SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
Each frame consists of short packets to indicate SOF and EOF. Optional short packets for start of line and end of line can be sent by the image sensor.
Some information before and after the picture data can be sent by the image sensor as SOF and EOF information. It is decoded by the receiver and is sent to the system memory through the OCPO port.
For each frame, the pixel data (arbitrary data or user-defined byte data) are valid only after an SOF short packet. If the data are invalid, they are discarded by the protocol engine.
A frame contains embedded data and image-sensor data. Figure 10-20 shows where the embedded data and image-sensor data are in the frame. The frame is scanned in raster order starting from the top-left corner, as shown in Figure 10-20 and Figure 10-21. The following definitions for a frame apply:
The CSI2 receiver does not use the information in the status lines. However, it extracts it and stores it in memory for use by software.
Because the data types are different, the data is carried using separate data types called virtual channels. Those must be mapped to the adequate context. The CSI2 receiver uses a different context for embedded data and image-sensor data. See Section 10.4.6.2.3.10, CSI2 Virtual Channel and Context.
Embedded data is supported as a context by the CSI2 receiver; therefore, there is no specific hardware support for embedded data.
Figure 10-20 CSI2 General Frame Structure (Informative)Figure 10-21 shows the frame structure of a YUV4:2:2 interlaced video frame without embedded data.
Figure 10-21 CSI2 Digital Interlaced Video Frame (Informative)The period between the LEC and the new LSC is called line blanking period. The time between the FEC and the new FSC is called frame blanking period. The receiver works with "near zero" line blanking period.
The embedded information (SOF & EOF lines) is never compressed (no DPCM). The embedded information covers full lines. The embedded information is not encoded in the same data format as the pixel data. The CSI-2 receiver extracts the embedded information but does not modify the data format.
The pixel data can be compressed.