[FFmpeg-user] Possible to encode a file with a broken header?

Mr M redpenguinmail at gmail.com
Sun Nov 25 01:08:54 CET 2012

I made an FLV recording which seems to have a broken header or similar.

ffmpeg says "Video: None" and "Cannot Determine Codec Info"

I have another FLV from the same source that ffmpeg converts easily.

MediaInfo claims the video codec is AVC.

The "corrupted" FLV only will play in Media Player Classic on Windows.
VLC claims it has "undf" video.

A sample from a working FLV is located at:


I attempted to do -f h264 but it just complained about a bunch of
invalid frames not detecting h264.

The file will play fine in MPC with no A/V sync issue, strange freeze
or blocking, totally normal.

Is there some way to even with a Hex editor fix the header?

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