You can find the latest builds of GPAC here: MP4Box.
Note: OS X users will find MP4Box under Osmo4.app/Contents/MacOS.
MP4Box supports a variety of command line options. Some important options include the following:
-v Indicates "verbose" mode, displaying more output within the console.
-inter Specifies the duration, in seconds, of the interleaved media data chunks.
-out Displays the output file name and path.
mp4box -v -inter 1000 [input-file] -out [output-file]
-tight Requires no value.
mp4box -v -tight [input-file] -out [output-file]
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