[Cybill]

OK,


sorry this is a bit long, but if you are interested in bit-perfect (non-resampling) playback via HTPC's, you may find this interesting or may be able to help me clarify what is happening here:



I have been reading for months and months now about the resampling issues of the Audigy cards (as well as all motherboard audio).


It seems that the general consensus is that such cards are not able to play PCM audio (e.g. 44.1KHz CD Audio) via SPDIF without resampling it to 48Khz first, thus causing:


a) resampling artifacts (which may or not be audible, depending on the listener) and


b) destruction of any embedded encoded streams, for example a DTS stream (that may be embedded in a PCM WAV file, or from a DTS Audio CD), resulting in loud static being played back by the receiver


Following the many threads on different boards on this subject, and being the owner of a Audigy2 ZS card, I tried to use Kernel streaming, ASIO output, etc. etc. and players ranging from Foobar2000 to WinAmp (and many others inbetween) to somehow get the elusive bit-perfect playback, but just like everybody says, on Audigy2 cards this simply does not work due to the hardware resampling to 48KHz.


Or so I thought, until I finally tried (gasp) Creative's own bloatware (Creative MediaSource Player) to playback my 44.1Khz DTS Audio CD (Queen - Greatest Hits). And much to my surprise, I found that my receiver's DTS lights came on, and the Bohemian Rapsody started playing in breathtaking 5.1 surround sound!


So here I need some help from the experts: Does this mean that I got bit-perfect playback via my Audigy2's SPDIF output? I think so. So what is it that Creative's MediaSource player does that WinAmp, Foobar2000 etc. with whatever output plugin have not been able to achieve??


Thinking that this may be some secret Creative hardware feature that they are exploiting here (since it's Creative software with Creative hardware), I thought "Great! But I am not about to switch to MediaSource as my main player", so I kept thinking about buying a soundcard that can do it more easily, with any player software.


Then, just out of curiosity, I tried one day to enable my motherboard onboard sound (AC97 ALC850), and I tested it's SPDIF capabilities. Again, no luck, everything resampled, whether I used KernelStreaming or whatever.


And here is the final surprise: When I accidentally launched Creative's MediaSource player to play my DTS Audio CD, it worked!! No resampling, my receiver picked up the DTS signal and played it. And it was now not using the Audigy2 card, but the motherboard SPDIF output (since I had set that as the default sound device).


So this suggests that it is not a Creative proprietary hardware feature that their MediaSource player is exploiting, but something that works for AC97 as well...


What is this "secret" playback mode that the MediaSourceplayer is using? Is it something that can somehow be made to work in WinAmp or Foobar as well?? If this is possible (and Creative's software suggests that it is) then I think a lot of owners of Creative or AC97 hardware would be very happy to find that they *can* achieve bit-perfect playback after all!


I would very much appreciate any input any of you might have!


Thanks in advance!

 

[Esben]

If you have enough time to read through the AC97 v2.3 specification, you'll encounter a part where it says that 48 KHz output is possible for outputting DTS CDs. I suppose Creative found a way to work it. If it is indeed possible to use it for bit perfect output, I'd say it changes my opinion about the Audigy2ZS quite a bit.


Intel has the specification on their site.

 

[thomaspf]

AC97 2.2 always had the capability in the specs to do digital out at native 44.1Khz since 2000. The sound cards never implemented this or so we thought.

ftp://download.intel.com/labs/media/...ad/ac97r22.pdf


When you play back your DTS tracks have you looked at the time of the track on the cover and measured the actual playback time. There has always been a solution for bit perfect playback but it ended up sending the 44.1Khz stream at a 48Khz rate and you ended up with the tracks being played back at 48/44.1 times normal speed.


There has been a recent report on head-fi where a member managed to get bit-perfect playback at 44.1Khz with a USB connected Audigy-NX.


Cheers


Thomas

 

[stanger89]

Quote:

Originally posted by Esben If it is indeed possible to use it for bit perfect output, I'd say it changes my opinion about the Audigy2ZS quite a bit.

I don't know, if it's possible, but only with their software, then it's even more stupid IMO, to force those of us who hate their SW with a passion (JRMC) to live with resampling.


And what about standard CD audio? Is that still resampled?


Like Thomas commented, I'd guess that player is playing it back at the wrong speed.

 

[Cybill]

First of all, thanks for all the replies!


The playback speed is perfectly fine. Both the DTS Audio CD and regular audio CDs play at the proper speed. I tried the "play 44.1Khz at 48Khz" trick before but of course it sounds entirely inappropriate even to the untrained ear.


And since MediaSource is the "default" player that Creative would like you to use with their soundcards, it would have surprised me (even from Creative!) if they could get away with playing regular audio CDs at the wrong speed in their default player.


By the way, even when playing back via AC97 onboard SPDIF output, both DTS Audio CD and regular audio CD play at the proper speed in MediaSource.


stranger89, whether standard CD audio is resampled as well, I was wondering about that. I played a regular audio CD and it sounds fine, but I am not certain my ears are trained enough to reliably (if at all) tell the difference between resampled and non-resampled CD audio (my main purpose for this exercise was to get my DTS Audio CD to play in my HTPC). Is there a (non-DTS) testfile out there that can easily show some flaws when resampled? How about the infamous udial.wav? If you could give me a pointer on how to test it (even with my untrained ears), I would love to try and find out!


Thanks!

 

[stanger89]

Maybe I'll get ambitious and try this with my Audigy (sitting in a pile of cards somewhere). My AVM-20 reports input sample rate so that should quite easilly answer the "Does Mediasource output 44.1k at 44.1k?" question. Besides, I needed a reason to foobar my HTPC anyway.


And no I'm not terribly surprised that they would only do it via their player, but IMO, that just makes the resampling issue even more moronic. If it's not a HW issue, then why the *#%*@)#(%#*)%)(#&%) do we have to deal with it!!!!!!


Of course this doesn't mean much, since 1) you have to use their player (I won't give up JRMC) and 2) since it's the digital out, you're wasting your money on an Audigy, the Chaintek would work easier for much less money and other cards for the same price (Revolution, Delta 410, Prodigy, etc) would work as better.

 

[thomaspf]

Well since the tracks on a DTS audio CD are just plain 2channel PCM data as far as the PC is concerned, it is pretty safe to say that normal CDs will behave just the same.


Stanger if you could verify the 441.Khz playback, this finding could make some waves. Someone might even be able to find out how this works and get it supported in other player software.


Cheers


Thomas

 

[Cybill]

Thomaspf, that was my thinking exactly! If Creative's software engineers (who sometimes seem to be not so... shall we say... creative) can do it, then I am sure one of the many brilliant minds writing plug-ins for WinAmp, foobar and the like can do it as well.


From all I've read up to now, it always seemed like the re-sampling was a *hardware* limitation in Creative and AC97 audio chipsets, but if this in fact turns out to be something that Creative's *software* can overcome (even for non-Creative audio chips e.g. AC97), then so can any other software, provided we can find out how it is done.

 

[Cybill]

stanger89, actually I think you can leave your Audigy in the closet, I just tried it and I figured out the answer. There's good news and bad news.


The bad news first: Unfortunately, MediaSource *does* resample regular CD Audio to 48KHz. Whilst I don't have anything that directly displays the sample rate, I simply opened up another player (foobar) while MediaSource was playing an audio CD, and tried to play a 48KHz wav file. And unfortunately, I was able to hear both the CD playing and the WAV sound, which means that the CD Audio must have been resampled.


To confirm my finding, I did another test and this is the good news: I played my DTS Audio CD in MediaSource (which played fine), and then played the foobar WAV file simultaneously. In this case, I was *not* able to hear the WAV file playing at all, which confirms that MediaSource is indeed playing the DTS Audio CD bit-perfect at 44.1Khz.


So while CD Audio still gets resampled to 48Khz by MediaSource, my tests did at least show that this is *not* a hardware limitation. It *is* possible in software to pass a PCM bitstream to the SPDIF output bit-perfect at 44.1Khz, both with my Audigy 2 ZS card and even with my AC97 motherboard onboard sound. It's just that no-one has implemented this yet (or so it seems), except for Creative in their MediaSource player, and they chose to only do it for DTS Audio CDs. (How they distinguish between an audio CD and a DTS audio CD I do not know).


Does *anyone* have any idea how MediaSource does this, or how we could go about reverse-engineering their methods? I think it's proven that it is possible to do it in software, and I think a lot of people would have great interest if we could make it happen for CD Audio in at least one of the more common, non-proprietary players.


Appreciate any input/feedback. I will keep looking into it but I will definitely need some expert help with this... Cheers!

 

[DJRobX]

I think you just answered your own question - It sounds like MediaSource detects a DTS audio CD, opens up the SPDIF port in raw mode (just like a DVD player would for Dolby Digital or DTS DVD sound) and outputs the DTS audio that way. If that's the case, there's nothing "secret" going on at all, and that would explain why it also works with your ac97 onboard audio.


I don't know how difficult it would be to output regular PCM audio in RAW mode.


-- Rob

 

[stanger89]

FWIW, I tried, and now remember painfully how much I hate Creative's software. First you can't install mediasource on an Audigy 1. Then I spent near an hour trying to get the Audigy 1 drivers/software installed. I finally did, the digital out worked, but their "Dolby Digital" soundfile included wasn't output as DD even in their own player. That was with my Yamaha RX. I drug the PC down to my AVM-20 and could get nothing out of the digital out. So I ripped the card out and restored the image I made before that painful journey.


Moral of the story IMO.


Trying to get bit-perfect 44.1k digital playback from a Creative card is a waste of time:

1) You have to use thier crappy software

2) It only works for encoded material not PCM (BTW, DTS in PCM is supposed to have some flag)

3) These cards are way more expensive than something that will work easier, like the $25 Chaintek AV-710.

Buy a card that works.


Sorry if that seems harsh, but this whole saga just gets more and more moronic. And I don't have much patience/sympathy for such stupidity especially from a company that proclaims "Purest Audio, Richest Sound" on it's main page.

 

[stanger89]

Oh, and so there's no confusion my comment is directed solely at Creative, not anyone here (unless they work for Creative and played a part in this oxymoronic policy)


-edit


Alright oxymoronic isn't the right word, but I felt like using it