Required frequency to transmit video?

[EngIntoHW]

Hi,
I wanna transmit video from one unit to another.

What's the required rate to transmit video, to get moderate quality?

I'm trying to figure out whether I could use PIC for that.

I got PIC18F4520 that its I2C can reach 10MHz, and I wonder if I can use that interface to transmit Video signal at moderate quality.

Thank you.

 

[Ian Rogers]

10Mhz for I2C is a bit ambitious... I don't think the humble pic has Ultra Fast I2C modules...

SPI however is fast.... But the humble pic will not be able to read a video signal... The Us video is just under 4Mhz ( just for black and white ) You'll need a bigger chip with more capability.

You can get JPEG / TTL still camera's that snapshot images and compress to jpeg... They can be transfered to a suitable video device... But I only managed 2 to 3 frames a second.. and that was a small 160 x 100 resolution..

 

[EngIntoHW]

Hi Ian,
Thank you.

oh you're right, for both I2C and SPI, the Max. Baud rate is only 1MHz.

Is that why the PIC not powerful enough for reading / transmitting video signal?

BTW, what do you mean by Us video?

 

[unclejed613]

US video, also known as NTSC video..... the bandwidth of NTSC video is about 4 Mhz, however that includes the chroma subcarrier at 3.58Mhz. the actual video bandwidth is 3Mhz (monochrome video).

 

[crutschow]

US video, also known as NTSC video..... the bandwidth of NTSC video is about 4 Mhz, however that includes the chroma subcarrier at 3.58Mhz. the actual video bandwidth is 3Mhz (monochrome video).

And that's an analog bandwidth, not digital.

 

[large_ghostman]

what about pic32? there is a thread here somewhere called who is afraid of the pic32 (or something like that) posted by blueroom electronics, anyway it was a pic32 connected to a webcam that also acted as the web server. would that be fast enough?

 

[crutschow]

Do you want to transmit in digital format? That requires high speed conversion from the analog video to digital and back.

What is the source for the video?

Is the link to be wired or wireless?

 

[MikeMl]

I think the question should be
Required bandwidth to transmit video?

 

[ronsimpson]

I think the question should be
Required bandwidth to transmit video?

NTSC is 3mhz for B&W. (analog)
B&W 8-bit (256 gray levels)
Thats 24,000,000 bits/second. (digital)
Then there likely are start and stop bits or some other overhead needed.
So SPI and I2C need 25mhz minimum to make ok quality B&W pictures.
Color will 3x that speed. (depending on how the color is made)
Reducing to 160 x 100 resolution will really help.

Most little computers (PICs) don't have enough memory to hold more than one line of video. Not a whole picture.

 

[misterT]

I don't know about PIC, but the 8 bit AVR xmega can do this:

And this is what ATmega644 can do:

All you need is mad coding skills (forget I2C)

 

[Jibby]

Hi,
I wanna transmit video from one unit to another.

What's the required rate to transmit video, to get moderate quality?

I'm trying to figure out whether I could use PIC for that.

I got PIC18F4520 that its I2C can reach 10MHz, and I wonder if I can use that interface to transmit Video signal at moderate quality.

Thank you.

Better at 2.4 GHz

 

[ronsimpson]

The pictures from MisterT are low resolution, often (100 to 200) x (200 to 300). The 8 bit computer is outputting the data in parallel not serial. Usually it takes all the CPU power to send one line of video. The computer can only "think" during the blanking time of the video. Some of the video games, the CPU only 'thought' during vertical blanking.

 

[crutschow]

One microprocessor that can handle NTSC video at the full data rate is the Propeller multi-core chip from Parallax. It includes some built-in hardware to simplify the interface to the video display.

 

[ronsimpson]

I think the Propeller has 8 video interfaces.
https://www.sparkfun.com/products/10032

 

[crutschow]

I think the Propeller has 8 video interfaces.
https://www.sparkfun.com/products/10032

It has eight 32-bit processors and each has some registers and counters useful for generating video outputs. Here's a little more info on it.