Portsdown Audio Delays

[N6GKJ2]

Guys,

I have been having this issue for quite sometime. I am running Portsdown driving the DATV-Express.
After my transmitter has been keyed for 30 to 45 mins or so I have been noticing that my audio lags my video by 30 seconds or so.
I thought initially it was the USB resource issue of capturing video on the easy cap and dumping to the DATV_Express that was causing this.

I borrowed a friends Portsdown with FM Board and it does the same thing. Other users in our group have noticed this as well.

Here in Northern California, we all run with boxes coming up in TX mode, then we just key the PA when we want to talk.
de-keying the transmitter from ssh seems to clear the issue when TX is restarted.

I have been doing some testing and find the video capture card is clocking at 29.7fps our frame rate programmed into a.sh is at 30fps.

Could this .3 second difference build up to a lag?

I have not tested this theory as of yet, I just found this earlier today and was planning to dig in deeper. I thought I would throw this out first to see if anyone else has encountered this.

Any thoughts would be appreciated

Ron, N6GKJ

[G8GKQ]

Hi Ron

I had not anticipated such long running times, so had not tested these conditions. I will have a think about why you are getting these delays.

In the interim, it is possible to hardware key the transmitter without a touchscreen or network connection. The instructions on setting it up are here: https://wiki.batc.org.uk/Hardware-only_ ... _Switching. This might be a solution for you and your colleagues.

Dave

[G8GKQ]

Hi Ron

I don't think that the difference between 29.97 fps and 30.00 fps would cause this delay (my calculations say less than 3 seconds after 45 minutes). I think that it must be a problem with the configuration of ffmpeg - which the Portsdown uses to generate the MPEG-2 transport stream.

Please could you tell me what Symbol Rate and FEC you are using and I will try to reproduce the fault?

Dave, G8GKQ

[N6GKJ2]

Hi Dave,

I am using:
FEC 1/2
Symbol rate 2222 M/s
My Easy Cap was purchased from BATC Store.

I can replicate this all the way back to 201803181

I can use a different PI 3 and get same results.

I use sd cards from different vendors all class 10 with same result.

Things in common are video camera, USB capture device and power supply

Popping in the audio is a common issue. We can see errors on our IRD status screen and see very high error counts in the audio decode.

Another strange event, when the DATV Express is used in a Linux environment with a Hauppage encoder, there is a different bit rate than when using rpi3 with fm board or with datv express.

Fred is running 201802221 and does not experience any audio issues in any form.

My hardware tested in his platform does not experience the issues.

This kind of points to a change happening in early 2018.

One other note ...

On my rpi3b+ I am using the 7 inch display plugged into the RPI3B+ I don't know how this can impact the system.

My current test bed environment is an rpi3b no display of any kind. Tx is controlled via ssh menu screen.

Same audio delays experienced

I would be happy to arrange a time that you can see my stream and that might give a clue

Again,

Thank you for all you do!

Ron, N6GKJ

[N6GKJ2]

Correction to my last post

2.222 M/s

The period got dropped

[G4KLB]

I have had this problem with certain receivers when using the express, but I guess you have tried resetting the RX to see if the fault remains.