Function open_input 

pub fn open_input(
    url: &CStr,
    formats: &CStr,
) -> Result<DemuxInput, OpenInputError>

Opens url and reads its stream information with only the demuxers named in formats (comma-separated FFmpeg short names) and only the file protocol, for the input and anything it opens in turn.

A still image opens with its own demuxer, chosen by its signature, when formats names it. FFmpeg otherwise picks from the file’s name as well as its first bytes, and stops reading bytes once a demuxer is fairly sure: the image2 demuxer, for numbered image files, claims any file named like an image on its name alone, above the JPEG demuxer, which is sure of a JPEG only once it has seen the whole picture. A JPEG larger than the first probe was image2 input, which formats leaves out.

Errors

OpenInputError::Refused for a container formats leaves out, else the FFmpeg failure.