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Old 07-21-2020, 12:46 PM
 
422 posts, read 123,200 times
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I want someone to please explain to me why all tablet brands will display pixelation especially on walls if it's a dark scene. This is for all HD videos downloaded directly to internal tablet space. Sometimes it looks like blobs of pixelation or just pixelation. On walls in dark scenes you can actually see the transition of different shades- the actual seperation of these different light to dark shades. I don't ever remember seeing this on TV back in the 90s. I don't have a TV so I can't compare. I haven't watched TV since early 2000s. Is it just tablets or also TV with this problem?
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Old 07-21-2020, 01:00 PM
 
Location: San Antonio/Houston/Tricity
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Low quality tablets? Slow Internet connection?
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Old 07-21-2020, 01:46 PM
 
422 posts, read 123,200 times
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Quote:
Originally Posted by elnina View Post
Low quality tablets? Slow Internet connection?
High resolution. Kindle 10 HD. Samsung Galaxy Tablet S6 which has even higher resolution. Very high speed internet. This is why I even mentioned videos directly downloaded to tablet internal space.
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Old 07-22-2020, 05:14 AM
 
Location: Metro Washington DC
14,061 posts, read 21,713,883 times
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Quote:
Originally Posted by Ritzui View Post
I want someone to please explain to me why all tablet brands will display pixelation especially on walls if it's a dark scene. This is for all HD videos downloaded directly to internal tablet space. Sometimes it looks like blobs of pixelation or just pixelation. On walls in dark scenes you can actually see the transition of different shades- the actual seperation of these different light to dark shades. I don't ever remember seeing this on TV back in the 90s. I don't have a TV so I can't compare. I haven't watched TV since early 2000s. Is it just tablets or also TV with this problem?
I haven’t seen this on my iPad Pro. I’m not saying you’re wrong though. I’m just saying that I have not seen that happen. If it did, i didn’t notice it.
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Old 07-22-2020, 05:23 AM
 
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This is due to digital compression of the source material. In the 90’s and before TV and movies were analog so you didn’t have this problem.
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Old 07-22-2020, 08:16 PM
 
19,697 posts, read 59,585,832 times
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The below is a summary, strictly in layman terms and not intended to be picked apart by engineers who understand the full complexity of the issue.

RGB colorspace.

Loosely, the analog signal for the NSTC-M standard has to be translated into digital. That digital colorspace has luminance levels from 12 to 255, only allowing 243 steps. (In reality, there are more, but that is the general effect.) When there is texture and movement in a scene, everything is hunky-dory and you don't see the blocking. When the general luminance of the recording and the device are set well, the extremes don't show the blocking to the viewer. If, however, the brightness is turned up, the few blacks become grey and the differences are more apparent. Or, in scenes that were originally dark, the information hidden in what used to be the "roll-off" gets boosted, and blotches show up.

There are various ways that program material gets copied, and the end result varies. Major TV productions were often shot on 35MM film. Where that exists, a direct to digital transfer gives fantastic results. If Joe Blow has made a copy of the signal from a VHS tape, good luck. There are all sorts of variations in-between. With image data, the poorest link in the system is the limiting factor on the output.

Hearkening back to the old days, the video cameras and film chains looked for the brightest spot in an image and defaulted that to white. The darkest spot was more problematic, and a black level was set, with the signal level of all the greys in-between derived from those. A scene with a candle in a dark room could be problematic, with much of the image down in the mud. Transfer that to digital and the information in the mud got lost.

There are errors in the above explanation, but it is the easiest way to describe the general issues without getting into eyes-glazing-over territory.
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Old 07-25-2020, 07:04 AM
 
Location: (six-cent-dix-sept)
6,020 posts, read 3,120,007 times
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contrast ratio ?
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