[FFmpeg-user] Help with metadata writing (mp4)... what's possible?

Gyan Doshi gyandoshi at gmail.com
Thu Dec 6 21:57:49 EET 2018

On 07-12-2018 12:49 AM, Karen Norton wrote:
> Just a few more questions:
> 1. Where do I find your SU answer that you mention? Is there a link to see
> it?

It's the SuperUser page you linked to :)

> 2. To make sure I understand using that -movflags use_metadata_tags does
> this mean my command line would now be:
> ffmpeg -i input.mp4 -metadata media_type="10" -metadata show="Law & Order"
> -metadata season_number="1" -metadata title="Prescription For Death"
> -metadata episode_id="66209" -metadata episode_sort="1" -metadata:s:a:0
> language=eng -movflags use_metadata_tags -metadata episode_number="Episode
> 1" -c:v libx264 --c:a aac output.mp4

Looks right.

> 3. Will custom tags display in ffprobe?

Yes. They do, for me.

> 4. Can episode_sort be changed from Int8 to general number that allows more
> than 255 or maybe alphanumeric? As mentioned I can't use this for Law &
> Order Special Victims Unit and Law & Order because they are well over 255.

Here's the weird thing. The muxer does write 32 bits. But the demuxer 
treats the high 24 bits as padding and ignores it. In effect, ffmpeg 
will show    (stored-value % 256)

Mediainfo does the same, which would indicate that this is the iTunes 
spec. However, I find other sources which treat it as full 32-bits. Let 
me look into it. But it can't be a string.


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