slau Posted January 9, 2004 Report Share Posted January 9, 2004 I am wondering what will be the optimium image resolution (i.e. 720X480) of PTE images if the targeted final product is for NTSC DVD . When I was doing video with Ulead MSP6.5, I stretched the still image from 640X480 to 704X480 (please don't ask me why as this was from trial-and-error) before I dropped them on the timeline, which seems to avoid or minimize distortion (square pixel in computer vs non-sqaure pixel in video). As I have no idea what PTE does when it creates the intermediate .AVI file, does anyone know whether there is any adjustment during the avi file creation process?I am attaching part of the message from the Ulead site regarding Image Distortion (http://www.ulead.com/learning/video5/page1.htm):Image distortion Images are always displayed on a PC screen using square pixels. All image file formats also use square pixels. This means that if an image is for example 640 x 480 pixels, it will display at an aspect ratio of 4:3.The same is not always true of video frames. For example the DV format is 720 x 480 for NTSC and 720 x 576 for PAL, but in both cases the final image when rendered on a TV is 4:3. When these frames are displayed on a computer (e.g. in a preview windows while editing) they are usually slightly distorted - NTSC is horizontally stretched, and PAL is horizontally squashed.When a still image with square pixels is incorporated the different pixel shape must be allowed for, otherwise the image will be distorted the opposite way when shown on a TV. Some editors are smart enough to compensate automatically, others require you to do it manually. One way of doing the latter is to save copies of all your images "pre-distorted" to the equivalent of your video format. Use an image editor to stretch or squash the images horizontally, and use these copies to import into the video. Stretch by a ratio of 720/640 if working in NTSC, or squash by 720/768 if using PAL. Quote Link to comment Share on other sites More sharing options...
Eric Athroll Posted January 9, 2004 Report Share Posted January 9, 2004 Hi StephenI posted a reply to you in my other post earlier.I note your comment on the distortion and the advice given by Ulead - this is exactly the sort of information I am seeking. It seems so basic to technophiles perhaps, but to me I didn't know that the video image changes from the square pixel to an oblong one. This can be easily and rapidly corrected as a batch process in my imaging software (Photoshop).As you know, a digital still image displayed on a PC Monitor at 100% is optimum and only needs to be sized to fill the screen resolution. I assume that if there is such a thing as pixel equivalents for the various TV formats that is all that is necessary to do the appropriate conversions.Then, presumably, all the various bits of software (PTE, The Encoding Software, The Burning Software) need only be set to default for the type of disc being produced to give an optimum result. Or am I being too simplistic? Quote Link to comment Share on other sites More sharing options...
slau Posted January 10, 2004 Author Report Share Posted January 10, 2004 Hi Eric,The only reason that I know about square and non-square pixels is because I have been doing video editing for years. But, from reading my message, you know that I am still not sure about the image size 'should' be used for generating NTSC DVD.The reason we have been using/recommending image resolution of 800X??? for PTE slideshow is ONLY because of some viewers still have set thier computer monitor to low resolution like 800X600. It has NOTHING to do with the video format. Also, the recommendation of using file size ~ 100KB may not be appropriate any more for simialr reason. Should I be using 300MB files if my computer can handle the PTE process to generate .AVI? That is why I am asking the question like:Is there any benefit to go higher resolution than 800X??? or 720X??? if my final product is NTSC (or PAL) DVD movie? My experience in using still images in video is that the resolution can definitely be a lot higher than 720X480 (e.g. when you are planning to do a zoom-in effect) and it is only important to keep the aspect ratio. But I cannot remember can one see the difference in the final product. Also, how much do we gain from using larger file size (i.e. less jpeg compression--> better image quality)? Can we see the difference after all kind of rendering?I am just hoping someone here has already done the test and can save me hours of testing myself. Well, I will wait a bit before I jump right in. Quote Link to comment Share on other sites More sharing options...
Eric Athroll Posted January 10, 2004 Report Share Posted January 10, 2004 Hi StephenI know absolutely nothing about video having only used my camcorder (analogue Hi-8) to capture recent family stuff (grandchildren etc) I then carry out some basic editing to a master tape on my SVHS Video Recorder from which I make VHS copies for all the family.I have been a photographer for 50 years and digitally for three years so I am familiar enough with that aspect of the process.From my recent excursions into PTE I have found that the on-screen TV quality using jpeg images of a width of 768 pixels compressed to middle quality look very acceptable. A trial at 1024 pixels wide looked no better to my eye.As I have said before, all that is needed is information on optimum pixel count and compression of image files and details of any subequent stretching/compressing of the image to "fit" the various TV/DVD formats.Is this too much to ask? Quote Link to comment Share on other sites More sharing options...
potwnc Posted January 10, 2004 Report Share Posted January 10, 2004 Also, the recommendation of using file size ~ 100KB may not be appropriate any more for simialr reason. Should I be using 300MB files if my computer can handle the PTE process to generate .AVI? That is why I am asking the question like:Is there any benefit to go higher resolution than 800X??? or 720X??? if my final product is NTSC (or PAL) DVD movie? Stephen,I have not done exactly the test you are asking for, but I did post some time back asking about file sizes and I'm still wondering the same thing!In my experience I use the same format of JPEGs for both .exe and .avi -> DVD output - 800x600, the dpimakes no difference. For .exe I compress to about 200KB/file, but for DVD I don't compress and so thesame files are around 800KB typically. I keep the 4:3 ratio simply because most TVs are still 4:3. If someonewanted 16:9 I would re-scan all the slides! Setting the AVI option to 90% of the screen and putting the AVI through Roxio Easy CD/DVD creator, I get excellent results (most of the time - I have experienced someweird frame flicker, which nobody else seems to have experienced and to which Igor has not responded).I have also had excellent results going SVI -> TMPGenc -? Roxio.Even though I use 800x600, the actual video frames are 720x480 (NTSC). My (and most) DVD players are able to realize that the actual video is 4:3 and reproduce that faithfully on 4:3 TVs.I don't see any reason why larger sizes - e.g., 1024x768 would result in better DVD quality. I guess using TIFF files instead of JPEGs would, but it would likely only be noticeable on the higher quality digital and plasma TVs.Ray Quote Link to comment Share on other sites More sharing options...
potwnc Posted January 10, 2004 Report Share Posted January 10, 2004 I have also had excellent results going SVI -> TMPGenc -? Roxio. I meant going AVI -> TMPGenc -> Roxio Quote Link to comment Share on other sites More sharing options...
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