Feature Request: Support updating chapter names in M4B

[SenorSmartyPants]

Chapter metadata is stored in the M4B, not as separate files. If possible, (not sure if beets is capable of editing this metadata, perhaps @seanap would know ) it would be great to update chapter names with the names from audnexus if the chapter time marks are within a small margin of error.

Existing chapter (ffprobe output)

    Chapter #0:7: start 8412.031000, end 10245.433000
      Metadata:
        title           : 6

Audnexus chapter data

{
  lengthMs: 1833401,
  startOffsetMs: 8414167,
  startOffsetSec: 8414,
  title: "6. Loopholes"
},

Start time difference is 2136ms, length difference is 1ms
ffprobe length 10245433 - 8412031 = 1833402ms

Only update the titles, not the start times.

[SenorSmartyPants]

Ideally this could be run manually as well as optionally during import. Manually so the chapters could be compared with audnexus data on the off chance that existing M4B chapters are more detailed.

[Neurrone]

This would require a huge rearchitecting of how Beets works to support the concept of how m4b files can contain tracks (i.e, multiple tracks in one file). See beetbox/beets#4269 for details.

[SenorSmartyPants]

Understandable. Thanks for let me know.