User guide

3–8 Chapter 3: Interfaces
Avalon-ST Video Protocol
Video and Image Processing Suite January 2013 Altera Corporation
User Guide
When a video data packet uses a subsampled color pattern, the individual color
planes of the video data packet have different dimensions. For example, 4:2:2 has one
full width, full height plane and two half width, full height planes. For 4:2:0 there are
one full width, full height plane and two half width, half height planes. In these cases
you must configure the width and height fields of the control data packet for the fully
sampled, full width, and full height plane.
The interlacing value in the control packet indicates whether the video data packets
that follow contain progressing or interlaced video. The most significant two bits of
the interlacing nibble describe whether the next video data packet is either
progressive, interlaced field 0 (F0) containing lines 0, 2, 4.... or interlaced field 1 (F1)
containing lines 1, 3, 5... 00 means progressive, 10 means interlaced F0, and 11 means
interlaced F1.
The meaning of the second two bits is dependent on the first two bits. If the first two
bits are set to 10 (F0) or 11 (F1), the second two bits describe the synchronization of
interlaced data. Use the synchronization bits for progressive segmented frame (PsF)
content, where progressive frames are transmitted as two interlaced fields.
Synchronizing on F0 means that a video frame should be constructed from an F1
followed by an F0. Similarly, synchronizing on F1 means that a video frame should be
constructed from an F0 followed by an F1. The other synchronization options are don't
care when there is no difference in combining an F1 then F0, or an F0 then F1. The final
option is don't know to indicate that the synchronization of the interlaced fields is
unknown. The encoding for these options are 00 for synchronize on F0, 01 for
synchronize on F1, 11 for don't care, and 10 for don't know.
1 The synchronization bits do not affect the behavior of the Deinterlacer because the
synchronization field is fixed at compile time. However, they do affect the behavior of
the Frame Buffer when dropping and repeating pairs of fields.
If the first two bits indicate a progressive frame, the second two bits indicate the type
of the last field that the progressive frame was deinterlaced from. The encoding for
this is 10 for unknown or 11 for not deinterlaced, 00 for F0 last, and 01 for F1 last.
Table 3–4 gives some examples of the control parameters.
Table 3–4. Examples of Control Data Packet Parameters
Parameters
Description
Type Width Height Interlacing
15 1920 1080 0011 The frames that follow are progressive with a resolution of 1920×1080.
15 640 480 0011 The frames that follow are progressive with a resolution of 640×480.
15 640 480 0000
The frames that follow are progressive with a resolution of 640×480. The frames
were deinterlaced using F0 as the last field.
15 640 480 0001
The frames that follow are progressive with a resolution of 640×480. The frames
were deinterlaced using F1 as the last field.
15 640 240 1000
The fields that follow are 640 pixels wide and 240 pixels high. The next field is F0
(even lines) and it is paired with the F1 field that precedes it.
15 1920 540 1100
The fields that follow are 1920 pixels wide and 540 pixels high. The next field is F1
(odd lines) and it is paired with the F0 field that follows it.
15 1920 540 1101
The fields that follow are 1920 pixels wide and 540 pixels high. The next field is F1
(odd lines) and it is paired with the F0 field that precedes it.