merge

FFmpeg tiny cheat sheet

 in Applications  tagged audio / concat / copy / export / ffmpeg / ffprobe / fps / frame rate / frames / hstack / libmp3lame / libx264 / merge by

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

 in ImageMagick  tagged composite / convert / imagemagick / mask / merge / overlap by

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.

How does ‘git pull’ and ‘git fetch’ differ?

 in Applications  tagged fetch / git / git fetch / git merge / git pull / merge / pull by

In simple terms, the difference between the two Git commands is that git pull is composed by a git fetch followed by a git merge.

When you use git pull, Git will automatically merge any pulled commits into the branch you are currently working in, without letting you review them first. You will get a prompt only if there is conflict found during automatic merging.

When you use git fetch, Git retrieves any commits from the target branch that do not exist in your current branch and stores them in your local repository. However, it will not merge them with your current branch. To integrate the new commits into your current branch, you need to use git merge manually.
This command is particularly useful if you need to keep your repository up to date, but are working on something that might break if you merge your files.
For example, if you will go offline and you need to have those commits available to you but cannot merge at the time, using git fetch you will download the new commits to your machine without affecting your current code. Later you will be able to merge the new commits to your branch as/when you please.