Why can't Finder quicklook the mp4 I just encoded with ffmpeg?

Question

I just did ffmpeg -i My\ Movie.mov vid.mp4 to convert iMovie output to an MP4.

I can't quicklook the mp4 as usual (by pressing space), nor does Finder show a thumbnail for it.

Here is ffmpeg -i information for a quicklookable mp4:

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'playable.mp4'
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:00:21.04, start: 0.000000, bitrate: 746 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x360 [SAR 1:1 DAR 16:9], 612 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : ISO Media file produced by Google Inc.
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler

Here is ffmpeg -i vid.mp4:

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'vid.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    title           : My Movie
    encoder         : Lavf58.45.100
    keywords        : iMovie
  Duration: 00:00:53.40, start: 0.000000, bitrate: 316 kb/s
    Stream #0:0(und): Video: h264 (High 4:2:2) (avc1 / 0x31637661), yuv422p10le, 480x270 [SAR 1:1 DAR 16:9], 190 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : Core Media Video
      timecode        : 00:00:00:00
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 119 kb/s (default)
    Metadata:
      handler_name    : Core Media Audio
    Stream #0:2(eng): Data: none (tmcd / 0x64636D74)
    Metadata:
      handler_name    : Core Media Video
      timecode        : 00:00:00:00

How am I meant to use ffmpeg to turn My Movie into an MP4 that can be quicklooked?

Answer 1

You may not have the same issue, but in my case, the problem was that the handler_name cannot be more than 29 characters. To fix, you could try a command like this instead:

ffmpeg -i 'My Movie.mov' -metadata:s handler_name=SoundHandler vid.mp4

https://trac.ffmpeg.org/ticket/3623