Video -> Binary -> Video

[TiagoSilva]

Hi, I was checking on the forum, like I usually do, and I remembered a problem that i had some time ago, I didn't do anything then, but now, since I’m here, what is needed to convert a video signal (AV) to binary code (Microcontroller) and then back to video signal (AV) ?

I thought that i could need a DAC to convert the video signal to binary, and then to a ADC, the main idea then was to send the digital signal (binary) to another remote microprocessor through wireless, decode the binary signal and then send the video binary signal to an ADC.

-> But my doubt was, how fast the DAC needed to be ? ... or how many bits of precision it is needed to do that ? ...

 

[ericgibbs]

hi tiago,

Is it 'broadcast' quality A/V, colour or monochrome.
Give us more detail on the video signal.

These factors will influence the ADC/DAC and radiolink bandwidth. etc.

Eric

 

[Nigel Goodwin]

Hi, I was checking on the forum, like I usually do, and I remembered a problem that i had some time ago, I didn't do anything then, but now, since I’m here, what is needed to convert a video signal (AV) to binary code (Microcontroller) and then back to video signal (AV) ?

I thought that i could need a DAC to convert the video signal to binary, and then to a ADC, the main idea then was to send the digital signal (binary) to another remote microprocessor through wireless, decode the binary signal and then send the video binary signal to an ADC.

-> But my doubt was, how fast the DAC needed to be ? ... or how many bits of precision it is needed to do that ? ...

You've also got the problems of colour as well, and it's certainly NOT a micro-controller job - you've got to convert, store, and transmit, HUGE amounts of data, and require huge bandwidth to send it wirelessly. Bear in mind digitising data makes it need much more bandwidth to transmit than the original analogue data - it's only huge amounts of compression that make it smaller than the original.

The entire idea seems pointless though?, why not just send the analogue video signal wirelessly? - you can buy cheap video senders, or even cheap modules to build your own.

If you want to work out how much data you will need, work out your required resolution, then assume 24 bits per pixel (one byte per colour), so three bytes per pixel - so for full PAL resolution you need:

720x576x3=1,244,160 bytes, 25 times per second

So you need to send 31,104,000 bytes per second - this is a LOT of data!.

Bear in mind standard CAT5 ethernet only does 100 megaBITS per second, more than a third too slow for the video!.

 

[TiagoSilva]

color ... that much resolution ? ... those small cmos cameras don't have that mutch, its abouth some 300x200 or less, but even so it's too mutch, the ideia was to send all signals mixed and decode them in the other side (computer) ... but like this it's dificult, but even so, if it was to be done, how fast it needs to be ? Anyway, isn't the converted signal just the wave level ?!?!?! how come it needs that mutch bandwidth ? I was asking abouth the DAC and ADC precision ... I'm not doing anything, it's just to know abouth it.
Thanks by the way.

 

[Nigel Goodwin]

color ... that much resolution ? ... those small cmos cameras don't have that mutch, its abouth some 300x200 or less, but even so it's too mutch, the ideia was to send all signals mixed and decode them in the other side (computer) ... but like this it's dificult, but even so, if it was to be done, how fast it needs to be ? Anyway, isn't the converted signal just the wave level ?!?!?!

I've no idea what you mean?.

how come it needs that mutch bandwidth ?

Simple maths!.

I was asking abouth the DAC and ADC precision ... I'm not doing anything, it's just to know abouth it.

As I said above, it depends on what quality you want - 24 bit is fairly normal, for excellent quality (8 bits per colour). The conversion speed is obvious from the bandwidth requirement - you need to do over 31 million conversions per second for full resolution 24 bit PAL.

 

[TiagoSilva]

Do you know any concrete DAC to do that ?

 

[Nigel Goodwin]

Do you know any concrete DAC to do that ?

Look for 'flash video dac'

How about:

Part: SPT5230

Category:
Data Conversion
-> DAC (Digital to Analog Converters)
-> 10-14 bit

Description: 10-bit, 36 MWPS Triple Video DAC

Company: Signal Processing Technologies

 

[Hero999]

Also don't use 24-bit, 16-bit colour is more than good enough for most applications.

This looks like a good application for a mini-PC.

 

[Nigel Goodwin]

Also don't use 24-bit, 16-bit colour is more than good enough for most applications.

So how do you divide 16 bits by three?.

 

[TiagoSilva]

he's probablly thinking abouth 16bit per pixel most likelly lol but it could be 12bits if they were 4 bit quality (16 colors) 4x4x4, with that i can also make a video to computer digitalizer
Well i've had tought that it was easier ...

Thanks again.

 

[Hero999]

So how do you divide 16 bits by three?.

Try setting your display mode to 16-bit high colour.

5 bits for the red channel.
6 bits for the green channel.
5 bits for the blue channel.

It's called 5-6-5 bit colour and is still used a lot in mobile phones and small portable computers.

 

[Nigel Goodwin]

What a horrible idea!!

 

[TiagoSilva]

lol ...

 

[Hero999]

Horrible?

I suppose it is now but it weasn't compared to the alternatives when computers weren't as powerful.

Either use 8-bit palleted 256 colour which was terrible or 24-bit true colour which was too slow. 16-bit high colour had the best of both worlds, speed (on a 32-bit processor you could write 2 pixels at the same time) and acceptable bad quality.

 

[TiagoSilva]

Try doin'g it with 8 bit micro's lol