Fastest way to add -movflags +faststart to an MP4 using FFMPEG, leaving everything else as-is

Question

I want to add -movflags +faststart to an mp4 file. Basically that is all I want to do, nothing else should be changed. I am using ffmpeg.

What's the fastest way to do this? Do I have to re-encode the whole video? Or is there a better/easier way?

Mayce

Answer 1

As simple as:

ffmpeg -i in.mp4 -c copy -map 0 -movflags +faststart out.mp4

Or if you can compile FFmpeg from source, make the tool qt-faststart in the tools/ directory and run it:

qt-faststart in.mp4 out.mp4

You can also use mp4box, which lets you move the MOOV atom to the start via this command:

mp4box -inter 0 in.mp4 -out out.mp4

Or if you want to fully optimize for streaming by also interleaving the audio/video data so that the file can be easily streamed in realtime:

mp4box -inter 500 in.mp4 -out out.mp4

Parkland

You may want to add -map_metadata 0 too in order to preserve any metadata – Thomson

Is there any way to "fully optimize" with ffmpeg instead of mp4box? I would be doing a transcode with ffmpeg, so it would be nice not to run a separate command. – Lobel

@Parkland I'm sorry, I meant is there also a way to interleave with ffmpeg like with mp4box. Or, are you saying faststart will interleave the results? Not finding anything on Google – Lobel

The MP4 muxer in ffmpeg does not support custom interleaving delta. faststart only relates to where the metadata is placed. – Parkland

@Parkland just seeing your reply now. Thanks a lot. – Lobel

The ffmpeg command above (with either "+faststart" or just "faststart") gives me "moov atom not found" (the same error I'm trying to fix) I'm running on an .m4v file. – Transfiguration

Is there a way to not do it under a new file and add it to the same header of the main file without reading the entire data of the file, so that we can reach the goal faster? – Meunier

@Parkland Do you know what is the default A/V interleave duration/logic in ffmpeg when writing MP4? This appears to be incredibly difficult to find any information about. I was using MP4Box to re-interleave but now suspect I don't need to, as probably ffmpeg interleaves by default, but when I try to find out roughly the size chunks it uses... 100s of irrelevant results :( – Fragrance