How can I make ffmpeg be quieter/less verbose?

ffmpeg -hide_banner -loglevel error

This is alluded to in a comment below the current answer.

The option -hide_banner was introduced in late 2013 -- https://lists.ffmpeg.org/pipermail/ffmpeg-devel/2013-December/152349.html )

-loglevel warning leads to more verbose output as it shows all warning messages

-loglevel panic is the least verbose output (omitting even error messages) but is undocumented.

I haven't tested it out, but I see an option in the man page to do:

ffmpeg -loglevel panic [rest of your ffmpeg stuff]

Should make it so only serious errors are logged, in theory

Here you have loglevels from the source code (FFmpeg version 0.10.2.git)

const struct { const char *name; int level; } log_levels[] = {
        { "quiet"  , AV_LOG_QUIET   },
        { "panic"  , AV_LOG_PANIC   },
        { "fatal"  , AV_LOG_FATAL   },
        { "error"  , AV_LOG_ERROR   },
        { "warning", AV_LOG_WARNING },
        { "info"   , AV_LOG_INFO    },
        { "verbose", AV_LOG_VERBOSE },
        { "debug"  , AV_LOG_DEBUG   },
    };