keyframes, what are they?

[mrucs]

Just wondering what in the blue hell are keyframes?

I've been using divx3.11 and LayerIII, with these settings,

Keyframe every 1 second
100% on Crispness
2000kbit

Audio at 192kps


But im not happy with the quality, what the picture to be sharper, should I up the kbit? to say 4000? (The file I would be encoding is from a DVD)

a dvd is 6000kbit correct?

what about the keyframe? is lower better quality?


cheers

[khp]

Re: keyframes, what are they?

Originally posted by mrucs

But im not happy with the quality, what the picture to be sharper, should I up the kbit? to say 4000?

If you are using divx3.11 fast motion, upping the bitrate wont make much difference. If you are using the low motion codec, you will get better quality, but at the cost of much larger filesize. To get the best possible quality at a resonable bitrate, you should use a 2-pass encoding method, either using nandub with divx3.11 or M$ mp4v2, or using divx5 or xvid, with whatever encoding app you prefer.

Originally posted by mrucs

a dvd is 6000kbit correct?

I'am not quite sure what the exact limits are. But on average 6000 kbps is probably a resonable estimate. But of course, a divx encoding of a DVD source will never get as large as the DVD. (Maximum quality in divx is not as good as DVD quality). And of course the DVD is Mpeg-2 while divx is Mpeg-4.

Originally posted by mrucs

what about the keyframe?

Keyframes, are complete frames, which can be decoded independently of other frames, as opposed to partial frames and bidirectional frames, which are encoded as the difference between itself and one or two of the frames nex to it. Key frames generally takes up more space then p- or b-frames.
So on average you should get better quality by having fewer keyframes, placed futher apart (10 seconds is usually a resonable value).
But on a low quality encode, having a long space between keyframes, will mean than any artifacts are visible longer.

[mrucs]

thanks for the information dude

[scottws]

I usually just leave the default setting for keyframes in the DivX codec. Something like a keyframe every 300 frames.

However, for a certain DVD I want to divide it up into 9 episodes. 300 frames was too much gap for splitting, as keyframes wouldn't fall in convenient places. So I reduced it to an interval of 75 frames. It should be done encoding by now. I'll have to check the results when I return from work.

[xviddivxoggmp3]

upgrade

go to a more advanced codec.

divx5.0.5 is very clear.

gordian knot is very smooth.