The -c copy command instructs FFmpeg to copy the video and audio streams exactly as they are. It strips away the broken container wrapper and builds a fresh MKV structure with a healthy index. Method 3: Avidemux (Best for Visual Editing)
ffmpeg -i input.mkv -c copy -no_index output.mkv
This command tells FFmpeg to take the input, "copy" the streams directly into a new container, and generate a fresh index automatically.
ffmpeg -i original.mkv -c copy -map 0 fixed.mkv mkv index free
In a Matroska (MKV) container, the (or index) function as a map of the file. This index allows media players to "seek"—or jump to a specific timestamp—instantly without reading every byte of data sequentially from the start.
Point the indexer to your root MKV folder (e.g., D:\My_4K_Movies ). Click "OK."
Properly preparing your MKV files is the single most important step for this kind of index to work correctly. The -c copy command instructs FFmpeg to copy
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Download Jellyfin from their official website. It works on Windows, macOS, Linux, Docker, or even a Raspberry Pi.
An is essentially a database or a catalog of your MKV files. Unlike a simple file list (like Windows Explorer or Mac Finder), a true index reads the metadata inside your videos. This includes: ffmpeg -i original
: A powerful tool for quick fixes using the following command: ffmpeg -i input.mkv -c copy output.mkv
If a file transfer or download is interrupted, the video data might be present, but the index at the end of the file never finishes saving.
Some older converters don't write the index properly during the muxing process. The Best Free Tools to Rebuild MKV Indexes 1. MKVToolNix (The Gold Standard)