[alsa-devel] Stale data at start of audio recording on Freescale i.MX28 EVK with SGTL5000

[Craig McQueen]

I was testing the 3.14.19 kernel on Freescale i.MX28 EVK. Since then, 
I've retested and confirmed this also on 3.18-rc4 kernel.

I am doing audio recordings through the SGTL5000 driver as such:

     arecord -D hw:0,1 -f s16 -c 2 -r 16000 -d 5 test.wav

I'm finding that the first 400-500 ms of the saved data is actually 
stale data from the end of the previous recording. To see this, do the 
following:

    1. Provide some test audio input in the LINE INPUT jack. E.g. a 100 
Hz sine wave, or some music.
    2. Record audio with e.g. arecord -D hw:0,1 -f s16 -c 2 -r 16000 -d 
5 test1.wav
    3. Change the test audio input, e.g. a 150 Hz sine wave, or some 
different music.
    4. Record a new audio file with e.g. arecord -D hw:0,1 -f s16 -c 2 
-r 16000 -d 5 test2.wav

Observe that the first 400-500 ms of test2.wav contains stale data from 
the end of the previous recording.

-- 
Craig McQueen