[ISSUE] Wrong MIME with Youtube-dl / ffmpeg -acodec copy on .m4a .mp4a files

[ISSUE] Wrong MIME with Youtube-dl / ffmpeg -acodec copy on .m4a .mp4a files

[Bumbadawg]

[-- Attachment #1: Type: text/plain, Size: 1030 bytes --]

New issue by Bumbadawg on void-packages repository

https://github.com/void-linux/void-packages/issues/30486

Description:
<!-- Don't request update of package. We have a script for that. https://alpha.de.repo.voidlinux.org/void-updates/void-updates.txt . However, a quality pull request may help. -->
### System

* xuname:  
  *Void 5.11.16_1 x86_64 GenuineIntel notuptodate rrrrmmnFFFF*
* package:  
  * youtube-dl-2021.04.17_1
  * ffmpeg-4.3.2_1

### Expected behavior
`xdg-mime query filetype audio.m4a` should output `audio/mp4`
NB: it works with the same package versions on Arch.

### Actual behavior
`xdg-mime query filetype audio.m4a` should output `video/mp4`

when reusing ffmpeg afterwards to try to fix the MIME, this is what i get 
`ffmpeg -i in.m4a -acodec copy out.m4a`
`xdg-mime query filetype audio.m4a` => `audio/x-m4a`

`grep m4a /etc/mime.types` => `audio/mpeg     m2a m3a m4a mp2 mp2a mp3 mpega mpga`

### Steps to reproduce the behavior
`youtube-dl -x --audio-format best [YTlink]`

Re: Wrong MIME with Youtube-dl / ffmpeg -acodec copy on .m4a .mp4a files

[Bumbadawg]

[-- Attachment #1: Type: text/plain, Size: 2383 bytes --]

New comment by Bumbadawg on void-packages repository

https://github.com/void-linux/void-packages/issues/30486#issuecomment-826299964

Comment:
example

```
> youtube-dl -xvvv "`xsel -b`"
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-xvvv', 'https://www.youtube.com/watch?v=X9uk9IcoQ0w']
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, pref UTF-8
[debug] youtube-dl version 2021.04.17
[debug] Python version 3.9.4 (CPython) - Linux-5.11.16_1-x86_64-with-glibc2.32
[debug] exe versions: ffmpeg 4.3.2, ffprobe 4.3.2, rtmpdump 2.4
[debug] Proxy map: {}
[youtube] X9uk9IcoQ0w: Downloading webpage
[debug] Invoking downloader on 'https://r1---sn-cv0tb0xn-gonl.googlevideo.com/videoplayback?expire=1619367974&ei=xkOFYISgD9HHWq2mtdgJ&ip=176.143.127.88&id=o-AIA_SGBH80v6x_P58sFu8sfzeeP3y9wgqIVioUwIhZJV&itag=140&source=youtube&requiressl=yes&mh=BZ&mm=31%2C29&mn=sn-cv0tb0xn-gonl%2Csn-25ge7nsk&ms=au%2Crdu&mv=m&mvi=1&pcm2cms=yes&pl=18&gcr=fr&initcwndbps=1016250&vprv=1&mime=audio%2Fmp4&ns=t46mhipsPJBeWemq3S8eEJoF&gir=yes&clen=4460950&dur=275.597&lmt=1576471049434363&mt=1619346038&fvip=1&keepalive=yes&fexp=24001373%2C24007246&c=WEB&txp=5531432&n=aolcXAKgf_g6J-HPww&sparams=expire%2Cei%2Cip%2Cid%2Citag%2Csource%2Crequiressl%2Cgcr%2Cvprv%2Cmime%2Cns%2Cgir%2Cclen%2Cdur%2Clmt&lsparams=mh%2Cmm%2Cmn%2Cms%2Cmv%2Cmvi%2Cpcm2cms%2Cpl%2Cinitcwndbps&lsig=AG3C_xAwRQIhAI-wkcgjiSXshCNjW4RanYbuob0-DoZU5pdpvkhCwFDtAiB6ZKvclV75zLhAn0udS57O6szL0siOKyUwOu5GCBJYvQ%3D%3D&sig=AOq0QJ8wRQIhALdoCTIjnIUSBfAopMblmKf5cGfslZ4yksOLL5WzQ_wNAiBA3SkqkPeemUyxRrCiucEHT0y-VjOXYstPjfw5NRcbZw=='
[download] Destination: Primus - The Devil Went Down To Georgia-X9uk9IcoQ0w.m4a
[download] 100% of 4.25MiB in 00:00
[ffmpeg] Correcting container in "Primus - The Devil Went Down To Georgia-X9uk9IcoQ0w.m4a"
[debug] ffmpeg command line: ffmpeg -y -loglevel repeat+info -i 'file:Primus - The Devil Went Down To Georgia-X9uk9IcoQ0w.m4a' -c copy -f mp4 'file:Primus - The Devil Went Down To Georgia-X9uk9IcoQ0w.temp.m4a'
[debug] ffmpeg command line: ffprobe -show_streams 'file:Primus - The Devil Went Down To Georgia-X9uk9IcoQ0w.m4a'
[ffmpeg] Post-process file Primus - The Devil Went Down To Georgia-X9uk9IcoQ0w.m4a exists, skipping

> xdg-mime query filetype Primus\ -\ The\ Devil\ Went\ Down\ To\ Georgia-X9uk9IcoQ0w.m4a
video/mp4
```

Re: Wrong MIME with Youtube-dl / ffmpeg -acodec copy on .m4a .mp4a files

[Duncaen]

[-- Attachment #1: Type: text/plain, Size: 382 bytes --]

New comment by Duncaen on void-packages repository

https://github.com/void-linux/void-packages/issues/30486#issuecomment-826330127

Comment:
Looks like its either using `mimetype` or `file`, `file` will say `video/m4a` and `mimetype` from `perl-File-MimeInfo` will print `audio/m4a`.

In pacman `perl-File-MimeInfo` is an optional dependency, so you probably had this installed.

Re: Wrong MIME with Youtube-dl / ffmpeg -acodec copy on .m4a .mp4a files

[Bumbadawg]

[-- Attachment #1: Type: text/plain, Size: 203 bytes --]

New comment by Bumbadawg on void-packages repository

https://github.com/void-linux/void-packages/issues/30486#issuecomment-826389125

Comment:
installing perl-File-MimeInfo solved it, thanks @Duncaen !

Re: [ISSUE] [CLOSED] Wrong MIME with Youtube-dl / ffmpeg -acodec copy on .m4a .mp4a files

[Bumbadawg]

[-- Attachment #1: Type: text/plain, Size: 1033 bytes --]

Closed issue by Bumbadawg on void-packages repository

https://github.com/void-linux/void-packages/issues/30486

Description:
<!-- Don't request update of package. We have a script for that. https://alpha.de.repo.voidlinux.org/void-updates/void-updates.txt . However, a quality pull request may help. -->
### System

* xuname:  
  *Void 5.11.16_1 x86_64 GenuineIntel notuptodate rrrrmmnFFFF*
* package:  
  * youtube-dl-2021.04.17_1
  * ffmpeg-4.3.2_1

### Expected behavior
`xdg-mime query filetype audio.m4a` should output `audio/mp4`
NB: it works with the same package versions on Arch.

### Actual behavior
`xdg-mime query filetype audio.m4a` should output `video/mp4`

when reusing ffmpeg afterwards to try to fix the MIME, this is what i get 
`ffmpeg -i in.m4a -acodec copy out.m4a`
`xdg-mime query filetype audio.m4a` => `audio/x-m4a`

`grep m4a /etc/mime.types` => `audio/mpeg     m2a m3a m4a mp2 mp2a mp3 mpega mpga`

### Steps to reproduce the behavior
`youtube-dl -x --audio-format best [YTlink]`