Faulty file when using the 'faststart' option in Muxer

  • Vouk January 28, 2026 at 7:45 AM

    Added the label Missing Information
  • Sure, everything's inside. When faststart (movflags 64) is enabled in the MP4 muxer, the resulting file is unreadable. The same file processed with standalone FFmpeg (-movflags +faststart) works fine. Maybe the post-processing step to move the moov atom is failing or corrupting the file.

  • Sorry, mate, I'm here to report only. It will only take a minute for you to test: Muxer Properties > MP4 > Faststart=true, if the rendered file actually plays back – congratulations, you've fixed it. I'll be upgrading my Voukoder to a newer version, once the adjustable NVENC codec tag is implemented. Otherwise it's all good, don't wanna mess up anything in my current workflow.

  • Vouk January 31, 2026 at 11:30 AM

    Set the label from Missing Information to Fixed