AM5728: ARGB DSS issue

Samual.Pang

Part Number: AM5728

Hi,

Our production need to combine stream from AM5728 via DSS with other source. We're using QT widget to do painting.

So we need to keep Alpha(ARGB) full information. But DSS already re-calculate it to lower RGB bits to trans from 32bit to 24bit. How to trans 32bit to DSS with Alpha channel full information? How can I keep it after DSS trans? The RGB bits lossing can be accepted.

Thx in advanced!

over 5 years ago

0 Krunal Bhargav34 over 5 years ago

TI__Mastermind 44675 points

Hello,

Could you please provide more information on what you are trying to display/use-case? In the AM5728 TRM, the following is stated:
• Three LCD outputs: primary (LCD1), secondary (LCD2), and tertiary (LCD3):
– Input pixel format: ARGB32-8888
– Output pixel format: RGB24-888 and YUV4:2:2 (YUV4:2:2 only available when BT mode output is enabled)

Regards,
Krunal

0 Samual.Pang over 5 years ago in reply to Krunal Bhargav34

Prodigy 180 points

Hi Krunal,

Thx for the reply.

In our production, only use 1 LCD output via DSS interface.

Now,

- Input pixel format: ARGB32-8888 (QT as UI mng)

We want the output via DSS is this format:

- Output pixel format: ARGB24-8565

0 Krunal Bhargav34 over 5 years ago in reply to Samual.Pang

TI__Mastermind 44675 points

Hello,

DSS never outputs the alpha channel. The alpha channel is "consumed" inside DISPC when doing the composition of the input planes, but the output is always just plain RGB or YUV.

Regards,
Krunal

0 Samual.Pang over 5 years ago in reply to Krunal Bhargav34

Prodigy 180 points

Hello Krunal,

Thx for your reply. It's the same as what we found.

Do u think it's a way to use glsl shader language to make it ?

Regards,

Samual

0 Krunal Bhargav34 over 5 years ago in reply to Samual.Pang

TI__Mastermind 44675 points

Hello Samual,

I do not understand your use-case because in most cases the LCD is 24 bits. It is only needs the RGB bits and that information is provided by the DSS.

Regards,
Krunal

0 Samual.Pang over 5 years ago in reply to Krunal Bhargav34

Prodigy 180 points

Hello Krunal,

Yes, most of the time, we dont need alpha information. But in my product, the steam thought DSS is part of display,

it will combined by a LCD driver(FPGA) with another steam.

So, what we want thought DSS, is 24bit including the alpha information.

0 Krunal Bhargav34 over 5 years ago in reply to Samual.Pang

TI__Mastermind 44675 points

Hi Samual,

In theory, it is possible to use the DSS as a "pass-through": you set the input and output formats to XRGB8888 and RGB888, and do not use any scaling or color-phase rotation or such. Then, the DSS will just use the RGB values of the input pixels as is, and pass them to the output. If you now manage to fill the framebuffer with your custom pixel format, it'll be sent through directly. It is still only 24-bits, that's the amount of output data pins DSS has and you will need to divide those 24 bits to ARGB components. Please keep in mind that TI has not tested the above use-case.

Regards,
Krunal

0 Samual.Pang over 5 years ago in reply to Krunal Bhargav34

Prodigy 180 points

Hi Krunal,

Thx a lot. I'll update this issue once I found a solution.

Regards,

Samual

0 user4227477 over 5 years ago in reply to Krunal Bhargav34

Prodigy 10 points

I have an idea:
Before the DSS input front end (or before ARGB8888 is synthesized into RGB888), a special formatting process is added to convert ARGB8888 to ARGB8565 into 24 bits.
I don't understand the DSS driver. Which great god knows where in TI's DSS driver or which file line can add this processing.

Processors

Processors forum

AM5728: ARGB DSS issue