added test file

2024-05-06 18:37:06 +02:00 · 2024-05-06 18:37:06 +02:00 · e9abea6b73
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+## alsa
+
+ALSA is part of the kernel.
+
+What is PCM or a PCM device?\
+https://en.wikipedia.org/wiki/Pulse-code_modulation
+
+#### aplay
+
+`aplay` is part of the package `alsa-utils` on Fedora.
+```
+aplay -l
+```
+List all soundcards and digital audio devices.
+
+```
+aplay -L
+```
+-L, --list-pcms\
+List all PCMs defined\
+(there is also `default`)
+
+You can use `aplay` to play audio files.\
+Without argument it works on wav/raw files:
+```
+aplay example.wav
+```
+With `-f` there are different formats available, but you would need to be an audio expert to understand what these mean.
+
+***
+speaker-test is another useful binary from `alsa-utils`:
+```
+speaker-test -l 1
+```
+This will produce some noise on the default playback device for 10 seconds\
+and print some info about it on the screen.\
+See `man speaker-test` for more.
+
+Also useful:
+```
+amixer
+``` 
+
+```
+amixer info
+```
+You can also specify the device
+```
+amixer -D default
+```
+(and you can also specify the card with `-c`)
+
+```
+amixer controls
+```
+
+There is also the package `alsa-topology-utils` which provides the command `alsatplg`.
+
+#### configuration
+
+```
+$ cat /etc/alsa/alsactl.conf 
+#
+# ALSA library configuration file for alsactl tool
+# (/usr/share/alsa tree is not necessary for alsactl)
+#
+
+ctl.hw {
+	@args [ CARD ]
+	@args.CARD {
+		type string
+		default "0"
+	}
+	type hw
+	card $CARD
+}
+```
+
+And there  is stuff here:
+```
+/etc/alsa/conf.d $ ls
+50-pipewire.conf  99-pipewire-default.conf
+```
+
+#### select default soundcard and/or pcm device
+
+https://www.alsa-project.org/wiki/Setting_the_default_device
+
+=> that works
+
+Find your desired card with:
+```
+cat /proc/asound/cards
+```
+
+and then create /etc/asound.conf with following:
+```
+defaults.pcm.card 1
+defaults.ctl.card 1
+```
+Replace "1" with number of your card determined above. 
+
+you can test with `speaker-test -l 1` or with the minimal pcm example code
+
+**Note: The problem is, that your USB headset might be card 0 one time and when you replug it another time it might be card 1.**
+
+***
+
+#### audioservers
+
+`pulseaudio` and `pipewire` are audio servers.\
+They are on top of alsa.
+
+## how to figure out if you are using pulseaudio or pipewire?
+
+```
+$ ps -ef | grep -i "pipe"
+bf          2079    1856  0 19:09 ?        00:00:10 /usr/bin/pipewire
+bf          2082    1856  0 19:09 ?        00:00:13 /usr/bin/pipewire-pulse
+```
+
+pipewire doesnt seem to have a systemd unit
+
+But there seems to a compatibility layer involved since `pulseaudio volume control` (or pavucontrol) does change my audio output volume.
+
+***
+
+## pipewire
+
+https://docs.pipewire.org/
+
+`/usr/share/pipewire/pipewire.conf`
+
+The program `qpwgraph` is supposed to be a gui help for pipewire.\
+Seems very chaotic though.
+
+#### pipewire - record audio
+
+If you use `pipewire` you can test your input device by recording like this:
+```
+pw-cat -r recordme
+```
+
+#### pipe audio to pipewire
+
+```
+cat Hitman_Budapest_Bath_Hotel.mp3 | paplay
+```
+
+***
+## pulseaudio
+
+#### installation
+
+```
+sudo pacman -S pulseaudio
+sudo pacman -S pavucontrol
+sudo reboot
+```
+
+#### pulseaudio commands
+
+```
+pactl info
+```
+
+```
+paplay <audiofile>
+```
+
+#### testing pulseaudio
+
+```
+pactl load-module module-sine frequency=440
+```
+stop the sound with
+```
+pactl unload-module module-sine
+```
+
+btw, to see all loaded modules:
+```
+pactl list modules
+```
+
+---
+
+#### ffmpeg
+
+Puts the audio of a .mp4 Video into a .mp3 file:
+```
+ffmpeg -i input.mp4 output.mp3
+```
+Converting to .webm works the same way:
+```
+ffmpeg -i input.mp4 output.webm
+```
+Reducing the resolution of a video:
+```
+ffmpeg -i <input> -vf scale=480x360,setdar=4:3 <output>
+```
+---
+
+#### play sounds on the command line
+
+Make sure "system sounds" are almost as high as the other sounds in `pulse audio volume control`.
+
+```
+mpg123 -q /path/to/myfile.mp3
+```
+
+or directly with pulseaudio:
+```
+paplay /usr/share/sounds/freedesktop/stereo/alarm-clock-elapsed.oga
+```
+
+---
+
+#### test microphone
+
+part of the `libpulse` package:
+```
+parecord file.mp3
+```
+
+```
+pacman -F parecord
+extra/libpulse 16.1-6 [installed]
+    usr/bin/parecord
+    usr/share/bash-completion/completions/parecord
+```
+
+The `pulseaudio-utils` package has the `parec` command:
+```
+parec --format=s16le --channels=2 --rate=44100 | pacat
+```
+This will record from your microphone and output it a couple of seconds later.
+
+## Volume problem in movies
+
+In movies the volume is always inappropriate, shootings and music is very loud,
+quiet conversations you want to hear are unhearable silent.
+In my experience while using headphones this problem is less dominant but still exists.
+
+***
+
+Using OpenShot:
+Imported movie, separate audio command took forever so I quit.
+
+Tried it another time. Waited 2 minutes switched to browser in the meantime.
+Then it worked.
+But how do I just cut the audio without cutting the video clip too?
+=> don't use short cut, use the mouse, left click to select the clip,
+right click on the clip -> slice -> keep both sides
+Then select the clip, right click and put the volume to 10% or delete the audio clip.
+
+=> this works ok, but the performance is a little slow, maybe reduce the quality of the video
+before doing this!
+
+Exporting was a problem at 720p 30fps medium quality.
+Took 1 hour and the file is now 4.3GB big which is way too much.
+The problem was the original file was 720X320 at 24 fps and the new file is 720x1980 at 30fps.
+So I chose the wrong export option.
+
+Rendering/exporting video has to be done in advanced mode.
+You need to view the video and audio settings of the original video in file browser (video bitrate,
+audio bitrate, sample rate, codec, dimensions).
+The file size of the exported video is ok now, but I still have problems with the resolution.
+The video is squished together and the black frames on bottom and top are bigger than orignal
+even though I selected the same resolution.
+Außerdem Audiotrack verschoben...
+
+***
+
+VLC Media Player:
+
+Tools -> Effects and Filters (ctrl + E)
+
+=> try experimenting with enabling equalizer and/or enabling compressor
+==> doesn't really seem to help, maybe you have to change some settings
+===> changed settings, doesn't help
+
+----------------------------------------------------------------------------------------
+
+Try that didn't get me anywhere:
+
+sudo apt install pulseaudio-equalizer
+
+command to start the program:
+qpaeq
+
+Error
+solution: https://linuxhint.com/install-pulseaudio-equalizer-linux-mint/
+
+sudo vim /etc/pulse/default.pa
+
+Add the below-given lines at the bottom of the/etc/pulse/default.pa file.
+load-module module-equalizer-sink
+load-module module-dbus-protocol
+
+Next, kill the PulseAudio service and restart it:
+$ pulseaudio --kill && pulseaudio --start
+
+Now, open the PulseAudio with the command:
+$ qpaeq
+
+=> Ok, jetzt funktioniert zwar das Programm, aber ich kann mit dem Programm nichts anfangen.
+Scheint auch keine Dateien zu manipulieren sondern nur generell den Output.
+
+***
+
+#### audacity
+
+```
+sudo apt install audacity
+```
+
+Cut out audio: Select a range with the mouse and hit <kbd>del</kbd>
+
+Keep everything but the selected: select a range with the mouse and go to `edit -> remove special -> trim audio`. (or <kbd>ctrl</kbd> + <kbd>t</kbd>\
+Then put it on the beginning of the track with `tracks -> align tracks -> start to zero`
+
+
+
+
+#### location of sound files that applications use
+
+chatgpt:\
+The location of sound files used by a Linux application can vary depending on the application and the specific Linux distribution being used. However, there are a few common locations where sound files are typically stored:
+
+1. /usr/share/sounds: This directory contains system sounds that are used by many Linux applications, such as notifications and alerts.
+
+1. /usr/share/sounds/{application-name}: Some applications may have their own subdirectory within /usr/share/sounds where they store their sound files.
+
+1. ~/.local/share/sounds: This directory contains sound files for user-specific applications, such as media players or games.
+
+1. /usr/lib/x86_64-linux-gnu/pulseaudio: This directory contains system sounds for the PulseAudio sound server, which is used by many Linux distributions.
+
+1. /usr/lib/x86_64-linux-gnu/gstreamer-1.0: This directory contains sound files used by GStreamer, a popular multimedia framework used by many Linux applications.
+
+For example this file existed both on Arch Linux and on Fedora:
+```
+$ paplay /usr/share/sounds/freedesktop/stereo/alarm-clock-elapsed.oga
+```
+
+## troubleshooting
+
+#### no audio input from headset
+
+I had no audio input from my headset.
+
+The solution was to go into `pulse audio volume control` or `pavucontrol`.\
+"Input devices" -> And set your headset as `fallback`
+
+With `pipewire` you can test it with `pw-cat -r myfile`, go into `nnn` and hit enter on the file.
+
+***
+
+#### no sound issue on Ubuntu
+
+I had the issue that no sound was working on Ubuntu anymore because of various system problems.
+
+Then I did
+
+```
+sudo apt reinstall alsa-base
+```
+```
+sudo apt reinstall pulseaudio
+```
+```
+reboot
+```
+And sound was working again.