Crackling and Popping X-Fi?

The full post from Creative:

We would like to update all Sound Blaster X-Fi users that are experiencing the popping/crackling issues with the very latest news on this issue.

We have been working extensively with a large number of systems and the vendors of those systems to diagnose and find remedies for reported symptoms of audio crackling and distortion, particularly during game playing. Thanks to the extensive and accurate reporting of these issues, approximately two months ago we were able to reproduce the crackling and distortion symptoms on some systems. All of those that exhibited the symptoms were high-end spec gaming systems. We have since been identifying other systems that exhibit these symptoms as well as working hard to identify the causes of these symptoms.

Before moving into the specific detail of our findings we feel it would be helpful to cover off some background information on how audio is handled and delivered in a PC system. Firstly it is important to understand the significance of system memory and relationship between it and the audio card. System memory is in fact the source of the many building-block streams of audio data that a sound card receives from a game or other application. Most importantly a sound card that is designed to significantly enhance and process system audio has a fundamental requirement for quick access to this system memory. Audio streams are continually being read in from system memory to the sound card, and the Creative X-Fi chip processes and mixes these streams into the final multi-channel output. The sound card does have on-board storage that allows it to tolerate being held off from memory access for some amount of time, and in fact, this tolerance for being held off, which we call latency tolerance, is higher for Sound Blaster X-Fi than it was for previous generations. At the same time, the enhanced capabilities of Sound Blaster X-Fi require that it read in a larger amount of data than previous generations of sound cards, although much less than a graphics card or hard drive requires. The impact of a delay in receiving data to a graphics card is slower frame-rate, whereas to audio there is a far more significant impact. Because audio is so “real-time” any delay in receiving data causes a break in the audio stream and this break translates to pops and clicks in the audio stream.

So now to our findings: We believe that the larger volume of data being requested is, in some systems, causing larger access delays to system memory, especially when Sound Blaster
X-Fi is sharing memory access with high-end graphics and/or hard drives. We have found that with certain high-end systems and configurations, Sound Blaster X-Fi is being held off from receiving data from the PCI bus for significant periods of time, in some cases for close to two-thirds of a millisecond. This causes our audio buffers to underflow, which produces crackling sounds. The obvious answer to this would be to increase the latency tolerance, but due to the requirement for audio to synchronize accurately with graphics, we cannot increase the latency tolerance beyond a certain point.

Our tests have proved that in many cases these problems can be remedied with a simple BIOS update but this did not resolve the issues for all customers experiencing the issues. We therefore continued to investigate and have made a significant finding. In some systems we have resolved the issues by setting the motherboards to dual-channel memory mode to improve the memory bandwidth and response. Below you can see the configuration of two of the systems that we initially experienced issues with and subsequently resolved by setting to dual-channel memory mode.

With these two machines we ran tests with Battlefield 2, which is the title with the most reported issues. We found that as long as the system memory was configured in dual-channel mode, the Sound Blaster X-Fi card did not crackle. When memory was not dual-channel, crackling could occur in the game and when crackling was occurring, the Sound Blaster X-Fi service requests on the PCI bus were being held off for long periods.

The way to invoke dual-channel memory mode differs by machine. For system 1, installing 1 GB memory DIMMs in memory slots 1 and 2 invoked dual-channel mode, whereas for system 2, installing 1 GB memory DIMMs in memory slots 1 and 3 invoked dual-channel mode.

We recommend checking your motherboard's manual to ensure that memory is configured for dual-channel.

N.B. Installing 4 GB (one DIMM in each of the four slots) is not advised for Windows XP 32-bit. It is recommended to install less than 3GB total memory, and the size of memory in both of the channels must be the same for dual-channel operation.

As highlighted before, in some cases a simple BIOS update resolved the issues, but in others these changes to memory configuration were required also.

These findings go a long way to resolving the issues that many customers are having, but we believe that there may be some other system-related issues that may continue to cause these symptoms for some remaining customers. We are therefore working with prominent motherboard and chipset manufacturers such as nVidia to explore ways to balance the needs of systems such that all of the components, including the sound card, are functioning at peak efficiency and we will be reporting back on these issues in the next 2 weeks.

However we want to highlight that some reported crackling issues were found to be normal clipping that can easily be resolved by balancing audio settings. We specifically found that some game titles produce a very strong audio output signal that in some circumstances can overload our hardware DSP algorithms, such as CMSS-3D and 24-bit Crystalizer. While this issue is not at all related to the PCI bus traffic issues described above, the result of this is a distortion that might be described as "crackling" (although technically it is "clipping"). We would therefore recommend that all customers run a very simple test. Please try turning down either the game volume, or the Windows "Wave" volume, to see if this remedies the problem. If it does, it would be really helpful if you would notify us of this.

As a final note, we understand the desire of our customers to squeeze every last drop of performance from your systems. In most cases once the very latest hardware has been purchased and installed, the CPU, graphics, USB and every other device has been overclocked there is only one last thing to do – find and install the very latest drivers and BIOS updates – and many customers do so even if they are beta versions. We would suggest to all of our customers that if they experience issues while using drivers or BIOS updates for any product that are labeled as "Beta" or that in any other way are not considered "released and supported" by their respective manufacturers, that they immediately downgrade back to the last release version. As such software / firmware is not fully qualified by the vendor's QA team, the chances of problems occurring when used in conjunction with Creative or any other 3rd party products is increased.

For any replies from X-Fi users and Creative check the Creative Forums.