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

Document created by Rob.Analog Employee on Jan 20, 2016
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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.

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