Categoria: multimedia

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MIDI keyboard and Linux

To get your MIDI keyboard working in Linux, you should do something like the following steps:

1) install Rosegarden, which automatically install jack and the related software in particular Qjackqtl (jack GUI). Maybe you could install directly Qjackqtl…

2) add your user to the audio group

sudo usermod -a -G audio <your_user_name>

3) install Qsynth,
4) do the following terminal command

sudo apt update; sudo apt full-upgrade -y; sudo apt install -y pipewire-audio-client-libraries libspa-0.2-bluetooth libspa-0.2-jack wireplumber pipewire-media-session-; sudo cp /usr/share/doc/pipewire/examples/alsa.conf.d/99-pipewire-default.conf /etc/alsa/conf.d/; sudo cp /usr/share/doc/pipewire/examples/ld.so.conf.d/pipewire-jack-*.conf /etc/ld.so.conf.d/; sudo ldconfig; sudo apt remove -y pulseaudio-module-bluetooth; systemctl --user --now enable wireplumber.service

Musescore and a MIDI keyboard

To get Musescore able to record from a MIDI keyboard I had to use the 4 release, so far with an appimage from their website.

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edit video metadata

To edit video metadata without re-encoding a video, you can:

  • if the video is an mp4 use VLC (tools/media info), with many options (besides title and date, you can set genre, artist, album, comment and so on).
  • if the video is an mkv use MkvToolNix Header editor (only for title and date)

Unfortunalely, MkvToolNix is not able to change other than title and date.

But a workaround can be

  1. convert a video from mkv to mp4 (copying audio and video: very fast)
  2. edit the new mp4 metadata file with vlc
  3. re-convert (if you want) the mp4 file to a mkv file (copying audio and video), keeping your added metadata.

I found that a good tool to make the conversion (from e to mkv, editing the preset and selecting copy audio and copy video, in audio and video tabs) can be MistiQ Video Converter.

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how to merge video files

Two ways:

1) via terminal

you can use this code 

mkvmerge -o outfile.mkv infile_01.mp4 \+ infile_02.mp4 \+ infile_03.mp4

2) graphically

by using f.e. Avidemux:

  • open the first video file
  • go to the end of that file
  • append the second, and go to the end
  • then append all other possible video files
  • if you plan to merge several video (such as several films), you can queue instead of save (immediately) the files
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VLC and chapters

VLC is a good player, but it can happen that if you create only one mkv chapter, it doesn’t recognize it (unlike other player such as, in Linux, SMPlayer).

To fix this you have to add at least two chapters,

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normalize audio volume

In Linux you can

1) change physically the volume, recodifying the files

such as

  • with ffmpeg-normalize, a tool for automatic changes
  • or with ffmpeg, for manual changes (i.g. ffmpeg -i input.mp3 -filter:a "loudnorm" -q:a 2 output.mp3 for a change with a re-encodig of high quality, or ffmpeg -i input.mp3 -filter:a "loudnorm" -b:a 192k output.mp3 to a bitrate of 192, and so on)

2) modifying only the way your file is read (by the audioplayers)

  • with normalize-audio, which don’t encode the files, but change only the volume metatag.
  • or with mp3gain  (mp3gain -r *.mp3, or mp3gain -r -k *.mp3, to avoid clipping problem)

This second way on the one hand is less invasive (and less destructive), but on the other hand the changes could be not correctly read by the audio player you use.

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embed a playlist in a web page

After many attempts I finally figured taht it’s impossible embed an audio playlist (such as m3u) to a webpage: you can add only multiple (audio) files, but not a playlist.

I tried with the <audio> tag: nothing to to, even with jquery or javascript. Neither with <embed> or <object> html tags: html developers allow only a single audio playing, not a playlist.

The mimetype “audio/x-mpegurl” doesn’t work.

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syncing subtitles troubles

framerate

Correcting subtitles framerate may be very important to sync it with audio/video. You can select all subtitles with an editor, and change framerate (for example to 25 from 23.976).

Thereby you should see the video correctly (with VLC or others).

the ultimate solution

If adjusting framerate didn’t fix your problem, you can try an excellent tool (for Linux, Windows and Mac as well): SubSync, whicth works syncing audio with subtitles, and was able so far to solve all my sincing subtitles problems.

You could have a permissions problem working the first time with SubSync, but you will find easily on the web.

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how split a mkv with subtitles

You can use mkvtoolnix, then go to -> output, and -> splitting -> by parts based on timestamps -> and there you can write the beginning and the end of the part you want extract (without spaces: like 1:02:07-1:04:40, for example).