[Libav-user] How FFMPEg or x264 pars the I-Frames (IDR or non IDR)

Amir Rouhi-Rmit amir.rouhi at rmit.edu.au
Fri Apr 29 03:49:42 CEST 2011

Those who has worked deeply with FFMPEG should know the answer of my
question. My question is that :
how the software find I-Frame by parsing bit-stream of the input video. Can
the software( FFMPEG, X264) can differentiate IDR and non IDR I-Frames?
Probably yes, in that case what's the starting word bit stream of these two
type of I-Frames? Some people believe that IDR I-Frames starting bit stream
is 00 00 00 01 y in hex which (y=25, 45, 65). Are you agree with this?
According to H.264 standard chapter 7 and annex B, The three byte start code
bit-stream  00 00 01 is correct for starting VCL NAL units. But the one Byte
header which start with 0, the rest of 7 bits can not be 0 if the picture is
IDR. I confused, please somebody advise.

Amir H. Rouhi
PhD Student/ CSIT RMIT University
Room: 14-09-04
rouhi_amirhossein at student.rmit.edu.au
amir.rouhi at rmit.edu.au
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