Grass Valley Imagestore 750 v.2.0.1 - Manual (Page 173)

Imagestore 750 User Manual Front Panel Operations
Miranda Technologies Inc. Page 173
Co-timed inputs will then have approximately half of a line buffered in their
FIFOs. Any sources that arrive earlier or later will increase or reduce the
FIFO depth respectively.
Line lengths of SDI standards:
•
525 NTSC 63.5
µ
s
•
625 PAL 64.0
µ
s
•
1080i/59.94Hz 29.6
µ
s
•
1080i/50 35.5
µ
s
•
720p/59.94Hz 22.2
µ
s
•
720p/50 26.7
µ
s
In our example, to buffer half a line of 1080i/59.94, increase the reference
timing to: 0 ln +5.6
µ
s (+15
µ
s) = 0 ln +20.6
µ
s.
Note, if the path delay of the SDI input sources is such that they are all offset
from reference by several lines then adjust the reference by the same number
of lines to align the output to the unusual input timing. Then add 10 to 20
micro-seconds to give some buffering in the line FIFOs.
Timing Delay Through the Imagestore 750
Refer to the 2D DVE section if the DVE is installed.
Without the DVE, the delay through the unit can be up to 1 line. The exact
data delay depends on the adjustment of the reference timing. The delay
consists of the input line FIFO depth plus a minimum processing delay.
•
For SD SDI standards the minimum processing delay is about 4.2
µ
s.
•
For HD SDI standards the minimum processing delay is about 2.6
µ
s.
Embedded audio delays are different to those of video. Embed and de-embed
circuits are required by SMPTE standards to buffer many samples before
processing. This inevitably means that embedded audio samples present on
input video line L will be processed then output on video line L + N. N is
variable and depends on both the video standard and line L. As a rough
guide, N is 5 to 12 lines.