How to Remove sequentially duplicate frames when using FFmpeg

In video processing and editing, removing sequential duplicate frames is a common requirement, particularly when handling video files that contain duplicate frames due to errors in recording devices or encoding processes. FFmpeg is a highly versatile tool capable of performing such tasks. The following outlines the steps and examples for using FFmpeg to remove sequential duplicate frames from videos:

1. Environment Preparation

Ensure FFmpeg is installed on your system. Verify its installation and check the version by entering ffmpeg -version in the terminal or command prompt.

2. Using the mpdecimate Filter

The mpdecimate filter in FFmpeg detects and removes duplicate frames by examining differences between consecutive frames and retaining only those that differ sufficiently from the preceding frame.

3. Command-Line Example

Below is a basic command-line example demonstrating how to use FFmpeg with the mpdecimate filter to remove duplicate frames from a video file:

bash
ffmpeg -i input.mp4 -vf mpdecimate,setpts=N/FRAME_RATE/TB output.mp4

Parameter Explanation:

• -i input.mp4: Specifies the input file.
• -vf: Indicates the use of a video filter chain.
  • mpdecimate: Applies the mpdecimate filter to remove duplicate frames.
  • setpts=N/FRAME_RATE/TB: Recalculates timestamps to ensure accurate playback timing.
• output.mp4: Specifies the output file name.

4. Advanced Options

For finer control over the mpdecimate filter, set additional parameters such as hi, lo, and frac:

bash
ffmpeg -i input.mp4 -vf "mpdecimate=hi=64*12:lo=64*8:frac=0.33,setpts=N/FRAME_RATE/TB" output.mp4

Parameter Explanation:

• hi=64*12: Defines the maximum difference threshold between frames; frames exceeding this value are deemed different.
• lo=64*8: Defines the minimum difference threshold between frames; frames below this value are considered identical.
• frac=0.33: Sets the proportion of frames that must be marked identical before a frame is considered a duplicate.

5. Testing and Validation

Before applying production-level processing, test these settings on a short video segment to verify expected behavior and adjust parameters for optimal results.

By following these steps, you can effectively use FFmpeg to remove duplicate frames from video files, which is particularly useful for handling recording errors or optimizing video file sizes.