FFmpeg av_guess_format returns NULL

Question

I'm following the example code here: http://cekirdek.pardus.org.tr/~ismail/ffmpeg-docs/output-example_8c-source.html

My code is as follows:

fmt = av_guess_format(NULL, filename, NULL);
if (!fmt) {
        LOGE(1,"Could not deduce output format from file extension: using MPEG.\n");
        fmt = av_guess_format("mp4", NULL, NULL);
}
    if (!fmt) {
        LOGE(1, "Could not find suitable output format\n");
        exit(1);
}

The two times that I call av_guess_format, it is returning NULL both times. I am calling both av_register_all() and avcodec_register_all() beforehand.

Any ideas as to why this is returning NULL?

Thanks in advance.

Answer 1

av_guess_format was returning NULL because I hadn't properly configured FFMPEG to allow for ANY formats.

I re-configured FFMPEG to allow mp4 and others, and now it works

Answer 2

You need to recompile ffmpeg.make sure "--enable-muxer=mp4" was in configure's argument.after configure open config.h with editor,you will see "#define CONFIG_MP4_MUXER 1"