Javier Castellar (javier++at++sixty.asd.sgi.com)
Mon, 17 Feb 1997 17:43:19 -0800
This is not only for Performer but ... I though that you may find it
interesting. If you are using the encoder output of InfiniteReality this
message is for you. I describe a way to get a flicker free and fully genlocked
video out with no additional hardware.
As you know InfiniteReality provides two/eight video outputs. iR also
provides a video encoder (composite NTSC/PAL or S-VHS NTSC/PAL) for industrial
quality video recording. Off course, when using the encoder you cannot use
channel1 since both use common hardware.
TRICK1 (flicker free output)
======
Let's assume that you have two channels:
1280x1024_60 and the encoder output.
Since the NTSC/PAL signals are interlazed (two fields) and most of the
people uses single width horizontal lines in his motif/X widgets this lines
flicker in the final video signal.
One way to get a nice flicker free signal is using the iR dynamic video
resolution feature using ircombine. If you double click on the encoder button
you can adjust some parameters, use the "Source Channel" to select a video
channel to be scan converted (in this case from 0), and then you can adjust the
size of the encoder channel scan conversion. Now you can increase the size of
the encoder (up to 1280x1024), if you are looking for only video output you can
select an size slightly bigger than the 640x480. Then what you get is a flicker
free signal scanned and filtered form i.e 700x500 with a very solid image. The
DVR filter is cool.
TRICK2 (genlocking the pipe with his own encoder)
======
When recording video from the encoder in the previous example:
Chan0: 1280x1024_60
Encoder: NTSC
You will suffer a problem, NTSC is slightly slower than 60hz (it is
about 59.94), therefore you will suffer a passing line time to time, since the
pipe is working at 60hz and you encoder is NTSC (same for a 50hz 1280x1024 and
PAL), then you will be unable to record a stable image in your VCR, videodisk
... etc.
This is not a problem, it is life: NTSC is always NTSC, you cannot
genlock the encoder since then it will not be NTSC.
One solution will be to genlock the pipe with an external house Sync,
but people who use the encoder are not in the broadcast arena, therefore they
don't wish to buy a sync generator.
The trick is to genlock the iR pipe (1280x1024 ...) with his own
encoder. Here is how I made it last week:
InfiniteReality VCR/Video Disk
Channel 0 ---- 1280x1024 -> Hi-res Monitor
Encoder -----------------------------------> Video In
Genlock IN <---------------------------------- Video Through (75 ohm OFF)
Genlock OUT -> 75 ohm terminator
Video Monitor <------ Monitor out
Then you need to use ircombine to genlock:
a) Go to EditGlobals menu
b) Select "Sync Source" as external (genlocking)
c) Sync format (browse ..) : CCIR601_525.vfo (NTSC)
Remember to update (dowload combination) and check if the genlock is working:
# /usr/gfx/gfxinfo -v | grep Sync
Input Sync: Voltage - Video Level; Source - External; Genlocked - True
Sync Output(s):
Then you will get a "perfect" composite signal to be recorded with no
artifacts.
If you require higher quality (CIR601, broadcast) you must use either Sirius
Video Option (Onyx) or GVO (Onyx2).
Regards.
-Javier
"The cable guy"
--
*************************************************************************
* Javier Castellar Arribas * Email: javier++at++asd.sgi.com *
* * Vmail: 3-1589 *
* Member of Technical Staff * Phone: 415-933-1589 / 2108 (lab) *
* Core Design - Applied Engineering * Fax: 415-964-8671 *
* Advanced Systems Division * MailStop: 8L-800 *
*************************************************************************
* Silicon Graphics Inc. *
* 2011 N. Shoreline Boulevard, *
* Mountain View, California 94043-1386, USA *
*************************************************************************
"Violence is the last refuge of the incompetent"
Hardin Seldon
=======================================================================
List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
Submissions: info-performer++at++sgi.com
Admin. requests: info-performer-request++at++sgi.com
This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:54:40 PDT