HD video causing lockups

[g8lce]

I have been having some problems with Rydes and Portsdowns locking up on still frames when putting HD video through GB3NQ. They do it in a repeatable manner with particular video shots give or take a few frames. The local Portsdown receives my TX prefectly but through the repeater I get the lockups. A satellite RX keeps working. I thought that it could be a variable bit rate problem but all is constant bit rate. I know we are pushing the limits down here in Cornwall but has anyone got some idea what may be going wrong?
The Ryde feeds the stream from GB3NQ.

Martin G8LCE

[G3GJA]

Hi Martin

I have seen similar problems on my kit and on GB3EY. Running the 'top' command in the console whilst receiving HD content seems to show that the VLC thread is maxing out the CPU.

I say 'seems' because I'm not qualified to make a definitive judgement!

Clive G3GJA

[G8GKQ]

I may move this conversation to the Ryde Topic....

I think that the HD picture freezes are a hardware limitation. We use software video decoding in Ryde because hardware video decoding does not like (or even display) SR Systems-encoded video (such as the QO-100 beacon). When Ryde was designed and tested there were very few full HD transmissions, and so the CPU limitation of Full HD video decoding and downscaling to 576x768 (for Comp Vid) was not apparent. I think that we are running up against the limitations of the Raspberry Pi hardware capabilities with some input signals.

The best command to look at what is going on is "htop", then press F5. This will give you a tree view of the processes and their sub-processes, and also show the usage of each of the 4 CPU cores. So you can see how much resource VLC is using. I use this all the time in testing.

Dave, G8GKQ

[G3GJA]

I have tried a Ryde with HDMI output on the same content and I don't see as much freezing.

Perhaps the down-scaling is pushing the CPU to saturation. Presumably, an all digital repeater wouldn't suffer the same issue.

Clive

[g8lce]

The trouble is that the ryde/Portsdown receives the HD I am sending to the repeater but sometimes freezes on high detail and movement once the signal has been through the repeater. The beacon video contains HD and movement but has been processed through YouTube!! so may be filtered more. I may make a video to show the problem....

At least I am not the only one..

Martin G8LCE

[g8lce]

I have noticed another thing, if I let a short few minute HD video that locks up the Portsdown (after going through the repeater ) run on a loop, the Portsdown will unlock eventually and then the next time the same bit of video comes along the Portsdown does not lockup!!
I will see if a HD video with no movement for a few minutes then movement after a time makes any difference.

Martin G8LCE

[G3GJA]

Some further tests last night showed that 1920 x 1080 HD isn't possible except for short periods. The CPU saturates. Even worse with H265.

HD at 1280 x 720 H264 is better, but standard definition 1024 x576 25fps H264 is mostly freeze free. The CPU loading caused by H265 is around an additional 20%

It seems that whilst the flawed SR systems coder is supported the Ryde is unlikely reliably handle anything more than standard definition at normal frame rates.

I know Dave doesn't want to support two versions, but if HD on repeaters is to progress then the hardware decoding in the Pi might help. I don't have the expertise to implement that. Maybe someone in the ATV community can help?

Clive

[G8GKQ]

Hi Clive

Thanks to Tim's foresight, that is an easy one.

The last line of the config file should be:

Code: Select all

disableHardwareCodec: True

Just change it to:

Code: Select all

disableHardwareCodec: False

Save it and restart the receiver.

Dave

[G3GJA]

Hi Dave

Enabling the hardware decoding has made a massive improvement. It's now possible to use full HD without stuttering.

The CPU loading due to the Ryde/Long Mynd processes has dropped from over 100% to around 60% with H264 and 70% with H265.

(Martin: you need to enable the hardware decoding on your box!)

Regarding the other issue with the Ryde not starting or not outputting a lock signal, the problem has not shown up since I refreshed the SD card by running the latest update that you released following the VLC changes. I know the changes are only for new builds but somehow the update seems to have fixed it for now.

Thanks for your help

Clive

[g8lce]

I have tried more settings and found that even at 720P the same thing happened!
So I looked at other things and found that by reducing the data rate to 800kbps it cured the lockups.
720P or 1080P 2000SR now works without lockups on both Ryde and Portsdown 4 receivers. The satellite receiver always worked. If I increased the rate to 2Mbps they lockup after 2 seconds on this test video: https://youtu.be/24gQ-MquI0Q
I tried the enabling of the hardware codec but it made no difference (to the lock ups ).

Here are some of the settings from my vMix HD:

rtmp://192.168.123.100:7272/,1249,DVBS2,QPSK,2000,23,0,nocalib,800,32,

H264 1080p 800kbps AAC 64kbps

These work.

Martin G8LCE