FFmpeg tiny cheat sheet

We assume that the user has set the video filename to the variable named $video in the following commands.

FFmpeg export audio from any video to mp3

ffmpeg -i "$video" -vn -c:a libmp3lame -y "$audio";

FFmpeg export frames from video to images

ffmpeg -i "$video" "$frames_folder/%08d.ppm";

Retrieve the frame rate from the input video

#To view it on screen
ffprobe -v 0 -of csv=p=0 -select_streams v:0 -show_entries stream=r_frame_rate "$video";
#To assign it to a variable use the following
frame_rate=`ffprobe -v 0 -of csv=p=0 -select_streams v:0 -show_entries stream=r_frame_rate "$video"`;

To create a video out of a folder with frames/images and an audio file.

ffmpeg -framerate "$frame_rate" -i "$frames_folder/%08d.ppm" -i "$audio" -pix_fmt yuv420p -acodec copy -y "$output_video";
#To set a custom starting index for the frames you can use the -start_number argument
ffmpeg -start_number 62 -framerate "$frame_rate" -i "$frames_folder/%08d.ppm" -i "$audio" -pix_fmt yuv420p -acodec copy -y "$output_video";
#To use the MP4 coded use -vcodec libx264
ffmpeg -framerate "$frame_rate" -i "$frames_folder/%08d.ppm" -i "$audio" -vcodec libx264 -pix_fmt yuv420p -acodec copy -y "$output_video";

To merge an audio less video with an audio file

ffmpeg -i "$no_audio_video" -i "$audio" -shortest -vcodec copy -acodec copy "$output_video";

To change the frame rate of a video

ffmpeg -i "$video" -filter:v fps=20 "$output_video";

To merge two videos side by side

ffmpeg -i "$left_video" -i "$right_video" -filter_complex hstack "$output_video";

Concatenate multiple videos into one

The easiest way without writing huge commands is the following: First, create a file named parts.txt and add content similar to what we list below:

#Lines starting with # will be ignored
file 'part00-03.mp4'
file 'part04.mp4'
file 'part05-07.mp4'
file 'part08-09.mp4'
file 'part10.mp4'
file 'part11-13.mp4'

Then execute the following command to concatenate all those videos into one:

ffmpeg -f concat -safe 0 -i parts.txt -c copy "$output_video";

Speed up a video

Using the following command, you can speed up a video by dropping excess frames:

ffmpeg -i "$video" -filter:v "setpts=0.5*PTS" "$output_video";

The above example will double the speed (the value 0.5 controls it.)

To speed the video up without losing frames, you can increase the FPS value of the output video. To retrieve the frame rate, please see the command that was posted earlier.

ffmpeg -i "$video" -r 80 -filter:v "setpts=0.25*PTS" "$output_video";

In the second example, we assumed that the input video had 20 frames per second. Using the 0.25 value, we decided to speed the video up by a factor of 4. To preserve the input frames, we increased the frame rate from 20 to 80 using the parameter -r.

ImageMagick: merge two images using a black and white mask

Recently, we wanted to merge two images into one using a custom black and white mask. To avoid using heavy GUI-based software, we decided to do it using the composite command of the ImageMagick package. Using the composite program, you can overlap one image over another. The command used is straightforward once you get the order of the parameters in the command line.

convert black.jpg white.jpg mask.png -composite masked.jpg;

The above command accepts four parameters:

convert "${BLACK_PART}" "${WHITE_PART}" "${MASK}" -composite "${OUTPUT}";

The first parameter (${BLACK_PART}) is the input picture you want to be placed in all black parts of the mask. The second parameter (${WHITE_PART}) is the input photo you wish to use on all white parts of the mask. The third parameter (${MASK}) is the black and white image that you will be used to merge the previous two images. The final parameter (${OUTPUT}) is the filename to write the final results.

Below we present the results of a demo we created using the above command:

The first parameter (${BLACK_PART}) is the input picture you want to be placed in all black parts of the mask.
The second parameter (${WHITE_PART}) is the input photo you wish to use on all white parts of the mask.
The third parameter (${MASK}) is the black and white image that you will be used to merge the previous two images.
The final parameter (${OUTPUT}) is the filename to write the final results.

LibreOffice Calc: Finding duplicate / common entries between two columns

This video demonstrates how to find all matching values between two columns in LibreOffice Calc. Precisely, in this video, we fill in columns A and B with random integer values between the numbers 1 and 100 (inclusive). The formula to generate the random values was the following:

=RANDBETWEEN(1;100)

After we filled in columns A and B with random values, we used the following formula in each cell of column C to find all common values between the first two columns:

=IF(ISERROR(MATCH(B1;A:A;0));"";B1)

LibreOffice Cal commands used in this video

  • RANDBETWEEN(Bottom; Top) – Returns an integer random number in a specified range.
  • IF(Test; ThenValue; OtherwiseValue) – Specifies a logical test to be performed.
  • ISERROR(Value) – Tests for error conditions, including the #N/A error value, and returns TRUE or FALSE.
  • MATCH(SearchCriterion; LookupArray; Type) – Returns the relative position of an item in an array that matches a specified value. The function returns the position of the value found in the lookup_array as a number.

FFmpeg: Could find no file with path ‘%08d.ppm’ and index in the range 0-4 %08d.ppm: No such file or directory

During some work that we were doing, we used the following command to export the frames of a video using FFmpeg:

ffmpeg -v quiet -i "$video" "$input_frames_folder/%08d.ppm";

The above command exported the video frames into the selected folder and using eight digits zero-padding it named all the images in an increasing order starting from the number 00000001 (00000001.ppm).

Later on, we processed those frames and deleted some of the first ones (specifically, we deleted the first 61 frames, so the first available frame was named 00000062.ppm). When we tried to rebuild the video using the command below, we got the error that is listed after the command:

ffmpeg -framerate "25/1" -i "$input_frames_folder/%08d.ppm" -pix_fmt yuv420p -y processed.mkv;

Could find no file with path '%08d.ppm' and index in the range 0-4 %08d.ppm: No such file or directory

To fix the issue, we used the -start_number parameter with the value 62. The parameter sets the file starting index for the matched image files.

ffmpeg -start_number 62 -framerate "25/1" -i "$input_frames_folder/%08d.ppm" -pix_fmt yuv420p -y processed.mkv;

Please note that we also used -pix_fmt yuv420p as we were getting a video with black frames only, so we had to define the format of the pixels to use manually.