time in helping me make sense of all of this.

 

[Activate: AMD]

Hi everyone. I've recently become interested in the HTPC concept, and after browsing the forums and looking at a fair amount of threads in detail, the audio portion is still a bit confusing for me... I think. I've been building PCs for about 15 years now, and I've always just thrown a decent sound card into the system, plugged in my $100-$200 5.1 PC speaker system, positioned them accordingly, and called it a day. But, in the middle part of next year, I'll be moving into a more permanent residence for the first time, and I want to create a home theater with an HTPC at its heart. I also have an obsession with minimalism, so reducing the number of components and wires is key.

HDMI is the best for this, only 1 wire carrying audio and video

-I don't need a sound card, just the SPDIF capability on the motherboard. I'd connect it to an external receiver, and all of my system sounds, movies, music, etc will be audible via the speakers I connect to the receiver.

Works, but not the best option (see below)

-When I play DVD's, movies, or play games that provide an option to output 5.1/7.1 DD, DTS, etc, as long as my receiver supports the format, I'll get surround sound. Can SPDIF handle 7.1 LPCM?

No, SPDIF cannot handle anything more than stereo PCM. DD/DTS 5.1 works, but thats the only way to get multichannel audio out over SPDIF (sidenote: this is why SoundStorm was so sweet back in the day)

-I will only hear 2.0 PCM sound for playing MP3s, watching Youtube, hulu, etc, unless I get one of those fancy sound cards that encodes everything into some type of surround sound format regardless of the source. I think there are also some newer motherboards that do this encoding for me eliminating the need for a soundcard.

The number of delivered channels can't exceed the source unless you apply some kind of software effect like Pro Logic II. Yes, there are soundcards and software that can encode surround effects into these types of sources, but they aren't fantastic. Again, its kinda irrelevant since without DD/DTS encoding you're limited to 2.0 PCM by the SPDIF link regardless. I'm not sure how these software effects work if you do audio over HDMI, maybe someone else can chime in

--I can also get a video card that supports bit-streaming audio over HDMI. This part is murky to me; do I need audio over HDMI if I'm using SPDIF? Will the video card also pass system sounds, web-browsing, you tube, etc over HDMI as stereo, or does this bit-streaming just apply to compressed digital streams like DD and DTS?

Audio over HDMI would replace the use of SPDIF. Yes, it will output all sounds over HDMI, so system sounds and everything would be sent too. The same thing applies here as above. Stereo is stereo, so the HDMI would just be sending the source unless you have some kind of software creating artificial channels. the advantage of HDMI is that it will put out 7.1 LPCM, which SPDIF can't do, so non-DTS/DD encoded multi-channel sources can be output without encoding them on the fly. This can come in handy if you want to play a game with surround sound, or watch a movie with a multichannel FLAC soundtrack. A bitstreaming video card will also let you send the DTS-MA/TrueHD audio tracks that are found on all Blu-Rays to your receiver without downgrading to the lossy "core" track, which is just DTS/DD

Bottom line: HDMI does everything SPDIF does, and a lot more, with fewer wires overall

 

[Numan]

I'm not sure what format games would send out but it's not Dolby or DTS unless that game actually has it. I guess it's PCM? I'll have to check out COD or WoW on the HTPC and look at the receiver next time.

I think the only vid cards that can do the full bitstream are the Intel Clarkdale CPUS (i3 520 works wonders for an HTPC doing 1080p even before using DXVA decoders), ATI 5000 series and the newer Fermis but I am not sure which models. I want to say 460 but not sure, think the 430's do it.

 

[Activate: AMD]

I'm not sure what format games would send out but it's not Dolby or DTS unless that game actually has it. I guess it's PCM? I'll have to check out COD or WoW on the HTPC and look at the receiver next time.

Yup, hence my statement:

the advantage of HDMI is that it will put out 7.1 LPCM,(...). This can come in handy if you want to play a game with surround sound

I think the only vid cards that can do the full bitstream are the Intel Clarkdale CPUS (i3 520 works wonders for an HTPC doing 1080p even before using DXVA decoders), ATI 5000 series and the newer Fermis but I am not sure which models. I want to say 460 but not sure, think the 430's do it.

The intel Clarkdale CPUs, AMD 5xxx & 6xxx do it along with the fermi 460, 450 and 430

 

[xrintrahx]

"-I will only hear 2.0 PCM sound for playing MP3s, watching Youtube, hulu, etc, unless I get one of those fancy sound cards that encodes everything into some type of surround sound format regardless of the source."

Just want to note that basically ALL receivers now-a-days will be able to take a stereo signal and process it so that it sends information to all speakers. This could be Dolby PLII, DTS Neo 6, or other propriety methods. So you don't need a soundcard to do this, if your receiver can do it (and you'll need a receiver if you want anything better than PC speakers, and if you want to go HDMI). I'd highly recommend going the receiver route because of this. Speakers are the #1 most important part of a sound system, and if you limit yourself to powered speakers or PC speakers, you won't be able to upgrade past a certain point. Even if you don't have the money now for nice speakers, you can always plug newer speakers into your receiver's amp.

 

[Activate: AMD]

"-I will only hear 2.0 PCM sound for playing MP3s, watching Youtube, hulu, etc, unless I get one of those fancy sound cards that encodes everything into some type of surround sound format regardless of the source."

Just want to note that basically ALL receivers now-a-days will be able to take a stereo signal and process it so that it sends information to all speakers. This could be Dolby PLII, DTS Neo 6, or other propriety methods. So you don't need a soundcard to do this, if your receiver can do it (and you'll need a receiver if you want anything better than PC speakers, and if you want to go HDMI). I'd highly recommend going the receiver route because of this. Speakers are the #1 most important part of a sound system, and if you limit yourself to powered speakers or PC speakers, you won't be able to upgrade past a certain point. Even if you don't have the money now for nice speakers, you can always plug newer speakers into your receiver's amp.

Neither of the receivers I have do this. The problem is that by setting windows to 5.1 (or your setup), you're basically creating a continuous 5.1 PCM stream, so the receiver will be getting full 5.1 channels even if theres only sound on 2 of them. Think of it like 2 active channels and 3 non-active, but stil present channels. Most receivers will only default into PLII or Neo 6 mode if they only detect fewer than 5.1 input channels, and then create the missing channels artificially. Since the windows source isn't "missing" the other channels, the receiver won't create them. I think to force PLII mode on your receiver you'd have to change your computer to stereo mode in the windows audio panel. Alternatively, there are software and drivers that can apply the PLII-type effect before sending the signal out, but I don't know if they work using the HDMI audio out

Sorry if this is kind of OT. Not saying you're wrong BTW, I'm actually curious to see if I have it set up wrong

 

[af22]

Neither of the receivers I have do this. The problem is that by setting windows to 5.1 (or your setup), you're basically creating a continuous 5.1 PCM stream, so the receiver will be getting full 5.1 channels even if theres only sound on 2 of them. Think of it like 2 active channels and 3 non-active, but stil present channels. Most receivers will only default into PLII or Neo 6 mode if they only detect fewer than 5.1 input channels, and then create the missing channels artificially. Since the windows source isn't "missing" the other channels, the receiver won't create them. I think to force PLII mode on your receiver you'd have to change your computer to stereo mode in the windows audio panel. Alternatively, there are software and drivers that can apply the PLII-type effect before sending the signal out, but I don't know if they work using the HDMI audio out

Sorry if this is kind of OT. Not saying you're wrong BTW, I'm actually curious to see if I have it set up wrong

my receiver does that fine. since i have 5.1 speakers, i set all the stereo inputs to use PLII or Neo6 (on the receiver settings) so that it can use the center channel. the audio is artificially generated on the receiver side to have playback on all the channels.

also, make sure in windows sound properties, you check the box "Allow application to take exclusive control of this device" or else your PCM won't send correctly.

 

[xrintrahx]

I can confirm on my system that my receiver detects stereo signals vs. multichannel signals just fine. It's a Denon 1611. I think you need to select something like "Do not encode stereo PCM" in AC3 filter or ffdshow.

 

[Activate: AMD]

Hm, i will check it out since its been bugging me for a while that my re-encodes only play with stereo. I resorted to duplicating the R/L stereo channels to their corresponding rears just to fill out the sound. /threadjack

 

[CrimandEvil]

Alternatively, there are software and drivers that can apply the PLII-type effect before sending the signal out, but I don't know if they work using the HDMI audio out

They do. My WMC based HTPC is set up with AC3 filter installed and it will "re-encode" music to fit my 5.1 audio set up connected to my reciever using only HDMI.

 

[quanta15]

Just wanted to say thanks for all of the replies--you guys pretty much answered all of my questions and then some. Yea, so HardForums pwns all, and holy cow I'm looking forward to building this thing soon!

 

[SirMaster]

My recommendation is to get a cheap AMD HD5450 for ~$50. This card has HDMI and supports all of the formats possible. It's also fast enough to decode 1080p in hardware if you choose to do so, but even a cheap dual core can manage that so its not a huge deal.

Also, you can get passive cooled HD5450s so thats great for a HTPC.

If you want to game on it as well then any card from AMD 5xxx and Nvidia 4xx will do just fine with HDMI audio.

 

[mike_j_johnson]

I am about to do the same thing using HDMI out from my non-bitstreaming GTX 480 until a bitstream model comes out in the 5xx series.

My question is, will the audio work fine if I do not have a sound card and my onboard sound is disabled? The reason I ask is because I found a guide that said the onboard audio has to be enabled for HDMI to work. This does not make sense to me.

 

[SirMaster]

No, on-board audio does not been to be enabled for the HDMI sound to work. It shows up as its own sound device to windows and programs.

Also, why wait for another card, the 480 can already do what you need. Simply set your software player to decode the DTS-HD MA or Dolby TrueHD into PCM and send it via the HDMI cable as an 8 channel lossless LPCM signal. the GTX 480 fully supports 8 channel lossless PCM at 24/96 and 2 channel lossless PCM at 24/192.

Bit-streaming the encoded streams doesn't really offer any real benefits unless your receiver cannot handle multi-channel LPCM correctly.

 

[mike_j_johnson]

Good to know thanks!!!