Re: [ANNOUNCE] Videobuf improvements to allow its usage with USB drivers

["H. Willstrand" <h.willstrand@gmail.com>]

On Sun, Apr 13, 2008 at 10:34 PM, Markus Rechberger
<mrechberger@empiatech.com> wrote:
>
>  --- Mauro Carvalho Chehab <mchehab@infradead.org>
>  schrieb:
>
>
>
> > On Sun, 13 Apr 2008 18:17:54 +0200 (CEST)
>  > Markus Rechberger <mrechberger@empiatech.com> wrote:
>  >
>  > > >        Conclusion:
>  > >
>  > > > The time consumption to receive the stream where
>  > reduced from about 33.38 seconds to 0.05 seconds
>  > >
>  > > the question is moreover what made capture_example
>  > go
>  > > up to 100% CPU in the first try and to 0% in the
>  > > second one.
>  > > I'm not sure about the old implementation in the
>  > > original driver, although I'm just curious about
>  > the
>  > > details here. xawtv usually uses very little
>  > cputime
>  > > at all.
>  > > If I use
>  > > "$ time mplayer tv:// -tv driver=v4l2" it shows up
>  >
>  > >
>  > > real 0m40.972s
>  > > user 0m0.230s
>  > > sys  0m0.050s
>  > >
>  > > your benchmark is a bit unclear.
>  >
>  > The advantage of using capture_example for benchmark
>  > tests is that it is a very
>  > simple mmap loop, without multi-thread, and just
>  > discarding the return. With
>  > this, you're timing just the minimal requirements
>  > for receiving frames.
>  >
>  > A TV application will also need to use the video
>  > adapter to present images, and
>  > may do some other tasks, like running DSP algorithms
>  > for de-interlacing. It may
>  > also discard frames, if there's not enough CPU to
>  > work will all of them. So,
>  > you will never know how much of those times are due
>  > to V4L kernelspace part.
>  >
>  > On the tests I did here with TV applications, the
>  > amount of performance,
>  > reported by "top" also indicated that the previous
>  > approach were worse.
>  >
>  > For example, on the same centino machine @1.5 GHZ,
>  > mplayer with "-tv driver=v4l2"
>  > were ranging from 30% to 75% of CPU. With videobuf,
>  > the CPU consumption were
>  > close to 23%, without much variation.
>  >
>
>  my eeePC shows up 0-5% CPU usage with mplayer
>  fullscreen without videobuf, seems more like
>  something's broken in your testapplication or
>  somewhere else?
>

Using the em28xx?
My is about 40-70% CPU...

Br H.Willstrand

>  mplayer uses the memory mapped interface for this.
>
>  Also the command
>  "$ mplayer -benchmark tv:// -tv driver=v4l2"
>
>  CPU Intel 620 Mhz
>
>  Markus
>
>
>
>  --
>  video4linux-list mailing list
>  Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe
>  https://www.redhat.com/mailman/listinfo/video4linux-list
>

--
video4linux-list mailing list
Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe
https://www.redhat.com/mailman/listinfo/video4linux-list