SDI II Intel® FPGA IP User Guide

ID 683133
Date 10/08/2021
Public

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5.3.3. Insert Payload ID

The SMPTE ST 352 specification defines an ancillary packet type that provides specific information about the video payload carried by a digital interface. These payload ID packets carry information such as the interface type, sampling structure, component bit depth, and picture update rate.

Recent SMPTE interfaces such as dual link HD-SDI and 3G-SDI require the payload ID packets because it is very difficult to properly interpret the video data without the packet information from the payload ID packets.

The payload ID packet must be on specific video line locations at the beginning of the horizontal ancillary (HANC) space in one of these two conditions:
  • Right after the EAV.
  • Right after the CRC words that follow the EAV (for interfaces using CRC words).
Table 12.  Recommended Payload ID Packet LocationThe table below lists the payload ID packet location recommended by SMPTE specification. You may observe SDI data having payload ID packets located in different line numbers.
Video Format Field Line Number

525i

1

13

2

276

625i

1

9

2

322

1080i

1

10

2

572

525p

13

625p

9

720p

10

1080p

10

For dual link HD-SDI interface, the payload ID packets are placed only in the Y data stream of both links. This submodule in the transmitter data path modifies the Y data stream that passes through.

Note: This submodule introduces a latency of a few clock cycles. The C data stream is delayed by a few clock cycles to keep it synchronized with the Y data stream.

The following rules apply for inserting and overwriting payload ID packets:

  • Rule 1: If there is no ancillary packet at the beginning of the HANC space on a line where the payload ID packet is supposed to occur, the submodule inserts the payload ID packet at the beginning of the HANC space.
  • Rule 2: If there is an existing payload ID packet at the beginning of the HANC space on a line specified by tx_line_f0 or tx_line_f1, the submodule overwrites the packet with the new payload ID information if the tx_vpid_overwrite signal is high. If the tx_vpid_overwrite signal is low, the submodule does not overwrite.
  • Rule 3: If there is a different type of ancillary packet(s) at the beginning of the HANC space on a line where the payload ID packet is supposed to occur, the submodule does not overwrite the existing ancillary packet(s). Instead, the submodule looks for empty space in the HANC space to insert the payload ID packet after the existing ancillary packet(s). If the submodule finds a payload ID packet later in the HANC space before finding an empty space, it overwrites the existing payload ID packet with the new data if the tx_vpid_overwrite signal is high. If the tx_vpid_overwrite signal is low, the submodule will not overwrite.

For correct payload ID insertion, assert the tx_trs signal for the first word of both EAV and SAV TRS as shown in the Line Number Insertion timing diagram.

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