Efficient Way of Stacking Two Videos Vertically Using FFmpeg

Efficient Way Stacking Two Videos Vertically Using FFmpeg

In this article, we will cover the process of stacking two videos vertically using the FFmpeg tool. This technique is particularly useful when you want to present a slideshow alongside a speaker video in a single screen. By the end of this article, you will be able to combine multiple talks into a single video file efficiently.

What is FFmpeg?

FFmpeg is a free and open-source software project consisting of a vast software suite of libraries and programs for handling video, audio, and other multimedia files and streams. It is widely used for format transcoding, stream encoding, video editing, and many other tasks.

Prerequisites

Before diving into the process of stacking videos vertically, ensure you have the following prerequisites:

• Two video files with similar durations
• FFmpeg installed on your system

Stacking Videos Vertically

To stack two videos vertically, you can use the FFmpeg hstack filter. However, this filter places the videos side-by-side (horizontally). To stack them vertically, you need to use the vstack filter, which is not available in the FFmpeg distribution by default. To enable it, you need to recompile FFmpeg with the --enable-libplacebo configure option.

Assuming you have FFmpeg with the vstack filter, follow these steps to stack two videos vertically:

1. Create a text file named vertical.ffmpeg and include the following command:

   ffmpeg -i input1.mp4 -i input2.mp4 -filter\_complex "[0:v][1:v]vstack[outv]" -map "[outv]" output.mp4

   Replace input1.mp4 and input2.mp4 with your video file names, and output.mp4 with the desired output file name.

2. Run the FFmpeg command from the terminal:

   ffmpeg -f concat -safe 0 -i vertical.ffmpeg output.mp4

Creating a Temporary Overlay for Horizontal Stacking

If you do not have the vstack filter available, you can create a temporary overlay for horizontal stacking using the hstack filter:

1. Create a text file named horizontal.ffmpeg and include the following command:

   ffmpeg -i input1.mp4 -i input2.mp4 -filter\_complex "[0:v][1:v]hstack=inputs=2:shortest=1[outv]" -map "[outv]" output\_temp.mp4

   Replace input1.mp4 and input2.mp4 with your video file names, and output\_temp.mp4 with the desired output file name.

2. Rotate the output file by 90 degrees:

   ffmpeg -i output\_temp.mp4 -vf "transpose=1" output.mp4

Considerations and Best Practices

• Ensure that both input videos have similar durations for seamless synchronization.
• Use the shortest option in the filter complexity to avoid excessive processing time when input video durations differ.
• Consider recompiling FFmpeg with the --enable-libplacebo configure option for the vstack filter for better performance and flexibility.

In this article, we have discussed how to efficiently stack two videos vertically using the FFmpeg tool with the vstack filter or by creating a temporary overlay using the hstack filter. By following the steps outlined in this article, you can now combine multiple talks, including a slideshow and a speaker video, into a single screen for easier presentation.

References

• Type: Online Resource

  Title: FFmpeg Documentation

  https://ffmpeg.org/documentation.html

• Type: Online Resource

  Title: FFmpeg Filters Documentation

  https://ffmpeg.org/ffmpeg-filters.html