ID3v2 comment unsupported

[bitennui]

Summary of the bug: id3v2enc.c does not encode "comment" metadata using ID3v2 tag "COMM", it instead drops though and gets encoded using the "TXXX" catch-all. The metadata mapping table in id3v2.c needs to be updated with the "COMM" tag for the "comment" key; and id3v2_check_write_tag in id3v2enc.c should not expect valid tags to start with "T" since "COMM" is an obvious exception to that constraint.
How to reproduce:

% ffmpeg-i mp3_with_COMM_id3v2_tag.mp3 -f ffmetadata -c copy -map_metadata 0 -id3v2_version 3 -write_id3v1 1 incorrect_mp3_with_comment_mapped_to_TXXX_tag.mp3
ffmpeg version
built on ...

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

[bitennui]

Sorry, forgot to add the build info:
ffmpeg version N-49042-gcaabe1b495-static ​https://johnvansickle.com/ffmpeg/ Copyright (c) 2000-2019 the FFmpeg developers

built with gcc 6.3.0 (Debian 6.3.0-18+deb9u1) 20170516
configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-6 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
libavutil 56. 28.100 / 56. 28.100
libavcodec 58. 53.100 / 58. 53.100
libavformat 58. 27.103 / 58. 27.103
libavdevice 58. 7.100 / 58. 7.100
libavfilter 7. 55.100 / 7. 55.100
libswscale 5. 4.101 / 5. 4.101
libswresample 3. 4.100 / 3. 4.100
libpostproc 55. 4.100 / 55. 4.100

Hyper fast Audio and Video encoder
usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...

[Carl Eugen Hoyos]

Please test the command line you provided again and post it together with the complete, uncut console output to make this a valid ticket.

[bitennui]

I've closed the ticket as I've already repaired the defect locally and have no more time for back and forth nonsense. I pointed out the code areas involved, and the defect is glaringly obvious ... the pedantic response points out why the overall quality and coverage is low.