How do I resize an MKV file without re-encoding?

[gabrielpf3]

Just gonna go straight to the point:
I want to resize a 1512x1072 video to 1520x1080 or 1512x1080. I just need the vertical resolution to be 1080 pixels.
Is there any simple way to do that without having to re-encode the whole thing again?
Maybe using MKVToolNix?
Thanks in advance.

[sneaker]

You can use MKVToolNix' Header Editor to change the display resolution but I don't know if that is what you want. Some video formats have cropping information that can be changed but 1072 lines are already mod16 so this is very unlikely to be possible unless the video was coded as e.g. 1088 line HEVC.

[Case]

I just need the vertical resolution to be 1080 pixels.

You may be able to change the display parameters, so that it will be scaled on playback, but if you need the actual pixels to have a certain vertical resolution, for editing or post-processing, then you’ll likely need re-encoding.

[gabrielpf3]

Well... shit. Apparently I'll have to re-encode. If i just put the exact same bitrate of the original video:



On Handbrake or whatever, select 2-Pass Encoding and Very Slow preset, will I lose any of the quality?
Because that's what I really fear.

[sneaker]

Technically yes. If you'll see it is a different question. 6800 kbps is relatively decent so maybe you won't notice.

Is this an attempt to create a file that's compatible with a media player or phone or something and you want to change the resolution because you think that's what's causing the file to be incompatible? Because it's more likely to be the 10 bit depth causing the compatibility problems (but that also needs re-encoding to change).

[gabrielpf3]

No, it's actually because this cropped 1072p resolution makes the subtitles included in the file scale badly.

Just look at these screenshots. In this first one, I downloaded episode 1 from another batch that had an uncropped 1520x1080 resolution just to see if it was a problem with the subtitles or the video, and the subtitles scaled perfectly. The reason I don't just keep this new one I downloaded is because it has a noticeably lower bitrate, not to mention not being able to finish the download because it barely has any seeders.


And this second one is from the 1512x1072 file, which looks much better, but has some kind of aliasing on the subtitles because of the odd resolution.


It may not seem like much, but it's incredibly noticeable and annoying when trying to watch.

[sneaker]

What are you using to render the subtitles? With e.g. MPC-HC's internal renderer or XySubFilter you can render at display resolution and without chroma subsampling. There are also options to assume different resolutions (like aforementioned option to change the mkv dar).

[sneaker]

Hmm.. Looking at the screenshots: is the resolution (1520x1072 vs 1520x1080) really the only difference? Same player, subtitle renderer etc.? They really look a lot different. Second also has some white parts at the outer edges. I think they were not rendered using the same chain.

[gabrielpf3]

Yes, they are the exact same subtitles from the exact same .ass file, playing on VLC. The only difference is the video resolution. Those "white parts at the outer edges" are annoying me beyond belief, I really don't think I'll be able to watch it like this.

[jagabo]

Turn down any sharpening filters, including upscalers that sharpen (Bicubic, Lanczos, etc.).

[gabrielpf3]

Alright, playing the file with MPC fixed te problem. A shame, really, because I prefer VLC. Thanks guys.