Video Input Stream Interface - 1.2 English

HDMI 2.1 Transmitter Subsystem Product Guide (PG350)

Document ID
PG350
Release Date
2022-04-27
Version
1.2 English

The AXI4-Stream video interface supports four or eight pixels per clock with 8 bits, 10 bits, 12 bits, and 16 bits per component for RGB, YUV444, and YUV420 color spaces. The color depth in YUV422 color space is always 12-bits per pixel.

When the parameter, Max Bits Per Component, is set to 16, the following figure shows the data format for four pixels per clock to be fully compliant with the AXI4-Stream video protocol.

Figure 1. Four Pixels Data Format (Max Bits Per Component = 16)

If the actual bits per component is greater than Max Bits Per Component set in the Vivado IDE, video formats with actual bits per component larger than Max Bits Per Component should be truncated to the Max Bits Per Component. The remaining least significant bits are discarded. If the actual bits per component is smaller than Max Bits Per Component set in the Vivado IDE, all bits are transported with the MSB aligned and the remaining LSB bits are padded with 0. This applies to all Max Bits Per Component settings.

Table 1. Max Bits Per Component Support
Max Bits Per Component Actual Bits Per Component Bits Transported by Hardware
16 8 [7:0]
10 [9:0]
12 [11:0]
16 [15:0]
12 8 [7:0]
10 [9:0]
12 [11:0]
16 [15:4]
10 8 [7:0]
10 [9:0]
12 [11:2]
16 [15:6]
8 8 [7:0]
10 [9:2]
12 [11:4]
16 [15:8]

The video interface can also transport four and eight pixels in the YUV420 color space. The following figure show the data format for four pixels format.

Figure 2. YUV420 Color Space Four Pixels Data Format (Native)

Similarly, for YUV 4:2:0 deep color (10, 12, or 16 bits), the data representation is the same as shown in the previous two figures. The only difference is that each component carries more bits (10, 12, and 16). However, the current data format is not compliant with the AXI4-Stream video protocol. Therefore, a remapping feature is added to the HDMI 2.1 TX Subsystem to convert AXI4-Stream into HDMI native video. This feature will be enabled by default from the HDMI 2.1 TX Subsystem GUI when the AXI4-Stream video interface is selected. To illustrate how the data remapping feature works for YUV 4:2:0 video from AXI4-Stream into native video, the previous figure is extended and represented in the following figure to show native video data associated with the clock and control signals.

Figure 3. Native HDMI Video Interface (Four Pixels per Clock)

When transporting using AXI4-Stream, the data representation must be compliant with the protocol defined in the AXI4-Stream Video IP and System Design Guide (UG934). With the remapping feature, the same native video data is converted into AXI4-Stream formats, shown in the following figure. As stated in AXI4-Stream Video IP and System Design Guide (UG934), the 4:2:0 format adds vertical sub-sampling to the 4:2:2 format, which is implemented in Video over AXI4-Stream by omitting the chroma data on every other line.

However, in the native HDMI video interface, the video data representation must be as shown in the following figure.

Figure 4. YUV 4:2:0 AXI4-Stream Video Data (Four Pixels per Clock)
Note: For RGB/YUV444/YUV422 formats, video data is directly mapped from AXI4-Stream to the native video interface without any line buffer. Therefore, the four Pixels Data Format graphics shown previously, represent the data interface for both AXI4-Stream and native video. The control signals are omitted in the figure.

In the native DE HDMI video interface, the video data representation must be as shown in the following figure.

Figure 5. Native DE HDMI Video Interface (Four Pixels per Clock)

For more information on the video AXI4-Stream interface and video data format, see the AXI4-Stream Video IP and System Design Guide (UG934). The remapping feature, which is to convert between native video data format and AXI4-Stream format, is also described in the AXI4-Stream Video IP and System Design Guide (UG934).