# ffmpeg -f lavfi -i sine -t 10ms -write_id3v1 1 -metadata title=test -f mp3 pipe:1 | fq - '.footers[0]._bytes' > id3v1
$ fq -d id3v1 dv /id3v1
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.{}: /id3v1 (id3v1) 0x0-0x7f.7 (128)
0x00|54 41 47                                       |TAG             |  magic: "TAG" (valid) 0x0-0x2.7 (3)
0x00|         74 65 73 74 00 00 00 00 00 00 00 00 00|   test.........|  song_name: "test" 0x3-0x20.7 (30)
0x10|00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00|................|
0x20|00                                             |.               |
0x20|   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00| ...............|  artist: "" 0x21-0x3e.7 (30)
0x30|00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   |............... |
0x30|                                             00|               .|  album_name: "" 0x3f-0x5c.7 (30)
0x40|00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00|................|
0x50|00 00 00 00 00 00 00 00 00 00 00 00 00         |.............   |
0x50|                                       00 00 00|             ...|  year: "" 0x5d-0x60.7 (4)
0x60|00                                             |.               |
0x60|   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00| ...............|  comment: "" 0x61-0x7e.7 (30)
0x70|00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   |............... |
0x70|                                             ff|               .|  genre: 255 0x7f-0x7f.7 (1)