34

I have a library of videos, all of which should have been adjusted for web-streaming by putting the moov atom ahead of the rest of the video. This allows playback to begin before the client has completely downloaded the video.

Is there a reliable way to check if a certain video has been adjusted by locating how many bytes in the moov atom occurs? This is for debugging purposes only.

Zombo
  • 1
Jamie Taylor
  • 1,501

5 Answers5

25

FFmpeg won't show you this information, really.

You could use AtomicParsley to parse the file, e.g.:

AtomicParsley input.mp4 -T

This will show you the location of the atoms in a tree. If the moov atom is at the beginning of the file, it'll have to come right after the ftyp atom, so you could try parsing the output, e.g. in Bash, only printing the second line and checking whether it contains moov:

AtomicParsley input.mp4 -T | sed -n 2p | grep -q "moov" && echo "yup" || echo "nope"
Zombo
  • 1
slhck
  • 235,242
19

Using this qtfaststart (not the same as ffmpeg's qt-faststart), qtfaststart -l input.mp4 will display the order of the top-level atoms.

$ qtfaststart -l bad.mp4
ftyp (32 bytes)
free (8 bytes)
mdat (559619 bytes)
moov (52916 bytes)
$ qtfaststart -l good.mp4
ftyp (32 bytes)
moov (52916 bytes)
mdat (559619 bytes)
$
mark4o
  • 5,552
15

The way to do this using ffmpeg is described in this answer to another question. Run the following Bash command:

$ ffmpeg -v trace -i file.mp4 2>&1 | grep -e type:\'mdat\' -e type:\'moov\'

The output will look something like this:

[mov,mp4,m4a,3gp,3g2,mj2 @ 0x55ea95500ac0] type:'mdat' parent:'root' sz: 52958326 32 52971704
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x55ea95500ac0] type:'moov' parent:'root' sz: 13354 52958358 52971704

In this example, since moov appears after mdat, the moov atom is not at the beginning of the file and faststart is not enabled. If moov were to appear before mdat, then the moov atom would be at the beginning of the file and faststart would be enabled.

Trevor
  • 339
  • 2
  • 6
6

You can do this with FFprobe:

ffprobe -v trace infile.mp4

Or with Bento4:

$ mp4info infile.m4a
File:
  major brand:      isom
  minor version:    200
  compatible brand: isom
  compatible brand: iso2
  compatible brand: mp41
  fast start:       no

$ mp4info outfile.m4a
File:
  major brand:      isom
  minor version:    200
  compatible brand: isom
  compatible brand: iso2
  compatible brand: mp41
  fast start:       yes
Zombo
  • 1
2

Alternatively, without tools, you can just read the first 50 bytes of the file. If the string "moov" is in there, you're good.

Sinus tentaclemonster
  • 346
  • 1
  • 3
  • 10