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. 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 _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
