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JKMabry
Maniac (V) Inmate

From: out of a sleepy funk
Insane since: Aug 2000

IP logged posted posted 01-08-2002 17:00 Edit Quote

HELP! I'm having trouble getting the optimum compression to quality ratio out of the divx codec...

I've made a few divx movies and they're excellent quality video and audio but they're about twice the filesize of som other work I've seen of comparable quality. One test movie I did runs about 6MB per minute whereas a movie like Robot Bastard weighs in around 3MB per minute.

Can omeone help me out here? Point me to a good resource on video compression?

It's a little frustrating for me since graphics compression is so easy to optimize compression to quality but video I suspect has a ton more variables to consider. I'm up to date on codecs and which does what but I need to take the next step (maybe it should have been the first step) and learn more about all the variables that go into compressing video.

Any help here is greatly appreciated, if there's one thing that bugs me it's wasted bandwidth and this is really gonna get under my skin. THANKS!

Jason

Steve
Maniac (V) Inmate

From: Boston, MA, USA
Insane since: Apr 2000

IP logged posted posted 01-08-2002 17:56 Edit Quote

I'm going to be lurking here waiting for an answer too!

mobrul
Bipolar (III) Inmate

From:
Insane since: Aug 2000

IP logged posted posted 01-08-2002 18:22 Edit Quote

Since you didn't give any specifics concerning what you have and have not tried, I can only speak in generalities.

One of the main thing that I do to keep file size low is reduce frames/sec.
*Normally* one can get by with 15, 12 or even as low as 10 frames/sec without significant, noticable quality lost...especially when dealing with video being played back on a computer. Obviously if you have a lot of detailed movement, lean toward a higher number. Talking heads can usually be compressed at a lower number.
Compared with the 29.97 fps of NTSC video, you can cut frames in half, or even by 3.

Audio is another place you can cut some space.
Mono vs Stereo saves a resonable amount of file size. If you don't need stereo, don't use it.
Also, cut your audio down to 22 or even 11 khz. No need for the 44 or 48 khz when most people can't hear that well anyway (either due to most people having crappy computer speakers or simply lack of need of frequency). You lose your highs when you come down from 44 or 48, but a lot of video simply doesn't need those high frequencies. Your midrange will still be crystal clear at 22khz.

Think about how it is gonna be shown.
Do you need to show you video at 640x480?
Will 400x300 suffice?
How about 320x240?
This will make a huge difference in file size.
(I do understand sometimes you must have 640x480...cool, but don't automatically assume that is the case.)

These are some of the basics...maybe you know them, maybe not.
A more thorough version can be on the way if you desire.

mobrul


JKMabry
Maniac (V) Inmate

From: out of a sleepy funk
Insane since: Aug 2000

IP logged posted posted 01-08-2002 21:03 Edit Quote

excellent mobrul, as always, thanks.

I had lunch with a guy today that helped me out some. As I suspected frame rate was the major culprit but I really wasn't sure how low you could go (for web delivery mainly). Makes sense if I'm at 30 frames and drop it to 15 I miht get that half size I'm looking for. Still, if you know of a good technical reference on video compression, I'd read it.

BTW I use Premiere for the capturing, editing, rendering. Is this good or is there a tool out there that would be better in the case of divx? I've gotten quite used to Premiere and like it but there's a lot of other freeware/shareware tools being hocked out there in divx circles.

This was a great help. I'm sure I'll quiz you more soon

Jason

mobrul
Bipolar (III) Inmate

From:
Insane since: Aug 2000

IP logged posted posted 01-08-2002 21:23 Edit Quote

I use Premiere as well. It is a really good program, as long as you're keeping length down less than, about 30 min. Premiere can do 2 hr movies, just not as well. It was built for the short stuff.

Are there better? There are always better. Just be willing to spend the $$$.
Avid is a company that makes good turnkey video editing systems...expect to spend, oh, $15,000 for the cheap ones.
Media100 is another good company. Again, you're gonna spend the money. (A little less than Avid systems)

There are some other, in between -- 'pro-sumer', products too:
Fast
Panasonic has one...DVedit, or something like that
Final Cut Pro
...there are more, just can't think of them right now.

Honestly, unless you're trying to open your own post-production company, Premiere is probably the very best product for you. It is very stable (within that 30min range, and even a bit beyond) and allows you capability to do most anything the higher end products do. Plus it is built to integrate well with AfterEffects and Photoshop.
(not that some of the others won't...they will, but Premiere is part of the family...)

Anymore help, just yell.

mobrul

JKMabry
Maniac (V) Inmate

From: out of a sleepy funk
Insane since: Aug 2000

IP logged posted posted 01-09-2002 07:11 Edit Quote

I'm not looking at anything post-production yet, maybe never. But the friend from lunch is looking into a turnkey system and he mentioned the Canopus DV Storm. Just wondering what you thought since you hadn't mentioned it.

He uses Premiere now and has done several movies at about an hour with no problems and his target market is a 15-20 minute college sports scholarship thing. I think he's getting the itch for the better editing capabilites along with a few longer type job opportunities, branching out. Price may be a factor, dunno much about the packages he talks about but I would think 15,000 is high for what he's thinking. May be wrong.

Jason

mobrul
Bipolar (III) Inmate

From:
Insane since: Aug 2000

IP logged posted posted 01-09-2002 15:03 Edit Quote

Never worked with the Canopus DV Storm.
I've never worked with most of the ones that I named earlier...just remember names off brochures and sales people.
Work with Premiere, for my current job; Avid Symphony on an internship I did a few yrs ago; and some Media 100 work occasionally when a local shop gets into an 'oh-shit-we-took-on-too-much-work-do-you-want-to-help-us' situation.
Now that I think about it, I don't even know of any places on the web that review this sort of thing...
One thing you're friend may want to try--a lot of video supply places also rent equipment. See if they'll let your friend rent one of these Canopus systems for a week. If he is going to buy from that store, he may be able to get a big discount on the rental.

JKMabry
Maniac (V) Inmate

From: out of a sleepy funk
Insane since: Aug 2000

IP logged posted posted 01-09-2002 18:13 Edit Quote

this is one of the prefaces where I say how I just typed a massive post and lost it so I'm angry and not as verbose and congenial as I was a minute ago

Uh, thanks for the advices on the Canopus and whatnot, I'm sure he'll go with Canopus, he has really good experience with their stuff but I'll tell him about the rental idea.

Now, more questions. check it out:


To be perfectly honest the vast majority of the tweakers in there have me confused, save the quality slider

In particular, the bitrate/bitstream stuff, I thought that was to do with streaming and divx doesn't stream right? Well, anyhow, any enlightenment on the stuff in that box will help if you have info to give, gracias.

oh yeah by the way, I've cut the frame rate in half and third for my test project and the file size difference is negligible, hence the further delving here I guess... quality didn't suffer to much but I sure thought the file size would drop a lot more. mebbe there's a clue in the GIF there. thanks man.

Jason

JKMabry
Maniac (V) Inmate

From: out of a sleepy funk
Insane since: Aug 2000

IP logged posted posted 01-09-2002 18:49 Edit Quote

alrighty, it's me again. Heckuva notepad I have here...

I've sat down with the help file again, it's a little later in the day and I have a little more coffee in me and a little time to tinker. The first 2 drop downs in that dialog box are the keys to the rest of the tweakers. I've had some nice results with the 1 pass quality-based variable bitrate mode, esepcially in tandem with the 'fastest' 'performance/quality' selection. Getting down to 4.8MBish per minute now with really good quality.

I think I'm gonna figger it out if I can keep the monkeys off my back for the rest of the day

Jason



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