i.MX ProcessorsのトピックRe: MIPI CSI interface maximum capability

MIPI CSI interface maximum capability

Issac_20200908 — Tue, 12 Jan 2021 01:55:58 GMT

Hi,

We wanna interface 2x1080p60 YUV422 format camera to IMX8DX processor.

(1)Can MIPI CSI interface support it?

(2)Does SDK have sample code for it?

thx.

Re: MIPI CSI interface maximum capability

joanxie — Tue, 12 Jan 2021 03:42:11 GMT

1) refer to the data sheet, The MIPI CSI-2 IP provides MIPI CSI-2 standard camera interface ports. The MIPI CSI-2 interface supports up to 1.5 Gbps for up to 4 data lanes, so the mipi csi can support up to 6Gbps, but one 1080p@60 needs 3.54Gbsp, so I thinks imx8dx only can support one 1080p@60 camera

2)I checked imx8qxp sdk, can find the mipi csi driver, the code is under folder devices

Re: MIPI CSI interface maximum capability

Issac_20200908 — Tue, 12 Jan 2021 05:30:24 GMT

Thanks for your help.

I have a question on the total bandwidth needed for one 1080p60 YUV422 format video. I added 35% extra blank bits for the MIPI CSI tranfer (a estimation formula in an iMX6Q doc), and got 2.687Gbps. That's

1920x1080x16x1.35=2.687G bps

How did you get that one 1080p@60 needs 3.54G bps?

Re: MIPI CSI interface maximum capability

joanxie — Thu, 14 Jan 2021 06:49:03 GMT

the forum you use isn't correct, for the forum you use is for frequency (Mhz), not for bandwidth(bps)

The required operating frequency of the interface is calculated in the following way:
F = FH * FW * FPS * BI * DF
Where
• FH = frame height (in pixels)
• FW = Frame width (in pixels)
• fps = frame rate (frames per second)
• BI = typically 35% overhead, should be assumed as 1.35. The actual blanking
intervals are a parameter of the attached device.
• DF = data format, defines the number of cycles needed to send a single pixel.
The number of cycles needed to send a single pixel depends on the interface and the data
format.
Data format examples:
• YUV422 over 16 bit = 1 cycle/pixel
• RGB888 over 8 bit = 3 cycles/pixel
• RGB565 over 16 bit = 1 cycle/pixel
• Bayer/Generic data = 1 cycle/pixel
• YUV422 over 8 bit = 2 cycles/pixel
• BT.656, YUV422 format = 2 cycles/pixel
• BT.1120, YUV422 format = 1 cycle/pixel

sorry for my mistake, I don't find you use yuv422, if you use yuv422 16bits, imx8 can support dual camera, for 1080p, typical frequency is 148.5MHZ, the bandwidth is 148.5MHZx16bpp=2.376Gbps