Chooppy footage on Stratos only?

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#89426 4-Oct-2007 10:38

cyril7: Naah the Statos feed on my FTA reciever is in a different league to TVNZ/Canwest, very soft and has a short echo in the image. Scanned D1 lastnight, I could not see Stratos and Parliment in any Sky mux, so they must be pointing at the FreeView one.

Cyril

I've looked in the NIT and bouquet info for Sky and they are simply pointing at the freeview transponders.

Generally known online as OpenMedia, now working for Red Hat APAC as a Technology Evangelist and Portfolio Architect. Still playing with MythTV and digital media on the side.

grolschie

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#89717 5-Oct-2007 20:45

cyril7: Naah the Statos feed on my FTA reciever is in a different league to TVNZ/Canwest, very soft and has a short echo in the image.

This is because Stratos are grabbing their feeds from Optus B3 FTA channels which are lower quality e.g. 1.68mbit 544x576px video + 128kb stereo audio, or worse. Whereas Sky is usually 2.5mbit or better video, with Sky Box Office being close to 4mbit.

Artifact

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#90053 8-Oct-2007 10:12

rpmnz: It has me wondering if my dish is not aligned properly as I get great signal strength but not quality ( ~50%) for the transponder that Tv3 and stratos are on. TV2 etc are fine.

Check the polarity alignment of your LNB. A poorly aligned LNB will exhibit symptoms of good TV1/TV2 reception but troublesome TV3/C4/Stratos reception.

I've seen a case where the transponder containing TV3/C4 could not be found at all during an initial scan, whereas the transponder with TV1/TV2 was found.

The isssue was LNB polarity alignment being very poor - tweaking the LNB by, in this case, around 60 degrees fixed it.

cyril7

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#90057 8-Oct-2007 10:45

The Skew of the LNB needs to be correctly set within a few degrees, if you had a spec analyser and did a cross pol null you will find that the skew can visibly be set correctly within 5deg or less. If its 60deg off its not just a "bit out", its totally out.

Cyril

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#90061 8-Oct-2007 11:00

cyril7: The Skew of the LNB needs to be correctly set within a few degrees, if you had a spec analyser and did a cross pol null you will find that the skew can visibly be set correctly within 5deg or less. If its 60deg off its not just a "bit out", its totally out.

You are absolutely right - it was totally out. I was amazed we got any signal at all.

It was just starting to rain when we finished peaking the dish, which is why the job was rushed.
I thought the LNB was correct - but I obviously overlooked the correct peak.

We used a simple signal strength meter, and when the LNB was adjusted the next day it made a large difference in the signal strength.

I wish I had a spectrum analyser to do this - but I don't, so I have to make do with the signal strength meter.

cyril7

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#90081 8-Oct-2007 12:27

The $50 satellite finders are no good for alignment, in the absence of a spec analyser or a proper satellite meter somehow get a video feed from your STB to the roof, and peak the quality, not just the signal strength. The quality figure shows the last couple of dB that is important that a signal meter (including the signal strength reading on the STB) will not show.

The Sat finders are just that, they tell you when you have found a satellite or within a few degress of it, nothing else.

Cyril

ZollyMonsta

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#90118 8-Oct-2007 15:03

I heard garbled audio.. to me it sounded like the PC couldn't keep up with the encoding of the audio.
Video was fine.

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rpmnz

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#90403 10-Oct-2007 09:36

cyril7: The $50 satellite finders are no good for alignment, in the absence of a spec analyser or a proper satellite meter somehow get a video feed from your STB to the roof, and peak the quality, not just the signal strength. The quality figure shows the last couple of dB that is important that a signal meter (including the signal strength reading on the STB) will not show.<

All of the tuning I did was for quality rather than signal strength, I have optimised the skew as far as I can manually. Since I dont have access to spectrum analyser this is about as good as I can get. I have re-scanned the channels and tv 3 is much better. I guess if I want to improve it any more I'll need to get a professional in or a larger dish :).

allstarnz

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#90533 10-Oct-2007 19:41

strangely I have found the same thing with Parliament TV, really choppy audio.

Only the two new non network channels do this all TVNZ channels (inc TVNZ6 and TVNZ Sport Extra) are fine, as well as the two Canwest channels.

Very very odd.

I don't think it's the dish, as it's perfect for Sky and all other freeview.

grolschie

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#90800 12-Oct-2007 11:01

What is the signal strength and quality readings on your STB for these channels? Is it worse on a cloudy/rainy day? Have you tried a factory reset, and rescanning of channels?

cyril7

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#90804 12-Oct-2007 11:10

Interesting these issues only seem to effect folk using PC based decoders, I have not seen any of these problems with hardware sytems.

The fact that the sound is choppy, is it because the PCR is not correct or not loaded at all, the PCR is used to sync the A and V streams.

Cyril

grolschie

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#90806 12-Oct-2007 11:14

If it's PC based, is the hardware up to it? Does the DVBs card have decent hardware decoding, or it is all done in the software?

cyril7

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#90808 12-Oct-2007 11:22

From what I have seen the PC based cards consist of a hardware tuner, and decoder, the transport stream in its entierty or in some case parts of the TS are shipped via the PCI bus to the processor for sub stream stripping and mpeg decoding, ie the cards have no on board mpeg decoders.

Cyril

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#90809 12-Oct-2007 11:22

cyril7: Interesting these issues only seem to effect folk using PC based decoders, I have not seen any of these problems with hardware sytems.

I have had identical reports (choppy video and sound) from viewers using standard Freeview receivers.

I personally have seen brief picture pauses myself on my Freeview receiver (Zinwell with v6.0 SW).

So I know for a fact it is not limited to folk with PC based decoders

cyril7

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#90811 12-Oct-2007 11:27

Hmm, have not noted it at all on any of my decoders. As its Parliment and Stratos but not TVNZ I wonder if the encoders they are using are different (a reasonable presumption) and also the way they react with the stat mux may be causing a break in the stream, however that does not explain why I have not noticed this nor many others.

Will have a look at them both over lunch.

Cyril

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