[Libav-user] ffmpeg and JM I_Frame nonconformity

[amir.rouhi at rmit.edu.au]

Oh, Thanks Alex, In the FFMPEG DOCUMENTATION says the format of usage
should be:
‘-force_key_frames[:stream_specifier] time[,time...] (*output,per-stream*)
so for example i should write:
  ffmpeg -f image2 -r 0.1 -i C:\test%1d.bmp -an -vcodec libx264 -threads 0
 -f  h264 -r 0.5 -force_key_frames time[0,5,10,15,20] -s 360x240
C:\5frameTest.264
Is that correct?
BTW, if the time stamps are long , i.e every 5 second from start of the
video, is there any other simplified form to use in time stamp?
and would you please let me know whats the difference of  -force_key_frames
time  and -g ?

Thanks
Amir

On 24 May 2012 16:24, Alex Cohn <alexcohn at netvision.net.il> wrote:

> On Thu, May 24, 2012 at 4:28 AM,  <amir.rouhi at rmit.edu.au> wrote:
> > I use the below command for making video out of 5 different bmp images:
> >
> > ffmpeg -f image2 -r 0.1 -i C:\test%1d.bmp -an -vcodec libx264 -threads 0
>  -f
> > h264 -r 0.5 -force_key_frames 0.1 -s 360x240 C:\5frameTest.264
>
> -force_key_frames expects a comma separated list of timestamps, not a
> "step" or something
>
> BR,
> Alex
>
> > I used  -force_key_frames  instead if -g to inforce the ffmpeg to
> generate
> > i-frames. BTW with -g i did not get even the correct video.
> > The generated video shows the images but not in same interval distance
> but
> > shows all 5 images in the video.
> >
> > then i use JM decoder and tried to get the frames with s-type=2 nad the
> > result was just 3 , not 5.
> > Question is why 5 i-frame in ffmpeg can not be detected in JM?
> >
> > On 22 May 2012 20:02, Alex Cohn <alexcohn at netvision.net.il> wrote:
> >>
> >> On Tue, May 22, 2012 at 11:47 AM,  <amir.rouhi at rmit.edu.au> wrote:
> >> >
> >> > I have noticed that the I-Frames in a pure h264 video created by
> ffmpeg
> >> > is
> >> > not same as what JM detect as I-Frame in the same video.
> >> > In JM software s_type=2 means I_Frame. the number of s_types frames
> are
> >> > always lower than what ffmpeg shows.
> >> >  What is your advice?
> >> > Amir
> >>
> >> Would you like to upload an example?
> >>
> >> Alex
> > --
> > Amir H. Rouhi
> > PhD Student/ CSIT RMIT University
> > Room: 14-09-04
> > http://raws.adc.rmit.edu.au/~s3288736/blog2/
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-- 
Amir H. Rouhi
PhD Student/ CSIT RMIT University
Room: 14-09-04
http://raws.adc.rmit.edu.au/~s3288736/blog2/
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