Where can I find 'mdat' spec of f4f?

Hi,

I create f4f file with f4fpackager, only h264 video, no audio. When I parse f4f file, first mdat atom has format:

...6D 64 61 74 00 00 00 00 00 07 18 EF 09 00 00 20 00 00 00 00 00 00 00 17 00 00 00 00 01 4D...

that means:

... mdat 00 00 00 00 00 07 18 EF 09 00 00 20 00 00 00 00 00 00 00 17 00 00 00 00 and here h264 info begins (sps, pps, data), i.e. information from mdat atom from f4v file, avcC atom...

So my question: what these mdat bytes mean -

00 00 00 00 00 07 18 EF 09 00 00 20 00 00 00 00 00 00 00 17 00 00 00 00

?

They are absent in f4v mdat atom but present in f4f mdat. I think that it is info about chunks, but where can I find scpecification of these bytes?

Thanks.