[TelstraClear] Telstra's Digital TV - is it recompressed MPEG-2 from Sky?

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digitalepsilon

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Topic # 10007 30-Oct-2006 02:37

Last night I was watching Sky Sport 1 over Telstra's Digital/Cable TV and there was an interruption to the signal from Sky's end that caused the Sky "Rain fade" decoder notice to appear, and when the signal resumed, the Sky decoder channel info OSD appeared over the coverage. As far as I can see, Telstra must have either an actual Sky decoder (or some device running that firmware) at their end and are sending the signal from that out over their Digital TV network.

I was under the impression from previous posts on this board that Telstra didn't recompress the MPEG-2 signal from Sky and just somehow transmitted it over their cable network without recompression. But that isn't consistent with what I saw, at least not on the Sky Sport 1 channel.

If there's decoder OSD graphics being overlaid on the video, then it can't be the raw MPEG-2 signal from the Optus satellite that Telstra customers are receiving since there's a device modifying the video in the stream.

Is my reasoning here correct? Is there any possible way you can overlay graphics on a MPEG-2 stream without decompressing it first, overlaying the graphics, and then recompressing it afterward? If not, then it's fair to assume the digital signal we (Telstra customers) receive isn't as clean as the one Sky subscribers get which is disappointing, given the overcompressed Sky source signal to begin with.

I'd be interested if anyone does know the setup Telstra uses to send out the Sky channels.

Cheers

digital

JonC

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Reply # 50244 30-Oct-2006 10:33

I've seen a similar "rain fade" notice as well. I can only make the same conclusion that you have - TCL has some Sky decoders (one for each channel) that decode the sky signal. This is then re compressed for broadcast over their cable network. Makes for poor quality viewing. I don't work for TCL, so can't say for sure, but it seems the most likely explanation.

I hooked up my computer to my TV last night and watched a highly compressed (divx at 984 Kbps) video and it seemed to be about the same or even better quality than a typical TCL channel. Although I've found the quality varies from channel to channel.

If you want higher quality video - it might be better to download the show you want to watch using TCL's (excellent, I must say) cable broadband via BT - kinda ironic :-)

digitalepsilon

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Reply # 50247 30-Oct-2006 10:50

If they are using decoders, the worrying thing is last time I checked, Sky's digital STBs only offered analog outputs. The video and audio would both be further degraded through the digital -> analog -> digital conversion before being recompressed.

Even with some of their Digital TV decoders now coming with SVideo output, it's not exactly an incentive for me to purchase a widescreen LCD.

And yeah, given their network is able to handle (and more importantly, really deliver) 10MBit broadband with capacity to spare, it seems like a waste knowing that the technology has room to deliver a much higher video bitrate if they choose to. I wonder what TCL's strategy will be when Sky goes HD.

Cheers

digital

JonC

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Ultimate Geek

Reply # 50250 30-Oct-2006 11:09

We only really noticed how poor the TV quality was when bought a widescreen LCD a few months ago. Having good quality outputs from their decoder seem a waste of time when the signal quality is so poor in the first place. But the good thing is that the content that TCL actually provide themselves (the PPV movies) seem to be good quality.

I agree that TCL has plenty of scope to improve the quality of their product - HD, PVR, etc. Here's hoping....

cyril7

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Reply # 50741 2-Nov-2006 08:40

I was always of the understanding that TCL did not decode Skys streams but just pass them through, and did write so in earlier threads. This was based on my experience in Europe a couple of years ago where I was involved in commisioning such ASI retransport units for a large cable/sat system. This more elegant ASI retransport methode is the norm in Europe.

However having had the misfortune recently to see the TCL service in action I can clearly see that TCL have taken the cheap option and full decode and recode. I was at a friends home recently who had the service and was shocked, so much so that as their home had a dish (due to a previous tenant) I went home and collected my Sky box and put it up along side TCL STB. It was clear they are not the same stream, the TCL one appears to be recoded.

Your observation of Rainfade screens and Sky STB graphic plane overlays confirm that TCL infact fully decode and recode.

Pretty poor show

cyril

lchiu7

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Reply # 50747 2-Nov-2006 09:44

THey provide their on TV3 feed captured from an antenna, filtered, compressed and sent. I suspect they don't do much with TV1 and TV2 which they get from Optus I was told. The rest is unknown.

I don't have the exact numbers but it takes about 5Mhz for an analogue channel and perhaps much less for a digital channel. So if they could get rid of the analogue signal, they would probably free up enough bandwidth to provide better digital pictures, and HDTV one day. If they mandated digital I wonder what the customers would say

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sbiddle

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Reply # 50750 2-Nov-2006 10:13

lchiu7: THey provide their on TV3 feed captured from an antenna, filtered, compressed and sent. I suspect they don't do much with TV1 and TV2 which they get from Optus I was told. The rest is unknown.

I don't have the exact numbers but it takes about 5Mhz for an analogue channel and perhaps much less for a digital channel. So if they could get rid of the analogue signal, they would probably free up enough bandwidth to provide better digital pictures, and HDTV one day. If they mandated digital I wonder what the customers would say

I heard a few months ago that the analogue channels would still be staying for some time yet but will be phased out. Current FTA channels will apparently still stay.

Their C4 feed is also from an aerial, hence the crap picture on C4. Most people in Wgtn who get their TV from KauKau get a poor picture on C4 as it used VHF CH2 and gets interference from TV1 on VHF CH1.

lchiu7

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Reply # 51035 4-Nov-2006 17:59

Well luckily I don't watch C4. But I watch TV3 a lot and the PQ is not good. I often am tempted to go check my aerial since I think I have a decent view of KauKau

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cyril7

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Reply # 51036 4-Nov-2006 18:16

You would think they could at least front up with a Sky decoder to at least get a somewhat better pic for both TV3 and C4.

Maybe that indicates how seriously TCL take picture quality.

Cyril

lchiu7

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Reply # 51041 4-Nov-2006 19:46

Probably licensing issues or something. Sky I suspect gets their signal from TV3 as a direct feed so it's quite good. However TCL being based in Wellington cannot get that feed (easily) - there is nothing on Optus B so the resort to the aerial. When I asked a friend of mine, what about the BCL feed that gets sent around the country to retransmit all channels for OTA transmission, he said the signal format that BCL uses was quite different and would require some costly conversion gear to be able to tap into it. I think that would be the right way to go about it.

With Freeview next year, maybe they will grab the signal off the satellite

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cyril7

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Reply # 51045 4-Nov-2006 20:47

TV3, and C4 are transmitted on Sky, so why is it so hard to retransmit them. They manage to get the retransmission rights for all the other 40odd Sky channels.

Cyril

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Reply # 51078 5-Nov-2006 08:26

cyril7: TV3, and C4 are transmitted on Sky, so why is it so hard to retransmit them. They manage to get the retransmission rights for all the other 40odd Sky channels.

Cyril

Politics. There are lots of issues involed in the TCL/Sky deal.

lchiu7

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Reply # 53110 21-Nov-2006 09:21

cyril7: TV3, and C4 are transmitted on Sky, so why is it so hard to retransmit them. They manage to get the retransmission rights for all the other 40odd Sky channels.

Cyril

But do they get the channels from a Sky dish or from a different feed? As you say TV3 is on Sky (I guess - I don't have Sky) and that would be a much better source than what they use now

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cyril7

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Reply # 53114 21-Nov-2006 10:37

Yes they do just get them off the satellite just like everone else, however as sbiddle pointed out, it is more likely politics rather than technical reasons that they get TV3 off KauKau rather than Optus D1/B1.

Cyril