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Are Multiple Video Streams over Single MIPI CSI-2 Link Possible on the ADV728x ?

The following post applies to the ADV7280-M, ADV7281-M, ADV7281-MA and ADV7282-M.

Hi All,

I have been asked a few times if it is possible to feed multiple video sources into the ADV728x-M and output them all over a single MIPI CSI-2 stream and use the virtual channel identifier to differentiate between each video source.

Unfortunately this is not possible on the ADV728x-M.

Multiple analog video sources can be connected to the ADV728x-M (upto 8 CVBS inputs on some ADV728x models). The ADV728x-M will then output a MIPI CSI-2 stream.

The Virtual Channel of the ADV728x-M MIPI CSI-2 output can also be programmed to one of four values.

However the ADV728x-M contains a single ADC. It can therefore only process one analog video source at a time. Therefore only one video source can be fed over the MIPI CSI-2 link at a time.

So is it possible to quickly switch back and forth between analog video sources and output all over the MIPI CSI-2 stream? Unfortunately this is also not possible on the ADV728x-M. Locking to analog video is not a straightforward task as many analog video standards are very similar. Even in fast switch mode it can take the ADV728x-M upto 250 ms to lock to an analog video source.

It is also not possible to connect the MIPI CSI-2 outputs from two or more ADV728x-M's together. MIPI CSI-2 is designed to be a single point to point standard (i.e. a single Tx to a single Rx). The input/output termination of the Tx/Rx are constantly changing in a MIPI CSI-2 stream as the high speed and low power states are being entered/exited. Connecting more than one MIPI CSI-2 Tx together will cause the termination scheme to violate the MIPI D-PHY specification. 

Regards,

Robert Hinchy,

Senior Applications Engineer,

Automotive Infotainment Group,

Analog Devices Inc.

Comments
Anonymous
    •  Analog Employees 
    over 3 years ago in reply to chris_analog14

    Sorry the answer to this question is no.

    Please see this post for more information. ADV7280-M 

    regards,

    Robert Hinchy

    Applications Engineer,

    Analog Devices Inc.

  • Hi FormerMember,

    I am planning to use multiple ADV7280M in my design with FPGA interfacing with MIPI CSI2.  If I synchronize all my ADV7280M system clocks, will I be able to use only one of the ADV7280M's MIPI clock for all my MIPI RX interfaces on FPGA?

    My problem is that I do not have enough PLLs on FPGA for each ADV7280M's MIPI clock. 

    •  Analog Employees 
    over 4 years ago in reply to ranaya

    Hello,

    The lock time is mainly set by the clamping circuitry (i.e. setting the DC level) and the autodetect algorithm in the ADV728x. Since there are many analog video standards and many of them are very similar it takes time for ADV728x to determine the correct input standard.

    Using an external switching device will not improve the time it takes for the ADV728x to lock to an analog video source or switch from one input source to another. 

    The ADV728x  "fast switch mode" speeds up the lock time of the ADV728x. See this post for more information.

    Fast Switch Mode- ADV728x 

    regards,

    Robert Hinchy

    Senior Applications Engineer,

    Analog Devices Inc.

  • Hi FormerMember

    This locking time you mentioned, is it because of the internal sampling and settling times required by the adc ? Or if not would this switching thing be achievable with aid of an external faster analog video switch ?

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