SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
For Progressive Source, FIELD ID is always ‘0.’
For Interlaced Source, FIELD ID needs to be extracted consistently.
In some cases, vertical sync is active on the first pixel of a line in the vertical blanking period and it stays active until the last line in the vertical blanking period.
However, the pixel where the FIELD ID signal transitions can be quite variable and depends on the external chip driving the VIP_PARSER. Many parts that generate digitized raw video have a programmable feature to specify when FIELD ID changes. FIELD ID is valid at the same point for every field. That is, if FIELD ID is read at one particular place in a field, the polarity of the signal will be reversed at the same location in the next field. So, FIELD ID can be corrected with a programmable polarity configuration bit FID_POLARITY (within VIP_PORT_A and VIP_PORT_B registers) that is XOR’ed with the captured value.
For discrete sync mode, FIELD ID will be registered on the first active pixel capture cycle of each line in both styles of HSYNC and ACTVID usage as specified in Figure 11-36 and Figure 11-37.