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Old 15th April 2009, 05:58   #1  |  Link
videophool
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Join Date: Nov 2008
Posts: 91
Parsing h.264

I am working on an H.264 parser reader. I have some confusion with regards to SEI NAL Units. Table 7.3.2.3 in the spec says to loop while(more_rbsp_data()), I am finding some SEI NAL have extra bytes that I can not define in the spec. For example, I see an SEI type 0 with 9 bytes payloadSize. Immediately after the 9 bytes of data, there is a 0x40, and an SEI type 5. The 0x40 appears to be a delimiter, but I can not find any description in the spec,a nd so my parser misses the second SEI in the NAL. In another SEI in the stream, there is a type 1 with 7 bytes payloadSize. The payload data is followed by two additional bytes (0x25 0x10), and then 0x80.

There is always a 0x80 at the end of every SEI, which looks like a byte alignment value (10000000b). However, the spec does not seem to require this byte since the SEI was already byte aligned. But the 0x80 appears to be useful for parsing an SEI.

I don't want to implement my parser based on guesses from what I see in a stream. I must be missing some piece of information from the spec. Any SEI parding tips would be greatly appreciated. Thanks.
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