Hi Would you explain more clearly? As far as i know in VCL NAL units we have a 3 byte start code prefix which startwith 0x00 00 01. after that we have a byte which the first most significant bit (the most left bit) should be zero, the next two bits are nal_ref_idc which for I-Frames should not be zero, and the last 5 bit which are called nal_unit_type, they can be a number from 1 to 32. for frames they can be 1 to 5. ant it seems for i-frames the value of these 5 bit should be 5 according to standard. I would be pleased if you explain more about the values of 2,4,7,9 which u believe are i-frame codes..
On Sat, Apr 30, 2011 at 3:25 PM, Jaroslav Korchevsky <[email protected]> wrote: > > > In VCL videoslice header there is a Variable Length coded field SliceType. > Types 2,4,7,9 - correspond to I-frames > > Fri, 29 Apr 2011 11:49:42 +1000 письмо от Amir Rouhi-Rmit < > [email protected]>: > > 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 > [email protected]<http://sentmsg?compose&[email protected]> > [email protected] <http://sentmsg?compose&[email protected]> > > > _______________________________________________ > Libav-user mailing list > [email protected] <http://sentmsg?compose&To=libav%[email protected]> > http://ffmpeg.org/mailman/listinfo/libav-user > > > > _______________________________________________ > Libav-user mailing list > [email protected] > http://ffmpeg.org/mailman/listinfo/libav-user > > -- Amir H. Rouhi PhD Student/ CSIT RMIT University Room: 14-09-04 [email protected] [email protected]
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