[FFmpeg-user] -movflags +faststart has no effect

Ted Park kumowoon1025 at gmail.com
Tue Feb 25 22:49:36 EET 2020

> When reading the mov mp4 ismv section I have some question:
> 1. Are there differences between these 3 formats?
> 2. When only using output.mp4, the video is NOT fragmented, right?
> 3. Does -movflags +fastrstart revert the fragmentation, i.e. move all
> metadata to the start?
> 4. What is the difference of using -movflags -ismv - or -f mov/mp4/ismv?
> 5. Why is -movflags -ismv missing in the options list (it's only in the
> examples below).
> 6. What is the difference between -faststart and +faststart


1. To start I think the most obvious is the brand names in the ftyp atom. These indicate the different standards/specifications that each format follows. I think mov is either QuickTime or ISO MBFF (MPEG-4 part 12), mp4 is MP4 as in MPEG-4 part 14, and ismv I’m not entirely sure except that it writes fragments by default, but based on the name I’d guess it follows the specs from Microsoft primarily implemented in IIS silverlight.
2. Not by default, right.
3. I don’t think faststart does anything that complicated, in fragmented files I think the sidx is moved up instead of the moov atom, or maybe both.
4. Do you mean the isml flag? It’s for windows server streaming it looks like.
5. See 4
6. + sets the flag, - clears it.

Ted Park 

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