Make error message more helpful when RTSP stream is used without RTSP support about motion HOT 2 OPEN

What if motion is built with rtsp support, but the stream URL is malformed?

from motion.

I can see four possible situations:

1. There is RTSP support and the URI is correct.
2. There is RTSP support and the URI is malformed.
3. RTSP support is missing and the URI is correct and doesn't start by rtsp://.
4. RTSP support is missing and the URI is correct and starts with rtsp://.
5. RTSP support is missing and the URI is malformed.

Currently, the cases 2, 4 and 5 produce all the same “Invalid netcam_url” error. Especially at the level of regular expressions, as currently implemented, there is no way to differentiate the case 4 and 5.

What I suggest is only to make an additional check for the prefix only in the situation where regular expressions fail and the support for RTSP is missing, thus differentiating the case 4 from the case 5. Regular expressions remain unchanged.

I imagine that instead of:

if (!url.host) {
    MOTION_LOG(CRT, TYPE_NETCAM, NO_ERRNO, "%s: Invalid netcam_url (%s)", 
               cnt->conf.netcam_url);
    netcam_url_free(&url);
    return -1;
}

the changed code will look like this (I haven't written C for the last ten years, so I have no idea about the exact syntax; otherwise I would have forked the project to do the change myself):

if (!url.host) {
    char[] error_pattern = "%s: Invalid netcam_url (%s)";
    #ifndef have_av_get_media_type_string
    // RTSP support is missing.
    if (strncmp("rtsp://", tolower(cnt->conf.netcam_url)) == 0) {
        error_pattern = "%s: Invalid netcam_url (%s). RTSP is not supported by the current build; consider compiling the application with have_av_get_media_type_string option.";
    }
    #ifndef
    MOTION_LOG(CRT, TYPE_NETCAM, NO_ERRNO, error_pattern, 
               cnt->conf.netcam_url);
    netcam_url_free(&url);
    return -1;
}

So:

What if motion is built with rtsp support, but the stream URL is malformed?

This situation is not concerned: only the case where RTSP support is missing is.

from motion.