Ok, here is my first run at a compilation post. I'm hoping that we can tweek this out a little bit and start a new thread with it so that the information is a bit more compressed and more focused on DIY. Perhaps Glimmie's post about the rp56 can be the first follow up to this on the new thread to sort of get the ball rolling.
Feel free to rip this apart. I have no qualifcations to actually be doing this. Everything I know about SDI I learned here.
The first record that I can find on this board of someone modifying a plain old piece of consumer electronics for SDI output is from about a year ago. In that time it seems that less interest has developed for this idea than I would have guessed. For such a relatively cheap and accessible modification that can be done to such a wide variety of devices I would have expected a lot more excitement.
What I am particularly interested in is the do it yourself aspect of this. There is certainly a higher than normal amount of technical skill involved in this sort of modification. It does not, however, have to be something only doable by the electrical engineering elite (eee from now on). If we can compile a good set of documentation about a wide range of devices with specific instruction, I lot more people will be able to enjoy a pure digital signal path. Obviously we need the help of the eeeâ€™s to accomplish this but I think we have a few of them on this board.
To this end I have attempted to compile as much information as I can from a year of posts. This is mostly taken from the â€œPoor manâ€™s SDIâ€ thread. (http://www.avsforum.com/avs-vb/showt...128&perpage=20
) There are quite a few contributors. Robert Cobler is the one that started the thread and obviously a lot of this is right out of his posts.
SDI stands for Serial Digital Interface. In reality SDI is more of a protocol than a specific device. It does pretty much what it says -- serial communication of digital information. This makes it a very useful method for transporting digital data over relatively long distances. The data that we are interested in is 480i data. There is HD-SDI but that is a topic for another day (another year?).
Whatâ€™s the goal of this?
What we are trying to do is high jack the parallel data coming out of the mpeg decoder of whatever device we are dealing with. Once we have this data, we convert it to serial so that we can send it off to be processed. This can be input into any device with a standard SDI input. These include many video processors and htpcs with SDI Silk cards. By doing this, the video processing is being done on a digital signal that has always been digital. (not really always, but it hasnâ€™t been analog while in our possession at least) The processor can do a much better job with this data because it free of any of the artifacts that are introduced in analog to digital and digital to analog conversions. If you have a digital out on your processor and a digital in on your display device, you can successfully skip any conversions al together. Sounds fun right?
What is needed to perform the modification?
National Semiconductor's CLC020 digital video serializer with integrated cable driver seems be just what the doctor ordered. Conveniently, National makes an evaluation board (part # SD020EVK) with bnc outputs that basically has everything needed to do a modification to a SMPTE compliant device. This board is $100 and while it takes a while to get, does seem to be available from National Semiconductorâ€™s distributors. We could of course use a design for a home made version of this if any of the eeeâ€™s are interested.
What sort of devices can be modified?
For starters the device needs to represent the video data digitally somewhere. That 1989 Sony VCR isnâ€™t going to be modifiable. Weâ€™re talking about DVD players and set top boxes primarily here. These devices decode mpeg data into the digital video and then do their business with it (convert to analog, de-interlace, . . .) and output an analog signal via component, s-video, etc.) We need to grab the data after it is decoded from mpeg but before it gets to any of these other steps. For this reason the device must not have a mpeg decoder that is integrated with other pieces of this puzzle. Further the data needs to be SMPTE (whatever that means) compliant 8 bit parallel data. There also needs to be a 27mhz clock signal available for the evaluation board. If there is no clock signal available or the data is not compliant there is still the possibility of successfully modifying the device. It will just take more work and more help from an eee. What devices are these specifically? Well, part of the goal here is to find out. Right now it seems that Pioneer (727, 939A, 37, 38A, 444, 434, 545), Denon DVD3300, Technics A10, and Panasonic (A7, RP56, RP91) are fully compliant and modifyable. DirecTV Tivoâ€™s, and Dish 6000 are not compliant but can be modified with more work. It seems likely that there are more.
What are the basics of this modification?
Given a fully qualifying device as listed above the installation is fairly straightforward if not simple. You simply solder a ribbon cable onto the device being modified and plug the other end into the SD020EVK board. Simply is probably not the right word as this is TINY stuff and fine tipped solder iron, a microscope/magnifier and some amount of skill working with surface mount devices is required. But heh, learn by doing, right?
What if my device has no clock or the signal is not SMPTE compliant?
All might not be lost. In all likelihood the clock is just hard to find. If it is inaccessible creating your own is a definite option. As for a non-compliant signal, well this is tougher. What seems to happen is the start of active video (SAV) and end of active video (EAV) signals are not present in the data. These have to be there. The only option is to add a programmable logic device into the equation that adds these signals. If this is done, everything else is the same.
What do we do now?
The goal is DIY SDI for the masses. If you have accomplished this on a player and wouldnâ€™t mind sharing/showing off, lets have some specific instruction for the device that you have successfully modified. How about some close-ups of your soldering? How about some detailed descriptions of locations. Imagine that you have a group of technically savvy people that may be able to accomplish the physical task of soldering this together but probably donâ€™t know an 8 bit parallel SMPTE compliant bus from a school bus. Create the instruction necessary for them to try and pull this off while only ruining a couple of DVD players.