Talk:Key frame

From Wikipedia, the free encyclopedia

	This article is within the scope of Wikipedia:WikiProject Filmmaking, an attempt to better organize information in articles related to filmmaking. If you would like to participate, you can edit the article attached to this page, or visit the project page, where you can join the project and/or contribute to the discussion.
Start	This article has been rated as Start-Class on the assessment scale.

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 ?

[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)