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audio lost and reverse when playback beep audio

Question asked by yang chen on Apr 28, 2019
Latest reply on Apr 28, 2019 by igorpadykov

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 .

 

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