Re: Video overlay generator

First of all, thanks a lot for the interesting discussion - at first I
thought there would be no response, but after two days I find more
than 10!

Second, I would like to point out my view on going the FPGA-route.

Using a FPGA+encoder+decoder seem to make a very flexible solution - I
have almost all possible overlay techniques available, I could f.e.
implement a alpha blending routine, vary the overlay resolution very
easily and I should be able to not worry as much about flickering
edges or trimming color/white levels.

The cost of the system is not primary, rather reliability and picture
quality.

The main concern of this route is that I'm not sure how much
degradation of the video quality is to be expected(although there
certainly are other factors like routing to take into consideration).

Also, I'm more of a digital/firmware-guy so I feel "safer" knowing
that I can control a lot more by firmware and HDL.

The analog switching route also is interesting, but I feel a whole lot
more uncertain in how to implement such a circuit reliably.
Are there any "modern" (not to be obsoleted in the next year or so)
circuits that are more suitable for this task that I should look for,
or have reference designs that share my application?

Best regards,
Andreas Eriksson

On 15 Aug, 14:34, Frank Raffaeli <SNIPrf_man_frT...@xxxxxxxxx> wrote:
On Aug 15, 2:14 am, Andreas <bloodd...@xxxxxxxxx> wrote:





On 13 Aug, 15:32, bloodd...@xxxxxxxxx wrote:

Hi!

Im starting a design process for a utility that needs to implement avideooverlaygenerator. Previously we've been using the "classic"
STV5730-chip for text-overlaybut since this IC is quite outdated and
hard to get hands on we've decided to implement our ownoverlay
generator.
The reason for this is that we want to be able to display graphical
items(such as a customer logo) and also because we need delecate
control of synchronization signals.
Thevideosignal is CVBS in/out and could be either PAL or NTSC.
We've thought of using these three major parts to implement the
design: avideodecoder (f.e. Texas Instruments TVP5150) that feeds a
digitalvideostream into a FPGA (f.e. Xilinx's Spartan 3), that
performs blending between the digitalvideostream and a "overlay
buffer" that gets generated from a microcontroller, and finally into avideoencoder (f.e. Analog Devices ADV7171).

I would really appreciate some feedback or input to this solution if
someone out there has done something similar.

Should I count with a noticeablevideoquality loss due to the AD ->
DA conversion?

Our application has some specific requirements, f.e. there is a frame
counter that has to be updated each frame which probably will require
us to implement a character generator inside the FPGA.

Do you think this is a viable solution - is there any existing ICs
that will do some or most of this work for me?

Best regards,
Andreas Eriksson

No suggestions?

Best regards,
Andreas Eriksson

Most of the loss will be in the chroma-luma separation. If you can
somehow overlay a simple color graphic by replacing the video with the
overlay (like an OSD), then you can pass-through the CVBS and only
change the signal where the overlay is.

The reason video / audio decoders are going out of style is because
now they're all custom ASICs. Even for analog signals.

Frank- Dölj citerad text -

- Visa citerad text -


.

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