rocky11
Posts: 2
Joined: Fri Jan 19, 2018 6:22 pm

1080p 60Hz HDMI to CSI-2 via TC358743

Mon Apr 23, 2018 11:07 am

Hello,

I'm trying to handle a 1080p 60 Hz RGB24 signal using TC358743 and Raspberry Pi 3.
Since 1920*1080*60*24 ~= 2.98 Gbps it requires ~4 CSI-2 data lanes while only 2 are available on Rpi3 (I could use a Compute Module with 4 lanes, but for now I have to use Rpi3).

My question is: Can I somehow accept this configuration from source device and downsample it to 30 Hz ?
In my script I need only 5-10 fps, so if it's possible I could downsample it even more.

I would be grateful for any support :)
Cheers

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 13567
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: 1080p 60Hz HDMI to CSI-2 via TC358743

Mon Apr 23, 2018 12:00 pm

Simply no. The TC358743 has about 512 pixels worth of buffering, therefore the input and output data rates have to be closely matched(*). There is no way that it can store even a whole line, let alone full frames.
Getting the TC358743 to convert to UYVY gets you down to 16 bits/pixel instead of 24. WIth that you can get 1080P50 down 2 lanes, but that is the limit.

Set your EDID up to not advertise 1080P50 or 1080P60 and your HDMI should abide by that and put out something that both devices believe they can support.


(*) It does have a FIFO trigger levels so the incoming HDMI rate can be lower than the CSI-2 rate by deliberately filling the FIFO to a point where it can then run at the significantly higher CSI-2 rate.
Software Engineer at Raspberry Pi Ltd. Views expressed are still personal views.
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