Grass Valley PVS Series System Guide v.4.0 Dec 10 200 - Manual (Page 114)

Chapter 5 Modifying a Channel: Video Settings
114 Profile XP System Guide July 27, 2001
Options for timing asynchronous feeds
All video inputs include an input frame buffer. You must select how the frame buffer
handles asynchronous feeds based on your application. The two video timing modes
for the frame buffer are described here.
• “Auto-time using the internal frame sync (default)”
This is the frame buffer default setting. When selected, the frame buffer
synchronizes and times the input relative to the system reference: zero time +16
lines by default. This mode allows clean switching between the video input and
decoder outputs (playback) provided E to E playback timing is also selected (see
“Adjusting playout timing to match E to E timing” on page 110).
A maximum delay of slightly more than 1 frame can occur to time the video
input. Audio channels assigned to the same video channel automatically track
the video delay to eliminate lip sync errors.
In order to synchronize an asynchronous input, the frame buffer may drop or
repeat frames from time to time. This artifact is captured if you are recording at
the time. If this artifact in the recorded video is not acceptable, either use a
synchronous input or do not use this timing mode.
• “Allow signal to pass asynchronously”
This input timing mode allows an asynchronous signal to pass through the input
frame buffer, clock locked only. No attempt is made to time the signal to the
system reference so that no frames are repeated or dropped. Select this mode
when you want to be sure that all video frames are recorded.
The clock locking that occurs in this timing mode may result in non-standard
horizontal blanking interval on the video input. This artifact is visible in the
video in E to E mode, such as when you are monitoring a channel during record.
The recorded clip is not effected since horizontal blanking is not recorded; it is
reinserted during playout