FFmpeg can't convert eia_608 subtitles: "Data Ignored since exceeding screen width"

Question

I'm trying to convert iTunes movies that were previously decrypted to an mkv file with FFmpeg for use with Kodi. I want to keep stereo audio and h264 video the same, which I can do. Subtitles I want to convert to some other format, like subrip. On some movies this works, namely ones with "mov_text" subtitles. However some iTunes movies have eia_608 subtitles which, when I try to convert them, throw this error:
[Closed caption Decoder @ 0000014b2b92eec0] Data Ignored since exceeding screen width
It continues to throw this error hundreds of times until it finishes.

Here's an example of the output. The eia_608 stream isn't the default subtitle format for this one, but you get the idea: https://pastebin.com/uerFwFna

Is there anything I can do to fix this? I've tried updating FFmpeg to the latest build, copying the subtitles format (Matroska is apparently incompatible with it), and extracting it to a separate .srt file results in garbled subtitles. What can I do to fix this?

Also, this warning message cuts off the progress text a bit which is funny. Idk why that's happening, lol.

Answer 1

It's a warning, not an error. The subs are still converted.

The EIA-608 standard specifies a maximum of 32 characters per line and the ffmpeg decoder is enforcing that.

A workaround is to use ccextractor to get a SRT file, and then proceed with that.