Fails when converting mp3-m4b or m4a

[mammothguns]

I have been attempting to convert some mp3 audiobooks into m4b format but keep getting a failed.

2025-06-04 22:24:52.753652+00:00Stream mapping:
2025-06-04 22:24:52.753678+00:00Stream #0:1 -> #0:0 (mjpeg (native) -> h264 (libx264))
2025-06-04 22:24:52.753704+00:00Stream #0:0 -> #0:1 (mp3 (mp3float) -> aac (native))
2025-06-04 22:24:52.753729+00:00Press [q] to stop, [?] for help
2025-06-04 22:24:52.753768+00:00[libx264 @ 0x1491e0673840] height not divisible by 2 (402x605)
2025-06-04 22:24:52.753793+00:00[vost#0:0/libx264 @ 0x1491e27d6b40] Error while opening encoder - maybe incorrect parameters such as bit_rate, rate, width or height.
2025-06-04 22:24:52.753819+00:00Error while filtering: Generic error in an external library
2025-06-04 22:24:52.753848+00:00[out#0/ipod @ 0x1491de1996c0] Nothing was written into output file, because at least one of its streams received no packets.
2025-06-04 22:24:52.753885+00:00frame= 0 fps=0.0 q=0.0 Lsize= 0kB time=N/A bitrate=N/A speed=N/A
2025-06-04 22:24:52.753912+00:00Conversion failed!

any idea on why

thanks

[C4illin]

it seems like it is trying to encode the jpeg cover art as h264 video. It should work if we add -vcodec copy when converting to m4a