| Author | Message | ||
     ken_tetterington Rating: N/A |
Where can I get an NTSC VCR videotape formatted for lenticular televisions? Ideal is a tape with a single pixel offset alternating between left and right imbedded images. The one image (left or right) needs to be on the vertical odd lines while the other image needs to be on the vertical even lines. Thanks in advance . . ================== Ken Tetterington ken@selectrics.com | ||
| Anonymous Rating: N/A |
You can't, none exist off the shelf! Plus trying to get left/right views to align with the lenticular lenses on a standard CRT TV would be a nightmare. | ||
| ken_tetterington Rating: N/A |
Thanks; I find it hard to beleive that no one has a 3D sequential tape converted to lenticular format. Did the old 'HeadMax' HMD come with a double lined lenticular style formatted tape? ========= Ken | ||
| Christoph Bungert (Admin) Rating: N/A |
###Ideal is a tape with a single pixel offset alternating between left and right imbedded images. With analogue video technology this is impossible. Even on DVD it's nearly impossible. Even if you use an LCD-screen or DLP/LCD-projector with DVI-input it could hardly work, because the scaling of the device would destroy the order of vertical columns. The best way to do it would be to use a frame sequential DVD and a PC-software-player which remaps the stereo pairs to vertical-line-sequential-format in accordance to the choosen screen resolution. Maybe Peter Wimmer could add this mode to his Stereoscopic Player. http://mitglied.lycos.de/stereo3d/ Christoph | ||
| M.H. Rating: N/A |
In DepthQ (www.depthq3d.com) this functionality is already implemented (vertical interlaced pattern output for autostereoscopic devices). Eventual support for multiple views could be easy added ... | ||
| Anonymoose Rating: N/A |
If you're just looking for no glasses 3D, there are off the shelf solutions available. DTI's autostereo displays (www.dti3d.com) accept input in standard formats including interlaced, etc. You can play standard 3D movie DVDs and tapes through them. Stereographics (www.stereographics.com) and 4D-Vision (now owned by X-3D) have multi-view lenticular lens displays, but there is no video content available for them. | ||
| Ken Tetterington Rating: N/A |
Hi Christoph; Although I have not worked extensively with video reformatting - my understanding of NTSC and PAL analog is that there are two fields per frame. On a sequential 3D tape, the one eyes image is in the first field and the other eyes image is in the other field. Both fields make a frame (in Interlaced TV). The pixel structure of a TV and PC are different with the TV pixels output in small R,G and B rectangles (which make a complete pixel). These pixels are rowed top to bottom, although not exactly vertically aligned. It seems that it should be simple to format a sequential 3D tape into a crude lenticular style. Although interpolation of the aspect ratios may be needed. Each TV pitch would need a different lenticular grid to compensate for the various TV screen sizes. All standard interlaced NTSC TV's have the same resolutions. What am I missing ? Is it not as simple as taking the first pixel from the first field and placing it in the 0,0 position of field 1, and taking the first pixel from the second field and placing it on 0,1 of field 1 - and so on? ======== Ken | ||
| David C. Qualman Rating: N/A |
As Cristoph suggests, it is almost impossible to record lenticular images on the recorded medium in any useful manner. Not all TV displays have the same number of phosphor dots across the screen. This is different than monitors, in which each phosphor dot is meant to represent a pixel from the computers memory. Instead, in NTSC or PAL TV land, the image is just a stream of analog data. There is almost no concern if a particular portion of the image hits a particular phosphor dot, or instead, hits its neighbor. Thus, the scaling problem. If the image is recorded in vertically interlaced format, but the one TV screen has different timing or phosphor density is than another, the image on one TV screen may be right, but the other will be terribly wrong. Also, if the lenticular grid is aligned to the image PERFECTLY on one monitor, then it wouldn't align with the image on the other. This would be a severe problem if the video was recorded with 640 vertically interlaced lines, but was played on a display with 800 vertical lines. (Don't forget that the standard assumption of 640 by 480 for NTSC signals is a convenience used by us digital guys. It has no reality when compared to the analog NTSC signal. It is just as easy to digitize the NTSC signal with 642 pixels across - which is what would occur if a CRT phosphor mask had 642 dots horizontally) As you can see, you need to solve two problems - keeping the dots on the screen aligned with the lenticular grid for all monitors, and to keep the timing of the playback constant for all monitors to match the lenticular grid. The first problem could be solved with LCD TV's, or other digital displays. The second could be solved by separating the stereo-encoding method from the playback method, as Cristoph mentioned. Record the left and right images separately - field or line sequential. Then, encode the two images into a vertically interlaced image during playback, so that it will match the resolution and timing of the TV. BTW, Ken - the RGB information in an NTSC signal is aligned left to right, not top to bottom. So, it is nearly trivial for image data to shift horizontally when coming from an NTSC signal - especially when coming from a physical device such as a VCR head. Also, all NTSC TV's do not have the same horizontal "resolutions" - especially the CRT's. They have different overscans, and a different number of phosphor dots (since they are for analog and not digital signals). So, an image can be stretched a small amount horizontally. Keep in mind that with lenticular, you need registration accurate to at least 1/2 pixel, or about 1/1280'th the screen. This means no more than 0.078% variation in horizontal timing and scaling. You can safely assume that a consumer-quality VCR cannot provide this. | ||
| Christoph Bungert (Admin) Rating: N/A |
Hello Ken, what you are missing is that the horizontal lines in PAL and NTSC which are used for 3D-VHS and 3D-DVD are part of the standard. PAL always has 625 lines, NTSC 525 lines. These lines remain stable, even on a very bad VHS tape recording. So it's easy to use the lines to seperate the two stereo-channels. The pixels within a single line however are defined by an analogue wave-form. The no. of pixels or vertical lines you can display depends on the quality of the recording, the player, the cables, the TV-set, etc. etc. The signal is very vulnerable, so the no. of pixels/vertical rows can change from frame to frame. You can't address Pixels 1, 2, 3, etc., because the precision isn't there. On CeBIT I saw a 30,000 $ lenticular autostereo display with a professional VGA-board connected via analogue VGA - and it was bad! There was ghosting. They told me this is due to the VGA-connection. It's vulnerable to temperature, etc. They also showed me the same display type with DVI-connection and it was almost perfect. If you can't address the pixels precisely vertical-line-sequential-stereo is a mess. Christoph | ||
| Ken Tetterington Rating: N/A |
Thanks for the great input David / Christoph. ========= Ken | ||
| M.H. Rating: N/A |
Ken: On the fly direct conversion of analog stereoscopic (e.g. from VHS or DV camera)signal to any other output format (page flipping, vertical interlaced for autostereoscopic monitor) is a solved problem. We can use instead of file source a real input source (reorcder, camera) for the DepthQ rendering engine .... | ||
| Anonymous Rating: N/A |
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