Averlogic AL250 and scan doubling

Does anyone have experience with the Averlogic AL250 Video Scan Doubler IC?

Datasheet is here


and Application notes

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As far as interfacing to this IC, do think it's out of reach for a beginner? They don't provide a schematic for their evaluation board, but the parts list doesn't look too crazy.

It has I2C control, which should be easily accessed from any microcontroller.

I've got a simple application for the IC, and it would be setup in a fixed configuration mode. There's no need for multiple connectors, multiple display modes, etc. One NTSC input(~15khz), one VGA output(~31khz).

In general, is scan doubling/de-interlacing a hard thing(TM) ? This IC does some fancy things, but would simply sampling one side, buffering, and then outputting the other side generally work?



Reply to
Keith M
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Not directly but doing various resolution video deinterlacing to various resolution LCD panels.

Depends on definition of beginner as various things with video are beyond most beginners.

For a fixed input to LCD you will have to use NTSC YUV mode and note that the effective 24 bit colour input is cropped to 16bit colour by the chip. Anything non-square pixel or using 601 formats requires a CRT that hopefully can sync to that rate. Anything using an LCD would need register setups to CROP the image.

Line doubling is one way to go. This device sort of claims interpolated doubling which is usually better method for handling different resolutions. But it only partially does this.

As this chip has to use an external video decoder/digitiser, the I would look at other alternatives. Logic Devices make various chips for digital processing which can be setup quite easily to do various interpolation schemes, even changing horizontal resolution for full image display.

A good resource for this type of thing is the book

Video Demystified (I have first and fourth editions) By Keith Jack (ex Brooktree engineer)

ISBN 0-7506-7622-4

-- Paul Carpenter | snipped-for-privacy@pcserviceselectronics.co.uk PC Services Timing Diagram Font GNU H8 - compiler & Renesas H8/H8S/H8 Tiny For those web sites you hate

Reply to
Paul Carpenter

In my case I'm coming analog RGB NTSC to standard analog VGA HD15. I think that the AL250 requires digital inputs, so I think I'd need to front the AL250 with an AL875.

Thanks for the pointer, I'll check there.

Excellent. Thanks for the reference. I've actually looked at that book before.



Reply to
Keith M



If you have RGB NTSC consider almost ANY triple Video ADC or for that matter even 3 off TDA8702 NXP 8bit 40Mhz video ADC (available everywhere farnell Digikey...) These are very cheap.

Comapnion chip is TDA8703 8 bit DAC, but I generally use Fujitsu MB40760

10bit 60MHz DAC.

If you just want to line double without interpolation, it can be acheived digitally very simply by PLD and a selection of FIFOs or memory.

At NTSC video rates, most memorys/FIFO's can be obtained with much faster rate than pixel rate.

If this is for experimentation building one from PLD and memories/FIFOs, is very instructional to understanding timing and what you then require when looking at specs for much more integrated solutions.

To drive NTSC RGB to VGA (640x480) display I would choose either LCD with

18 bit digital interface and/or full 24 bit analog o/p for better performance. With PLD solution and FIFOs becomes a module you can tweak or add methods.

Look at Logic devices structures I used to use LF3330 a lot.

-- Paul Carpenter | snipped-for-privacy@pcserviceselectronics.co.uk PC Services Timing Diagram Font GNU H8 - compiler & Renesas H8/H8S/H8 Tiny For those web sites you hate

Reply to
Paul Carpenter

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