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Scratching noise during audio playback

Question asked by Naman Thaker on Apr 23, 2020
Latest reply on May 26, 2020 by Naman Thaker

Hello,

 

I'm working on IMX8M Mini EVK with Android Pie (p9.0.0_2.3.0) OS. I have integrated CX9000 Synaptics audio amplifier and CX20921 Dual MIC voice processor to the EVK. The speaker amplifier supports two word size, 16-bit and 32-bit.

 

I am observing a kind of scratching noise either continuously or only at beginning of the playback on the speaker in various use-cases as mentioned below.

 

Use-case16 Bit Setting32 Bit Setting
DMICBeginningBeginning
Text-to-speech (TTS)ContinuousBeginning

 

For DMIC use-case, the audio is captured from the 2 DMICs on the system (refer dmic_noise.mp3 for the noise at beginning right before 'hello' is said). For TTS use-case, an online generated text to speech audio file is played on the speaker. During a VoIP call on the system, the noise is heard same as during TTS use-case (refer voip_noise.mp3 for the continuous noise).

 

Several points of observations:

  1. The noise is present while playing through Tinyplay and in other Android music app in GUI also.
  2. Noise is present for .wav and .mp3 also.
  3. When a longer message is played of 1 min 30 sec length, then also noise is heard only in starting.
  4. The noise is not present when playing a song/music file.
  5. The noise is not present when the same audio file is played on PC on VLC or other music player applications.
  6. The noise is not present when the TTS converted audio or recorded audio file is played on Bluetooth speaker or headphones connected to NXP.

 

Please help to debug the issue.

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