AD9984A to output 24-bit

Hi,

  AD9984A can't output 24-bit 444 RGB and to output 24bit we can try some of the output's bits being unconnected or ignored from the 30 bit.

  Please find some of our video decoders which can support 24bit RGB 4:4:4 output,

    "ADV7401/ADV7403/ADV7800/ADV7842/ADV7441A".

Thanks,

Poornima 

Hello,

I am confused, datasheet says 30-bits of RGB at 444 at "output formatter" part. if not, then at which subsampling does it output the RGB 30-bits?

hmmm disconnecting the least significant bits... will it do harm?

I don't need HDMI and I don't have its license. ADV7800 seems ok and it is 19$ from Rochester, but I am afraid it will be hard to control and learn especially no cheap dev board available.

plus, I need SCART RGB to have the ability to take 480p RGB not SD signals only... all SCART RGB will come with pure csync on pin 20 not CVBS signal. I wonder if that is allowed.

I need it to operate without manually selecting input resolution, like telling it the input is 480p or 720p or so.

Hello,

I am confused, datasheet says 30-bits of RGB at 444 at "output formatter" part. if not, then at which subsampling does it output the RGB 30-bits?

hmmm disconnecting the least significant bits... will it do harm?

I don't need HDMI and I don't have its license. ADV7800 seems ok and it is 19$ from Rochester, but I am afraid it will be hard to control and learn especially no cheap dev board available.

plus, I need SCART RGB to have the ability to take 480p RGB not SD signals only... all SCART RGB will come with pure csync on pin 20 not CVBS signal. I wonder if that is allowed.

I need it to operate without manually selecting input resolution, like telling it the input is 480p or 720p or so.

Hi,

   Sorry, that was my typo error AD9984A can output 444 RGB 30bit.

disconnecting the least significant bits... will it do harm?

     I don't think it will create problem So you can remove LSB bits to support 24 bit RGB.

I need SCART RGB to have the ability to take 480p RGB not SD signals only... all SCART RGB will come with pure csync on pin 20 not CVBS signal. I wonder if that is allowed.

    Please note SACRT RGB is only intended to go up to 54MHz So the SCART is limited to 480p60 and also it must be sync'd to the CVBS input.

    SCART RGB does not provide timing signals but must be synchronized to another input signal

 I need it to operate without manually selecting input resolution, like telling it the input is 480p or 720p or so.     

   If you are using software driver, then no need to manually configure the AD9984A registers to adapt the current resolution.
But if you are using the script, in that case you need to configure the registers manually according to your current resolution.

Thanks,

Poornima

PoornimaSubramani said:

     I don't think it will create problem So you can remove LSB bits to support 24 bit RGB.

yes that could be a potential solution. but AD9984A does not support composite and s-video so I would either get adv7401 or another separate ic for them.

PoornimaSubramani said:

Please note SACRT RGB is only intended to go up to 54MHz So the SCART is limited to 480p60 and also it must be sync'd to the CVBS input.

ok, 480p60 seems fine. other higher resolution RGB will go to graphics port. my other point was that the pin 20 of scart is usually CVBS or Y but mostly CVBS. my applications will have pure csync in that line... so we will have R G B CSYNC for the scart input, will it be ok? I mean feeding pure csync instead of cvbs. << that is if we feed this pure csync or cvbs into sync-on-green input of this IC. what do you think?

otherwise I will just use a sync separator to extract h and v syncs.

PoornimaSubramani said:

 If you are using software driver, then no need to manually configure the AD9984A registers to adapt the current resolution.
But if you are using the script, in that case you need to configure the registers manually according to your current resolution.

hmm i didn't understand that. the final application will be a board with a small microcontroller with it to send commands. what should I do for smooth easy operation?

I mean if the user picked scart, i send the command for scart... but the ic should operate perfectly fine if the scart is 480i or 480p or transition between the 2 of them. similar to YPBPR and graphics.

ADV7401 and ADV7800 seem a better choice if they offer 24-bit 444 RGB output and take all these signals but I also need the same things discussed here... what do you think?

Hi,

 If Pin 20 is dedicated for CVBS then we can use that pin only for CVBS input but i don't think we can use that pin for pure CSYNC.

 I didn't understand that. the final application will be a board with a small microcontroller with it to send commands. what should I do for smooth easy operation ?

     Then OK, if it is an application based then it will do the things automatically according to the input resolution.

Kindly note ADV7401 can support 24 bit 444 RGB.

Thanks,

Poornima

Hello

hmmm isn't ad9984a and any other IC which deals with scart requires csync signal on pin20? i mean, if it has cvbs on pin 20, the ic must extract the csync signal out of it and use it to sync the rgb input... no need for cvbs itself.

the point is, my applications are mostly having just the csync on pin 20, so when operating in scart rgb mode, the ic will get the csync it needs. i don't think there should be a problem at all... please check.

now when i want actual cvbs input, then i use a switch to put cvbs on the ic pin.

right now i am in contact with analog devices rep on emails to give me support for ad7186 which should be better than all these options right? i think it can do all my required signals, please check.

thanks

Hi,

  As per AD9984A/ADV7401/ADV7800 datasheet, Pin20 is dedicated for some other purpose So let us know in which IC that deals with CVBS signal on Pin20.

Kindly note you can generate Csync signal by using register 'HS_OUT_SEL' (Allows the switching of a CSync output on the HS pin).

     i.e HS_OUT_SEL = 1, the CSync is output on the HS/CS pin.

Please refer below links which will help to generate the 'Csync' with defined circuits Instead of giving the 'Csync' with any other input pins.

     VGA to RGB+sync converter (epanorama.net)

     Engineering CSYNC - Part 2: “Falling” Short — HD Retrovision

Thanks,

Poornima

Hi Vegeta,

        Please refer the below FAQ ,We created this FAQ recently to get customer details and primary check points for custom based boards.

        Also we suggested some Video parts with feature details.

Queries and Primary Suggestions for our Video Customers! - Documents - Video - EngineerZone (analog.com)

Kindly check and provide your feedback on this.

Thanks,

Poornima

hello

so i should answer the 2 sets of questions, then post them here? or where?

thanks

Hi,

  Here you can post your response.

Thanks,

Poornima