encode with shortest seeking time ?

[surfer]

I want to encode instructional DVDs and already compressed MPEG1&2 with XviD, in which the most important aspect for me is the seeking time, the possibility to search/skip/jump in the video fast and at short intervals.

What are the best settings for encoding and getting an optimal seeking?

[foxyshadis]

DVD maximum GOP size is already half a second, so you're covered there; about the only thing you could do is use such a low bitrate that it reads and decodes twice as fast - but I doubt you want to butcher your video just for that.

mpeg-4 codecs usually default to 300 frames, which is 10-12 seconds. You'd probably want to use one second or even a half second if you need lots of skipping around or rewinding. Certain codecs also let you place I frames at specific points, though simply having a scene change there is good enough.

[surfer]

Thanks for your answer!

so i put the "maximum key frame" at 10 or 12 ? No problem with that?


What's GOP?
I want to encode DVDs but also already compressed MPEG1 and MPEG2 with XviD.

[foxyshadis]

Yes, exactly like that. A GOP is the "Group of Pictures" from one I frame to the next. Since whenever you seek you have to decode back to the last key frame, a shorter maxmum distance means most seeks will take less time. It can be as short as you want; the tradeoff you make is that it hurts quality somewhat, more the shorter it is. It's a good idea to make a few encodes with different maximum GOP sizes and test them on the machines you'll be using them on.

Oh, and definitely don't use qpel or gmc, which significantly increase decoding time (and thus seeking time).

[surfer]

ok, thanks once more!

So i suppose i let the GOP with my DVDs as it is and donot have to change anything.

But where do i change the GOP for encoding into Xvid of my MPEG1&2 ? i do not see any setting for that in the settings of the XviD codec.
And what would be some good setting for optimal seek/skip?

[quake74]

I believe you are looking for the "Maximux I-frame interval" which in my build is in the window started by clicking "More..." next to Quality presets. Usually that is set to about 10 times the fps (so at least one I-frame every ten seconds) but if you need easier seek then lower it.

[foxyshadis]

If you use the vfw (virtualdub/gk) hit the "more" button at the bottom, it opens a panel where you can set the interval. If you're using MeGUI... well, shoot, the option isn't there. I'll have to get it added. You can add it to the command line yourself with -max_key_interval, but that's a pain. Not sure how other software does it. (edit: haha, it was right on the first tab, I'm blind.)

Good settings to start with would probably be double your framerate (2 seconds). If it still isn't responsive enough you can always go to the same or 1/2, but even on my old laptop I found 4 or 5 seconds (100-120 frames) to be ok and take under a second to seek.

[Guest]

What are the best settings for encoding and getting an optimal seeking?Please read and follow forum rules, specifically, rule 12: do not ask what's best. Thank you.

http://forum.doom9.org/forum-rules.htm

[surfer]

hmmm, i'm a bit confused now....

I'd be happy to use the GUI "SimpleDivX". In this software there is a "Maximum Key-Frame" on the 4. Tab which i put to, let's say, "10":
http://www.simpledivx.org/Guides/SimpleDivX_Guide/English%20Guide.htm

I read in the "FAQ" that...
I-frames (Intra frames) ... are commonly called key frames

I thought "GOP" was a different, another thing, i had to set and i asked as well where to set this.

The "Maximum I-Frame interval" can be change in the general settings of the codec in windows XP in "Start/programs/XviD encoder/quality preset/more..../Motion Tab".

But this, i suppose, is the same as the "Maximum Key-Frame" you can set in the SimpleDivX interface. Or am i wrong?


but what about the GOP? Or did i misunderstand something?

[foxyshadis]

That's exactly the one you want, yep. GOP-length is just another way of saying keyframe interval, sorry.

[surfer]

aaa, ok, thanks! i thought those were 2 different things.

I've already encoded a PAL video at 12 "key-frames" and it seems to work excellently.

But one more question:
Is the "seek, skip or jump" not a function of a player only?
I can skip "frame by frame" or 1 second back and forth in ZoomPlayer even if the video is encoded with the key frames at "300".
Media Player Classic has a feature of skipping by values of miliseconds.

So what's the reason of a lower value of the "key frames" at all?

Are those things not only relevant for cutting/editing an encoded AVI?

[foxyshadis]

Long seek speed, and seeking backwards. And for cutting, since you can only cut the start on a keyframe. Short seeks like one frame forward, or even a dozen, wil never cause a noticeable delay. It's more for when you jump a long ways forward, a hundred frames or even more.