Are variable keyframes possible?

[x2x3x2]

This is for the encoding gurus out there.

Would it be possible to write some kinda script which would encode video with variable keyframes instead of regular xx frame intervals. Say for example, to use a keyframe only when there are >50% pixel difference between frames?

[poisondeathray]

What type of compression? What encoder ?

Advanced encoders (e.g. h.264 using x264) already allow control over keyframes, and have variable keyframes by default. You can change max or min intervals, and change sensitivity to scene changes (i.e. a large change between frames would induce a new keyframe)

[x2x3x2]

Yes I was hoping for h.264, but I don't see this option in Adobe Media Encoder though. When I choose to output to one of the h.264 profiles, there's only the option for setting keyframe distance when the option is checked. Does this mean that with the option unchecked AME uses variable keyframes?

[poisondeathray]

The encoder that ships with AME is a licensed version of Mainconcept's h.264 encoder. It is limited in functionality (you don't have much control over things like sensitivity, or min keyframe interval). Keyframes are still dynamically placed, but the default max interval is 33 when you leave it unchecked (depends on which profile you use). You need mainconcept reference or their SDK to access more control and functions

[jagabo]

SceneCut threshold in x264.

[x2x3x2]

Sorry that was abit brief for me to grasp, what do you mean by SceneCut threshold in x264?

[poisondeathray]

It's the parameter used by x264 for sensitivity to keyframe placement , higher values make placement more common (i.e. more sensitive to scene changes, increasing likelihood that it places an IDR frame)

Maybe if you describe exactly what you are trying do to or change, we could give you better directions ?

[x2x3x2]

Thanks. I see, how would i edit/apply this parameter in AME?

[poisondeathray]

x264 is a different encoder

You don't have access to it in AME (at least not directly). As mentioned above, the encoder used by AME is very limited in control

You do have control over everything with x264 , it's the open source implementation / encoder for h.264 , and consistently the best in terms of quality, speed, configurability

[x2x3x2]

I see, which free/open source package would you suggest? I know there are quite a few like Handbrake, XVID4PDP, etc. ?

[jman98]

x2x3x2 - I have never used Handbrake, but based on the people I personally know who have used it, I suspect that Handbrake is too much of a low tech, newbie type tool to be what you are looking for. I could be wrong, but I suspect that it will not offer the kind of control over the encoding process that you want.

[poisondeathray]

I see, which free/open source package would you suggest? I know there are quite a few like Handbrake, XVID4PDP, etc. ?

If you're talking about a GUI , the most comprehensive, but most difficult to use would be megui . Most give you access to control over many options.

The commandline isn't that hard to use either, x264 introduced a system of presets and tunings a while ago

You can see a list of commands here
http://mewiki.project357.com/wiki/X264_Settings

If you are using premiere pro, many people export a lossless intermediate (e.g. uncompressed avi) then use that to import into x264 (or one of it's GUIs)

[x2x3x2]

it's a shame there isn't an option for somehow add h.2364 support in premiere. guess will have to do it 2-step as mentioned. thanks.

[poisondeathray]

You can use x264vfw in premiere pro , it integrates with AME, but it's not very stable and lacks some features. For me, it's worth the extra step. It's that much better.

http://sourceforge.net/projects/x264vfw/

[x2x3x2]

Cool i'll have to give x264vfw a go. Btw when you mentioned that it isn't very stable, do u mean like random crashes while encoding? I usually leave encoding jobs on overnight for between 8-12 hours, will i be safe with this option?

Edit, i tried installing x264vfw. seems to be a standalone app. How does it integrate with AME?

[poisondeathray]

If you select "microsoft avi" as the format, you can access it through the video codec menu, and it's codec settings. All VFW type codecs installed on your system can be accessed through AME when you select through "microsoft AVI" . It's not very stable though AME , but it's fine though other software like vdub. For some people it doesn't even work at all through AME, for others it seems to work ok, YMMV

When I said it's worth the extra step, I meant exporting lossless and using the normal, x264CLI version (or a GUI for it)

Note the hotlink in videohelp is incorrect (it points to the CLI version) , use the sourceforge link above or this one
http://sourceforge.net/projects/x264vfw/
http://komisar.gin.by/