h.264 - What does this H264 NAL Header Mean?

Question

0000 0109 1000 0001 6742 0020 e900 800c
3200 0001 68ce 3c80 0000 0001 6588 801a

As far as I know, 0000 01 is the start prefix code to identify a NAL Unit. What does "09 .... " mean? Is it the header type byte?

Answer 1

0x000001 is the NAL start prefix code (it can also be 0x00000001, depends on the encoder implementation). 0x09 is 0b00001001, which means F=0, NRI = 0, and type is 0b01001. That particular type is an access unit delimiter. Notice that it is immediately followed by another NAL unit defined by 0x67, which is a NAL type of 7, which is the sequence parameter set.

There's also the picture parameter set:

00 0001 68...

...and the start of a keyframe:

0000 0001 65...