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Old 11-08-2009, 12:32
elan_vital
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Halleluja!!

Reading this column, I'm glad that I'm not the only one that dislikes low motion temporal rates.

The broadcast equipment company Snell & Wilcox did some early HD experiments with 75Hz at 768 lines and found it gave better results than 1150 lines at 50Hz.

Doug Trumball in the States experimented with higher picture rates and found that 72fps was the maximum rate that produced the most EMOTIONAL response in viewers. He settled on 60fps for his 'Showscan' film format to harmonise with US TV.

Do the math; 720@72 or 1080@50. As someone mentioned, line structure becomes much less significant at high frame rates (and faster shutter speeds!) All for a less punishing bit rate! It seems that temporal resolution needs to increase in proportion with spacial definition.

With many Red Camera users shooting high frame rate stuff, and recoding to 24/5fps, its easy to download stuff captured at 72 or 75 fps clips and play them in VLC or quicktime at 3x speed to see what 'natural motion' looks like. Be warned though, because once seen, it'll spoil how you look at 24/5 or 50fps forever!

After all, 24fps came about purely to save on the cost of film. Regrettably a 'film look' is seen to be aspriational, attributed to big budget productions so therefore it must be 'better'.

A parallel can be drawn here. CB was orginally illegal. There was a boom in imported US AM CB tranceivers. When CB was legalised, FM was specified but most CBers hated it because it sounded 'boxy' compared to their preference for the warmer sounding AM, even though FM is technically superior.
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Old 11-08-2009, 17:33
Everything Goes
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A parallel can be drawn here. CB was orginally illegal. There was a boom in imported US AM CB tranceivers. When CB was legalised, FM was specified but most CBers hated it because it sounded 'boxy' compared to their preference for the warmer sounding AM, even though FM is technically superior.
CBers hated FM not just because of the change of mode. UK 27/81 FM was put up at the top part of 27Mhz on offset channels that weren't used in any other country in the world.

On an AM CB you could happily use it with the Squelch turned off. On an FM CB you really did need the Squelch on to block out the harsh hissing noise when there was no signal.

Most of the world use FM CB or a mixture of different modes now but on the more standard FCC / CEPT part of the band (which the UK now have allocated). In the USA they still use AM however.

FM offers much better sound quality but AM can be a bit kinder on the ears at low signal levels where it gently fades out and sounds soft.
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Old 11-08-2009, 19:00
Bob_Cat
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elan_vital,

Personally I want to see 1080p300 as soon as possible, at the encoder it actually has some significant advantages because the difference between each frame is substantially smaller and thus the temporal motion estimation is made much easier. Plus because it is not interlaced you get a simpler image for modern compression.

Unfortunately the current camera technology isn't quite up to it yet, but time will tell. Also on our side there is no mechanism for connecting a decoder to a display yet and there aren't many true panels capable of that speed (some high frequency displays flash black frames alternately). Also there isn't really a SoC processor capable of that kind of rate but this is just subject to the march of time.

I would like to see GPGPU technology (or check out the work of ZiiLabs) advance to the price/performance ratio where it can be used and perhaps we need to switch to low-cost optical HDMI? Mezzanine compression in connecting devices together has been used in broadcasting to get HD over SD circuits and in theory could be used in the domestic arena.

For the benefit of tghewett:
The BBC has done a number of papers about how small cameras fit into the broadcast chain:
http://www.bbc.co.uk/rd/pubs/whp/whp034-add30.shtml

Regards,

Bob
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Old 11-08-2009, 20:23
elan_vital
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Everything: Agree 100% with your comments. The frequencies were chosen deliberately for no DX contacts. They wanted to call it 'Open Channel' originally! Not at all out of touch with popular opinion!

Bob: Even the BBC have experimented with high-motion 300Hz. No doubt you've seen the BBC White Paper 169. The nearest using multiples of 72 would be 288 Hz of course.

72Hz would settle the age-old question over the 50Hz-60Hz debate for a Common Interchange Format too. And no more 3:2 or 48:50 pull down. But there's no chance of a universal rate is there?

The trouble is that for 50Hz motion, only 1080i25 is available as a BBC programme source. Apart from one exception, 720p cameras are actively discouraged. (BBC_HD_Delivery) However, Interlace is not the best delivery format. In fact it would be possible to transmit 1080P50; in European tests (source missing) it was shown to be more robust than 1080i in a limited bandwidth! (coding gains etc.)

So '540.5 p50' is seen to be technically superior to 720P50!

Worse still, on SD, some programes originate in 25p making the picture subjectively poorer in spacial AND Temporal resolution. The reason is simple. To flog programmes to the 60Hz universe. There is no earthly reason why documentaries and other programmes need be in 25P.
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Old 11-08-2009, 21:44
tghewett
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For the benefit of tghewett:
The BBC has done a number of papers about how small cameras fit into the broadcast chain:
http://www.bbc.co.uk/rd/pubs/whp/whp034-add30.shtml

Regards,

Bob
Bob,

Thanks for the link. The issue is different though - there have been recent posts from BBC people that it is difficult to produce good quality H.264 1080i-coded streams in real time and that to do it at 9mbps is impressive, and to go further would be hard without using batch processing. My point is that these AVCHD camcorders already do it, on batteries, for hours, at lower bit rates yet the same resolution, with impressive if perhaps not directly comparable results.

The papers are to do with using camcorders for generating broadcast material, which is a bit different.
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Old 11-08-2009, 22:44
Bob_Cat
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elan,

As a distinguished gentleman at BBC R&I pointed out: 300Hz could be a universal framerate because it is a multiple of both 50Hz and 60Hz!

1080p50 very nearly became a requirement for reception devices used in the UK recently, but it isn't practical to make products that can support this format at this time. It was a choice between launching an HD service for DTT by 2010 or waiting another couple of years (because you don't want a legacy issue that requires two simulcast HD channels in different formats). While it is almost possible to broadcast 1080p50 the fact is that you can't consider a transmission standard without factoring in the availability of receivers and any legacy issues.

My suggestion to the standards groups has been to plan now for high frame rate TV and implement it in the v.long term. The industry needs to avoid another issue such as with the now infamous "2k/8k" where early products don't support the full spec for DVB-T.
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Old 11-08-2009, 22:47
scoobiesnacks
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This is getting a bit technical for me so I'm getting back to the new encoder..

I've completed a benchmark comparison between the same episode of Wallander from last Sunday (with the new encoders) to the original transmission of December last year. For both transmissions I recorded the original feed on a Vantage HD satelitte recorder which doesn't play around with the picture to "improve it"

Its taken me about an hour to do this so bear with me.

I compared a scene when Wallander discovers a girl who has taken an underdose. Just before he discovers the girl, there is a scene with a lot of detail in it, leaves, weeds, and a small house with detailed brickwork next to a pond. I focused on the definition/clarity of the brick work.

Neither transmission impressed me greatly, but there was a winner, In both transmissions the house and its brickwork looked VERY unreal, PC like quality. I was quite surprised by this digitised effect.

In the scene he walks up to the house and the camera pans in slowly. I focused on how many bricks I could see in certain area around a window. In BOTH transmissions most of the time showed the bricks as a fuzzy moving mess.

As he got closer to the house though the bricks came into clearer definition.

On the December 08 transmission I could see about 90% of the brickwork clearly defined as distinct bricks rather than a fuzzy mess at his closest point to the house

In last Sunday's tranmission I could only see about 70-80% of the brickwork defined.

To come up with this result I compared both transmissions at least five times, replaying the 10 second scene.

My conclusion is:

The new encoder's picture is slightly WORSE than it was before, between 10-20% on scenes that have a medium demand on the encoder.

I wasn't able to find a scene that placed high demand on the encoder in Wallander because I got bored after a while. A lot of the programme is quite slow paced, slow panning camera, closeup face shots. If anyone can remember a really encooder demanding scene from the programme (something like a landscape helicopter shot) then I could take a look.
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Old 12-08-2009, 01:20
nomis89
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Would be interesting to see some numbers (PNSR, SSIM) if anyone knows how to do that.
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Old 12-08-2009, 01:43
gaptag
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The new coders are a great step forward and we are still working on improvements based on the tools we get (not just the blunt instrument of bit rate)

Andy
Andy,

Great to see the new encoders in and the audio issue fixed!

I was suffering with that problem where the audio wasn't being decoded properly in DVBViewer, PS3, etc because the audio stream wasn't encoded according to the broadcasting standards. No more need to run all recordings through a "fixer" before being able to watch them.

Unfortunately, this fix seems to have been accompanied by a number of new problems.

I'm not going to bring up the encoding rate as it's being discussed plenty already, but I have noticed a couple of other things.

Firstly, with the PS3's decoding, I've also been experiencing this "blocking" (random squares that appear over the picture on and off) reported by others (in particular Windows 7 users). It appears occasionally, but only when starting to play a video stream on the PS3. If it appears, just stopping and starting playback at a different point usually clears the problem suggesting that it's incomplete packets of video or something to do with the handling of the particular encoding when a partial packet is experienced that is triggering this. Never had this problem when the old encoder was being used.

Secondly, and something minor thankfully but still annoying, is that video stream playback now isn't being picked up as a 16:9 widescreen picture by the PS3's decoder any more. It was always detected properly with the old encoding, but now necessitates manually changing to "full screen" mode all the time to get it to show in 16:9.

Unfortunately my server running DVBViewer itself is only a "dumb" server that runs the recording service and tuner cards so I'm unable to check how DVBViewer reacts to this now.

Best of luck with the "tweaking" of the encoders!
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Old 12-08-2009, 07:50
Br1an242
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My experiences are very much subjective, but I am not impressed with current BBC HD transmissions - Artifacts are all too common and, I guess, associated with encoders/bitrates. Is this anything to do with the proposal to introduce a Freewiew HD service? And, if it is, how much is it down to the BBC and not Ofcom, where the motto seems to be 'if it ain't broke, break it!'
BBC HD can, in my opinion, surpass anything that is available - including 1080p blu ray. But, if we are heading this way to allow Freeview to 'take the HD crown from Sky' then we need a rethink. The present quality will hand the crown to Sky on a plate. I don't recall ever seeing an artifact on Sky HD.
Brian.
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Old 12-08-2009, 10:50
Everything Goes
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My experiences are very much subjective, but I am not impressed with current BBC HD transmissions - Artifacts are all too common and, I guess, associated with encoders/bitrates. Is this anything to do with the proposal to introduce a Freewiew HD service? And, if it is, how much is it down to the BBC and not Ofcom, where the motto seems to be 'if it ain't broke, break it!'
BBC HD can, in my opinion, surpass anything that is available - including 1080p blu ray. But, if we are heading this way to allow Freeview to 'take the HD crown from Sky' then we need a rethink. The present quality will hand the crown to Sky on a plate. I don't recall ever seeing an artifact on Sky HD.
Brian.
If I recall correctly the BBCs policy is to have the a Platform Neutral stance on Picture Quality. This means that the Picture Quality should look the same on Freeview & DSAT. Freeview has limited bandwidth so the lowest common denominator wins.
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Old 12-08-2009, 11:38
elan_vital
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elan,

1080p50 very nearly became a requirement for reception devices used in the UK recently, but it isn't practical to make products that can support this format at this time. It was a choice between launching an HD service for DTT by 2010 or waiting another couple of years (because you don't want a legacy issue that requires two simulcast HD channels in different formats). While it is almost possible to broadcast 1080p50 the fact is that you can't consider a transmission standard without factoring in the availability of receivers and any legacy issues.

My suggestion to the standards groups has been to plan now for high frame rate TV and implement it in the v.long term. The industry needs to avoid another issue such as with the now infamous "2k/8k" where early products don't support the full spec for DVB-T.
Personally, I think they did the right thing to go for DVB-T2 and leave out 1080P50 for now. We've reached a 'bandwidth' ceiling in terms of coding with the use of turbo codes etc. I think that the 9Mbps bit rate is the most practical figure to aim for, for current picture standards. The theoretical advantage of MPEG4 over 2 was a halving of the bit rate. With DVB-T2 36Mbps capacity one can fit four channels @9Mbps.
I think that it was probably right, technically to set the target rate NOW and work towards improving the quality for the public service next year (and beyond). As Andy Quested has repeatedly said, it's not just about bitrate.

HOWEVER; There is political pressure from OfCom to fit even more channels on a multiplex and that means a bit reduction which will seriously degrade quality. Ofcom has the mentality that 'choice' is more important; more channels=more revenue.

I've not seen any confirmation that the half-Freeview relays will get HD - and OfCom want to sell off spectrum! Well, I'm sure some one will get his knighthood.

I agree with your view on long term planning for the reasons you stated.

I just hope that *other* broadcasters are brave enough to transmit 720P50 programmes.
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Old 12-08-2009, 11:59
Ray Cathode
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I've not seen any confirmation that the half-Freeview relays will get HD - and OfCom want to sell off spectrum! Well, I'm sure some one will get his knighthood.
All 1100 Freeview relays will get an HD mux leaving only 2 muxes for SD!

http://www.ofcom.org.uk/media/news/2008/10/nr_20081017
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Old 12-08-2009, 12:08
elan_vital
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All 1100 Freeview relays will get an HD mux leaving only 2 muxes for SD!

http://www.ofcom.org.uk/media/news/2008/10/nr_20081017
Thanks for the info! That passed me by somehow.

That IS a postcode lottery!
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Old 12-08-2009, 21:25
robbie2
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Hmmm interesting, i can no longer watch BBC HD in DVB Viewer using the Microsoft native decoder in Windows 7.

It was all i needed until now. I will mess about with it tomorrow and see if i can get it working again.

Constant blocking of the picture is all i get now.

I can see me having to dust off the old Cyberlink codec again to maybe get it working again.
Likewise viewing BBC HD using Windows 7 Windows Media Center. Had no previous problems with the picture but it now starts off unwatchable - the blocking clears after a few seconds. As far as I am aware it is not possible to use anything other than the Microsoft native decoder for WMC.
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Old 12-08-2009, 23:07
Andy Quested
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Posted on the BBC Blog from this:

182. At 1:40pm on 11 Aug 2009, Sidisacat wrote:

If anyone at the BBC ever reads this, check out this link to see what you are doing by dropping your bit rate!!! Is this another example of unique funding I wonder...

http://thegreenbutton.com/forums/t/73544.aspx




Dear Sidisacat

For HD broadcasts we currently support the Freesat HD, Sky HD and Virgin V+ platforms and only test for compatibility against those receivers.

Our satellite transmissions are compliant with H264 High Profile, Level 4.0. Not all software decoders are "High Profile" compliant and cannot be guaranteed to continue receiving our services as we continue to upgrade our coders.

We currently recommend viewers use a Freesat HD, Sky HD or Virgin HD receiver for reception of BBC HD broadcasts.

Andy
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Old 12-08-2009, 23:48
White-Knight
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If I recall correctly the BBCs policy is to have the a Platform Neutral stance on Picture Quality. This means that the Picture Quality should look the same on Freeview & DSAT. Freeview has limited bandwidth so the lowest common denominator wins.
That's a stupid policy to adopt. Lets ruin one service to make it match another.

As I've said before, the 2 services aren't the same content wise so why not differentiate them on quality and amount of HD content?

That then gives people a choice - Freeview for those who are quite happy to receive a simple to set up tv service with cheap to purchase boxes and aerials.

Freesat for those who can't get Freeview or who are enthusiasts and want the ultimate in quality and are prepared to invest in more expensive equipment to receive it.

The 2 services aren't the same so why do Freesat / BBC Trust keep pretending they are?

It would be far better to acknowledge their differences and use each one to its own strengths - Freesat to its bandwidth and potential quality / ability to carry large amounts of HD, and Freeview to its cheap and easy availability, than to dumb down the quality of public service broadcasting on one simply so it matches the other.

Posted on the BBC Blog from this:

182. At 1:40pm on 11 Aug 2009, Sidisacat wrote:

If anyone at the BBC ever reads this, check out this link to see what you are doing by dropping your bit rate!!! Is this another example of unique funding I wonder...

http://thegreenbutton.com/forums/t/73544.aspx
Andy, I notice they're all reporting using VERY low end video cards - Nvidia 9400 and ATI 4550:

http://www.tomshardware.com/reviews/...rd,2362-6.html

Both are at the level of an Nvidia 6600GT according to Tom's Hardware Charts.

That's really entry level for HD decoding anyway. I wonder if maybe these cards aren't coping with the increase in decoding requirements (after all a reduction in bit rate = increase in compression = increased in decoding require = increase in graphics power required to do the extra decoding).

It would be interesting to see if someone with a top level gaming card was also experiencing the same problems.
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Old 13-08-2009, 01:33
Scrapanatchi
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Works fine here on Windows 7 Ultimate RTM, using hauppauge hvr-4000, nvidia 6800 ultra with latest drivers. now i just need to get ITV HD working
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Old 13-08-2009, 01:54
Ray Cathode
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The 2 services aren't the same so why do Freesat / BBC Trust keep pretending they are?
Both Freeview and Freesat PSB HD channels (BBC, C4 & ITV) are likely to launch together at an average bit rate of ~11Mbps. Satellite needs more error correction and more robust constellations so Terrestrial would be better quality for the same bit rate.
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Old 14-08-2009, 21:02
scoobiesnacks
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There is a reply to the countless (ok circa 100) complaints in the past week about the picture quality on the BBC blog.

http://www.bbc.co.uk/blogs/bbcintern...y_and_dol.html

210. At 6:22pm on 14 Aug 2009, andyquested wrote:

Dear Scorf2008

Thanks for understanding. I have said in the BBC blog we need to reduce the unsustainable bit rates for HD transmission or it will have no future or will only be available to those willing to pay for and able to get super premium services. We are continuing to work on the setting for the new coders and the pictures are overall better than before.

The Proms last Saturday, Tom Jones and Gardener's World were all stunning. The racking in the football highlighted a mix/fade issue that has always been there but got worse but that is being given the highest priority.

We are also working on noise reduction to help where the original material is noisy - remember I have the advantage of being able to look at the master tapes as well as the transmitted signal so know when it's a coder issue or a noise issue.

I will continue to post and discuss PQ issues with everyone who has a reasonable point of view and understands that the BBC is there for all

Andy
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Old 15-08-2009, 02:45
d'@ve
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Andy, I notice they're all reporting using VERY low end video cards - Nvidia 9400 and ATI 4550:

http://www.tomshardware.com/reviews/...rd,2362-6.html

Both are at the level of an Nvidia 6600GT according to Tom's Hardware Charts.

That's really entry level for HD decoding anyway. I wonder if maybe these cards aren't coping with the increase in decoding requirements (after all a reduction in bit rate = increase in compression = increased in decoding require = increase in graphics power required to do the extra decoding).

It would be interesting to see if someone with a top level gaming card was also experiencing the same problems.
Well I have a Nova HD-S2, Asus EAH 3450 g.card, Athlon x2@2700MHz, all fairly low end-ish these days and the g.card is likely similar to the ones you mentioned.

I've had no problems at all recording or playing back BBC HD in DVB Viewer since the new encoders were introduced.
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Old 16-08-2009, 08:30
Stig
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Well I have a Nova HD-S2, Asus EAH 3450 g.card, Athlon x2@2700MHz, all fairly low end-ish these days and the g.card is likely similar to the ones you mentioned.

I've had no problems at all recording or playing back BBC HD in DVB Viewer since the new encoders were introduced.
I have an ATI HD3470, and I saw the blocking on a recorded BBC HD program for the first time last night. Doing a quick 'skip backwards' cured it though (as recommended somewhere else).

It there somewhere where this problem with HTPCs and BBC HD is already discussed, or should we start a new thread to discuss it specifically?
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Old 18-08-2009, 00:40
White-Knight
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Ok I finally had another look at BBC HD tonight - just gone 7pm - Athletics.

I have to say that whilst still this was the best picture quality wise I've ever seen on BBC HD - stunning!!!!

I couldn't see the artefacts many of you have talked about - question therefore whether its the Humax scaling or LCD tv's having the problems.

I did see one problem though mentioned above, the writing on the advertising hoardings became very blurred and the letter edges seem to "lag" even on quite slow pans. Other than that, everything looked OK to me - no artefacts on the lane lines or other blocking in the crowd as others had mentioned.
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Old 18-08-2009, 00:46
scoobiesnacks
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Ok I finally had another look at BBC HD tonight - just gone 7pm - Athletics.

I have to say that whilst still this was the best picture quality wise I've ever seen on BBC HD - stunning!!!!

I couldn't see the artefacts many of you have talked about - question therefore whether its the Humax scaling or LCD tv's having the problems.
.
Actually BBC HD admitted to these problems tonight but blamed the source material. See their HD blog

286. At 9:41pm on 17 Aug 2009, andyquested wrote:



If you watched various sections of the picture - the grass on the final bend just above the runners heads for example you could see what the codecs were up to. The blue smearing was common to both transmissions as was the highlight smearing on the crowds (when they were in the sun).
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Old 18-08-2009, 09:20
White-Knight
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Thanks Scooby, I'll post my findings over there as well.

Must admit hoardings apart I had no artefacts last night although I did only watch 2 minutes worth so maybe they occurred at a different point in time.
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