Glitches streaming audio between two AM335x EVM boards

Andrew Ness

Other Parts Discussed in Thread: WL1837MOD

I am working on a solution for streaming audio over Wi-Fi. I'm evaluating the WL1837MOD and the AM335x processors based on TI's Streaming Audio Reference Design.

I have three AM335x EVM boards and am using GStreamer. I am using the latest SDK - version 1.00.00.03.

The problem is that I'm getting glitches/dropouts in the streaming audio while listening via the on board headphone output.

I was directed to this forum from the guys over in the Sitara Processors Forum. I initially posted there as I was having some issues just over ethernet, however with some pipeline optimization and buffering, it is now working smoothly over ethernet.

I am using one EVM as the server, creating a Wi-Fi network using hostapd - there is no router involved. I'm using the best channel I can find at 5GHz. I am using another EVM as the client (and have tried a third EVM as a client to make sure it wasn't just this particular device). Using iperf, I can get up to 100Mbps over the Wi-Fi link sending UDP packets.

There are four scenarios where it is working fine:

Stream from server EVM to client EVM over ethernet, playing back via on board headphone output.
Stream from server EVM to laptop over Wi-Fi.
Stream from server EVM to client EVM over Wi-Fi, saving the data to a .wav file on the local RAM disk, transferring it to my laptop, and playing it back there.
Stream from server EVM to server EVM over localhost, playing back via on board headphone output (only uses ~50% CPU, so not over doing it)

I am streaming a 96k, 24 bit, 2 channel flac file. I have resampled it down to 8k, and the problem persists. So I'm wondering if it is a bus contention issue or some other type of issue when using Wi-Fi and the EVM's on board audio codec (connected via I2S and the McASP) simultaneously.

Gstreamer does not indicate any buffering or packet loss/order problems when this occurs (it did before I got the buffering set up etc).

Even if I set the buffer to 5 seconds it behaves the same.

My pipelines are as follows:

Server:

gst-launch-1.0 -v filesrc location=/run/dsb.flac ! flacparse ! flacdec ! audioconvert ! rtpL24pay ! udpsink host=10.192.0.100 port=5000

Client (streaming to on board audio codec):

gst-launch-1.0 -v --gst-debug=udpsrc:5 --gst-debug=rtpL24depay:4 --gst-debug=rtpjitterbuffer:4 udpsrc port=5000 caps="application/x-rtp, media=(string)audio, clock-rate=(int)96000, encoding-name=(string)L24, encoding-params=(string)2, channels=(int)2, payload=(int)96" ! rtpjitterbuffer mode=2 latency=1000 ! rtpL24depay ! audioconvert ! alsasink

Client (streaming to .wav on RAM disk):

Any suggestions?

Andrew

over 10 years ago

0 Joseph Gigi over 9 years ago

TI__Guru* 85400 points

Hi Andrew,

Let me check internally about this.

In the meantime, it would help if you could share an air sniffer log - both working (EVM to Laptop over wifi) & non working (EVM to EVM over wifi) ) case would help.

Regards,
Gigi Joseph.

0 Andrew Ness over 9 years ago in reply to Joseph Gigi

Intellectual 450 points

Hi,

Thank you. What procedure do you suggest for capturing the sniffed packets? I was using wireshark on the laptop but my understanding is I shouldn't capture from the laptop while it is an endpoint.

I suppose I could probably use my third EVM? I'm in a remote office so I don't have extra commpiters around

0 Andrew Ness over 9 years ago in reply to Andrew Ness

Intellectual 450 points

Here is a Wireshark sniff of the EVM to EVM case, which has glitches in the audio. I put it on Google Drive as it is about 150MB and this forum only allows up to 20MB.

drive.google.com/open

I'm trying to compile the text mode version of wireshark for the EVM but there are a lot of dependencies and I haven't done much cross-compiling before.

Thanks for your help.

Andrew

0 Andrew Ness over 9 years ago in reply to Andrew Ness

Intellectual 450 points

It's taking too long to get wireshark compiled for the other EVM. I tried it running on my laptop while streaming to the same laptop and it seemed to work.

I also uploaded it to Google Drive: drive.google.com/open

Andrew

0 Andrew Ness over 9 years ago in reply to Andrew Ness

Intellectual 450 points

Have you had a chance to review the sniffed packets? I am anxious to get this working as otherwise I need to find an alternate platform to develop this application.

Andrew

0 Joseph Gigi over 9 years ago in reply to Andrew Ness

TI__Guru* 85400 points

Hi Andrew,

I have sent you a request to grant me access to that file. Please approve.

Btw, I checked about this internally. The suspect this could be a problem with the lack of resources in the EVM. If it was a WLAN issue (dropped frames), then it would've been dropped in the copy file as well...

Regards,
Gigi Joseph.

0 Andrew Ness over 9 years ago in reply to Joseph Gigi

Intellectual 450 points

Hi,

I approved your request - sorry, I didn't realize it need that.

If it is a resource issue, how does your streaming audio reference design work? Was it ever tested our was it just a concept?

Thanks for your help.

Andrew

0 Andrew Ness over 9 years ago in reply to Andrew Ness

Intellectual 450 points

This is the streaming audio reference design I was referring to: www.ti.com/.../TIDEP0009

It claims that it's been validated...and links to the evaluation kits that I purchased. It also uses the 3352 processor while the EVM has a 3358, which should have many more resources as far as CPU goes. I have also monitored CPU usage and it is only about 25%...of course this could be an I/O bottleneck.

Andrew

0 Joseph Gigi over 9 years ago in reply to Andrew Ness

TI__Guru* 85400 points

Hi Andrew,

I haven't been able to download the problem log. Can you please check the permission again?

Regards,
Gigi Joseph.

0 Andrew Ness over 9 years ago in reply to Joseph Gigi

Intellectual 450 points

Hi,

Try now. Does TI have a file upload service?

Andrew

0 Joseph Gigi over 9 years ago in reply to Andrew Ness

TI__Guru* 85400 points

Hi Andrew,

I have downloaded both the files, and forwarded it to our technical team.
I will revert back once I have an update.

Regards,
Gigi Joseph.

0 Andrew Ness over 9 years ago in reply to Joseph Gigi

Intellectual 450 points

I've stripped away some layers and am having what may be the related, underlying problem. Please see my new post: e2e.ti.com/.../455637

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Glitches streaming audio between two AM335x EVM boards