audio lost and reverse when playback beep audio

[yunyangsihai]

Dear community:

   platform：iMX6 DualLite + Linux BSP4.1.15

   1. We can hear pop noise when playback beep audio.  beep device configured as below in asound.conf

      aplay -v -D beep  beep1.wav

2. we found the audio lost  1~2 waveform in the beginning when capture the audio by hardware connecting to the amplifier as above configuration.

3. we could acquire complete waveform whe configure beep device as plughw like this.

4. add 20ms null data to the beginning of the beep file, then we could acquire complete waveform. but the waveform reversed .   upper is original beep file, below is beep file adding 20ms null data

why dmix lost some audio?  and the audio be reversed?

Thanks a lot for any tips .

[igorpadykov]

Hi yang

one can try to decrease pop using volume control or codec stby signal as

described on

iMX6Q+SGTL5000 have pop noise in suspend/resume and shutdown processes 

try with latest NXP Linux L4.14.98,   link
https://source.codeaurora.org/external/imx/linux-imx/tree/?h=imx_4.14.98_2.0.0_ga

Best regards
igor
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