In this article, we will explore how to split a video into different segments based on resolution changes using the FFmpeg tool. This technique is useful when you want to separate various sections of a video that have different resolutions, allowing for more straightforward editing or processing.
What is FFmpeg?
FFmpeg is a free and open-source tool for handling multimedia files, including audio, video, and images. It supports various formats and is highly extensible through plugins and libraries. FFmpeg is widely used for video encoding, decoding, transcoding, muxing, demuxing, filtering, and more.
Why Split a Video by Resolution Changes?
Splitting a video by resolution changes offers several benefits:
- Easier editing: It allows editors to work on specific resolution segments without affecting other parts.
- Better performance: Processing individual segments with a consistent resolution may speed up rendering or compression.
- Tailored output: You can create separate outputs with specific resolutions for various platforms or devices.
How to Split a Video using FFmpeg
To split a video based on resolution changes, you can use a script to find moments when the resolution changes and then use the FFmpeg command-line tool to cut the video at those timecodes. Here's a step-by-step guide:
Step 1: Find Moments of Resolution Changes
First, you need to determine when resolution changes occur in a video by analyzing its frames. You can use a FFprobe script to extract the resolution and timestamps information.
ffprobe -select_streams v:0 -show_entries stream=width,height,pkt_pts_time -of csv=p=0:s=x input.mp4 | awk -F'x' '{if (a!=$1 || a=="") {print $2" "$1} a=$1}'
In this command:
ffprobe: the FFmpeg tool to extract video information.-select_streams v:0: selects the first video stream only.-show_entries stream=width,height,pkt_pts_time: shows the width, height, and timestamp of the video stream.-of csv=p=0:s=x: outputs the result as comma-separated values.| awk -F'x' '{if (a!=$1 || a=="") {print $2" "$1} a=$1}': parses the output, printing only the timestamps and new resolutions.
This script generates a list of timestamps and resolution changes in the following format:
0.500 640x360
2.423 960x540
5.000 1280x720
Step 2: Split the Video
Using the output from the previous script, you can now split the video using the FFmpeg command-line tool.
for time in $(cat timestamps.txt); do ffmpeg -i input.mp4 -ss "$(echo $time | cut -d' ' -f1)" -t "$(echo $time | cut -d' ' -f2)" -c copy output_"$(echo $time | cut -d' ' -f2 | cut -d'x' -f1)"_"$(echo $time | cut -d' ' -f2 | cut -d'x' -f2)".mp4; done
In this command:
for time in $(cat timestamps.txt); do: iterates over the list of timecodes and resolutions.ffmpeg -i input.mp4: defines the input file.-ss "$(echo $time | cut -d' ' -f1)": sets the start time based on the timestamp.-t "$(echo $time | cut -d' ' -f2)": sets the duration based on the difference between the current and next timestamp.-c copy: copies the video and audio codecs from input to output without re-encoding.output_"$(echo $time | cut -d' ' -f2 | cut -d'x' -f1)"_"$(echo $time | cut -d' ' -f2 | cut -d'x' -f2)".mp4: generates output files named based on the timestamp and resolution.done: ends the loop.
In this article, we have discussed how to use FFmpeg to split a video into multiple segments based on resolution changes. This allows you to handle specific resolution segments more easily and efficiently. The process consists of extracting a list of resolution changes and corresponding timecodes using FFprobe and then cutting the video at those moments using FFmpeg.