What's the difference between analog, ddl or ddl/dts? Which is better for a gaming machine? Is the x-fi XM still recommended after these questions?
DDL is Dolby Digital Live and DTS is another form of multi-positioned Audio. Both are encoding algorythms done in realtime. In games, either of the two are inferior to EAX. All they do is take a non Dolby Digital or DTS audio stream and convert it on the fly. This is of course not near as precise as using a native EAX Multi-positioned audio stream.
Also you're stuck with an audio stream that is decoded, converted then re-decoded. Therefore the audio at the end of the stream has gone through quite a few changes.
The best Audio positioning is Dolby Digital EX, or 5.1 as well as DTS. But a native Audio stream of the sorts would take considerable space on the hard drive. That's why EAX exists.
DDL and DTS encoding are nothing more then upmixes.
For games.. X-Fi all the way.
ill agree about audio being re encoded on the fly, but the rest, well, not quite so much...
'when' a source (eg, a game for example), includes multiple surround audio channels by default (and then is re encoded in an ac-3 or dts format by a ddl/dts interactive card), those channels dont get misplaced, or misconstrued, or 'faked' at all... they are correctly positioned to the appropriate channels, audio quality in the worst instance being 16bit (the same as commercial cds and dvds), dts is 20bit audio, hence even better
the main advantage that going digital in that scenario, has over analog... is the ability to take advantage of an external digital signal decoder/processor and high quality speakers even then (which in all cases are noticably superior audio quality to pc speakers, due to a pc speakers typically compact size, so theres a few acoustic sacrifices made in exchange... a few naysayers may object to that though)
sure you can go multicabled analog to your external signal decoder, and acheive roughly the same thing, though you also risk having analog hissing, humming and such being introduced into the sound too... but thats why going analog for gaming again, with pc speakers even, is better suited to an x-fi
but, i have to correct this though... saying ac-3 and dts are only upmixes of 2 channels sources, is simply wrong... take a game that has 6 channels on average (as most games have), the card then reencodes those 6 channels into a digital stream, the external decoder decodes those 6 channels, and you end up with 5.1 on the receiving end, just how it was to begin with, aside from the digital compression that took place for transmission over the digital stream (16bit for ddl, and 20bit for dts, and 24bit for dvd-a as a comparison)
saying however that dolby digital ex, or dts es, are upmixes, is more correct... cuz theres not many sources that carry more than 6 channels (5.1, most ac-3 does, some dts), fewer that carry 7 (6.1, most dts formats do), and very little that carry a native 8 channels (7.1)... so, after the decoder decodes the ac-3/dts signal, it can then be matrixed up to 7.1+ by DD EX or DTS ES
when a source only contains 2 channels (most mp3s as an example), sure, the audio is then upmixed, as it doesnt contain more than 2 channels in most cases... but not if the source contains more than that... its like, upmixing from 6 channels, to 6 channels... that wouldnt be upmixing then, theres no matrixing even... UNLIKE with EAX that you brought up... ...EAX on the other hand is entirely a simulated matrixed surround sound algorithm, taking 2 discrete front channels, and matrixing additional channels off of that, just like dolby surround, or dts:neo... ...taking 2 channels originally, and gives a more surround feel, and even a different surround feel depending on the matrixing algorithm used, like the difference between eax 2.0 and eax 4.0 even, they may not sound the same, but they have the same basic principal, everything is derived from 2 channels (though i know every audio source starts as 2 channels to begin with anyhow, but, thats beside the point)
speaking of which, EAX can also be carried over a digital stream as an ac-3/dts signal... so you end up with 6+ correctly positioned discrete channels with the addition of EAX, including all the other benefits the external decoder and quality speakers can provide
x-fi falls abit short there in that respect... it cant do digital surround for gaming, limited strictly to 2 discrete channels in that respect, as it would only send its digital audio stream out as a 2 channel pcm signal, whichcase, you could then perform very similar processing as EAX, with prologic and such... and those other external decoder algorithms can be applied to all sound sources, and isnt just limited to games that support eax
so... analog for x-fi, it has some quality dacs which would be used then too... digital for ddl/dts (the dacs from the card arent anything to worry about then, as its strictly a digital signal when its output from the card, and then the decoder can worry about it at that point)... quality comparison between the two cards isnt worth going into, unless you really dont like how most dvds sound, whichcase, eh
but again, if you dont even have a digital signal decoder and mediocre speakers even... then x-fi is definetly the choice to go with for gaming.
edit: come to think of it, i can imagine the reason creative didnt want to pay the licensing fees to introduce ddl/dts into their sound cards, is because of the performance hit that would occur... you do take a loss of about 5FPS with ddl/dts encoding enabled, but that shouldnt matter if you have at least semi capable hardware... ...creative is known for their low cpu usage gaming cards, and i guess they didnt see losing that slight FPS advantage as being remotely worth it, compared to the definite audio improvement and advantage that would occur if they did choose to include either format...
...its very possibly why they sell the DTS-610 as a seperate component, rather than integrating it into their cards... so i guess licensing aside, they probably didnt include it, most likely due to the performance hit, if anything... cuz they offer it as a seperate interconnect component regardless.