I am trying to extract and parse KLV data from a video stream. I found the following example in a Github repository. I am wondering what does the mapping option data-re do?
$ ffmpeg -i Day\ Flight.mpg -map data-re -codec copy -f data -
I understand the rest of the command, and know that -map is used to choose streams from inputs. But what does data-re mean. I couldn't find any explanation for it (or similar mapping option or stream identifier) in the documentation, e.g. here and here.
It's a typo and incorrect. The only time you use arbitrary label names is when using -filter_complex.
Use:
$ ffmpeg -i Day\ Flight.mpg -map 0:d -c copy -f data -
I could understand a user trying data, but data-re? Might be a double typo for -map data -re, where -re is intended to be the "Read input at native frame rate" input option (-map data is still invalid in this case).
It's not a valid value currently. It could possibly have been a value historically, but I doubt it. Most likely, it "worked" because the map arg parser would ignore additional letters if a lazy evaluation matched a stream and the d in data-re would match data streams. The parser is no longer that clumsy.