i.MX6 Quad | Audio Record can't recording high frequency voice ( > 8KHz )

[rickchu]

Hi,

We have an issue with audio recording on i.MX6 Quad Core Platform. The hardware is made by our self (based on SABRESD board), and running Android 4.4.2 (BSP based on android_kk4.4.2_1.0.0-ga).

When the audio source frequency higher than 8 KHz, we can't record any data with our device.

We have confirmed that Microphone can received high frequency (at least 20 KHz) and audio chip (ALC5640) also can record  from 8 KHz to 96 KHz data no problem (tested with audio EVB).

The audio chip vendor mention that the limitation may caused by freescale i.MX6, but we have not see any discussion about this topic on support forum.

Have any one have such experience to record high frequency audio on i.MX6 platform? Our requirement is to support 18 KHz~ 20 KHz audio record for audio payment solution.

Our hardware information list on below:

CPU: i.MX6 Quad Core

Audio: Realteak ALC5640-VB

Microphone: Digital Microphone

Android Version: android_kk4.4.2_1.0.0-ga

I2S clock

MCLK : 11289600Hz

BCLK : 1411200Hz

LRCLK: 44100Hz

Rick

7KHz source is okay

8KHz source is NG

[igorpadykov]

Hi Rick

I think this may be caused by ALC5640 internal filtering, because

it is difficult to imagine how linux may cause this filtering.

Suggest to check this with SDK, for narrow down possible reasons and

avoiding Linux OS side effects.

i.MX 6Series Platform SDK : Bare-metal SDK for the i.MX 6

Best regards

igor

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[rickchu]

Hi Igor,

Thanks for your response.

We have make sure all ALC5640 internal filtering have been disabled in our driver (also using i2c utility to read out register value when recording).

Is it possible to measure if record data have been filter and no output to i.MX6 (to monitor AUDn_RXD)?

Rick

[igorpadykov]

Hi Rick

I think you can take two boards with ALC5640

and connect Tx one board to Rx another, in such

way you will avoid linux influence.

Best regards

igor

[rickchu · Accepted solution]

Update:

We have contact local FAE support, and found this issue not happened on Linux BSP, but fail on Android BSP.

We have another hardware platform (Intel SoC) with same audio chip (ALC5640), and running Android 4.4.4 on it. No problem with this test.

Rick

[oway]

We have this same issue of audio 7kHz working, but 8kHz not working.  Did you find a solution for Android?

We are using an external A/V decoder -> I2S -> AUD6_RXD.  This is when we have the problem.

Note that in Android, playing an audio file from a USB drive does not have this problem.