Video editing¶

DaVinci¶

sudo apt install pulseaudio pulseaudio-utils pulseaudio-module-x11 libasound2-plugins
LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0 /opt/resolve/bin/resolve
Tutorial / Intro.
Changing speed.

Below are stages of workflow in Davinci.

Re-encode

See intermediate codecs below.

New Project

Create new project.
Choose resolution (UHD) & fps (60fps) of timeline (this is the most important part)
Choose same or lower resolution in Video Monitoring.

Import media, organise, mark

On the “Media tab” import media.
Merge multiple physical videos into a single logical one: put them on timeline (in the Edit tab) -> select -> right click -> New Compound Clip
Organise & Cut
- Use bins, for example
  - a bin for clips on timeline vs not-yet-on-timelne
  - bin with timelapses
  - etc..
- Use markers: select clip and press M. Press it a second time to adjust colour/text.
- Use the blade tool
Use multiple timelines: At the upper-left corner of timeline, click “Timeline view options” button, press “Stacked timelines”, at the upper-right corner, a new button with plus sign appears, press it.

Cutting

Temporarily speed up video: j (speeds up backward), k, l (speeds up forward).
Move cursor to the edges of clips and adjust their length/start/end. You can always expand later (nothing is removed).
Use both viewports to adjust start/end with high precision.
Use Blade tool: B. Note, blade tool does not remove anything, you can you expand again the clip later.
Cut from curr pos to the right: Ctrl+Shift+]
Cut from curr pos to the left: Ctrl+Shift+[

Other Tools¶

ffmpeg¶

List available encoders: ffmpeg -encoders

Mencoder¶

Reduce resolution of video:

mencoder -aid 1 -slang eng  -ovc lavc -vf scale -zoom -xy 640 -oac mp3lame -lameopts cbr:br=160 Click.2006.720p.BluRay.ac3.x264-HqF.mkv -o click.avi

Recording¶

OBS Studio
SimpleScreenRecorder: a very user-friendly software which has a wizard-like setup process.
Kazam
VokoScreen
Peek

~~recordmydesktop~~

Record video from desktop:

recordmydesktop --no-sound --v_bitrate=2000000 --width=1500 --height=1380 --fps 29 \
                --full-shots --no-wm-check --workdir /mnt/freedata/home/Void -o myfile

Codecs¶

Main doc. Comparison table.

There are several groups of codecs for different purposes:

Capture codecs¶

Codecs that are used by device that records a video:

Most consumer-grade devices use H.264 codec because it is highly compressed. But it is not the best codec for editing because it is very computation-heavy.

Edit codecs¶

Codecs that used for editing, intermediate codecs: DNxHD, DNxHR, ProRes and Cineform. If your camera is not using them directly, you will need to convert source video to one of them.

More info:

This means that they’re designed to be used to trans-code footage from other sources into a form that’s easy for video editing programs to work with while maintaining quality. So, unlike most h.264 implementations, they focus on low CPU usage, retaining as much detail as possible, and an ability to be re-compressed several times without significant loss in quality. They have larger bitrates than consumer video codecs, but they still represent a significant space savings over fully uncompressed video.

Export codec¶

A highly compressed codec, such as H.264, should be fine.

Intermediate codecs¶

DNxHR¶

DNxHR is for resolutions bigger than 1080p (2K, 4K, and 8K) (as opposed to DNxHD).

ffmpeg -ss 00:04:00 -i out.mp4 -c:v dnxhd -profile:v dnxhr_hq  -pix_fmt yuv422p     out_dnxhd_dnxhr.mov
ffmpeg -ss 00:04:00 -i out.mp4 -c:v dnxhd -profile:v dnxhr_hqx -pix_fmt yuv422p10le out_dnxhd_dnxhr_444.mov
ffmpeg -ss 00:04:00 -i out.mp4 -c:v dnxhd -profile:v dnxhr_444 -pix_fmt yuv444p10le out_dnxhr_444.mov

Instead of _hq in the name of profile, you can specify:

LB — Low Bandwidth. 8-bit 4:2:2 (yuv422p).
SQ — Standard Quality. 8-bit 4:2:2 (yuv422p). Suitable for delivery format.
HQ — High Quality. 8-bit 4:2:2 (yuv422p).
HQX — High Quality. 10-bit 4:2:2 (yuv422p10le). UHD/4K Broadcast-quality delivery.
444 — Finishing Quality. 10-bit 4:4:4 (yuv444p10le). Cinema-quality delivery.

Output format container for DNxHD is typically MXF or MOV.

Script:

# cd to a dir, where you have ./source dir and ./intermediate dir
for s in (ls -1 ./source)
  set s ./source/$s
  set d ./intermediate/(basename $s).mov
  echo "$s => $d"
  ffmpeg -i $s -c:v dnxhd -profile:v dnxhr_hqx -pix_fmt yuv422p10le $d;
end

libxvid¶

ffmpeg -ss 00:04:00 -i out.mp4 -c:v libxvid -q:v 2 out_libxvid.mov

ProRes¶

PROXY (bad): -c:v prores_ks -profile:v 0 -qscale:v 5 -vendor ap10 -pix_fmt yuv422p10le -acodec pcm_s16le
LT: -c:v prores_ks -profile:v 1 -qscale:v 5 -vendor ap10 -pix_fmt yuv422p10le -acodec pcm_s16le
SQ: -c:v prores_ks -profile:v 2 -qscale:v 5 -vendor ap10 -pix_fmt yuv422p10le -acodec pcm_s16le
422 HQ: -c:v prores_ks -profile:v 3 -qscale:v 5 -vendor ap10 -pix_fmt yuv422p10le -acodec pcm_s16le

Output / export codecs¶

h.265 (new/better codec).¶

See the guide.

You can see available options with: ffmpeg -h encoder=libx265

    Supported pixel formats: yuv420p yuvj420p yuv422p yuvj422p yuv444p yuvj444p gbrp yuv420p10le yuv422p10le yuv444p10le gbrp10le yuv420p12le yuv422p12le yuv444p12le gbrp12le gray gray10le gray12le
libx265 AVOptions:
  -crf               <float>      E..V...... set the x265 crf (from -1 to FLT_MAX) (default -1)
  -qp                <int>        E..V...... set the x265 qp (from -1 to INT_MAX) (default -1)
  -forced-idr        <boolean>    E..V...... if forcing keyframes, force them as IDR frames (default false)
  -preset            <string>     E..V...... set the x265 preset
  -tune              <string>     E..V...... set the x265 tune parameter
  -profile           <string>     E..V...... set the x265 profile
  -x265-params       <dictionary> E..V...... set the x265 configuration using a :-separated list of key=value parameters

Use -ss 00:00:20 -t 00:40:00 before -i to specify start & duration of the clip to encode (for faster tests)
Add -loglevel debug for more info.
Choose crf:
- No difference in high-contrast areas between -crf 10, 14 18, 19, 20 (21 & 22 barely differs, but you cannot tell which one is worse).
  - 24 is still perfectly fine, but you can tell the difference.
  - 25 — this is where compression starts to get noticeable.
  - In other words, 24 +-1 is good for distribution.
- As for clouds (low-contrast) regions:
  - crf 16 is worse than the original.
  - crf 12 same as the original.
  - In other words, 12-14 is good for personal use.

Example of command:

do not forget to remove -ss and -t

cd ~/Videos/export/
set basename "Swiss-Part-1.2";
set codec libx265;
set crf 24;          # Lower is better quality, 12 for internal use, 24 for sharing
set preset veryslow; # medium, slow, veryslow
set pix_fmt yuv420p;
ffmpeg -ss 00:00:40 -t 00:00:10 -i $basename.mov -c:v $codec -crf $crf -preset $preset -pix_fmt $pix_fmt -c:a aac -b:a 192k \
$basename-$codec-crf=$crf-preset=$preset-pix_fmt=$pix_fmt.mkv

Reduce priority: sudo renice 19 -p (pgrep -x ffmpeg).

VP9 (produces much larger output)¶

Single-pass:

set basename "Swiss-Part-3.2";
set codec libvpx-vp9;
set crf 38;         # Lower is better quality. 0–63
set deadline best;  # realtime, good, best
set passes single
set pix_fmt yuv420p;
ffmpeg -ss 00:00:20 -t 00:00:40 -i $basename.mov -c:v $codec -crf $crf  -b:v 0 -deadline $deadline -cpu-used 0 -pix_fmt $pix_fmt -c:a libopus -b:a 192k -row-mt 1 $basename-$codec-crf=$crf-$passes-pass-deadline=$deadline-pix_fmt=$pix_fmt.webm

Comparison of qualities’ parameters of vp9 and h.265:

crf=30 of vp9 (visual quality is better)
crf=24 of h.265 is ~same as crf=38 of vp9
crf=40 of vp9 (visual quality is worse)

Two-pass:

set basename "Swiss-Part-3.2";
set codec libvpx-vp9;
set crf 20;         # Lower is better quality. 0–63
set deadline best;  # realtime, good, best
set passes 2
# set pix_fmt yuv420p;
ffmpeg -ss 00:00:20 -t 00:00:40 -i $basename.mov -c:v $codec -b:v 0 -crf $crf -pass 1 -deadline $deadline -cpu-used 0 -an -f null /dev/null
ffmpeg -ss 00:00:20 -t 00:00:40 -i $basename.mov -c:v $codec -b:v 0 -crf $crf -pass 2 -deadline $deadline -cpu-used 0 -c:a libopus -b:a 192k -row-mt 1 $basename-$codec-crf=$crf-$passes-pass-deadline=$deadline-pix_fmt=$pix_fmt.webm

Note: two-pass quality is substatially worse than 1 pass quality, so you need to take this into account by lowering the crf value.

h.264 (old codec).¶

See the guide.

ffmpeg -i LakeDistrict2.mov -c:v libx264 -crf 16 -preset veryslow -c:a copy LakeDistrict2_crf_16_veryslow.mkv

Pixel format is not supported on phones and mplayer (-pix_fmt yuv420p is needed?)
You might want to to consider adding -x264-params opencl=true, but see below
- But you you probably do NOT want to add -hwaccel auto. Hardware encoders typically generate output of significantly lower quality than good software encoders like x264, but are generally faster and do not use much CPU resource. (That is, they require a higher bitrate to make output with the same perceptual quality, or they make output with a lower perceptual quality at the same bitrate.)