ABOUT BENCH FORUMS PODCAST LOGIN REGISTER
PC Components
Smartphones & tablets
Systems
ENTERPRISE & IT
GUIDES

X-Fi and the Elite Pro: SoundBlaster's Return to Greatness

 by Derek Wilson on August 30, 2005 11:59 AM EST
110 Comments | Add A Comment
110 Comments

X-Fi Processing Elements: Exploring the SRC

Sample rate conversion is one of the causes of poor audio reproduction in current sound cards. So, why make such a big deal out of sample rate conversion on the X-Fi? This time, Creative has implemented an SRC that generates very low noise and distortion, and the Audio Ring allows data that doesn't require sample rate conversion to bypass the step altogether. For the conversion of a 997Hz signal from 44.1kHz to 48kHz, the SRC demonstrated -136dB THD+N and +/- 0.00025dB pass-band ripple. Creative says that this is 300 times the quality of the SRC step in previous generation SoundBlaster products. These excellent results allow data to be passed multiple times through the SRC without any significant distortion of the data, making the SRC a key part in effects processing.

Pitch shifting can now easily be done on the SRC. Multitasking the sample rate conversion hardware for effects further allows creative to justify the efforts that they put into its development. One thing that Creative says can be dynamically applied to sound in realtime through the SRC is the Doppler effect. This could allow game designers, for instance, to apply a Doppler effect to all moving sound in a scene relatively easily. Sound synthesis can also use the SRC to change the pitch of a sound easily. The SRC also fits into 3D audio processing.

In pro audio applications, the SRC can be used to avoid the necessity of an external clock for syncing audio signals. Synchronized audio is still possible on X-Fi, but audio from multiple sources can be mixed with very good results using the SRC. As we have said before though, applications that do not require sample rate conversion will be able to bypass the SRC all together.

In order to create such a high quality SRC, Creative created a three-step hybrid filter. First, the sample rate is linearly increased by a factor of 2 using fairly simple math - no complex filters are needed for this step. The next stop along the way to sample rate conversion is a poly-phase FIR filter that up-samples its input to 2*(desired_sample_rate / original_sample_rate). This gives us data with a sample rate that is 4 times the desired sample rate. The final step is to reduce the sample rate by a factor of four (which is also an easy computation). Aside from increasing the quality of the sample rate conversion, increasing the sample rate to 4x the desired final rate also serves as an effective anti-imaging filter. The highest frequency that can be represented in sampled digital audio is half the sample rate (as per Nyquist). Imaging is a "ghost" of the audio signal in the range between the sample rate and half the sample rate. Assisting with anti-imaging is a by-product of the X-Fi SRC.

The above is an example of the SRC employed to convert a 44.1kHz signal to 48kHz. The X-Fi has 256 sample rate converters in its SRC engine. The order of the poly-phase FIR was not given, though Creative maintains that their entire system gives better results than a single order 64 poly-phase FIR filter. The SRC engine also has a tunable cache that can adapt to different latency requirements, as well as its own DMA engine.

The X-Fi Audio Ring: Powerful and Flexible X-Fi Processing Elements: The Quartet DSP
PRINT THIS ARTICLE
Comments Locked

110 Comments

View All Comments

  • Reflex - Wednesday, August 31, 2005 - link

    Derek, please read the following http://www.microsoft.com/whdc/device/audio/uaa.msp...">article on Universal Audio Architecture. Between that and Intel's HD Audio spec, all the supposed benefits of the X-Fi driver architecture are achieved already, and in a standard fashion that other sound card manufacturers can follow. There is nothing unique about what Creative is offering, only the marketing surrounding it, and in fact its been on the market since Intel's HD Audio first came out.

    Multiple source/multiple channel audio is definatly a major application in the future, but Creative is not the company leading the charge on this, only following suit.

    Once again I feel that your article in its present state serves as an advertisement rather than an objective analysis. I am certain that was not the intention, however due to the lack of research it came out that way anyways.

  • HardwareD00d - Wednesday, August 31, 2005 - link

    Thanks for your post. I was thinking I'd upgrade from my Audigy2 to an X-Fi, but now I think I'll pass.

  • PenGun - Tuesday, August 30, 2005 - link

    Could not have put it better, thanks.

    PenGun

  • monsoon - Tuesday, August 30, 2005 - link

    guys, i'm looking for an HTPC config with dual-core AMD where i can use the opticl drive without turning on the PC...

    ...i know, seems a bit out of context; but if this card or any lesser ( ? ) can be used in such context, what product would you recommend ?

    i like the HP DEC form factor, but i'll take anything proven worthy WITH AMD DUAL CORE and and an optical drive independent from PC.

    thanks for feedback,
    cordially,
    a.

  • Calin - Wednesday, August 31, 2005 - link

    The ASUS boards have the capability to play audio CDs from BIOS (I remember something like that, I don't have the ASUS board/manual to check). Maybe if you start the CD it will play while your computer is stopped?

  • whymeintrouble - Tuesday, August 30, 2005 - link

    I believe HP has a media center pc that can run a dvd drive, but not need to be in windows to use it. I don't know if it has the option of the Dual Core X2s though.

    I want to see a few more reviews go up before I make my judgements on these cards.

  • RussG - Tuesday, August 30, 2005 - link

    This still won't make myself, and a lot of people, upgrade from onboard sound. What I would like to see is more comparisons of how this is going to affect my FPS in more then 1 game, and how it stacks up to common on board solutions. They bring out all of this marketing because realities are not many people care about sound greater then onboard, and with no game support or evidence of existing game improvement there is little reason to pick this up.

  • NeonFlak - Tuesday, August 30, 2005 - link

    I bought the $130 X-Fi last night at bestbuy. I haven't seen this mentioned anywhere but compared to all my other sound cards, including onboard sound, when listening to MP3s or any other sound format it is very muffled unless the crystalizer is turned on. But, just as the review says the crystalizer doesn't really work well with everything.

    Games sound fine though. I haven't tested any movies since I don't watch movies on my pc.

  • DerekWilson - Tuesday, August 30, 2005 - link

    Are you sure you don't have CMSS-3D turned on? I find that sound can get very muffled and muddied when playing music using CMSS-3D ... That could be your problem.

    Our experience is that the sound quality with no filtering is better on the X-Fi than most other solutions. Of course, we do still need to look at the XtremeMusic card.

  • knitecrow - Tuesday, August 30, 2005 - link

    Ok, SoundBlaster is the only game when it comes to games... but what about listening to music or watching DVDs?

    Does it sound any better than my $30 chaintech VIA ENVY24 card or M-audio Revolution? I would like to see some blind listening tests.

    You have many many software based solutions that claim to make mp3s and other lossy formats sound better, for example SRS WOW effects that come bundled with Windows Media Player or Qsound. Is the creative crystallizer any better when compared to such software solutions?

Copyright © 2024. All rights reserved.
BENCH
TOPICS
FOLLOW
ABOUT

Log in

Don't have an account? Sign up now