Hello Keith
Thanks for your reply.
According to my code, there is no *"BREAK"* in the *"STATE_SLICE*" [which I
had to forgot to mention in my previous mail] and so it executes the *
"STATE_END*" loop which has the stop timer.
This can be referred as the Computation Time.
If I have any more doubts, I will keep you posted.
With regards
Krishna Prasad
On Fri, Feb 22, 2008 at 5:35 PM, Keith Winstein <[EMAIL PROTECTED]> wrote:
> Hi Krishna,
>
> That sounds plausible. Make sure you're running mpeg2dec with "-o null" so
> that none of your time is consumed with drawing (aka displaying) the
> frame.
>
> It's hard to know for sure without seeing the code, but if the output is
> plausible and if adding up all the individual times is close to the
> total CPU time of mpeg2dec (measured with "time" or something) and if
> you're not wasting cycles on displaying the frames, then it's probably
> right.
>
> A more elegant approach might be to always start the new timer at the same
> place you stop the old timer. That way, you can be sure nothing is falling
> through the cracks.
>
> Note that STATE_PICTURE is for when libmpeg2 is *finished* decoding the
> Picture header and the Picture coding extension. I think STATE_SLICE is
> for when libmpeg2 is *finished* decoding the Slice, including all the
> macroblocks. (For most streams in real life, this means finished decoding
> the picture.) STATE_END is only for the end of an MPEG-2 sequence --
> you're probably not getting STATE_END ever.
>
> So a simpler approach might just be to always start the timer (and stop
> the previous timer) in STATE_SLICE. Again, make sure you're not trying to
> display the frames as well.
>
> Also, best not to call this the "decoding time" -- that's another thing in
> MPEG-2 that's totally different. Howabout "computation time"?
>
> Best,
> Keith
>
> On Fri, 22 Feb 2008, Krishna Prasad wrote:
>
> > Hi Keith
> >
> > This is in reference to the previous mails which I had send it you
> asking
> > for the decoding time.
> >
> > The problem was with the code [on the subtraction betwen the stop and
> start
> > time between the pictures] as you said. I have
> > removed the errror and I wanted to ensure, whether the following steps
> in
> > the below is the procedure to calculate the decoding time?
> >
> > In the function "void decode_mpeg2", in the *CASE STATE_PICTURE*, I
> start a
> > timer (t1) and end the timer(t2) in the *CASE STATE_SLICE. *I calculate
> the
> > difference in both the timers [t2-t1 = diff] which I suppose is the
> decoding
> > time for picture1.
> >
> > For picture 2, in the *CASE STATE_END,* I find the difference in the
> ending
> > time of picture2 along with the timer t1 and subtract it with the
> previous
> > difference [diff] to calculate the decoding time required for frame2.
> >
> > All the time values are positive here.
> >
> > This is how I am calculating the decoding times for all the frames in
> the
> > GOP and I think it works efficiently for closed GOPs.
> >
> > I am thankful to you for the replies you have given to me from time to
> time
> > which was quite useful.
> >
> > If there any more doubts, I will keep you posted.
> >
> > I request you to give me a feedback for the same.
> >
> > With regards
> > KrishnaPrasad
> >
>
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