Re: When is 60Hz not really 60Hz?

New Message Reply Date view Thread view Subject view Author view

Angus Dorbie (dorbie++at++multipass.asd.sgi.com)
Fri, 13 Jun 1997 15:39:32 -0700

Then you should genlock the video to a 60Hz source driven by the simulator
or sync the host to the video, those are your choices. You could dead
reckon over fractional frames, but almost every other way is easier.

This difference will be due to the VOF you have.

Cheers,Angus.

On Jun 13, 4:02pm, Troy Stephen wrote:
> Subject: When is 60Hz not really 60Hz?
>
> Hi all,
>
> I think this subject has been discussed in the past but I can't seem to
> find the mailings in the archives.
>
> We have a 3 Pipe Onyx RE2 with the pipes genlocked, and we are finding
> that the video refresh rate is dependent on the resolution of the screen:
>
> at 1280x1024 the video refresh is 59.998Hz
>
> at 960x680 the video refresh is 60.833Hz. <--this is the one we are using
>
> The hardware guys assure me that this is perfectly resonable, and I'm not
> suggesting that there is anything wrong with our hardware.
>
> The problem is, our Host Simulation program is running on another machine
> and maintaining a pretty firm 30.0Hz and the IG is doing ~30.4Hz.
> Unfortunately the Host and IG are communicating asynchronously and so the
> IG draws an extra frame using stale ownship position data every 2.5
> seconds and as a result we get a slight jitter.
>
> Does anybody have any suggestions for me to get around this? We have
> thought about syncing the Host off the IG but that is going to cause
> problems in other systems due to the curious frame rate that the Host
> would have to run at.
>
> What would be ideal is a vme card in the Host machine which generates a
> 60.0Hz genlock signal to the IG machine and an interrupt to the Host, so
> that our frames can be perfectly alligned.
>
>
> Cheers,
>
> Troy
>
>
>
>
> =======================================================================
> List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
> Submissions: info-performer++at++sgi.com
> Admin. requests: info-performer-request++at++sgi.com
> SGI DevForum 97 info: http://www.sgi.com/Forum97/
>-- End of excerpt from Troy Stephen

=======================================================================
List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
            Submissions: info-performer++at++sgi.com
        Admin. requests: info-performer-request++at++sgi.com
   SGI DevForum 97 info: http://www.sgi.com/Forum97/

New Message Reply Date view Thread view Subject view Author view

This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:55:26 PDT

This message has been cleansed for anti-spam protection. Replace '++at++' in any mail addresses with the '@' symbol.