Strange (random) behaviour when using ALSA with DSPLINK

Elias Kokkinis

Hello all,

I am using an OMAP3530EVM kit to develop some speech processing applications. I am using ALSA for audio input/output operations. I have a simple ALSA program that runs on the ARM side to test the library functionality and I/O. Everything is well and I have transparent audio. The same holds when using aplay, arecord, etc.

However, when I use ALSA to get some audio buffers process them on the DSP and get them back I get some very strange behavior.

It seems that when the PCM stream opens there is distortion, clicks, pops and something like a decaying ramp offset that distrubs the audio. I have to restart ALSA and the stream several times to get rid of it. I do not have buffer under- or over-runs.

Does DSPLINK affect ALSA? Is there some way to avoid this? Do I need to take care where my buffers are placed? Anyone had any similar problems?

Thanks for any suggestions,

Elias

over 12 years ago

0 Cvetolin Shulev-XID over 12 years ago

TI__Guru 65405 points

Hi Elias,

I had never seen such problem but I advise you to add some debug message printing and track the sequence of the processed samples.

Tsvetolin Shulev

0 Renjith Thomas over 12 years ago

Guru 31670 points

Elias,

I've seen the similar issue in another ARM + DSP platform(Davinci). The issue is with EDMA channels which is used by DSP as well as ARM. Can you enable print inside your DMA driver code to see whether any DMA error occurs or not?

0 Elias Kokkinis over 12 years ago in reply to Renjith Thomas

Intellectual 505 points

Hello Renjith,

thanks for your suggestion. I wll try to do so and see what it comes out.

Do you believe it may have also something to do with the beep I hear just before and right after an audio I/O operation? It is reported as a known issue in the DVSDK 3.

Thanks again and I will get back.

0 Renjith Thomas over 12 years ago in reply to Elias Kokkinis

Guru 31670 points

Hi Elias,

Elias Kokkinis said:
Do you believe it may have also something to do with the beep I hear just before and right after an audio I/O operation? It is reported as a known issue in the DVSDK 3.

I am not sure about this. Is it coming only after running any DSP application?

0 Renjith Thomas over 12 years ago in reply to Renjith Thomas

Guru 31670 points

Hi Elias,

This is the issue that I have debugged and saw DMA channel issues.

http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/231409.aspx

0 Elias Kokkinis over 12 years ago in reply to Renjith Thomas

Intellectual 505 points

Dear all,

while researching into the issue, I found out that when running the original readwrite demo of the DSPLINK framework, sometimes the buffer returned from the DSP is not verified by the ARM which means something goes wrong there.

What can be possibly wrong? Does this mean something interferes in the shared memory region and corrupts the buffer?

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Strange (random) behaviour when using ALSA with DSPLINK