Key frame in H.264 mainconcept

[LeoKac]

Hello I am Sorenson Squeeze 8 user, and please tell me what is "key frame" in H.264 codec. how many keyframes would be better for highest output video quality?

http://i.stack.imgur.com/9jsJr.png

[poisondeathray]

It's the maximum number of frames before the encoder forces an I-frame placement

Read about GOP's, I, P B frames
http://en.wikipedia.org/wiki/Group_of_pictures

There is no "best" setting. Leave it as is unless you have a specfic reason to change it

For example, some devices and blu-ray require a shorter interval

[jagabo]

A key frame (I frame) is a frame encoded in its entirety, much like a JPEG image. Other frames (P and B) are "predicted", ie, they contain only the changes from frame to frame. Hence I frames are typically 10x larger than P and B frames, so the fewer you have (the longer the GOPs, group of pictures), the more compression you can get. But very long GOPs make the video harder to seek because the decoder has to locate the I frame before the requested seek position and decompress all the frames from that I frame to the requested frame before it can resume with playback.

[Atak_Snajpera]

Use this formula -> 10 * FPS
if source is 25 fps then use 250
if source is 60 fps then use 600