coltoff@PRC.Unisys.COM (Chilly Willy) (02/25/88)
I have noticed something odd a few times during the Olympics and
I'm not sure what cuases it. What I am refering to here is not
from the mobile cameras (Skibootcam, Bobsledrunnercam, etc.) where
the microwave link looses line of site and the picture breaks up.
This has happened during the ice skating which I presume uses cameras
with cables. What happens is that a few frames seem to be lost.
Someone will be skating along and all of a sudden mysteriously is
a few feet from where they were last. It is as if they were doing
compulsory figures on a discontinuous function. I assume the feed
is lost but something appears to remember the last frame transmitted
becuase there is no apparent loss of synch. Can anyone eleaborate
on this?
--
- Joel
{psuvax1,sdcrdcf}!burdvax!coltoff (UUCP)
coltoff@burdvax.prc.unisys.com (ARPA)brian@ucsd.EDU (Brian Kantor) (02/26/88)
Because there's no convenient way to send synchronization signals out to field cameras from the central time base generator, it is common practice to process the signal through a digital framestore. The field signal is used to clock the image into the image memory at the sync that comes from the field camera, and then the image is clocked out of the image memory at the station (or production van, whatever) standard sync rates and timing. So if the signal goes away, the input clocking can be stopped, and you'll just continue to repetitively get the last good frame. You could override that and clock noise into the framestore, but why would you want to? There exist a couple of models of digital framestores that are N seconds deep, instead of a couple of frames. These are just the ticket for instant repeat action, and for editing something (like a 30 second commercial) that will fit, they are really superb. Brian Kantor UCSD Computer Graphics Lab c/o B-028, La Jolla, CA 92093 brian@ucsd.edu
dale@amc-vlsi.UUCP (Dale Wlasitz) (02/27/88)
>......the microwave link looses line of site and the picture breaks up. >This has happened during the ice skating which I presume uses cameras >with cables. What happens is that a few frames seem to be lost. >Someone will be skating along and all of a sudden mysteriously is >a few feet from where they were last....... I have not seen this problem myself, however your description leads me to believe that the source is begin fed through a digital scan converter or frame storage unit. These devices are capable of storing entire frames. When the source has been identified as unacceptable by the micro controller they fill that particular frame from the image in memory. If this continues longer than one or two frames the human eye begins to pick up on this. These frame store units evolved from the line storage units used to "fill" in lines which had drop-outs from the play back of video tape. The particular line being scanned would be passed through a delay line to enable the system to detect any drop-outs. If any drop-outs existed the previous good line would be used as a filler. The image appears to be quite good actually .....until you find a tape with a crease in it. Dale K. Wlasitz