X-Fi and the Elite Pro: SoundBlaster's Return to Greatnessby Derek Wilson on August 30, 2005 11:59 AM EST
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New Features, Possibilities, and ModesThe main new audio processing features of the X-Fi line are the 24-bit Crystallizer and CMSS-3D. These features, as well as the onboard RAM and the three modes of operation (gaming, entertainment, and creation) will be explored in this section. We know what each of these features is and the basic principles on which they operate. While we could make a much more thorough analysis of the quality of these features, if we had some actual math to go on, it is understandable that Creative would want to protect their investment by keeping the intimate details of the architecture private. What we do know should be enough to go on for now.
The 24-bit CrystallizerThe 24-bit Crystallizer takes 16-bit audio and tries to add dynamic range to the audio signal. If we were to convert our 16-bit audio stream to 24-bits, we could essentially do so by adding 8 zeros to the least significant end of each sample. It becomes clear that the highest value that a sample can take on is much less than the highest value possible with 24-bit audio. Likewise, on the low end, the audio stream isn't capable of representing values between zero and 256. The basis of the 24-bit Crystallizer is to fill in these least significant bits with meaningful data and thus, expand the dynamic range of the audio. What, exactly, is meaningful data in the least significant bits? We're glad that you asked.
Audio engineers are big fans of compression. Applying compression to a sound decreases the dynamic range of a sound in order to preserve the loudest and quietest parts without clipping or burying the subtleties in noise. This is very necessary to make good use of 16-bit audio, as things like whispering over a snare hit are not easily representable otherwise. Knowing the basic manner in which audio engineers go about applying effects to sounds, Creative can try to reverse-engineer the process to add more data where it seems necessary.
Details on the technique are fuzzy at best, but we do have some information. The algorithm doesn't simply expand the audio signal; it looks for recognizable patterns in frequency and time and applies algorithms that fill in the data where necessary. For instance, the X-Fi hardware is able to detect something like a kick drum hit and use the sound and proportionally weighted, transient, low-frequency data to boost the impact of the event.
The algorithms focus on the energy flux in different frequency bands in order to localize the impact of the effect. This means that things like snare and symbol hits, the plucking of strings on an acoustic guitar, the slapping of a string on a bass, and gunshots in games should all become more distinct. Each sound will be enhanced according to its energy flux, frequency, and waveform. Creative states that this can even help clean up the high end on MP3 encoded files. What this doesn't enhance quite as well are quiet subtleties in the audio signal.
CMSS-3DFor 5.1 sources played on headphones with CMSS-3D, Creative uses HRTF (Head Related Transfer Functions) to virtualize the position of each audio channel around the listener. This technique is augmented with simulated environmental reflections, which attempt to improve the externalization of sound to the listener. These environmental effects are more subtle than the Dolby Headphone effects and are meant to convey a listening environment that matches the recording rather than one that fits the room in which the listener is sitting.
When enabled for 3D virtualization with two speakers, the methods used are similar to that of the headphone implementation. Rather than adding environmental reflections, this CMSS-3D mode includes a cross-talk canceller to make sure that signals from one speaker are not destructively combined with signals from the other at the listening sweet spot. Unfortunately, there is still a sweet spot for listening to audio in this mode, but settings like speaker angle are easily adjustable.
Probably the best use for CMSS-3D has nothing to do with two speaker setups. Getting the most out of a 7.1 channel audio setup is much easier with CMSS-3D. We still don't recommend using CMSS-3D for stereo sources, but for listening to 5.1 audio, CMSS-3D will do a good job of fitting the 5.1 sound to 8 channels. For creating a multi-channel environment with a two-channel source (if we absolutely must), our favorite solution is still Sonic Focus' implementation on Intel hardware. It's a shame that they won't open up their software for other hardware.
64MB onboard RAMThe top two models in the X-Fi series feature 64MB of SDRAM on the sound card itself. This feature is called X-RAM, but that isn't a technical term. X-RAM is a marketing name given to maintain the X- moniker of the card itself. This RAM is supposedly included to enhance the performance of games. Until games are written to take advantage of this feature, we will have to simply accept the possibility for performance improvement.
Creative has shown us some numbers that they have run using UT2K4 and a special patch that allows for playing over 100 voices at a time (currently only 30 are supported in the game), as well as uploading uncompressed sound files to the onboard memory. The numbers show a pretty big performance improvement when X-RAM is enabled in this case. Unfortunately, we don't know how real world this test is. Without having the patch to test ourselves, we can't really know what's going on. If we are more than tripling the number of concurrent voices, we would hope to see some sort of quality improvement as well. A performance improvement for a feature that isn't necessary is a useless test.
We really need to spend more time with games that currently support X-Fi to see if we can find a case where the extra RAM affects performance. Our best guess is that we won't see real impact from this feature until developers realize that they can target the Creative solution to deliver a higher quality audio experience. Playing audio with higher sample rates, adding voices, using uncompressed audio to save CPU overhead, and freeing system RAM for other uses should be quite attractive to audio designers.
3 Modes of OperationThe final major feature is the inclusion of three distinct modes of operation. This feature is necessary because of the complexity and flexibility of the Audio Ring architecture. Tradeoffs are necessary for every type of audio application, but a configuration that can switch between modes depending on the task at hand could be a major development in the "one size fits all" audio department. These are the features of the different modes.
|Video Game Frame-Rate:||YES||NO||NO|
|Hardware 3D Audio Processing:||YES||NO||OPTIONAL|
|High-Resolution Audio Playback:||NO||YES||YES|
|Audio Enhancement Processing:||NO||YES||OPTIONAL|
|2-Channel to Multi-Channel Up-Mix:||OPTIONAL||YES||NO|
|Multi-Channel Audio Recording:||NO||NO||YES|
|Hardware MIDI Playback:||NO||OPTIONAL||YES|
|Sample-Synchronized Record and Playback:||NO||NO||YES|
|Low Audio-Streaming Latency:||NO||NO||YES|
|Bit-Accurate Audio Capable:||NO||OPTIONAL||YES|
Professional recording requires low latency, especially when using ASIO drivers. Therefore, it makes sense that Creative would implement a mode targeted at getting audio in and out of the Audio Ring as fast as possible. Effects possible in Creation mode are limited to those that can be performed very quickly, and audio comes through the chain as unmessed as possible. Less than 2ms latencies are possible in this mode. Again, our only complaint with the Elite Pro as a professional solution is its lack of balanced I/O.
Entertainment mode focuses on the music and movie experience. Options for enhancing both stereo and surround sources are pushed to the foreground and features like the 24-bit Crystallizer and CMSS-3D will likely be heavily used in this mode.
Gaming mode is optimized for creating a multitude of hardware accelerated voices and processing them to create the best real-time 3D that audio developers can throw at it. With up to 127 3D + EAX voices, extremely complex effects are possible. Under this mode, X-RAM can be used to assist in the storage and playback of audio files.