When using ADV7619KSVZ (without extension P, so with HDCP): Is it possible to switch off HDCP by software?
Best regards, Bernd
If the source doesn't want HDCP it won't request it. You don't gain anything by turning it off other then some test modes.
If you set HDCP_A0 = 1 then it should change the HDCP address to 0x76, which if the source does HDCP at 0x74, it won't respond. Never tried this.
I think there is an underlying misconception how HDCP works in practice.
By standard procedure the sink offers HDCP capability to the source and the source may use this if it deems it sensible or necessary.
In practice a source will additionally probe for HDCP independent of EDID information and it WILL USE HDCP independent of necessity or sense for the user. This is widely observed behaviour with the big graphics boards manufacturers.
Presumably this is to avoid issues of blanking or flickering when the source needs to switch to HDCP in a later situation because of protected content.
In most to all situations use of HDCP is unneccessary and unwanted.
Particularly in industrial or professional environments the content is unprotected and is needed unencrypted to make further use of it.
For this end it is necessary to be able to pose to a source as HDCP-incapable by all means.
What is the original purpose to switch HDCP_A0 from 0x74 to 0x76?
Presumably not for "turning HDCP off"?
I would like to be more assured that switching the address will actually work reliably to turn HDCP off.
I believe that HDCP_A0 only switches the internal access via I²C and has no influence on the external (HDMI) interface.
It's the source that decides if HDCP is required, period. If the sink can't do it-- the source can choose to not send video or it can not request HDCP.
In practice, as you say-- most sources simply won't work without it regardless of whether the content needs it.
Changing that register makes the keys inaccessible to our part so authentication will fail. This doesn't turn off HDCP at all-- it just fails to authenticate. What happens after that is up to the source.
There is no way to "turn off" HDCP in a sink-- only to force failure on authentication.
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