[Mp4-tech] H.264: NumBytesInNALUnit and start-code-emulation-prevention

[Shankar Moni]

This is a question on NumBytesInNALUnit and
start-code-emulation-prevention.
The written spec (JVT-J050.doc) expects an argument (NumBytesInNALUnit)
to be provided to the byte_stream_nal_unit( ) function. However, the
reference software computes this number by looking for the next start
code (0x000001).
Is it possible for the bitstream to generate this sequence of bits
within the residual_block_cavlc( ) function? For example, if the encoder
puts 
	- level_prefix = 15                                   (puts a
code 0000 0000 0000 0001) 
	- level_suffix = 512, levelSuffixLength=12  ( puts a code 0001
0000 0000 )
	- level_prefix = 15                                   (puts a
code 0000 0000 0000 0001) 
the last two lines could emulate a start code, unless there is a
mechanism to prevent it. 
I'd appreciate some insight into this issue. If it has already been
discussed, I'd appreciate a pointer to the discussion.
Thanks,
--Shankar.
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