How Changes By Microsoft Affected PC Audio
In the early years of computers, audio consisted of just a few series of beeps to simulate music and sound. Of course today we have multichannel surround sound with environmental effects. Then Microsoft went and rewrote the rules of audio on the PC with the Vista operating system. You may have already experienced this if you are running the new OS, but if you are thinking of upgrading your operating system or buying a new PC and audio is important then you need to know about the issue.
What Changed And Why
In previous versions of Windows, hardware audio support was developed as a means of improving the audio output and reducing the strain of audio processing by the CPU. In order to do this, the audio drivers allowed the sound hardware to tie into the kernel level of the operating system. This had unintended consequences that could reduce the stability of the whole OS. One driver error could cause the whole OS to lock up or even worse, blue screen.
In order to increase stability and security in the Vista operating system, audio processing was removed from the kernel level and moved to the user space similar to standard applications. What this meant is that direct hardware calls could not be done and must be handed by a software application. If there is now an issue with the audio software under Vista, only the audio application would be affected while the remaining OS will continue to function.
The Resulting Problem
Since all audio under Vista now runs through a software application at the user level, hardware acceleration has essentially be rendered useless. This is particularly true for any application that was written using the DirectSound3D audio calls or the Creative EAX audio extensions. Games or applications that were written to use these features are now handled by a software interpreter for the new audio stack. Positional audio is still possible, but environmental effects are lost. In some cases, the application may even fail to use positional audio and have only basic stereo output.
Now, for someone that was just using their PC computer to listen to digital audio tracks that were only stereo, such as MP3s, this doesn't really have much of an impact. What they may not know is that the audio hardware previously offloaded this audio processing away from the CPU. Much of that processing has returned to the CPU level under Vista. This is maybe a few percentage points on the CPU usage, but it can still make a difference. Direct3D positional audio with effects causes an even greater impact.
Vista Audio Solution
The industry knew about these changes from Microsoft well in advance of the release of Vista. Thankfully, Creative and Apple picked up development of a solution that was originally developed for use with the Linux operating system. A company called Loki Entertainment developed a platform called OpenAL as a means to provide cross platform hardware accelerated audio. Thus, an application written to use OpenAL could have full positional audio along with environmental effects whether the application was run on hardware used with Windows, OS X or Linux. Loki didn't survive, but their API was continued after they dissolved.
The only drawback to this new OpenAL system was that it requires both the audio hardware and the applications to be written with the API. There are a number of game engines that were developed with this in mind, but that still requires the hardware support. If both of these exist, then full hardware audio acceleration and environmental audio extensions will exist.
What It All Means
Hardware accelerated audio is still possible with Windows Vista, it just encountered a bit of a slowdown. Certain older games may have lost much of their audio processing and unless they are patched by the publishers (something not likely to happen) will not experience anything more than stereo audio in Vista. The main thing is that some existing games and future audio development with hardware audio acceleration is possible with the proper software and hardware.
If you are looking at purchasing a new computer with Windows Vista installed on it or are looking to upgrade to Vista with an existing system, is is important to look closely at the audio hardware on the computer. Check with the manufacturers to ensure that the hardware has compatible OpenAL drivers. This is the only way to experience the full audio potential within Vista. If not, get used to stereo audio output.
Friday, August 24, 2007
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