ITV HD World Cup Pixelation?

meansizzler

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Anyone else notice the pixelation on ITV HD, they are using what looks like a 10mb/s contant bitrate, and you can really see how it impacts the picture, it's like watching an upscaled dvd, even on a 12.1" 1280*800 display I can see it, the picture is not sharp at all.. currently watching world cup opening ceremony.

At the same time tennis on BBC HD looks much sharper and hardly any pixelation, they are using variable bitrate between 6-16mb/s but sadly anamorphic resolution, anyway they could of at least upped it to 1920*1080 20mb/s for the world cup.

Don't see the point in HD when the 2 main channels cripple the bitrate, 4 years ago the picture is great, now it's just terrible..

Am viewing on DVB-S wonder what the picture quality on DVB-T2 is like, I hear DVB-C is alot better...
 
Oh oh, not in front of my tv but this does not sound good!

Depends how far back you see, and if your using plasma it won't be that noticable.. most people watching on large screen tv's suit quite back so won't notice it, but those watching on PC will
 
Having watched both BBc & ITV World Cup broadcasts on my new Panny panel - it is noticeable the difference in PQ between the broadcasters...
Why is that - presumably the feed from the national broadcaster is the same?

(On SD Freeview)
 
A live broadcast cannot use anything but a constant bitrate unless it's stat muxed with another transmission on the the same transponder. vbr is only possible by pre-analysis of the motion content by pre-analysis of the footage for rapid motion content
 
A live broadcast cannot use anything but a constant bitrate unless it's stat muxed with another transmission on the the same transponder. vbr is only possible by pre-analysis of the motion content by pre-analysis of the footage for rapid motion content

How have BBC HD changed to VBR?
 
Having watched both BBc & ITV World Cup broadcasts on my new Panny panel - it is noticeable the difference in PQ between the broadcasters...
Why is that - presumably the feed from the national broadcaster is the same?

(On SD Freeview)

It depends on the bitrate and resolution used for the conversion from the original feed. SD resolution varies from 544 x 576, 704 x 576, and the full 720 x 576 with motion artefacts influenced by the bitrate used for the transmission.
 
How have BBC HD changed to VBR?

Have they ?. Unless they have a crystal ball how do they know the appropriate bitrate for something that's not yet happened ?
 
Have they ?. Unless they have a crystal ball how do they know the appropriate bitrate for something that's not yet happened ?
BBC HD is using VBR graham, encoders can analyse on the fly- as you know there is quite a delay between analogue and HD TV.
 
BBC HD is using VBR graham, encoders can analyse on the fly- as you know there is quite a delay between analogue and HD TV.

The delay is a measured in a few seconds compared to live action it's totally insignificant. How about a link to your information ?. You can't possibly change the bitrate for something that's not yet happened even with a processing delay which would apply equally to the delay introduced by the encoding process. Of course it's possible to dynamically change the live bitrate of multiple channels by analysis of the multiple streams and dynamically allocate the total pot between the two (stat muxing) a different process. How would for example a run by Owen from one end of the pitch to the other and score (if only :cool:) benefiit. There is no problem with recorded content, true vbr requires at least two runs through the total data,
 
Of course it's possible to dynamically change the live bitrate of multiple channels by analysis of the multiple streams and dynamically allocate the total pot between the two (stat muxing) a different process.
Graham there is no real difference between what is being used now and stat muxing, except only one channel is being analysed with a fixed amount of space to work in i.e. 4-18Mbps, stat muxing analyses the picture of all channels and allocates more bitrate for fast movement, complex patterning etc.
 
How have BBC HD changed to VBR?

Simple they ether have the BBC HD H.264 encoder negotiating for bandwidth with the 2 SD encoders sharing the space on that transponder, or there is still the 16.5mbit is still available from the old BBC HD and they are experimenting.

those transponders carry about 33-34mbit/s of usable data bandwidth. The 2 SD channels use 8-16mbit/s
 
Graham there is no real difference between what is being used now and stat muxing, except only one channel is being analysed with a fixed amount of space to work in i.e. 4-18Mbps, stat muxing analyses the picture of all channels and allocates more bitrate for fast movement, complex patterning etc.

Unless the freed up bandwidth is being used for another channel what's the point, might just as well us cbr. How can it analyse the picture on a live transmission the action has not happened yet. VBR on a dvd requires the content to be prescanned at least twice it can't be done on the fly. Luxe_HD prescans there transmissions but none of it's live.
 
Simple they ether have the BBC HD H.264 encoder negotiating for bandwidth with the 2 SD encoders sharing the space on that transponder, or there is still the 16.5mbit is still available from the old BBC HD and they are experimenting.

those transponders carry about 33-34mbit/s of usable data bandwidth. The 2 SD channels use 8-16mbit/s

That's stat muxing which if you read my post mentions. It's not a true vbr transmission, vbr is used to maximise quality on a medium with limited capacity like a dvd and always needs the full content to be preanalysed.

In any case at the present moment both SD channels and the HD channel are showing the same picture so apart from the very slight extra processing delay of the Hd channel how can they negotiate when using the same content ?
 
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That's stat muxing which if you read my post mentions. It's not a true vbr transmission, vbr is used to maximise quality on a medium with limited capacity like a dvd and always needs the full content to be preanalysed.
They are not stat muxing, the two SD channels are fixed bitrate and BBC HD is VBR....
 
That's stat muxing which if you read my post mentions. It's not a true vbr transmission, vbr is used to maximise quality on a medium with limited capacity like a dvd and always needs the full content to be preanalysed.

In any case at the present moment both SD channels and the HD channel are showing the same picture so apart from the very slight extra processing delay of the Hd channel how can they negotiate when using the same content ?

This got me thinking and I eventually joined the dots.

They are 'stat muxing' with the null bytes that will soon become BBC 1 HD. Looks like they are making sure they will both fit, assuming broadly similar picture demands.

linowsat_BBCHD_09-06_18-06.png

linowsat_null_bytes_09-06_18-06.png
 
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This got me thinking and I eventually joined the dots.

They are 'stat muxing' with the null bytes that will soon become BBC 1 HD. Looks like they are making sure they will both fit, assuming broadly similar picture demands.
lol it's not stat muxing with anything, you can't stat mux with null bytes. It is as Andy Quested has stated, VBR.
 
lol it's not stat muxing with anything, you can't stat mux with null bytes. It is as Andy Quested has stated, VBR.

Hence the quotation marks. LOL. :rolleyes:

grahamlthompson was asking about how the bits are allocated when the data isn't being preanalysed. This is the answer.
 
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Hence the quotation marks. LOL. :rolleyes:

grahamlthompson was asking about how the bits are allocated when the data isn't being preanalysed. This is the answer.
No, the data is pre-analysed, it analyses and then encodes with a higher or lower bitrate as necessary. Remember that the chips in professional encoders are considerably more powerful and optimized for that task than most PCs.
 
No, the data is pre-analysed, it analyses and then encodes with a higher or lower bitrate as necessary. Remember that the chips in professional encoders are considerably more powerful and optimized for that task than most PCs.

Yes, but the 'full content' is not pre-analysed, which is what Graham was talking about.

This is becoming a not very useful argument about what counts as VBR. The point I was making was that the null bytes form the bandwidth reserve, unsurprisingly, but moreover the limits and target bitrate (or whatever exact quality parameter they are using) on BBC HD seem to be set so that assuming broadly similar picture material the two HD channels will be able to coexist on the TX. I was suggesting this on the basis that the null bytes and the BBC HD graphs look pretty similar, especially the average bitrate. Fair enough? Or have I missed something?
 
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I was suggesting this on the basis that the null bytes and the BBC HD graphs look pretty similar, especially the average bitrate. Fair enough? Or have I missed something?
I see what you mean now:D, yes the nullbytes and BBC HD graphs looks very similar, is it possible to stat mux two H.264 channels together when you have two MPEG2 channels on the same transponder though?
 

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