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Playing a 1920 videos on a 1280 screen


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#1 noatom   Members   -  Reputation: 785

Posted 28 February 2013 - 02:18 PM

Suppose I have a max res of my screen of 1280 x 720.Will playing a 1920 x 1080 videos look better than playing an 1280x720 videos?

 

I thought that because there are more pixels,the interpolation between them will result a better quality.Is that true?



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#2 Nypyren   Crossbones+   -  Reputation: 4822

Posted 28 February 2013 - 02:35 PM

Sharp, high-constrast, one-pixel-wide lines in the original resolution may look really bad when downsampled, no matter what kind of interpolation is used.

If there aren't a lot of sharp features like that, it'll probably look about the same.

Edited by Nypyren, 28 February 2013 - 02:35 PM.


#3 TheChubu   Crossbones+   -  Reputation: 4787

Posted 28 February 2013 - 02:37 PM

I think that depends on the method of interpolation. Too high rest to low res might add a lot of shimmering, ie, making high frequency details stand out when they shouldn't.


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#4 noatom   Members   -  Reputation: 785

Posted 28 February 2013 - 02:46 PM

well there is another thing,the bitrate. There are 1080p videos that are 12 gb,and i can find the same 1080p video,with a higher bitrate,at 46 gb.



#5 Bacterius   Crossbones+   -  Reputation: 9289

Posted 28 February 2013 - 06:48 PM

In general, you are better off playing it back on a large screen and viewing it from a distance. Your eye does a much better job at downsampling.

 

Of course, that's not practical, and any form of downsampling on a raster medium will usually result in some aliasing, which can often be mitigated by using appropriate convolutions. I like the Lanczos block algorithm, which works fine for most medium-frequency material such as pictures and movies. For diagrams which are usually high-frequency, prefer bicubic, or, if at all possible, render it at the right resolution in the first place (vector graphics are nice for this).

 

well there is another thing,the bitrate. There are 1080p videos that are 12 gb,and i can find the same 1080p video,with a higher bitrate,at 46 gb.

 

The bitrate is, loosely, the amount of information per frame. Higher is better (but bigger). That said, a 46GB video doesn't seem legit - it's likely someone's just upsampled the bitrate without actually adding any new information, and tries to sell it off as a "high quality" video. Kind of like people who upscale 640x480 videos to 1920x1080 and claim they are "HD" on youtube.


Edited by Bacterius, 28 February 2013 - 06:48 PM.

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#6 mdias   Members   -  Reputation: 793

Posted 28 February 2013 - 10:38 PM

That said, a 46GB video doesn't seem legit - it's likely someone's just upsampled the bitrate without actually adding any new information, and tries to sell it off as a "high quality" video. Kind of like people who upscale 640x480 videos to 1920x1080 and claim they are "HD" on youtube.

 

It could also be that the video in question is very long and/or whoever has the source uncompressed video (imagine after post-processing in a PC) wanted to lose as little information as he could, and anything below 50GB is fine to save on a BluRay disc.

 

As for 1080p video looking better downsampled to 720p in realtime; it might*, but if the bitrate is high enough, or the video is uncompressed, it won't.

The 720p video was at somepoint downsampled, and the resampler used could be better than what you're going to need to use in real time.

 

The best thing to do is to convert your videos to the resolution they will be displayed at. Or if you're doing it with the intention to keep it indefinitely, go with the highest reslution+bitrate that makes sense (no upsampling, no unnecessarily high bitrate).

Also keep in mind the CPU/GPU power you will need to decode your videos.

 

* Compressed video is usually composed out of blocks, and if you're downsampling 1080p to 720p those blocks will look smaller on the target area. On the other hand 720p video needs less bitrate to achieve good quality with it's resolution.


Edited by mdias, 28 February 2013 - 10:40 PM.


#7 noatom   Members   -  Reputation: 785

Posted 28 February 2013 - 10:46 PM

the 46gb videos i was talking about are movies on blurays...



#8 HardlineDigital   Members   -  Reputation: 255

Posted 01 March 2013 - 03:43 AM

If the screen resolution is a ratio of 66.6%, 50%, 33.3% then it will look the same. Since 1280 is 66.6% of 1920 it should look the same as a 1280x720 video. Anything else will be actually less quality because the pixels won't line up and you will see some jaggies (aliasing). However, if you are editing video, it is generally always better to use higher resolution content whenever possible.



#9 HardlineDigital   Members   -  Reputation: 255

Posted 01 March 2013 - 03:44 AM

25% is also okay because it is half of half



#10 mdwh   Members   -  Reputation: 901

Posted 01 March 2013 - 08:02 AM

How was the 720p video created? If scaled down, why wouldn't that be done with interpolation too? (Plus potentially more expensive scaling algorithms could be used, as it doesn't have to be done at runtime, though I don't know if that difference exists in practice.)
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