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Video Aliasing

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#1 hp6L


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Posted 16 May 2010 - 09:06 PM

I first noticed this problem back in November on most channels.
I see shimmering in image areas that contain vertical or diagonal stripes or polker dot patterns.
occasionally I also see sudden resolution shifts back and forth between soft and sharp of the whole image with small camera movements.
Do others notice this?

Edited by hp6L, 16 May 2010 - 11:37 PM.

#2 CloudyClouds


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Posted 17 May 2010 - 06:51 AM

Yes. Its all part of Foxtel's bitrate management. A completely static picture appears to have a higher cut off applied than a picture with any sort of motion (including changes in brightness). High frequency detail such as thin vertical lines is the most obviously affected part of the picture with the detail rapidly blurring and unblurring. I find it very distracting and would prefer that if the filtering must remain it be applied all the time for picture consitency.

The exact behaviour depends on the channel being watched. I have seen instances of Fox Classics where the scene changed to a mostly dark picture, but with movement, and the entire picture blurred considerably, including the FOX Classics watermark.

#3 hp6L


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Posted 10 December 2011 - 01:24 PM

Its odd that no others seem to notice this problem.

#4 vallatv


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Posted 13 December 2011 - 02:47 PM

Yeah i have noticed it for a while now, most notiable as you said in vertical strips like in a persons shirt with stripes, also in cartoons like the simpsons.
Thought it was my TV but then plugged it into another TV and it was still there.

#5 wineoooo


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Posted 18 February 2012 - 01:00 PM

Is the box on 1080i setting ? Have u played with the refresh rate on the tv? That fixed mine

Edited by wineoooo, 18 February 2012 - 01:01 PM.



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Posted 18 February 2012 - 01:36 PM

I don't subscribe to Austar. However I have noticed that free to air standard definiton digital broadcasts these days often have visible aliasing. I assume there has been insufficient filtering when resampling from a higher pixel density source. Although the aliasing is annoying, the picture tends to look sharper.

#7 hidefdave


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Posted 19 February 2012 - 08:58 PM

General lack of bitrate by the looks of things...both on pay and FTA!


#8 DrP


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Posted 20 February 2012 - 06:31 AM

FTA could transmit SD at 15Mbit/sec and the aliasing* from HD > SD conversion with inappropriate filtering would still be present. The Austar/Foxtel problem is very much limited bit rates, but not a symptom of. Its a deliberate measure to allow lower bit rates without the picture turning into a blocky mess.

* I don't watch FTA so I haven't actually seen the issue that MLXXX is referring to

Edited by DrP, 20 February 2012 - 06:34 AM.