What do you mean by url protocol ?
The pseudo class (a C struct with function pointers) handling input from different url types (pipe:, file:, http:...). url_open() selects one of them based on the url. See libavformat/avio.h
Does adding my own url protocol implies modifying the source code of libav(codec/format) or is it possible to do without touching it (so people with the libavcodec library can use my program without altering their library) ?
No you can avio.h:register_protocol(), or just fake an open (open "/dev/null") and override the url field in the cookie to your own protocol, as I did.
Btw, did you find some documentation to add your own url protocol ? There's not much documentation on libavcodec I could find...
And finally, yes, I am very interested in your code, and I appreciate your help very much.
See attached files, part of some unreleased dead project. Sent them on the list in case other ppl are interested, for archival. Fran?ois.