Opus is superior for low (orange) narrowband 8kHz, (yellow) wideband 16kHz, (green) super-wideband 24kHz and fullband 48kHz for ultra low bitrate and latency which is important for real-time communication. Zoom, Discord, Playstation Network, Jitsi, WhatsApp all use Opus for their voice communication.

To reduce the file size of a video while retaining video resolution and quality. This is all I do with videomass (free GPL Windows, Linux or Mac) which is just a frontend GUI for ffmpeg which is also free.

1) Click Presets Manager then drag video into queue

2) choose the following preset (need to set up initially)

-c:v hevc -crf 28 -c:a libopus -b:a 16k -vf scale="-2:720"

3) remove -vf scale="-2:720" if you don't wanna upscale nor downscale this video to 720p

4) click Convert

5) click OK

containers there is mp4 and mkv. Telegram likes mp4 to be able to stream for iphones, etc.

Audio codecs aac (most common) and opus which I use since it's superior at lower bitrates.

-crf 28 I use for most video clips and use -crf 31 for VHS quality stuff. If you're doing a Hollywood movie use -crf 23 (lower is higher quality). Also you wouldn't re-encode audio so just -c:a copy instead of -c:a libopus and don't specify a bitrate -b:a 16k

ffmpeg 5.x no longer requires -strict -2 for opus with mp4

Videomass here are the presets I use. You can download here https://t.iss.one/geektips/331 it's just a text file All Opus, Subs, x265.prst and choose Import preset.
Obviously you must change the path in a few of them. Or you can copy and paste them in from this post.
https://t.iss.one/geektips/311

Easily remove line breaks in LibreOffice which can occur if you copy text from a PDF.

1) Shows line breaks

2) pressing Ctrl-Shift-L to activate the macro to remove line breaks

3) shows line breaks removed and the text flows to the end of the page

How to setup the macro in LibreOffice
https://t.iss.one/geektips/270

How to make an opus chaptered audiobook (quick overview)

Downloaded an m4a (m4b) audiobook 1.2GB but it didn't have chapters so had to download 8.6GB video text audiobook that had chapters and extracted the zip file. Could try to automatically to detect chapters based on silence and manually rename but decided against it.

Rename files in your filemanager then load in MusicBrainz Picard set Title (chapter name) metadata to be the same as the filenames by Ctrl-Shift-T

For those on Mac use MP3Tag which can
Rename files from tags Rename files based on the tag information and import tags from filenames.

Drag files into freac and set to Encode to a single file and Opus encoder to 16kbps.

Add a cover if there isn't one already there in the metadata. Also set Artist to the Author and Album to the Title of audiobook. Press Encode. Notice on telegram it shows Kevin B. MacDonald instead of Kevin MacDonald. You can use tageditor to fix that if you wish.

Telegram uses MiB (Mebibyte rather than Megabyte) which is International System of Units (SI)
100 MB = 95MiB (~5% less)
1GB = .93 GiB

Linux Mint terminal
ls -lh shows 182M which is 182MiB
ls -l --si shows 192M which is 192MB

Those on Linux Mint (or other distros it's on flathub) Warpinator has an iOS (requires iOS 13+) in beta app. Must start up warpinator first and then open app.

Beta Link for Warpinator iOS app
https://testflight.apple.com/join/7ndmZa31

LibreOffice Writer remove all Number References from a wiki article. [1][2][10][15], etc.
Search and Replace All (check regular expressions)
\[[\d]+\]

\[ and \] escape the [ ] characters
[\d] digits and + unlimited amount of digits

Remove all hyperlinks in document
Ctrl-A, right click and Remove Hyperlink

All Opus, Subs, x265.prst

8 Freac presets I use for video and audio encoding. Updated with audio filter Dynamic Audio Normalization / collection of mp3s prepare for opus chaptered audiobooks for getting correct chapter times.

Took me a couple of days to figure this one out but freac signal processing channel converter (mono) and Sample Rate Converter 48000 still resulted in incorrect chapter times on opus audiobooks. Videomass filter worked.

m4bs don't have this problem. Just usually a collection of mp3s since they all can contain various sample rates.

To see what the 8 freac presets are check here https://t.iss.one/geektips/311

I wasted over 30 hours on this but freac for whatever reason the Sample Rate Converter (48000) doesn't fix the opus chapter times nor it's channel converter to mono. It's gotta be a bug with it's signal processing. Videomass (frontend GUI for ffmpeg) does work. Now I can start producing some nice opus chaptered audiobooks from massive collections with confidence.

Converting mp3s to opus and errors messages such as

[mp3 @ 0x55fb83eaa680] Estimating duration from bitrate, this may be inaccurate
[mp3float @ 0x55fb83ef22c0] Header missing
Error while decoding stream #0:0: Invalid data found when processing input

are generally ok but other ones with bad header, etc. it's best to just delete and not use those damaged / corrupted mp3s. Otherwise your opus chaptered audiobook will not have correct chapter times.

videomass (ffmpeg) showing the audio filter dynaudnorm (Dyamic Audio Normalization). It doesn't just increase or decrease volume uniformly but rather does so in chunks so you get the result of the bottom graph.

Real World Results (Example)

Finally, the following waveform view illustrates how the volume of a "real world" audio recording has been harmonized by the Dynamic Audio Normalizer. The upper graph shows the unprocessed original recording while the lower graph shows the output as created by the Dynamic Audio Normalizer. As can be seen, the significant volume variation between the "loud" and the "quiet" parts that existed in the original recording has been rectified – to a great extent – while the dynamics within each section of the input have been retained. Also, there is absolutely no clipping or distortion in the "loud" sections.

Got tired of converting webp images to jpg for processing in Fotoxx before I could make a montage. This Firefox extension Save webP as PNG or JPEG saves me the hassle.

I've been using LibreWolf (privacy focused Firefox without telemetry {E.T. phone home spyware}) for about a month now. Since most users I doubt set up all the options in Firefox to disable E.T. phone home stuff it's a quick way to how it all setup and even comes with uBlock Origin pre-installed.

These are the extensions I use now for LibreWolf. For Qwant I don't use the official one as it's annoying just an unofficial one.

On VLC iOS don’t forget these playback gestures for audiobooks.

This error can be corrected with MKVToolnix
Error while decoding stream #0:0: Invalid data found when processing input
Audio packet of size 24 (starting with 00000000...) is invalid, writing it anyway

This error is fatal and the mp3 should be deleted

mp3float @ 0x5639205e7a40] invalid new backstep -1
[mp3float @ 0x5639205e7a40] big_values too big
[mp3float @ 0x5639205e7a40] Error while decoding MPEG audio frame.
Error while decoding stream #0:0: Invalid data found when processing input

Some errors with some mp3s so multiplexing them to mka with MKVToolnix solved the problem. ffmpeg -c:a copy and output to mka didn't. To batch multiplex mp3s all at once in MKVToolnix when dragging them into the app choose

Create new multiplex settings for each file

this will create a tab for each mp3
Click Multiplex then Action for all tabs then Start multiplexing
When done you can Multiplex then Action for all tabs then Close

Installed calibre which I haven't used for a couple of years now. https://calibre-ebook.com/download_linux
Tried using pandoc and it worked but couldn't get text to justify and it hyphenated which I despise.

These are the options I use to convert an epub to PDF

ebook-convert input.epub output.pdf --base-font-size=7 --change-justification=justify --embed-font-family=freesans