Talk:Key frame

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This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.

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Copyright issues, this is a plagiarism from Dictionary.com Dustin Asby 03:47, 28 Aug 2004 (UTC)

Huh ? Today http://dictionary.com/ redirects to http://dictionary.reference.com/ . Then I type "key frame" into the search bar there. It only gives me one result -- from the "Free On-line Dictionary of Computing". The article already credits FOLDOC. Why do you think there is plagiarism ?

Contents 1 what key framing does 2 Keyframing can apply to more than motion 3 Using shape hints flash animiation example mis-labeled? 4 Video compression

[edit] what key framing does

I think we need to include what key framing does. I mean, for myself, I am new to video and I am trying to learn as much as I can before I go out and start to ask questions. I now know what key framing is (thank you wikipedia), but how does it affect my output? For example: I want to export a movie I made with some video editing software on my computer at home. I choose to export it in Quicktime MPEG4 format. One of the options is "Key Frame every ___ ". What value should I put here? Well, I am not actually looking for a value in this example of course, but having an example like this I think would be quite benificial to many people. What does it mean to key frames every 24 frames? What does it mean to key frames at every time line marker and how does that effect my output if I am outputting to MPEG4, AVI, SWF, etc.? 143.232.84.80 19:42, 25 October 2005 (UTC)

The key frame rate should not visually effect the output at all. If you play back 2 movies, encoded from the same source with 2 different key frame rates, it should be difficult to tell the difference between either movie and the original (assuming you have a sufficient quality setting). Encoding a particular frame as a "key frame" will always require at least as many bits, and typically many more bits, as encoding that same frame as a P frame or a B frame. So to get maximum compression, you want to go as long as possible between key frames. However, most players can only fast-forward or reverse (rewind) to points marked by an I frame. If there were only one key frame per minute, people would be annoyed that they can only fast-forward or rewind in one-minute-jumps. Also, when digital video is transmitted over-the-air (ATSC or DVB), people would be annoyed if they have to wait a whole minute after switching channels before the TV found a key frame and started showing something.

Does that answer your question? If so, please improve this article. Feel free to copy my text into the article, then edit it for clarity.

-- DavidCary --70.189.73.224 05:32, 30 August 2006 (UTC)

[edit] Keyframing can apply to more than motion

Keyframing can apply to more than motion (ie Movement). This especially applies to keyframing in modern animation software. For example, in Flash, the tint (color) of the object can be animated by defining two keyframes and creating a tween. Keyframing can basically be used for any kind of animation, but this article limits it to motion.

I've wanted to make the relevant changes, but I figured it'll be better to get the opinion of others first, as making this change will mean making modifications to the entire page. So, I need your opinion on whether or not the changes should be made. — 0612 (TALK); Posted: 12:56, 24 February 2007 (UTC)

Hmm... No replies yet? My plan now is this. I'd go ahead and make the changes. Anyone who drops by, please edit as you deem fit. (i'll begin work now) — 0612 (TALK); Posted: 07:44, 11 April 2007 (UTC)

[edit] Using shape hints flash animiation example mis-labeled?

It appears to me that the "Shape transformations USING shape hints" example doesn't correctly show the start and end points of points "b" and "d." As I view the animation, it seems that they are reversed. That is, if you watch point b, it ends up at the bottom of the arrow (currently labeled "d"), and d becomes the second point down (currently labeled "b"). —Preceding unsigned comment added by Dahved (talk • contribs) 16:39, 24 September 2007 (UTC)

Yes. That is true. I'll look into it. Thanks for pointing it out. — 0612 (TALK); Posted: 06:08, 25 September 2007 (UTC)

[edit] Video compression

I visited this article to see what it had to say about key frames as they pertain to video compression, and found the article didn't cover the topic at all. I've added a section about video compression that I hope is not terribly confusing. I tried to cover what key frames are (a frame in which the entire image is stored), why they must generated (drastic visual changes in lossy compression), and the creation of arbitrary key frames (to allow the viewer to seek within the video stream). However I'm afraid my wording may be clumsy and redundant. Please feel free to clean it up if you are so inclined. --Dan East 00:41, 8 October 2007 (UTC)

Thank you very much for your contribution! However, I'm not very sure as to whether the content should be placed here. Please correct me if I'm wrong, but I was under the impression that Key Frames with regards to video encoding is better known as an I-frame. If that is so (which I am unsure), then the information that you had added should belong at the page Video compression picture types instead. — 0612 (TALK); Posted: 06:38, 8 October 2007 (UTC)