What is Interpolation to 1080p?

[kool123]

I was browsing through this guide, http://www.thehaloforum.com/videos/303811-fragtalitys-hd-quality-tutorial-2-0-x264-encoding-1080p-interpolation.html
and it says to interpolate 1280x720 footage to 1080p.
Whats the point? So you can get 1080 option on Youtube? I dont understand. :s Why not just render at 1280x720? What happens if you interpolate 1920x1080 footage? Sorry for so many questions. :o

[LoRd_MuldeR]

If you upscale 720p (1280x720) footage to 1080p (1920x1080), then your input obviously has fewer discrete pixels than the output. As data for the "missing" pixels simply isn't available, it can only be interpolated (http://en.wikipedia.org/wiki/Interpolation) ;)

Of course upscaling (interpolating) your footage to a higher resolution will not "magically" add more detail. The best you can do is pick an interpolation method (http://svn.int64.org/viewvc/int64/resamplehq/doc/kernels.html) that provides the best trade-off between the different interpolation artifacts.

In general, it is pointless to upscale your video. That's because, as said before, there won't be more detail. But there will be more pixel data, which means that you will need a higher bitrate to store the upscaled video.

Anyway, there may be specific cases where it still might make sense to upscale your video. For example, if you know you are going to watch your 720p video on a 1080p screen, then it will unavoidably be upscaled to 1080p at some point.

So if you know that your screen or video-renderer uses a lower-quality upsclaing (interpolation) filter than your favorite software interpolation filter (e.g. something like NNEDI3), it might make sense to upscale your video beforehand...

(I can only speculate that the idea behind upscaling 720p content to 1080p before uploading to Youtube is that Youtube will then encode it as 1080p and thus use a higher bitrate. But will this actually give better quality ???)

[Bloax]

LoRd_MuldeR: I can definitely tell you that upscaling 480p to 720p is going to skyrocket the quality, because the encoding used for 480p is absolutely terrible.

720p->1080p is a good question however.

[Chetwood]

That's ridiculous, if the encoding is terrible the interpolation will be as well. The information simply isn't there so an interpolation cannot "skyrocket the quality".

[Bloax]

You seem to have missed my point there:
The encoding used for 480p is absolutely terrible.
Upscaling 480p to 720p is going to skyrocket the quality.
This is me indirectly suggesting that the encoding for 720p is much better, and it is - which is why the quality skyrockets if you do so.
If it was just as terrible for 720p as for 480p I really wouldn't say such silly things.

[the_weirdo]

That's ridiculous, if the encoding is terrible the interpolation will be as well. The information simply isn't there so an interpolation cannot "skyrocket the quality".

I think he meant "the encoding of YouTube used for 480p is absolutely terrible" thus "upscaling 480p to 720p is going to skyrocket the quality". Normally, I would disagree that upscaling is going to improve the quality, but in case of YouTube, I may agree with him.

[Bloax]

Well go ahead (http://www.youtube.com/watch?v=XUf5mPmqkLQ) and take a look (http://www.youtube.com/watch?v=ub5xUeWMu8M). :p

[LoRd_MuldeR]

I think we all agree that an "upscaled" version of the video will have a higher bitrate requirement, while not containing more "detail".

However in case of Youtube we are not in control of the encoder settings.

Thus, if Youtube gives a relatively low bitrate to the "original" resolution clip but a more adequate bitrate to the "upscaled" version, it might make sense to upload the "upscaled" version.

Whether that is the case or not might depend on what resolutions you are comparing exactly. Also Youtube's behavior might change over time...

[kool123]

Ahh, thanks for the explanations. I get it now. Interesting, never knew upscaling from 480p to 720p would make such a difference.

480p
http://gyazo.com/093911eadd365b3853298ecb44d8cfca.png
720p
http://gyazo.com/f1e84038aa5926f10b7cb99a0cf65e10.png?1365438422

Going to test the quality difference from Interpolation to 1080p and normal 720p footage. (1280x1024 cropped to 1280x720)

[macaraig115]

Ahh, thanks for the explanations. I get it now. Interesting, never knew upscaling from 480p to 720p would make such a difference.

480p
http://gyazo.com/093911eadd365b3853298ecb44d8cfca.png
720p
http://gyazo.com/f1e84038aa5926f10b7cb99a0cf65e10.png?1365438422

Going to test the quality difference from Interpolation to 1080p and normal 720p footage. (1280x1024 cropped to 1280x720)

I hope you can post photos of your experiment with 1080 and 720 videos. I am interested to see how much would be the difference.

[x265]

Do all media players interpolate pixels when we view in fullscreen?

[kypec]

Do all media players interpolate pixels when we view in fullscreen?
When the fullscreen resolution in pixels is not equal to that of source media file then obviously somewhere before the rendering on the screen must be interpolation performed.:p

[loriryan]

honestly… I'm lost in the discussion. O_0

[LoRd_MuldeR]

honestly… I'm lost in the discussion. O_0

Please respect the forum rules, especially #11:
http://forum.doom9.org/forum-rules.htm

Don't post just to increase your number of posts. If you have nothing to say on a certain matter then don't post.

If you have a question related directly to the discussion, feel free to ask. But tell us what exactly you don't understand, so people might be able to actually give a helpful answer ;)