- Introduction |
- Hardware |
- Software |
- Sound Quality |
- Reference |
- Enjoy
An introduction to computer audio
Driver
A sound card driver provides the communication interface between an application and the audio system hardware. In general it is hardware-specific and/or is compatible with a standard like ASIO or Microsoft's Universal Audio Architecture.
Bypassing XP audio using a ASIO driver or Kernel Streaming is a common practice to circumvent the XP K-mixer.
On Vista and higher often WASAPI is used to bypass the audio engine.
Replacing the third party audio drivers by core Windows audio drivers is an option too.
You can't choose a driver on OSX but third party software might use the HOG mode, a data path straight through the Core Audio
Some drivers simply don't deliver bit perfect output.
The latter applies to the C-Media based soundcard's: while the hardware is fully capable of bit perfect playback at a multitude of sample rates, all versions of the official driver process the sound. Some versions even cripple the sample size of the sound data from regular 16 bit down to 14 bit which results in a hefty loss of dynamic range (roughly estimated from 96dB/16 bit to 84dB/14 bit).
Source: DogBer1
Obvious drivers can have their impact on sound quality.
When using playback software with native EMU ASIO support (Wavelab, Cubase, Reaper, JRiver Media Center, Foobar with ASIO Plug-In), I got bit perfect true data. With theses software I got jitter values of random nature with approximately 2.5 ps. In this case, it doesn't matter which software I using, they all deliver nearly the same results and the difference between two measurements is in the same range as between the different software.
When using playback software that uses direct sound output (Winamp, Media Monkey), the digital data is shifted one bit into the LSB direction (just one bit, not one byte), so I receive no longer a 1:1 bit true data (but this is a different story). When I then measure the jitter a will receive the same amount of random jitter with approximately 2.5 ps, but relatively high discrete jitter with about 10 ps. (when I compare a DAC output with this two different digitals, than the direct sound output with the higher discrete jitter delivers much more worse analog out as the random jitter).
When using a playback software with wave out (Winamp, Media Monkey), I also get no bit perfect true data, because the wave driver add some dither to the signal. It is “only” a dither at the 24.th bit, but compare to only toggling the 24.th bit, it really being added to the signal, so a get a different signal with a slightly lower resolution. When I then measure the jitter, I will receive a random jitter of approximately 3.5 ps without discrete jitter frequencies.