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Edit: I've updated this post due to input from other forum members about its original tone and my own personal opinions being sprinkled in.
Going through that new Creative thread is incredibly baffling. How the heck people have become so confused about the various technologies (and their respective acronyms) behind computer audio amazes me.
Reading peoples' posts in which many reiterate the same misconceptions over and over is rather frustrating. So, once and for all, let's clarify this.
Miscellaneous stuff, just in case you were wondering:
Possible setups:
PC -> Analog 5.1 computer speaker set (card only needs 5.1 output; EAX support adds environmental effects, so that would be an ideal addition as well)
PC -> Digital 5.1 computer speaker set (same as above; most digital 5.1 sets also have analog input; I don't think they make digital 7.1 sets, so you're better off with setup #3)
PC -> Encode with DTS Interactive / Dolby Digital Live -> Digital 5.1 computer speaker set over S/PDIF (digital optical or coax; this compresses and then passes the stream to your speakers over a single cable, and then the decoder and DAC in your set will do the rest of the work; in this case, a $30 sound card with these features will perform about as well as a $130 card)
PC -> Analog output -> A/V receiver -> Speaker set (if your receiver can take analog inputs)
PC -> Encode with DTS Interactive / Dolby Digital Live -> A/V receiver / decoder -> Speaker set over S/PDIF (if your receiver can decode a DTS or AC3 stream over S/PDIF input)
PC -> HDMI (!!!) -> A/V receiver -> Speaker set (in an ideal situation, this is hands down the best solution, as we're sending the highest quality signal possible; you're passing uncompressed 7.1 straight to your receiver here; however, only newer receivers have this, you'll need to check for LPCM over HDMI support; the final output quality depends on your receiver and speakers)
Voila. That's the basic rundown of surround sound and those silly acronyms. Stop it with the nonsense now.
Going through that new Creative thread is incredibly baffling. How the heck people have become so confused about the various technologies (and their respective acronyms) behind computer audio amazes me.
Reading peoples' posts in which many reiterate the same misconceptions over and over is rather frustrating. So, once and for all, let's clarify this.
- AC-3: Also known as AC3, Dolby Digital, DD5.1 and DD. This is an audio compression format, like MP3, WMA, etc. It is special in this regard because it is a popular format that supports multiple (surround) channels.
- DTS: AKA Digital Theater System, by DTS, Inc. It is a competitor to AC3 / DD, but is superior to it in every possible way.
- EAX: An acronym for Environmental Audio eXtensions. This is important, pay attention, EAX DOES NOT CREATE SURROUND SOUND OUT OF THIN AIR! It is MERELY an addition to the sound API that allows your PC to perform environmental audio effects. See below about game surround sound.
- Why would you need or want DD / AC3 / DTS? Your fancy S/PDIF cable was originally designed to pass an uncompressed 2-channel audio stream. It lacks the bandwidth for anything else. Then came along the idea to encode audio streams enough to fit on that cable. That way, you could use the cable for 5.1 channels of audio.
However, this presents a problem. Sure, you can pass film / TV audio right through, as those are already pre-compressed. But most of the sound on a PC is not already encoded as DTS or AC3. Thus came the need for...
- Dolby Digital Live / DTS Interactive / DTS Connect: These are real-time encoders. Basically, they take all of the sound that was supposed to go the analog output of your sound card, encode it to DTS or AC3 in real-time, and then pass it through S/PDIF. You only need this if you have an external decoder (usually an A/V receiver with speakers hooked up).
Note that these are software-based solutions, and as such use CPU cycles. The only home-user PC hardware ever created that does this in hardware was the nForce2, using NVIDIA's SoundStorm technology, created for the original Xbox. I consider that chipset to be one of the greatest advances in modern computer audio. Why NVIDIA stopped working on audio with later chipsets baffles me.
While DTS is technologically superior, Moofasa~ pointed out that not everyone may hear a difference between DDL and DTS-I. Another concern was that DTS-I uses more CPU cycles than DDL.
Neither of these features "create" surround sound -- they only encode a stream to AC3 or DTS.
- So, how do we get surround sound from various programs, media or games?
Simple. It must support the output of multi-channel audio. A game can have EAX but only be capable of outputting stereo audio. This is an example of what I mean when I say EAX does not create surround sound. It just simulates the environmental sounds in the game, so a bullet in a hallway sounds different from a bullet in the forest.
Hop on over to your game's audio settings, see if you can enable 4.0 (quadraphonic), 5.1, 6.1 or 7.1 surround. Sometimes, a game will only use the settings from your control panel / sound settings, so make sure you have picked the appropriate speaker setup there (ie. 5.1).
If you have a digital speaker set (ie. Z-5500) with digital inputs, a card with DTS Interactive / DTS Connect / Dolby Digital Live would be ideal, as you would be able to take your game's surround audio and compress it to pass through S/PDIF. The same applies if you have an external A/V receiver (or DTS / DD decoder) with S/PDIF input.
Some new graphics cards support audio over HDMI. This should eventually replace S/PDIF, because it can handle LPCM streams, so in the (near?) future, your computer will be able to pass all audio as-is to your external receiver -- WITHOUT encoding it. I don't know why the PC world is so far behind in this regard.
As for other media, such as films and HD TV shows, they will usually have surround sound encoded as AC3 or DTS, so your work here is pretty much done for you.
Miscellaneous stuff, just in case you were wondering:
- DD-EX / DTS-ES: Respective additions to AC3 and DTS, they add a rear channel for 6.1 surround.
- Dolby Digital Plus: AKA DD+ and E-AC3. It's better than DTS and AC3, but the increased bitrate means it's too heavy to pass over S/PDIF. You need to use HDMI for this, in which case you should use LPCM or one of the two below.
It is only used on Blu-ray and HD DVD discs when either the video takes up too much space for better audio formats like TrueHD, or the people behind the disc(s) were too ignorant to know any better.
- Dolby TrueHD / DTS HD Master Audio: Aka DTS-MA. These are both LOSSLESS audio compression formats, as such they are pretty much the same. They are only supported if you pass the audio over analog cables or HDMI (via something called LPCM, but not every A/V receiver supports it). Nothing else has enough bandwidth. Currently, only Blu-ray and HD DVD have this, but not every title.
Possible setups:
PC -> Analog 5.1 computer speaker set (card only needs 5.1 output; EAX support adds environmental effects, so that would be an ideal addition as well)
PC -> Digital 5.1 computer speaker set (same as above; most digital 5.1 sets also have analog input; I don't think they make digital 7.1 sets, so you're better off with setup #3)
PC -> Encode with DTS Interactive / Dolby Digital Live -> Digital 5.1 computer speaker set over S/PDIF (digital optical or coax; this compresses and then passes the stream to your speakers over a single cable, and then the decoder and DAC in your set will do the rest of the work; in this case, a $30 sound card with these features will perform about as well as a $130 card)
PC -> Analog output -> A/V receiver -> Speaker set (if your receiver can take analog inputs)
PC -> Encode with DTS Interactive / Dolby Digital Live -> A/V receiver / decoder -> Speaker set over S/PDIF (if your receiver can decode a DTS or AC3 stream over S/PDIF input)
PC -> HDMI (!!!) -> A/V receiver -> Speaker set (in an ideal situation, this is hands down the best solution, as we're sending the highest quality signal possible; you're passing uncompressed 7.1 straight to your receiver here; however, only newer receivers have this, you'll need to check for LPCM over HDMI support; the final output quality depends on your receiver and speakers)
Voila. That's the basic rundown of surround sound and those silly acronyms. Stop it with the nonsense now.
