audio issue: inaudible due to bad echo on iMX53

[varmas]

CPU - i.MX535

Audio Codec Chip – SGTL5000

Linux – 2.6.35.3

I am using VOIP stack on the i.MX53 which works well for the video calls. The issue is with the audio. During a call, there an echo which makes the sound output inaudible. I tweaked the VOIP stack and reduced a little bit of it. Now we further need to tweak into the kernel to reduce the audio latency during capture and playback which will reduce the echo.

I am pretty sure that the VOIP stack is not doing this. On the VOIP side, I am using PCMU and PCMA audio codecs.

Can noise/echo cancellation be achieved either through some kernel configs or settings in audio codec. Is there a built-in echo-cancellation in the SGTL codec chip?

Appreciate any help/pointers in suppressing echo.

Thanks

Varma

[igorpadykov]

Hi varma,

Freescale BSP does not support echo cancellation, so probably you will

not find kerenl configs for it. However recently on FTF2014 was announced about

Freescale Audio Solution Platform, it will support support echo cancellation

please check link below

http://cache.freescale.com/files/training/doc/ftf/2014/FTF-SDS-F0130.pdf

SGTL codec does not have internal echo cancellation,

echo cancellation should be implemented in software. I.MX53 has Cortex A8 core with NEON SIMD

coprocessor with capabilities to perform echo cancellation algorithms.

Probably you will not find free NEON echo cancellation sources, however you can start with

arm fft examples (fft are similar to echo cancellation algorithms), found for example in RVDS examples

(www.arm.com).

infocenter.arm.com/help/topic/com.arm.doc.dui0255g/DUI0255G_rvds_getting_started.pdf

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