Metadata should be added after container conversion

[fstirlitz]

$ youtube-dl -f worst b4NDjo3CuvU --recode-video mkv --add-metadata -o 'B.%(ext)s'
[youtube] b4NDjo3CuvU: Downloading webpage
[youtube] b4NDjo3CuvU: Extracting video information
[youtube] b4NDjo3CuvU: Downloading DASH manifest
[download] Destination: B.3gp
[download] 100% of 873.60KiB in 00:03
[ffmpeg] Adding metadata to 'B.3gp'
[ffmpeg] Converting video from 3gp to mkv, Destination: B.mkv
Deleting original file B.3gp (pass -k to keep)
$ ffprobe B.mkv 
[…]
Input #0, matroska,webm, from 'B.mkv':
  Metadata:
    COMPATIBLE_BRANDS: isomiso23gp4
    MAJOR_BRAND     : 3gp4
    MINOR_VERSION   : 512
    ENCODER         : Lavf56.31.100
  Duration: 00:02:58.12, start: 0.155000, bitrate: 43 kb/s
    Stream #0:0(und): Video: h264 (High), yuv420p, 176x144 [SAR 1:1 DAR 11:9], 12 fps, 12 tbr, 1k tbn, 24 tbc (default)
    Metadata:
      LANGUAGE        : und
      HANDLER_NAME    : VideoHandler
      ENCODER         : Lavc56.35.101 libx264
    Stream #0:1(eng): Audio: vorbis, 22050 Hz, mono, fltp (default)
    Metadata:
      LANGUAGE        : eng
      HANDLER_NAME    : SoundHandler
      ENCODER         : Lavc56.35.101 libvorbis 

Because ffmpeg cannot add metadata to the 3gp file, no metadata ends up in the resulting mkv file. Metadata should be added after the video is converted.

On a related note, there seems to be no option to put video in a different container without re-encoding it (i.e. -c copy).

[jaimeMF]

The reason why we add it first is that (If I recall correctly) ffmpeg copies the metadata, which can be useful if you use --keep-video.

On a related note, there seems to be no option to put video in a different container without re-encoding it (i.e. -c copy).

Open a new issue, handling multiple things in a single report is hard and they tend to be forgotten.

[Spenhouet]

A fix is still needed: #11116

[yan12125]

As the original reporter said:

Because ffmpeg cannot add metadata to the 3gp file

This applies to webm as well, which does not define "metadata" in the container officially. @jaimeMF mind a change?

[jaimeMF]

@jaimeMF mind a change?

I personally don't mind, should we just change the order of the postprocessors or run it twice?

[yan12125]

should we just change the order of the postprocessors or run it twice?

I guess moving FFmpegMetadataPP to just before XAttrMetadataPP should work fine. By intuition, only the final file needs metadata, and if the final format does not support metadata, users have to change it.

[jaimeMF]

I guess moving FFmpegMetadataPP to just before XAttrMetadataPP should work fine. By intuition, only the final file needs metadata, and if the final format does not support metadata, users have to change it.

It seems reasonable, it's fine for me.

[yan12125]

Sorry for being late. This will be fixed in the next version.