Why sporadic corrupt data in real time audio capture

Tommyjunge

Hi,

I try to read a few 10k samples from my sound card at 96k samples per second and then do some data analysis on them.

I have written a prog which captures one buffer via Windows Multimedia API and then stops recording.

When I analyze the buffer after capture I see occasionally jumps in the data: I capture a sine wave signal and I see phase jumps as if some samples would simply be missing. If this occurs it occurs always at the same sample position #2884 counted from the start i.e. at almost exactly 30 milliseconds after capture has started.

Can anybody give me a clue as to where my problem can come from and what I can do to avoid it?

BR Tom

Mojojojo

: Hi,
:
: I try to read a few 10k samples from my sound card at 96k samples per second and then do some data analysis on them.
:
: I have written a prog which captures one buffer via Windows Multimedia API and then stops recording.
:
: When I analyze the buffer after capture I see occasionally jumps in the data: I capture a sine wave signal and I see phase jumps as if some samples would simply be missing. If this occurs it occurs always at the same sample position #2884 counted from the start i.e. at almost exactly 30 milliseconds after capture has started.
:
: Can anybody give me a clue as to where my problem can come from and what I can do to avoid it?
:
: BR Tom
:
My guess would be that your buffer is getting full after 30 msec, and during the time you are copying the samples elsewhere, you are missing out some new input samples.