DiVX Low motion

[Enrico Ng]

I usually have to go up to 2000 on the fast motion codec just to pervent jerky/choppy playback. the file size is still too big.
I try the low motion codec, and even at 1500 I still have jerky playback. and the file size is bigger
I am using virtualdub to encode my divx.
a 4:33 video at 704x480@29.97 with mp3 192kbit stereo 44khz audio ends up to be 74MB.
thats why I always use the fast motion codec

[dZeus]

Try encoding it with low-motion codec at 1200Kbps with a resolution of 640x480....

you'll be surprised

[intomisery]

for myself, the choppiness is caused by the size of the image. 640 x XXX makes a huge difference. Also, have you thought about keyframing more frequently or if you've done 1 keyframe/sec, less frequently?

[intomisery]

for myself, the choppiness is caused by the size of the image. 640 x XXX makes a huge difference. Also, have you thought about keyframing more frequently or if you've done 1 keyframe/sec, less frequently?

[dZeus]

a keyframe once every 1 - 5 seconds is fine... 10 is not, since you'll experience quite some time waiting before the movie plays smoothly when resizing on the fly

[intomisery]

so you're saying that the less keyframes, the choppier the movie? i.e. Less keyframes equals more processor power to get through all the delta frames, etc.? So by choosing 1 keyframe/sec I will avoid glitches and stops...

[Dr Mordrid]

Each keyframe, or more properly for MPEG; I-Frame, is a bitmap. MPEGs are so small relative to other codecs because they use mathematically created frames (B and P frames) between the I-Frames. Codecs like MJPeg consist of nothing but I-Frames.

Using more I-Frames in a sequence gives great quality but at the cost of much larger files and higher data rates. Using fewer gives smaller files and lower data rates at the cost of quality when there is motion in the frame.

Playing back full frame MPEG, pick your variant, is no small chore. It takes some decent processing horsepower to decode the 40-60:1 compressions involved in software. As long as your system can decode the data fast enough it shouldn't hurt playback. If it can't handle it then playback suffers.

Since DivX is an MPEG variant the playback problem applies to it as much as it does to MPEG-1/2. Generally speaking if your system has problems playing DVD's in a software player without stuttering it'll have problems with DivX too. Perhaps even more so.

Dr. Mordrid


[This message has been edited by Dr Mordrid (edited 04 July 2000).]

[Enrico Ng]

I always set keyframes to 1.
I went up to 1500 on lowmotion and it was still choppy
I'll try 640

[dZeus]

yes, you left out the most important thing! always use 640 on a Matrox card... there seem to be problems playing 720x or 704x clips fluently on Matrox cards....

[Enrico Ng]

I tried, no difference

[intomisery]

then your clip must be some magical, mystical footage that cannot work with DivX since everyone gets fine results with the codec after screwing around with it. well, at least you tried.

[Enrico Ng]

I just dont get it.
with the fast codec, it has to be at 2000 to prevent choppyness. (with any video I capture)
with the low codec, I have to bring it up to 2000 to keep from choppynesss, then its bigger than the fast codec one.
I guess I'll have to wait till someone makes a program that will do a two pass system so the bitrates can change and be predicted

What is the correct setting to go from 704x480 to 640xXXX what is XXX
since 704x480 is non-standard, I cant go down to 640xXXX with out affecting the aspect ratio. usually this kinda change will cause lots of problemx

[This message has been edited by Enrico Ng (edited 04 July 2000).]

[intomisery]

720-640=80
so 480-80=400
the correct aspect ratio is about 640x400

Did you read all the articles listed in the Digital Digest, listed above in your last post by Mordrid. There they outline everything. good luck

[Enrico Ng]

no, if you do that, the ratio changes.
by that logic you could say
704-479=225
480-479=1

it needs to be 640x436.363636

[Joxx]

mpeg4 is a very intelligent codec who will insert keyframes itself where needed. The keyframe per second is just a safety so that you don't have to wait 20min if you skip to the end of a 120min long scene without any special need for keyframes..

correct me if I'm wrong... but I think that this is the case..