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H264 file way to big.

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dan freshman
H264 file way to big.
on Jun 18, 2009 at 4:49:30 pm

Hello,

I have a feature length film (just under two hours) that I am trying to get to a target size of 500 mb or less. I have already exported it w/ compressor using H.264 at 24fps at 320X180. the file was still 1.8gigs. Anybody have advice of what to do from here? Do I have export all over again using different settings? Can I compress the H.264 file even further w/ something like mpegstream clip?

Thanks for any help
dan


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Ed Dooley
Re: H264 file way to big.
on Jun 18, 2009 at 5:15:46 pm

Check this bitrate calculator out:
http://www.3ivx.com/support/calculator/index.html

Ed



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Craig Seeman
Re: H264 file way to big.
on Jun 18, 2009 at 6:40:51 pm

Very fundamental concept. Bit rate determines file size. I'm not sure how people miss this logic.
If you have x bits a second and your file is y seconds long, you have the total bits.
Kind like if you're driving 50 miles per hour you will travel . . . 50 miles in one hour.

I guess it's hard for some people to grasp that a file that's 500kbits/second is 500kbits in one second.
A 10 second file is then 5000kbits.

I'm grasping for an easy way to explain this. It just seems so self evident to me.



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Ed Dooley
Re: H264 file way to big.
on Jun 18, 2009 at 9:26:27 pm

But Craig, what if you're driving 50 MPH heading east and another car is 10 miles away heading west at 35 MPH, when will you meet up? :-)
Ed


[Craig Seeman] "Kind like if you're driving 50 miles per hour you will travel . . . 50 miles in one hour."





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Craig Seeman
Re: H264 file way to big.
on Jun 19, 2009 at 1:52:17 am



[Ed Dooley] "But Craig, what if you're driving 50 MPH heading east and another car is 10 miles away heading west at 35 MPH, when will you meet up? :-)
Ed "


Never. The Earth is flat.
Never. The roads are on different planes in 3D space.
Never. They started their trips years apart.
Never. They're only going 9 miles to their destination.
Never. They're on different latitudes.
Never. I'm on Facebook, not MeetUp.

Their data rates are constant though and the it takes to travel a given distance is predictable.



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Brian Alexander
Re: H264 file way to big.
on Jun 19, 2009 at 4:23:49 am

Wow, thanks for the insight Craig!

I looked at the calculator that Ed linked to and it's OK but it's missing a very valuable piece the bit rate/file size puzzle: FRAME SIZE! Now we could go into infinite detail about this and Dan, if you want that level of geek speak you'll get it but I'll keep this light.

When you encode your h.264 file, limit it to 500 Kbps. A 320 x 180, 500 Kbps movie at 2 hrs. will leave you with a 450 MB file. Be sure to be conservative when choosing your audio codec; the audio encoded at 256 Kbps sounds great but will not leave you any head-room for your video. I would not encode audio over 128 Kbps.

Be sure to leave Frame Reordering checked and Automatic Keyframes enabled if you are using any flavor of the QuickTime encoder.

This should do it for you.


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Steve oakley
Re: H264 file way to big.
on Jun 22, 2009 at 5:08:56 pm

you know its times like this were having some bad hardware can help keep your life easier. the matrox compressHD or MXO products with MAX can compress this way faster then real time to H.264. no matter what a bit rate calculator says, it can still vary a bit, and if you miss, go back to 1. when you are waiting 4-6hrs or more per pass, but could go down to around 1/2hr, maybe faster, that when hardware like this makes a lot of sense. if you do it nearly every day, its a no brainer for the amount of time you save. hte quality is great. when you can encode this fast, its easy to play with a bunch of settings too to figure out which one works best, although it does come with a bunch of good presets to start with in compressor. worth a look.


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Ed Dooley
Re: H264 file way to big.
on Jun 24, 2009 at 8:01:03 pm

Frame Size has absolutely nothing to do with the bit-rate or file size calculation. You decide that. And when you test a particular frame size at a particular bit-rate, *you* decide if it looks good enough.
Ed


[Brian Alexander] "I looked at the calculator that Ed linked to and it's OK but it's missing a very valuable piece the bit rate/file size puzzle: FRAME SIZE!"




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Brian Alexander
Re: H264 file way to big.
on Jun 26, 2009 at 2:32:18 am

Hi Ed,

I disagree with your last statement. Frame size has a definite relationship to the amount of bits applied to a frame; after all a frame size of 1920 x 1080 (2,073,600) @ 29.97 fps, has a lot more data requiring a higher bit rate than a frame size of 1280 x 720 (921,600) @ 29.97, doesn't it?

For instance, Apple ProRes HQ runs at 220 Mbps for a 1920 x 1080 frame. The exact same quality for a SD frame 720 x 486 (apple spec) runs at 63 Mbps.

According to your logic, shouldn't the 63 Mbps be much less quality when it is the exact same quality? It's because of the frame size that yields the same quality but a much lower bit rate.

I could start listing math containing pixels and bits per second but before I list differences showing math, would you please explain to me (or point me towards references), how you've determined this information.

This is basic math in my book. Please correct me if I'm wrong.

Thanks.


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Brian Alexander
Re: H264 file way to big.
on Jun 26, 2009 at 2:59:05 am

Clarification on my last post:

According to your logic, shouldn't the 63 Mbps be much less quality on the SD Frame when it is the exact same quality as the HD Frame? It's because of the frame size difference that yields the same quality between SD and HD but a much lower bit rate.


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Dave Puryear
Re: H264 file way to big.
on Jun 26, 2009 at 2:42:33 pm

The OP made no reference to quality, only file size. Frame size has nothing to do with the bitrate calculator because kbps = kbps. (We're also assuming CBR here). One minute of 500kbps at 320x180 is the same file size as one minute of 500kbps at 640x360. I learned this the hard way, too, by encoding a file to 2mbps 640x480 PAR 4:3/DAR 16:9 vs 2mbps 848x480 PAR 1:1/DAR 16:9. The output file sizes were the same, but the anamorphic encode looked better because there were fewer pixels, or more bits per pixel.


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