Divx ;) Encryption

[Brian23]

If you want to compress a 2.5 hour movie to fit on a CD what bitrate, and more importatly what crispness/smoothness ratio would you use?

 

[LocutusX]

I managed to "backup" Eyes Wide Shut (2h 40min) to a 698mb file. I used the High-Motion (Fast Motion) codec, 5 seconds per keyframe, 100% quality, and a bitrate of 1500. Resolution reduced to 512x384, Bilinear resizing in Flask, using the Fast x87 64-bit iDCT.

High-bitrate doesn't actually use the bitrate you mention there literally... it sticks it in some VBR formula. Anyways the movie was encoded at an effective bitrate of ~460kbit/second, which allowed me to mux it with a LAME 128kbps MP3 track and it looks/sounds quite decent. I've recieved compliments on the quality of the "backup" at any rate.

If I had to use low-motion codec instead of high motion, all scenes with the slightest bit of motion (camera panning) would have looked HORRIBLE. So contrary to what some "experts" say, DivX Fast-Motion has it's uses.

 

[Brian23]

I don't know if you have a different version of FlasK or what but I'm given these options:

Hi motion:
Keyframe every ____ seconds (default 10)
smoothness/crispness scrollbar (0 to 100, default: 100(max crispness))
Video bitrate scrollbar (default: 910)
Low motion:
Keyframe every ____ seconds (default 10)
smoothness/crispness scrollbar (0 to 100, default: 100(max crispness))
Video bitrate scrollbar (default: 910)

It doesn't have any "100% quality" setting, and the number you put into the Video Bitrate scrollbar is the actual bitrate of the video. For example if I put in 1500, the output .avi will take 1500 kilobits per second plus the audio bitrate. So I came up with this formula:

Megabytes = ( [Video bitrate] + [Audio bitrate] ) * 0.0075 * [Minutes in movie]

So that means in 698MB at 1500 video and 128 audio I could fit 57.1 minutes. Or if I use 698 MB in 160 minutes, that would be 128 Audio and 453 Video. In my version of FlasK this equation works reguardless of the resolution of the video. I'm not sure what you mean by a VBR formula and how you ended up with ~460 when you entered 1500. What I want to know is:

1) What should I set the smoothness/crispness scrollbar to so I don't get jerky video, and still not loose high detail graphics?

2) What is the Keyframe, and what should I set it to?

Thanks for your help!

 

[Theslowone]

Isnt mpeg4 suppose to do something like that. fit a dvd on a cd w/o any loss of quality.

 

[Brian23]

Yes, DivX is a software implamentation of the MPEG4 specification.

 

[LocutusX]

Brian23,

When I said "100% Quality" it refers to the smoothness/crispness slider bar (in the middle of the codec properties) which has values from 0 to 100. I call it the quality slider because in my opinion, more crisper images are better quality images. I have never had any issues with "loss of smoothness" at 100% crispness anyways.

Back to the main issue...

Only the DivX Low-motion codec will follow the bitrate you specify in the codec box. DivX high-motion does not follow the bitrate, it merely uses it as a cap. That's why if I set the bitrate to 1500, I get a file that actually only uses an average bitrate of 460kbits. If you do not believe me, I suggest you try it out yourself.

And remember I am referring to DivX FAST MOTION codec, not the low-motion codec, which is the more popular of the two.

What movie are you trying to backup anyways? If it's an action movie, it will most likely come out a lot bigger than a slow-motion drama like EWS.

But even then, it won't come out at 1500kbit/second. The Fast-motion codec is very conservative about bitrate. There was a message posted somewhere else where someone made a 1CD rip of HEAT (177 minutes movie) and he used the 6000 bitrate. But did the file end up using 6000bitrate? Nope... because he used FAST MOTION. Only the Low-motion codec tries to stick to the bitrate you specify. Fast motion has a mind of it's own.

 

[Brian23]

I'm collecting episodes of The Simpsons. I tried setting the bitrate to 6000 like you said, and it came out at ~1200kbps. That seems a bit high considering the resolution of the video was 352x240, and the audio was 128kbps MP3. Is it normal to get such high output bitrate? Or is it just that my video is an exception? I tried changing the keyframe to several different values, but I don't see any quality or filesize difference. What is the keframe for?

 

[pillage2001]

I'm driving myself crazy to just trying to figure out how to work this thingy! Can anybody recommend a good ripper? I'm new to this.

 

[LocutusX]

Brian,

Only if you use the Low-Motion codec will it come out to 1200kbps. If you use Fast Motion, it should come out fairly small, especially for a tiny-frame animated thing like a simpson's ep. My guess is that your codecs are somehow messed up.

 

[Brian23]

I was using the fast-motion codec. You may be correct about my codecs being messed up, but I have another theory. I live far from the FOX broadcasting station, and there is some static in the recording. It's posible that the static doesn't compress good. Later I'll try compressing something off of DirecTV and see if that compresses better.

 

[LocutusX]

There are a number of filters available for VirtualDub (if you're using that) which can do all sorts of static-removal and the like... check it out.