Gentoo Archives: gentoo-user

From: Michael <confabulate@××××××××.com>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] Dolphin and adding a option, if it exists.
Date: Thu, 24 Nov 2022 14:37:50
Message-Id: 10183335.nUPlyArG6x@lenovo.localdomain
In Reply to: Re: [gentoo-user] Dolphin and adding a option, if it exists. by Dale
1 On Wednesday, 23 November 2022 18:17:53 GMT Dale wrote:
2 > Frank Steinmetzger wrote:
3 > > Am Wed, Nov 23, 2022 at 06:16:12AM -0600 schrieb Dale:
4
5 > >> P. S. Now I'm trying to figure out how to change the resolution of all
6 > >> videos in a directory. Usually going from 1080p to 720p. If you have a
7 > >> script for that, awesome.
8 > >
9 > > I use ffmpeg for all my encoding stuff, and have been using wrapper
10 > > scripts
11 > > for years now to make things easier. However, none of them has resized
12 > > yet.
13 > > It’s not difficult to configure, but the wrapper needs much more logic. As
14 > > in: find out the current resolution, see if it is actually larger, then
15 > > calculate the new resolution while keeping the aspect intact and so on.
16 >
17 > I found commands for it but not a way to process lots of videos. Right
18 > now, I use the queue feature of handbrake. I set up a preset to make it
19 > the same each time. I set it to 720p and about 3MB data rate. Should
20 > be OK for my 32" TV.
21
22 It depends how close you sit to the 32" screen. The closer you are the higher
23 the resolution needed to avoid seeing individual pixels. If the size of the
24 file is not important, I'd leave it at 1080p. You never know, you may obtain
25 a bigger TV in the future.
26
27 With ffmpeg you can use its scale filter to retain the same aspect ratio, but
28 reduce the height:
29
30 ffmpeg -i blah-1080.mp4 -vf scale=-1:720 -codec:v libx264 -crf 0 -codec:a aac
31 blah-720.mp4
32
33 NOTES:
34
35 1. Run ffprobe to see what the original video codecs are and use an
36 appropriate video/audio codec to suit your desired output. The video will
37 have to be transcoded to a lower resolution, but the audio can be just copied
38 over.
39
40 2. The -crf controls the quality of the quantizer - default is 23. I've set
41 it at 0 to make it lossless, but this takes longer to process. You could
42 instead use some tuning preset provided in the H.264 encoding guide linked to
43 below:
44
45 https://ffmpeg.org/ffmpeg-filters.html#scale
46
47 https://trac.ffmpeg.org/wiki/Scaling
48
49 http://trac.ffmpeg.org/wiki/Encode/H.264
50
51
52 Once you find your desired stanza to arrive at some optimal size-quality-
53 processing time, you can modify Frank's script to resize and rename your
54 videos.

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