A quick note on how to boost the audio stream in a video using the volume filter in ffmpeg
#;For newer versions of ffmpeg ffmpeg -i input.mkv -filter:a "volume=4.0" output.mkv; #For older versions of ffmpeg (we use multiples of 256) ffmpeg -i input.mkv -vol 1024 -vcodec copy output.mkv;
Using the above command we were able to make the audio LOUDER!
The code below was used to generate the video countdown timers that are available in the following playlist using ffmpeg:
#This example will create a 3 second video, with 100 frames per second and it will print the elapsed and remaining times using a two second accuracy.
fps=100;
seconds=3;
mantissaDigits=2;
upperFont=600;
lowerFont=100;
ffmpeg -loop 1 -i ~/Pictures/Black-Background.png -c:v libx264 -r $fps -t $seconds -pix_fmt yuv420p -vf "fps=$fps,drawtext=fontfile='/usr/share/fonts/urw-base35/C059-Bold.otf':fontcolor=yellow:fontsize=$upperFont:x=(w-text_w)/2:y=(h-text_h)/2:text='%{eif\:($seconds-t)\:d}.%{eif\:(mod($seconds-t, 1)*pow(10,$mantissaDigits))\:d\:$mantissaDigits}',drawtext=fontfile='/usr/share/fonts/urw-base35/C059-Bold.otf':fontcolor=yellow:fontsize=$lowerFont:x=(w-text_w)/2:y=((h-text_h)/2)+$upperFont:text='Elapsed\: %{eif\:(t)\:d}.%{eif\:(mod(t, 1)*pow(10,$mantissaDigits))\:d\:$mantissaDigits}'" "$seconds seconds countdown timer.mp4";
fps variable we defined the number of Frames per Second for the video.seconds variable defined the number of seconds the duration of the video should be.mantissaDigits variable defines how many decimal digits should be shown after the dot.upperFont and lowerFont define the size of the fonts in the upper row and the lower one respectively.drawtext directive twice to write to the frames.fontfile='/usr/share/fonts/urw-base35/C059-Bold.otf' defines the font to be used for the text.fontcolor=yellow defines the color of the font of the text.fontsize=$upperFont defines the size of the font of the text.x=(w-text_w)/2 defines the X-coordinate of the location for the text on the frame, here we center the text horizontally on the frame.y=(h-text_h)/2 defines the Y-coordinate of the location for the text on the frame, here we center the text vertically on the frame.text='%{eif\:($seconds-t)\:d}.%{eif\:(mod($seconds-t, 1)*pow(10,$mantissaDigits))\:d\:$mantissaDigits}' We print the remaining seconds for the video to finish with specific decimal digit accuracy.drawtext=fontfile='/usr/share/fonts/urw-base35/C059-Bold.otf' defines the font to be used for the text.fontcolor=yellow defines the color of the font of the text.fontsize=$lowerFont defines the size of the font of the text.x=(w-text_w)/2 defines the X-coordinate of the location for the text on the frame, here we center the text horizontally on the frame.y=((h-text_h)/2)+$upperFont defines the Y-coordinate of the location for the text on the frame, here shift the text from the vertical center of the frame.text='Elapsed\: %{eif\:(t)\:d}.%{eif\:(mod(t, 1)*pow(10,$mantissaDigits))\:d\:$mantissaDigits}' We print the elapsed seconds since the video started with specific decimal digit accuracy.A couple of days ago we were asked to setup stackskills-dl on a Fedora 27 (x64).
Apparently stackskills-dl is a Ruby script that allows a registered user to download the StackSkills tutorials for which the user has access to.
Following the instructions at https://github.com/yoonwaiyan/stackskills-dl are not enough to get the application running as the json gem and the Ruby development files appear to be missing from the filesystem.
stackskills-dl and make it operational:sudo dnf install gem ruby-devel youtube-dl wget; gem install json; gem install bundler; git clone https://github.com/yoonwaiyan/stackskills-dl.git; cd stackskills-dl/; bundle install;
After the above steps were completed, we were able to use stackskills-dl from the clone/installation folder normally:
[george@banana stackskills-dl]$ ruby stackskills_dl.rb -u "[email protected]" -p "e#rf54HTw3se!fe678f." -s https://stackskills.com/courses/enrolled/007; Loaded login credentials from environment variables. Login Successfully. Finding https://stackskills.com/courses/enrolled/007 from your list of courses Number of courses found: 1 ... [george@banana stackskills-dl]$ ruby stackskills_dl.rb --help Usage: ruby stackskills_dl.rb [options] -u, --email NAME Email -p, --password PASSWORD Password -c, --course COURSE_URL Course URL in ID. -s, --course-slug COURSE_SLUG Course URL in slug.
With out the Ruby json gem you would get the following error:
[george@banana stackskills-dl]$ ruby stackskills_dl.rb --help; /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- json (LoadError) from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require' from /home/george/.gem/ruby/2.4.0/gems/mime-types-2.99.1/lib/mime/types/loader.rb:226:in `load_from_json' from /home/george/.gem/ruby/2.4.0/gems/mime-types-2.99.1/lib/mime/types/loader.rb:63:in `block in load_json' from /home/george/.gem/ruby/2.4.0/gems/mime-types-2.99.1/lib/mime/types/loader.rb:62:in `each' from /home/george/.gem/ruby/2.4.0/gems/mime-types-2.99.1/lib/mime/types/loader.rb:62:in `load_json' from /home/george/.gem/ruby/2.4.0/gems/mime-types-2.99.1/lib/mime/types/loader.rb:88:in `load' from /home/george/.gem/ruby/2.4.0/gems/mime-types-2.99.1/lib/mime/types/loader.rb:113:in `load' from /home/george/.gem/ruby/2.4.0/gems/mime-types-2.99.1/lib/mime/types.rb:296:in `load_default_mime_types' from /home/george/.gem/ruby/2.4.0/gems/mime-types-2.99.1/lib/mime/types.rb:323:in `<class:Types>' from /home/george/.gem/ruby/2.4.0/gems/mime-types-2.99.1/lib/mime/types.rb:63:in `<top (required)>' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require' from /home/george/.gem/ruby/2.4.0/gems/mechanize-2.7.4/lib/mechanize/pluggable_parsers.rb:5:in `<top (required)>' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require' from /home/george/.gem/ruby/2.4.0/gems/mechanize-2.7.4/lib/mechanize.rb:1361:in `<top (required)>' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:133:in `require' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:133:in `rescue in require' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:40:in `require' from /home/george/Videos/stackskills-dl/lib/course_finder.rb:1:in `<top (required)>' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in `require' from stackskills_dl.rb:4:in `<main>'
Using the youtube-dl command line application you can download videos and directly extract the audio of the video in various formats.
youtube-dl supports a large variety of online video hosts, including:
Note: Please be sure that you are allowed to download a video before you do that, many of these hosts do not expect that you will be downloading their videos as they do not allow that.
The following command, will download a video, convert it to an mp3 and delete the original video:
youtube-dl --extract-audio --audio-format mp3 https://www.youtube.com/watch?v=cwI-n3sI8ec
If you want to keep the original video, you just add the parameter -k or --keep-video.
The --audio-format parameter accepts other types of audio format outputs, specifically it supports
youtube-dl is a very powerful tool, advice the documentation for some of the great features it supports.
