What Communications Technology is used in Car Reverse Cameras?

Question

What communications technology is typically used in car reverse cameras? Analogue or digital, and what protocol? How is the data typically read into the MCU/MPU - via CSI or some other protocol?

Specifically, I am referring to the case where the camera view is displayed on the vehicles built-in multi-function display, which would usually be driven by an MPU running Linux/Android (i.e. not the case of aftermarket standalone displays); these MPUs usually have peripherals such as CSI / Ethernet, as well as the standard SPI/I2C/UART.

Answer 1

To start

How is the data typically read into the MCU/MPU

In typical reversing camera systems the data may not need to be input to any higher level system. The ultimate end-to end application layer is 'a view what's out the back of the car' to "users eye and brain". Exxentially a camera to monitor system often suffices.

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AHD and CVBS are certainly not the only formats you will encounter, but they are widely used in lower cost aftermarket and also OEM equipment.

Many older ones use analog CVBS (Composite Video Blanking & Sync)format.
Useful overview here. These can be viewed on typical composite video analog monitors.

Increasingly, more modern ones are liable to use AHD ("Analog High Definition") - a format common among modern security cameras. 'AHD is able to transmit video, audio and control (OSD or PTZ) over a single coaxial cable instead of requiring separate cables for each transmission.' Power supply is separate (without extra work). It allows substantially better bandwidths than "pure" analog on coax or even paired copper wire. How it works seems to be a well guarded secret - it is used by a wide range of manufacturers but I have not managed to find a technical description with a significant amount of searching. (Any sources gratefuly received).

This useful page covers CVBS and (mainly) AHD in backing camera use.

A number of security cameras that I have seen are able to be switched between AHD and video output.

AHD protocol description here . They mention up to 1080P capability but I am of the understanding (possibly incorrect) that up to 4k is now able to be used. TBD.

They say

AHD CCTV is an analog high definition closed-circuit television video surveillance standard that uses existing coax cable to transmit 720p and 1080p video resolutions HD video from security cameras to DVRs. AHD is able to transmit up to 1080p video resolution (1920 x 1080) in an uncompressed format over the same standard coaxial cable that is used for standard CCTV cameras.

This uncompressed video format is able to transmit over longer distances than either HD-SDI or Network IP cameras and without the latency and bandwidth issues that are so common with IP Cameras.

Additionally, AHD is able to transmit video, audio and control (OSD or PTZ) over a single coaxial cable instead of requiring separate cables for each transmission.

What is really separating this technology from the rest of the options for HD video transmission is the cost effectiveness of AHD. In most cases AHD is around the same price as the older analog CCTV technology and is far less expensive than HD-SDI or IP Network transmission.

This web search gives many good answers.

This is the same search in image mode - giving many related web pages, one per image.

Suggestion: It is very likely that the above will answer your question. It would be useful if you then self answered the question with a summary for others that provided useful technical specifics. Note that this should not be brand specific but rather a guide to the area of interest

Answer 2

Texas Instruments have serializers/deserializers which support Flat panel display link III (FPD-Link III). FPD-Link III – doing more with less contains the following as an overview, which mentions the ability for low-cost cable:

Flat panel display link III, better known as FPD-Link III, is an interface used in many automotive applications to transport video from point to point. This interface enables the transport of high-definition digital video, as well as a bidirectional control channel, over a low-cost cable, either twisted pair or coax. There are FPD-Link III serializers and deserializers (SerDes) that have been optimized either for the link between a processor and a display, or between the processor and a camera (Figure 1).

That document also mentions the option of Power over coax.

The Imaging Source 2022 Catalog is from a supplier of cameras, which includes 36 Series FPD-Link® III cameras, the description of which contains the following which shows the use of a single coax cable to connect the camera:

For embedded vision applications requiring cable lengths between sensor and computer platform of up to 15m, The Imaging Source offers FPD-Link III cameras (SerDes cameras) in several form factors. Image data, commands for triggers and I/Os as well as power supply are transmitted via a thin coaxial cable.

FPD-Link III cameras are suitable for both single and multi-camera applications in automotive, IoT and general machine-vision applications.

Answer 3

Texas Instruments FPD-Link III and Analog Devices GMSL SerDes are both technologies designed to address this scenario, and essentially simply extend the range of a CMOS or MIPI-CSI camera (which various MCUs/MPUs support reading from directly).

GMSL SerDes

FPD-Link III

It would be great to get input/insight from someone with actual industry experience, if that could be added to this answer.