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Old 15th Aug 2006, 1:42 pm   #1
atoof
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Default digital video converter

hi all
i want to make a circuit yhat convert digital video to analog
so i want to use SAA7128AH
but i want help in making interface and MPEG data which used as input to it.
plz anyone can help me in this topic plz do
atoof
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Old 21st Aug 2006, 8:44 am   #2
percival007
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Default Re: digital video converter

My advice would be to find a circuit in which the SAA7128AH is used. The chip is a Philips one so that would be a good start. Then just "copy" the relevant bits you need. Am not sure what you're trying to do. A little more detail may help me and any other forum member with experience in this field.
Chees, Percy.
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Old 21st Aug 2006, 10:18 am   #3
atoof
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Default Re: digital video converter

hi all,
percival007 asked about what am i trying to do,so i want to explain
simply i want to send MPEG file (from my PC) through the circuit (which i want to make ) and can see its output in my TV(i mean converter that its input from pc output to tv)
it's ok now?!
and i can not find any circuit that uses SAA7128AH to can study it!
so if any one have it or can help me by any word plz do
i want to understand pins (LLC,RCV1,RCV2,SCL,SDA)
thanks
atoof
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Old 21st Aug 2006, 10:46 am   #4
ppppenguin
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Default Re: digital video converter

The easiest way to do what you want is to buy a graphics card for your PC which has a TV output. You can also buy many converters that take the VGA output from a PC and convert this to TV. Some are very inexpensive though quality may suffer.

The actual conversion process is quite complex since the VGA from the PC has a different number of lines, frame per second and interlace when compared with TV. The SAA7128 is a simple PAL/NTSC encoder chip which will take digital RGB/YUV and syncs and convert to composite video. It cannot do anything to alter the timing or number of lines.

I believe that chips are available that perform the complex bits of VGA to TV conversion. I think some are made by Averlogic though I'm not sure.

If your aim is to display the output of your PC on a TV then I recommend you buy equipment to do this. It need not be expensive. If your aim is learn about video and its relationship to PCs in a very detailed way then you will have a lot of work ahead of you. I can recommend the book Video Demystified by Keith Jack.
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Old 21st Aug 2006, 12:54 pm   #5
atoof
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Default Re: digital video converter

hi all
thanks for your reply
sorry but i think that i didn't explain my aim to let you understand,so i will try agian
i want to make a circuit that convert MPEG fils to can see it in my TV without tv card
how can i do that??
let's say that i can send MPEG file outside my PC using parallel port(anyway MPEG is a type of data),so let's say again MPEG now at the input of SAA7128
and to try this idea i must make correct H/W of the circuit,so i need help to make it.
so first i need to understand pins (LLC,RCV1,RCV2,SCL,SDA)
and synch signals so anyone can help me plz do
and if i make it i will send full design S/W & H/W for all
thanks
atoof
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Old 21st Aug 2006, 1:19 pm   #6
Duke_Nukem
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Default Re: digital video converter

It'll be a major task to implement the hardware to do this - a very long job and then you'll have to write your own driver to send the MPEG stream to it.

Much better is to get a cheap capture card with "TV" and / or composite output. Provided you have an MPEG decoder codec (you may have to buy one seperatly as those shipped with DVD playing s/w are often locked to that player or you loose features - such as sound!!! - Elecard sell a good 'un thats reasonably cheap). You should be able to convert the stream to 24-bit RGB and stream it to the video output using DirectShow with very little software effort - and zero hardware effort ! In fact you need write no software - get a copy of "GraphEdt" which is part of the DirectShow SDK and you can manually build a graph to test if it all works.

BTW, I seriously doubt the parallel port is fast enough for streaming any MPEG stream that is of reasonable quality. Even if it is you will have a serious headache clocking the data out with any accuracy.

TTFN,
Jon
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Old 21st Aug 2006, 1:23 pm   #7
ppppenguin
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Default Re: digital video converter

I'm not sure how to explain this but you are a very long way from a workable design. If you are sure that you want to do this I strongly suggest that you get the book I recommended and understand the implications of what you are trying to do. It is not simple. Merely understanding the SAA7128 will get you just a very small part of the way.

For example, the terms SDA and SCL are very common and refer to the 2 signals of the I2C control bus that is widely used. If you have to ask what these are (and haven't bothered to type them into Google to find out) then there is little we can do to help you.

There are 2 people in this forum (possibly others too) who have the professional skills and experience to properly understand what you want to achieve. While we are often willing to help those who wish to learn it really isn't possible for us to run a distance learning course in the art of digital video. Yes, it is possible for enthusiastic amateurs to do some very good electronic design. There are a few here in the forum such as oldeurope (Darius) and Fernseh but they started from a good solid background in electronics maintenance. It's also worth reading the posts from Kat Manton about her excellent work in using modern PCs and Linux to do video tasks that were previously done only by specialised hardware.
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Old 21st Aug 2006, 1:54 pm   #8
Kat Manton
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Default Re: digital video converter

Hi,

I've not decided whether to call it "laziness" or "efficiency" but I don't see any point in reinventing the wheel. I can design complex digital electronics (and sometimes lash up an analogue circuit which works.) But if I can find a way of avoiding any design work and/or writing software, then I will - as I think a few forum members might have already noticed

Watching MPEG video files on a TV set has been done. It doesn't need reinventing.

To watch an MPEG video file on a PC using a TV set, all it takes is a video card with a TV output (usually they do S-Video and composite as well as RGB+syncs.) I have here nVidia GeForce 4 and nVidia FX5200 - each cost under £15 secondhand.

Then, with Linux on the machine I have a choice of mplayer, xine or vlc media players, all of which will play not only MPEG files but pretty much any other video file format as well.

I've not had to design any circuitry, write any software, spend more than £15 (I already have a few computers) or do anything all that complicated - and I can watch not only MPEG files but just about every file format you'll find. Not only that, I can watch them on (so far) 240p/25, 405i/50, 525i/60 and 625i/50, fullscreen.

I don't understand why you want to do what you want to do. If it's for academic interest and self-education then fair enough. But it'll take you a long time and cost far more than a second-hand nVidia FX5200 and a blank CD/DVD to burn a Linux distro onto.

If it's something like wanting to have the PC monitor connected as well as a TV set then fit two graphics cards in the machine.

The problem we're having is understanding why you want to do this the difficult way when the easy way has already been around for several years and works fine. Still, occasionally someone decides to swim across the English Channel even though there's a perfectly good tunnel and ferries...

Regards, Kat

Last edited by Kat Manton; 21st Aug 2006 at 3:12 pm. Reason: Bah. Typo.
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Old 21st Aug 2006, 3:51 pm   #9
Kat Manton
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Default Re: digital video converter

Hi,

I've just had a look at the datasheet for the SAA7128, it doesn't appear to be as versatile as the video encoders typically fitted to the graphics cards that have TV outputs. These encoders have a scaler in them as well as PAL/NTSC encoder. From a quick scan through the SAA7128 datasheet I don't think there's a scaler in it; it is a bit basic.

OK, I'll try to be constructive. The parallel port isn't going to work; you need something which supports higher data transfer rates. The PCI or AGP interfaces in the PC support quite high transfer rates and would be suitable for this; besides, fitting the device inside the PC is neater.

The SAA7128 appears to need feeding with digital video already scaled and interpolated to the resolution and timings of the TV you intend to use. So, you'll need a graphics controller as well. There are graphics controllers available which interface directly to the AGP/PCI bus. You'll also have to decode the MPEG data somewhere, you can either do this in software or use a hardware decoder somewhere in your circuit, or split the work of decoding MPEG between software and the graphics controller.

But, if you do this, what have you ended up designing? A one-off PCI/AGP graphics card with TV encoder and TV output. Do you think you can do better than the R&D team at nVidia? If so, I wish you the best of luck.

Regards, Kat
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Old 21st Aug 2006, 5:44 pm   #10
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Default Re: digital video converter

Wow, Kat, There's not much more to say on this subject!! You actually "lost" me after.........................Hi, !!!!!!!!!
Cheers, Percy.
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Old 21st Aug 2006, 6:31 pm   #11
Kat Manton
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Default Re: digital video converter

Hi Percy,
Quote:
Originally Posted by percival007 View Post
You actually "lost" me after.........................Hi
Sorry about that. What it boils down to is that my perception of atoof's requirements is that, instead of using a readily-available PC graphics card with a TV output and readily-available software, they want to design a PC graphics card with TV out and write the software for it from scratch. If you analyse the problem and come up with a good solution, you end up with something which already exists.

What was I demonstrating at the NVCF earlier this year? Not having an off-air source, I had some MPEG files on a PC and was playing them back though a 405-line TV. When Cobweb and I watch TV we're playing back MPEG files on a PC through a 25" PAL 625i/50 TV. It's been done...

The only way I can understand a desire to reinvent this is perhaps for a final-year university project or out of an interest in understanding how PC interfacing, MPEG encoding/decoding, scaling/interpolation, digital video and analogue video work. We've not really got a lot to go on...

Regards, Kat
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Old 22nd Aug 2006, 1:40 am   #12
arjoll
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Default Re: digital video converter

For what you've described you might also want to look at something like this - a small set top box that plugs into a LAN and can stream MPEG data from a PC running a small server application.

It means you don't need to have a PC plugged directly into your TV.

I'm skeptical of getting the best performance on 802.11g though, stick to a wired network for streaming.
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Old 22nd Aug 2006, 9:00 am   #13
atoof
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Default Re: digital video converter

hi all,
thanks for every reply
i want to explain something, i have a very good tv card in my PC
that can make me connect tv with pc as a second desktop and work while watching tv or movie from my pc
plz don't be angry
i want to learn and i think if i make it, it will be a very good experience but i need help even by word or book or link or advice that's all
return to my problem:
parallel port may be slow ,it's ok i can use PCI (as a first step )or USB(up to 480Mb/s)+FIFO device but i want to fully understand datasheet and may be i need help from my friend who work as a programmer so let's say i/p format is not the aim now i asked about (LLC,RCV1,RCV2,SCL,SDA)
i think SCL,SDA is not affect my case,LLC connect it to oscillator??
usage of RCV1,RCV2??
so any one pretend that the chip now is available (and i/p too) what will be the interface circuit?
thanks
atoof
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Old 22nd Aug 2006, 9:32 am   #14
ppppenguin
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Default Re: digital video converter

RTFM . You will soon see that the SAA7128 is only a small part of your project. Get the book I suggested.

May I politely suggest that you are not really in the right forum. While there are a few of us here who have some knowledge about what you are trying to do, it is very much a sideline to our main interest which is VINTAGE technology. I suggest that an electronics design or PC forum might be a better place for your ideas.
Attached Files
File Type: pdf SAA7128H_7129H_2.pdf (207.9 KB, 90 views)

Last edited by Duke_Nukem; 22nd Aug 2006 at 12:11 pm.
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Old 22nd Aug 2006, 12:06 pm   #15
Duke_Nukem
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Default Re: digital video converter

I guess this thread has reached it's conclusion.

Sorry atoof, but this really is outside the realms of vintage technology. What you are trying to achieve is very technical indeed and your best bet is to seek out a specialist forum. There may be some reference designs for the chip you intend to use and studying those will be the first step.

Good luck ! (You'll need it )

TTFN,
Jon
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