MPEG 2 Video Problem

Discussion about this major DATV Project. See https://wiki.batc.org.uk/The_Portsdown_Transmitter
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G4uvz
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Joined: Sat Dec 09, 2017 10:30 am

MPEG 2 Video Problem

Post by G4uvz » Thu Feb 01, 2018 4:59 pm

Finally connected a camera to the Portsdown today via the easy cap. H264 video working fine on tests with G4BVK in Bristol on 146.5 MHz
Mpeg2 card was also received no problems ...However when I tried Vidmpeg2 from menu 2 ..on both minitunes @ receive and transmit we both got a good still frame from the camera ...so we rebooted all round but this time no mpeg2 picture at either end ..checked the Mpeg 2 card...all ok and H264 video fine??????????
Adrian

G8GKQ
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Re: MPEG 2 Video Problem

Post by G8GKQ » Thu Feb 01, 2018 6:32 pm

Hi Adrian

The MPEG-2 video function only works well at 1000KS and above. You can improve it by turning the sound off (which allows the video a bit more bandwidth) but I guess that you are using MPEG-2 to get the sound!

As stated (in the release note for the capability) on the Wiki https://wiki.batc.org.uk/201707221_Release_Note "Performance is poor at below 1MS. The mode is designed for use at 1MS or higher, although with slow-moving pictures it is usable at 333KS (just)."

The combination of a noisy (compared to the test card) video signal, the software encoder and the MPEG-2 compression algorithm just do not work very well at those very low bit rates.

Dave

G4uvz
Posts: 219
Joined: Sat Dec 09, 2017 10:30 am

Re: MPEG 2 Video Problem

Post by G4uvz » Thu Feb 01, 2018 7:06 pm

OK Dave...thanks for the info ...all understood its a shame as the MPEG2 test card is being received particularly well!

At the moment my main option is 2 M ! On another point ...are there any plans for Portsdown to produce H265 at some stage as this the preferred mod used by ZZ?

Thanks
A

G8GKQ
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Re: MPEG 2 Video Problem

Post by G8GKQ » Thu Feb 01, 2018 7:44 pm

Hi Adrian

H265 is on my list to try. It's just a matter of finding the time to do it. I'm not sure whether the RPi 3 is up to it though; I know the Bristol guys have found that even some powerful PCs struggle.

Dave

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