Fix AVI Index Corruption with FFmpeg genpts

This article provides a straightforward guide on how to resolve index corruption issues in AVI video files using FFmpeg’s -fflags +genpts option. You will learn why AVI index corruption occurs, how the +genpts flag forces FFmpeg to regenerate missing or broken presentation timestamps, and the exact command-line steps required to reconstruct a healthy index and restore smooth playback to your video files.

Why AVI Files Get Corrupted Indices

The AVI (Audio Video Interleave) format relies heavily on an index table located at the end of the file structure. This index acts as a map, allowing media players to seek to specific timestamps and keep audio and video in sync. If a file transfer is interrupted, a download is incomplete, or a recording stops abruptly, this index is often missing or damaged. As a result, media players may fail to open the file, lose audio-to-video synchronization, or disable seeking.

How -fflags +genpts Solves the Issue

The -fflags +genpts flag instructs FFmpeg to generate missing Presentation Timestamps (PTS) during the input reading phase. By combining this flag with a stream copy operation, FFmpeg can read the raw video and audio packets, compute correct timestamps on the fly, and write a brand-new, healthy index structure into the output file. Because this process copies the streams rather than re-encoding them, the repair is instantaneous and causes zero quality loss.

The Repair Command

To fix a corrupted AVI file, open your command-line interface and run the following command:

ffmpeg -fflags +genpts -i corrupted_input.avi -c copy repaired_output.avi

Command Breakdown

• -fflags +genpts: This must be placed before the input file. It tells the demuxer to generate missing presentation timestamps based on the packet sequence.
• -i corrupted_input.avi: Specifies the path to your damaged AVI file.
• -c copy: Tells FFmpeg to copy both the video and audio streams without re-encoding. This ensures the output is generated within seconds.
• repaired_output.avi: The path for the newly generated, healthy AVI file.

Once the process completes, the output file will contain a newly generated index, restoring full seekability and correct playback across all standard media players.