I have successfully extracted the I P B frames from a video. But how to preserve the frame number of the I P B frames. Suppose I have the following GOP ..IPPPBPPP ... here frame one is I. frame....second, third and fourth are P fifth is a B frame and sixth seventh and eighth are once again P..... while extracting how can we name the frames as 1I.jpg, 2P.jpg, 3P.jpg, and so on....so that after encrypting the I frames Iit should be possible place them back at the same position....
M S Rohit B.E, M.Tech, Assistant Professor, Dept of Computer Science & Engineering, Jain Institute of Technology, Davanagere. 9663861707 On Mon, Jan 5, 2015 at 3:55 PM, Moritz Barsnick <[email protected]> wrote: > Hi Rohit, > > On Sun, Jan 04, 2015 at 23:46:26 -0800, Rohit wrote: > > ffmpeg -i delta.mpg -vf select="eq(pict_type\,PICT_TYPE_I)" -s 400x300 > -f image2 frame.mpg-%03d.tif > > You should always show us the complete, uncut output of your command. > > > which should extract all the I frames(as per -vf > > select="eq(pict_type\,PICT_TYPE_I)" ) in the input file. But I got 197 > > frames instead of 17 from this command and it looked like command has > just > > shown me all the frames. > > There's a Wiki entry covering this: > > https://trac.ffmpeg.org/wiki/Create%20a%20thumbnail%20image%20every%20X%20seconds%20of%20the%20video > > And though it doesn't explain why, it does hint that you need to use: > -vsync vfr > > This works for me. > > I believe the image2 muxer automatically assumes the same frame rate as > the input (i.e. automatically chooses "-vsync cfr"). Since you are > dropping all none-I-frames, it interpolates the missing frames to > produce the correct rate. BTW, I get less frames than the (my) source > video, because the muxers stops creating output at the last input > I-frame. > > Another BTW: The value PICT_TYPE_I, which is also used in the Wiki > entry, does not correspond to the documentation which says: > > > ‘pict_type (video only)’ > > > > The type of the filtered frame. It can assume one of the following > values: > > > > ‘I’ > > ‘P’ > > ‘B’ > > ‘S’ > > ‘SI’ > > ‘SP’ > > ‘BI’ > > But the source (libavfilter/f_select.c) tells me that the prefix > PICT_TYPE_ is also accepted. > > Moritz > _______________________________________________ > ffmpeg-user mailing list > [email protected] > http://ffmpeg.org/mailman/listinfo/ffmpeg-user > _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user
