On Wednesday 15 March 2006 23:08, Ola Theander wrote:
> Hi Hans
>
> I guess you've heard it before, but I must say that I am so impressed
> how much work you put into answering peoples questions, not to speak
> about the work you put into the driver. Now that it's said, to my
> actual reply.
>
> To be honest, I have no idea what differences there was when I tried
> it on the Windows platform, but as you say, an mpeg-transformation is
> certainly not done in an instant so it might be that it defaulted to
> the raw YUV or maybe removed the number of B-frames. I've talked to
> Hauppauge before buying the card and asked them about the latency,
> since it so important for my application, and they said that on
> Windows there should be a registry setting that circumvented the mpeg
> encoding, it might be so that it was set to that by default since I
> basically just installed the drivers and tried it with the bundled
> sample program.
>
> Anyway, I'll try the B frame setting, but do you perhaps know how I
> can use the raw YUV input instead of mpeg as you suggest below? I
> noticed that ivtv has some switches concerning YUV but it seems to
> have to do with interlacing.
/dev/video32 produces a non-standard YUV format (the raw PCM audio
arrives at /dev/video24, note that the audio is about 2 frames behind
the video if I remember correctly). You can play the YUV with mplayer
(search the mailinglist archives for the correct command invocation).
I can also mail you a simple prog to convert the ivtv YUV format into
something more standardized.
Basically you just read a full frame at a time from /dev/video32.
Hans
>
> Kind regards, Ola
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Hans Verkuil
> Sent: den 15 mars 2006 22:53
> To: User discussion about IVTV
> Subject: Re: [ivtv-users] How to lower the latency (delay) on
> compositevideo when capturing (PVR 150)?
>
> The latency messages you see are totally unrelated.
> One option is to use the raw YUV input instead of the MPEG input.
> That's near instantaneous (I think).
>
> I can't think how they would make mpeg encoding instantaneous in
> windows since mpeg encoding relies on a history. Perhaps you can play
> with the number of B frames (ivtvctl -c bframes=0) so no history is
> needed. If the firmware is really smart, then it might have a lower
> latency.
>
> Hans
>
> On Wednesday 15 March 2006 22:00, Ola Theander wrote:
> > Dear subscribers
> >
> > I'm right now trying out the Hauppauge PVR 150 card for use in a
> > project where I need to capture composite video basically in real
> > time. The video signal is received by the computer from a manually
> > operated camera. The camera is mounted on a long cable which the
> > computer operator guides in narrow pipes by the view on the
> > computer screen. To make the operation as easy as possible for the
> > operator I want as short delay as possible between actually moving
> > the camera and until the movement is reflected on the computer
> > screen.
> >
> > I realize that this isn't important if you e.g. capture a video
> > from an analogue video camera since the delay when the video stream
> > passes through the hardware/software until it's stored on the hard
> > disk isn't noticeable when you later playback the video.
> >
> > I know that the Hauppauge card is capable of virtually no latency
> > since I started out by trying it using Windows and on Windows the
> > screen update when moving the camera was more or less
> > instantaneous, at least the delay wasn't noticeable.
> >
> > The basic tests I've performed I just did "mplayer /dev/video0" and
> > moved the camera. The delay seems to be in the order of 0.5 - 1.0
> > seconds before the picture is updated. If I look in the output of
> > dmesg I notice one line stating "ivtv0: Unreasonably low latency
> > timer, setting to 64 (was 32)" and I wonder if that might have
> > something to do with this?
> >
> > Eventually I'll use GStreamer instead and I know that the latency
> > in the 0.8 code branch is much worse that it is in the latter 0.9
> > and 0.10. I've tried my solution with GStreamer 0.10 and an
> > external composite 2 firewire-dv converter so I know that it's
> > possible to have quite a low delay. Now I just hope that I can do
> > the same using the PVR 150.
> >
> > Any help on this matter would be greatly appreciated.
> >
> > Kind regards, Ola Theander
> >
> >
> > _______________________________________________
> > ivtv-users mailing list
> > [email protected]
> > http://ivtvdriver.org/mailman/listinfo/ivtv-users
>
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