http://www.wam.umd.edu/~walrus/DCTV.html (Amiga Plus Extra No. 5, 08/1997)HTML formatting provided by Udo Schuermann <walrus@wam.umd.edu>.
Joey McDonald can be reached by email as Joey.McDonald@209-254-8.genesplicer.org.
I did NOT include UUencoded files of the image(s) because I did NOT want to upset anyone in this group by uploading large binary files. If you would like to recieve the ALREADY CONVERTED froggie.dctv image discussed in Chapter 1, e-mail me and I'll send you the file -or- call the local BBS I use most often.. "ICON" (702) 646-3631 and download the DCTVpost.lha archive. (once logged on, enter "F", then "FI" at the files prompt to enter the search menu). I am not able to upload the images to an FTP site at the moment, if you can obtain the images (from me or the BBS) and uplaod them to an FTP site. it may make it easier for everyone to get to them.
All text/documents and information contained within is (c) copyright 1996 Joey McDonald. You may distribute these documents FREELY via any means possible as long as you do not charge a fee for the information/documents and do not alter them in ANY way.
If you do embark on a software project based on these ideas.. be sure to e-mail me and I will add the information to these documents.
Enjoy! And please feel free to e-mail me your responses, additions and corrections. Any technical data/info concerning DCTV would also be welcome.
Joey Mcdonald joey.mcdonald@209-254-8.genesplicer.org
DCTV constructs its composite video output from special screen data contained in an Amiga hi-res, 3 or 4 bitplane display. The 4-bit mode delivers the highest possible display quality, while the 3-bit mode sacrifices a small amount of image detail to produce smaller file sizes and animations that ply at a higher frame rate. Since there are no software options for a 1 or 2 bitplane display mode you may have assumed that DCTV requires at least an Amiga 3-bitplane display to function properly. You're in for a pleasant surprise. I have discovered that DCTV is quite capable of functioning in an Amia 2-bit mode while retaining most of its composite color palette and display quality. Since the 2-bit mode is not supported in any way by the software, it's currently impossible to directly create a 2-bit DCTV image. To demonstrate the potential of the 2-bit mode we will need to use a separate progrm to convert a previously created image. What follows is an explanation of the conversion process in the form of a mini-tutorial.
For this exercise you'll need DCTV disk#3 (included with DCTV) and the image processor Pixmate. I have not found another image processor capable of generating the required results. It's pointless to use a program that first converts an image into 24-bits (ADPro, ImageMaster) since DCTV only needs upto 4-bits to comprise an image. It's also important to note that the Pixmate program has been discontinued. All descriptions of screens and controls are representative of version 1.1.
Before we begin make sure your DCTV is connected, we'll want to view how our actions within Pixmate effect the composite image. When a Pixmate control window opens on the image it may distort or block the composite display. Holding the right mouse button down will temporarily remove the window allowng you to view your progress. A two monitor set-up is ideal, but a single monitor with RGB switching (such as the 1084s) will suffice.
I will describe the conversion process in two major steps. We'll start by converting the image into its 2-bit form, and then rap things up by making a few necessary color adjustments. After we have finished this tutorial I'll discuss the reasons some images do not convert well and further possibilites for this new display mode. Let's go!
Choose the DISPLAY item from the "effects" menu to open the display control panel. Looking at the gadgets that represent image bitplanes you'll notice that number's 1 through 4 are highlighted (indicating that we're working with a 4 bitplane image). When working with a 4 bitplane DCTV image you willalways want to discard plane numbers 1 and 2 (only plane number 1 for 3-bitplane images). We can't actually remove the planes at this time, so we will temporarily render them inactive. De-select the number 1 and 2 gadgets and then close the display window to exit back to the main screen. Our composie image should exhibit a noticeable loss of color and a small reduction in detail.
Next, go to the "color" menu and select the PACK COLORS item. Pixmate will then process the RGB image and re-map the palette. This process does not generate a viewable difference in the composite image, but it's a required step before performing any further actions. You can also use the LESS COLORS tem from the "color" menu to achieve the same results (by inputting a "4" for the number of colors to use) but the process is slower than simply selecting PACK COLORS.
Once again choose the DISPLAY item from the "effects" menu to open the display control panel. The bitplane gadgets will again indicate that we're working with a 4-bitplane image. This time de-select plane numbers 3 and 4 (you should not see a change in the image) and then select the REFORM gadget. Arequester will pop up informing you that "image bitmap change will permanently discard some bitplanes, reducing the number of colors." Since we have already processed and re-mapped the appropriate colors, we have nothing to lose by continuing. Select CHOP PLANES to remove the unwanted bitplanes and ransform our picture into a 2-bit image (figure 2).
Now that we have chopped the unwanted planes and reduced the number of colors, it's time to proceed to step #2 and do some tricky tweaking (say that 5 times, fast) of our images' palette.
There are two different methods we can use to achieve the results we desire. The first method offers fairly precise control over color correction, while the second method offers less control but is an easier and faster process to perform. Both are capable of excellent (and practically identical) reslts.
Before we begin adjusting color levels, it's important for you to remember that we're working with a DCTV image. The palette controls will effect our composite display in a vastly different way than an ordinary RGB display. Also, because of small differences between certain DCTV equipped Amiga systes the color values given below may be slightly different from those required on your system. If you experience problems, experiment to find the most effective values.
For this image (and the majority of images you will convert) only the blue-levels for each color need to be adjusted. We will start with the last color on the right (color 3) and work left to color 0. I have listed all 4 setting adjustments below as steps A through D.
Before we celebrate our successful conversion and rap up the tutorial, I'll quickly demonstrate the second method of correcting image color and detail. You may wish to save this image before we proceed in order to compare the separate results.
Choose The "color bias" option from the COLOR menu. A window will appear offering a variety of image enhancement controls. Unlike the RGB sliders offered by the palette window, these controls effect the entire range of colors, not just one specific color at a time.
The only control we need to adjust is the blue-level slider. Simply increase the value to 57 (the highest setting possible without causing distortion) and you'll see an immediate and vast improvement in the composite image. Using this single control you can quickly and easily achieve results similarto (if not identical to) those obtained using method #1.
By experimenting with the controls on the color bias panel and palette window you may find that other interesting enhancements or image effects are possible. It's also worth noting that DCTV is even capable of displaying composite data from an Amiga 1-bit image.. (although the display quality is ver poor).
A reduction in file size is one of the real advantages of generating a DCTV display within 2-bitplanes. The original file size of the 4-bit froggie.dctv image was 109614 bytes and our 2-bit version weighs-in at only 63734 bytes. That's a savings of 45880 bytes without any added file compression! Obvously the results will vary depending on the image being converted, but I have found that most images will yield at least a 40-50% reduction in file size, while in certain instances you may achieve a 50-60% (or greater) reduction.
We have not only achieved a savings in storage space, we have also gained an increase in display speed. Try viewing the image with a display utility and you should notice that it appears on screen faster than the original 4-bit image. Loading the image in to a program such as Deluxe-Paint and then ceating a small animation (using the MOVE requester) should make the speed increase even more apparent.
With such a dramatic reduction in image file size and a visible increase in display speed, the DCTV 2-bit display mode shows great potential in the area of animation. Let's take a quick look at what the requirements are to animate in this new mode.
To offer a rough idea of the potential anim file size reductions and increases in animation speed, I opted to manually convert the SceneryAnim.anim file found on DCTV disk #4. Not having the luxury of owning a commercial program capable of splitting and compiling animations, I relied on two programsavailable on most good BBS's. BuildAnim2 (by Christer Sundin), and AnimBuild (by Michael Hartman). BuildAnim2 can perform both splitting and compiling but had problems compiling this particular anim. I relied on AnimBuild for animation compiling.
Using BuildAnim2 I split the animation into individual frames. I then performed the 2-bit conversion on the first anim frame and saved the results. To speed up the tedious process of palette adjusting I used the Pixmate "Load Palette" option to load my set palette for each additional frame. After coverting all of the remaining frames I used AnimBuild to re-compile each 2-bit image back into an anim file.
The original anim file size was 452398 bytes. After conversion the size was reduced to 276810 bytes, a savings of 175588 bytes without any added file compression. Compressing the converted anim via PowerPacker yielded an additional 37% reduction in size, for a total file size of 175196k. That's neary 200k savings without added compression and nearly 300k with compression.
Satisfied with the reduction in file size I then proceeded to test the animation on a variety of popular anim viewers. View3.0 (contained on DCTV disk#4) and PPSHOW3.0 displayed the anim without any problems. View3.6, Superview3.12 and Viewtek2.1 also displayed the anim properly but required manual entering of the display via the arrow keys. For an unknown reason the Viewtek program played the anim with a "glitch" or color blotch on a few frames. This did not occur with any other viewer.
Whichever player program you use, look for the ability to manually center the display. An improperly centered screen will prevent DCTV from detecting and displaying an image or anim correctly. (The 2-bit display mode seems to be a bit more sensitive to centering, make sure animations are centered corectly when recording to video tape or you may end up with b/w or distorted output.)
As far as gaging an actual increase in animation speed, I relied on the information provided by the View3.6 program. On my SupraTurbo (28mhz 68000) enhanced Amiga 2000 the stats were as follows. Before conversion: 6742 avg DLTA, 44,9982 avg FPS. After conversion: 4092 avg DLTA, 60,0000 avg FPS. Admitedly not the most accurate test results, but fairly informative. There is a notable FPS (frames per second) increase and a reduction in avg DLTA (less pixel changes in the anim,.. which is not surprising considering we have chopped two bitplanes).
Overall I was very impressed with the results. Any loss of image quality due to the conversion process is far less noticeable while an animation is playing. I certainly don't believe that the SceneryAnim conversion is the most effective example of the quality of 2-bit DCTV animation, but I believe i does give us a basic idea of its capabilities. You'll have the ability to play longer, more complex animations at faster speeds while using less storage space and less memory.
A utility designed specifically for performing the conversion would not only be more convenient to use but also far more effective. It's possible that a variety of techniques designed to match, antialias or dither colors could be implemented to further enhance the quality of converted images. The reults would almost certainly be superior to what we have achieved using Pixmate.
The question then arises, why settle for conversion? Current software could be updated and new software designed to take full advantage of this new display mode. Paint and digitize software designed to work within the limitations of the DCTV 2-bitplane palette may not generate the image streaking orcolor distortion that often occurs during conversion. Imagine being able to directly digitize images equal in quality to our converted froggie.dctv picture while retaining file sizes in the range of 50-60k. Sounds good to me!
I would urge Digital Creations (or PLAY inc.) to support DCTV with new and updated software, but looking back at there track-record of only one update in four years, I don't think that's going to happen any time soon. If they will not support DCTV they should place all hardware specs and program cod in the public domain to promote the creation of new software. The P.D. approach certainly worked for BlackBelt's Ham-E device which enjoyed heavy support by 3rd parties, including direct support within various frame grabbers, as well as 3 separate paint programs (2 of which allowed animation). It wuld be nice to have those kinds of choices with DCTV.
While it's true that this new mode is nothing more than a hack of sorts and that it's certainly not a professional display, I'm sure there are plenty of artists and animators who can find many interesting uses for it. If you're working on a low memory or small HD system it may give you the extra wor space and speed increase you've been looking for. If there are some clever programmers looking for a challenge, it's a new frontier just waiting to be conquered. I hope to hear more about this exciting discovery in the future.
However when you try to load one of these images into a viewer that allows scrolling, you will encounter problems. When you scroll.. DCTV will not be able to decode the image data. The reason; DCTV requires the top scanline which contains special information, as well as the left "zipper" lines (2 vetical lines on the left side). When that data is moved off screen, the image will not register with DCTV.
While tinkering with a p.d. program called Dswitch (that allows you to do a few odd things with your DCTV.. such as pass video through, etc.) I noticed that when you select Dswitch's RGB mode that you can actually scroll from top to bottom of a LARGE DCTV display with virtually no problems. I am nota programmer and I'm not sure what the Dswitch program does to allow this (it was not designed for that purpose). But, when I found this out.. it got me thinking about HOW it would be possible to scroll a HUGE DCTV image without any problems.
There may be a much simpler approach to this... but I have at least presented an idea and a starting place for a NEW type of DCTV display. Imagine the possibilities of Huge 1200x1200 -SCROLLING- DCTV backdrops! I can see possibilities for incredible DCTV video titlers with "rolling" backdrops, etc.
I know that this will work. I entered DeluxePaint with two DCTV 640x200 displays and stamped them BOTH down on a 640x400 screen. Both images are displayable as a single scrolling image (the special viewer would be need for proper display). I did note that a program that combines many DCTV images int a super bit-map display might need to clip and remove the top line (magic cookie) from all images below the first (top image). The zipper must always be properly aligned upon combining images.
It would also be nice to have a PAINT program capable of scrolling through a DCTV super bit-map image.
This Tip will show you how to save time and create quick titles for your DCTV productions. The titles created can be used as a quick preview to get an idea of what your finished product will look like, or perhaps as low-budget titling!
Load your DCTV picture into DeluxePaint or similar paint program. try a 3-bitplane image.. Some 4-bitplane images seem to have a few problems handling this trick. De-select the menu bar to see the picture. Go to a spare page (j) and use one of the available colors to create a title.
Now cut-out the title as a brush and hit the J key to return to the DCTV image. If you check your DCTV output.. you'll see that you are now actually displaying an RGB brush OVER the dctv composite output. two of the colors available in the color selector will cause severe distortion so you'll need t select the correct colors. Try selecting the "color" option and browsing through the available colors to see how it appears on the composite output. (you may have problems with distortion when using very large fonts). From here on.... just create your title as if you were working with a standard IF pic.
You can use the move requester to flip, rotate, spin... and animate your title OVER the DCTV backdrop. Because the text is RGB it will be much more crisp than the text created within the DCTV paint program. (ALWAYS BE SURE NOT TO LET THE TITLE BLOCK OUT THE TOP Line or left "zipper" lines.. that wil distort the image or cause DCTV to not display it at all).
With a little practice you can get great results. The title cannot have many colors... usually 2 or 3... (Black and White are always available). You should use the outline option to outline your titles with a different color so they'll appear more detailed. (white text outlined by black, black outlied by white.. and if your really tricky you can add a grey in there somewhere :) Also as noted above, some 4-bitplane images seem to distort when titles are placed this way...especially when using large fonts. But remember, you're doing something you're really not supposed to be able to do (mixing RB with DCTV) so experiment to see the different results.
With this approach, you can quickly add RGB titles over a DCTV image without the use of a genlock or the DCTV RGB converter. The end result is not perfect, but for many low-budget purposes it may be just the trick! It's also a good way to preview an idea you may be working on.
Also, if you CUT a portion of the DCTV image and shrink it down ("-" key in Dpaint) .. you can create neat "rainbow" brushes that you can FILL your title with! It gives kind of a "sparkly" rainbow effect.
You can also add 2 color (black and white outlined) RGB animations (cartoons) over the DCTV million color display.
The techniques in this tip are really not very practical, but you never know, you may want to add a bizarre touch to one of your DCTV video projects.
When adjusting the cycling RANGE do not use the first two colors or any black colors in a range (this will cause the image to blank-out).
Adjust the ranges carefully, experiment a bit and you'll see that you can get some really weird results.
If you don't want to switch between RGB and composite using your monitor switch.. get my DC-WB program. It works in conjunction with the Dswitch program. Simply click a button or hit a function key to bring up your Amiga display through your composite DCTV output. NO MORE switching between RGB and cmposite with your monitor switch! If you can't find my DC-WB program on your local BBS.. it's available on my local BBS.. ICON (702) 646-3631 or e-mail me for it!
So, you have always wanted to animate in Hi-Res 16 color mode on your ECS Amiga, but the animations always play "choppy". Well, the DCTV 2-bit mode will allow you to play just about any 16 color Hi-Res animation at 2 or 4 color speeds and chop your old DCTV file sizes in half!
Take a 4096 color HAM (or better) animation and re-render it to dithered 16 color hi-res. Convert the animation to DCTV 2-bit mode and there will ussually be NO LOSS in detail between the dithered 16 bit anim and the DCTV 2-bit anim. You can also convert existing 16 color hi-res anims and chances ar they will convert without losing detail.
The DCTV 2-bit mode allows you to animate DITHERED 16 color hi-res animations without the "choppy" playback that ussually accompanies such animations, while offering incredible savings in storage space and memory use.
Once software appears that will allow you to convert anims automatically, then there will be much less grunt work involved.
I have not tested how well this aproach works on dithered 32, 64 or 4096 color ham animations.. but there may be some loss in the conversion. We will have to wait for new software to see if there are ways to get the most out of the DCTV 2-bitplane pallette.