User guide

Chapter 11: Clocked Video Output MegaCore Function 11–13
Functional Description
January 2013 Altera Corporation Video and Image Processing Suite
User Guide
Stall Behavior and Error Recovery
Once its input FIFO is full, the stall behavior of the Clocked Video Output MegaCore
function is dictated by the outgoing video. During horizontal and vertical blanking
periods it stalls and does not take in any more video data.
Error Recovery
If the Clocked Video Output MegaCore receives an early end of packet it will re-
synchronize the outgoing video to the incoming video data on the next start of packet
it receives. If the Clocked Video Output MegaCore receives a late start of packet it will
re-synchronize the outgoing video data to the incoming video immediately. Note that
when Genlock functionality is enabled the Clocked Video Output MegaCore does not
re-synchronize to the incoming video.
1 For more information about the stall behavior and error recovery, refer to “Stall
Behavior and Error Recovery” on page 1–3.
Latency
Table 11–5 lists the approximate latency from the video data input to the video data
output for typical usage modes of the Clocked Video Output MegaCore function. You
can use this table to predict the approximate latency between the input and the output
of your video processing pipeline.
The latency is described using one or more of the following measures:
■ the number of progressive frames
■ the number of interlaced fields
■ the number of lines when less than a field of latency
■ a small number of cycles O (cycles)
The latency is measured with the assumption that the MegaCore function is not being
stalled by other functions on the data path (the output ready signal is high).
1 The latency associated with the initial buffering phase, when a MegaCore function
first receives video data, is not included.
Table 11–5. Clocked Video Output Latency
Mode Latency
(1)
All modes with Video in and out use the same clock: On 3 cycles
(2)
Notes to Table 11–5:
(1) Add 1 cycle if Allow color planes in sequence input is turned on.
(2) Minimum latency case when video input and output rates are synchronized.