Creating keyframes without re-encoding

[iparout]

Hi.

I've got a DivX 3.11 file which unfortunately has very few keyframes and thus seeking through the movie is very slow.

Is there any way to create more keyframes without having to re-encode the file ?

Thanks.

[bond]

no chance

[aiXGen]

maybe this could help you:
http://www.doom9.org/virtualdub_procedures.htm#Rederive_Keyframes

good luck!

[esby]

definitely this would not help,
as bond said,
you cannot create what does not exist here,
rederive keyframes options is just to use when you are missing the index of the file,
and need to reconstruct the kf structure...
creating a new index of already existing keyframe.
If someone wants to add keyframes in a video , he can only go for reencoding it.

esby

[cheerow]

Theoretically it should be possible to turn any predicted frame into an intra or am I wrong? But anyway there is no such tool...

[esby]

@cheerow:
Only true if intra frames compression mechanism used is lowless.
Since it's depending the codec, I'll answer NO for general case.

esby

[stephanV]

how does it matter if the intraframes are encoded lossless or not?

[esby]

if you reencode an intraframe the lossy way,
you need to reencode all the following non I frames that are calculated on it.
Thus not reencoding one frame, but all the group of frame...
esby

[bond]

hm in the mp4 container it is possible to have non-adjacent references, which means maybe its possible to turn one p-frame into i, and still having the following p-frames referencing to the i-frame before the newly created one, without the need for reencoding them

dont beat me if this is totally nonsense ;)

[Stux]

Originally posted by bond
hm in the mp4 container it is possible to have non-adjacent references, which means maybe its possible to turn one p-frame into i, and still having the following p-frames referencing to the i-frame before the newly created one, without the need for reencoding them

dont beat me if this is totally nonsense ;)

Possible, and a clever idea, but not actually part of the MP4 spec as such (ie its in the ISO FF spec)

Of course, there are better ways of doing the same thing, for example, you basically join two different video tracks together. The problem is I don't know of *any* MP4 parsers which support this functionality.

[esby]

This kindly defeat the purpose of inserting keyframe,
since the stream is still linked with the ancient structure,
thus seeking will have the same speed globally.

esby

[stephanV]

heres what phaeron had to say about this:


A bigger problem is that the key frame is often used to store information besides the key image, such as video layer headers and base decoding information. A vector quantization (VQ) codec, for instance, would begin initializing a cumulative codebook, and even if you get the same image at that frame, you might end up with a differently-ordered codebook which would then cause all subsequent frames to be totally scrambled.


i dont know if this applies to MPEG4, but it doesnt sound hopeful