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Reduction of file size

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Roger Bansemer
Reduction of file size
on Apr 30, 2014 at 1:55:05 pm
Last Edited By Roger Bansemer on Apr 30, 2014 at 1:56:20 pm

I'm wanting to put some of our 1/2 hour programs on a website called Sellfy.com. They only charge a 5% fee for anyone wanting to purchase a download.
Our programs are 2.75 and 3 gigs using an mp4 format and they only allow no more than a 2 gig upload.
How can I best render them to fit their specifications?
Thanks
Roger

Roger Bansemer - PaintingAndTravel.com


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Norman Black
Re: Reduction of file size
on Apr 30, 2014 at 3:56:08 pm
Last Edited By Norman Black on May 4, 2014 at 12:29:42 am

You can target a file size by computing the bitrate.

For example, if you have a video 60 minutes long (3600 sec). 2GB max (2,147,483,648)(2*1024*1024*1024).

2147483648 / 3600 = 596,500 bytes per second (rounded down).
Bits per second (bytes * 8) = 4,772,000.

This is the sum of your video and audio bitrate. If audio is 128K bits per second, then you know what your video bitrate can be.
128K = 128 * 1024 = 131,072.

There are bitrate calculators around online you can use but the math is simple.

If using Sony AVC or Mainconcept AVC round down a little since they are not perfectly accurate in hitting your target bitrate. Sony AVC is better at this than MC AVC.

However I would suggest using Handbrake, or similar tool using the x264 encoder, to render your final file for best quality. If using Handbrake use two pass, target bitrate mode. The x264 encoder will nail your target bitrate.


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Roger Bansemer
Re: Reduction of file size
on Apr 30, 2014 at 8:42:01 pm

Thanks Norman. I appreciate the help.

Roger Bansemer - PaintingAndTravel.com


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Miguel Stephen
Re: Reduction of file size
on Aug 3, 2015 at 3:33:22 am

Hey man, I was intrigued by your formula for bit-rate calculation. I so happened to stumble upon this during a Google search for reducing the output file size of Sony Vegas. I know this post is over a year old, but it's still relevant today if it popped up on the first search page of Google.

I just wanted to verify that your formula calculations were correct. I was following along with the 3600 and 2GB= 2,147,483,648, then divide. I understood the solution of 596,500 bytes per second

However once you multiplied, you lost me. Shouldn't you divide again instead of multiplying? You already have the output in bytes so in order to get bits you should divide 596,500 by 8. You stated that there are 8 bits in one byte.


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Norman Black
Re: Reduction of file size
on Aug 3, 2015 at 3:07:54 pm

If you have 10 bytes, then you have 80 bits.
If your bytes per second value is 1000, then your bits per second value is 8000.

In file encoders we specify bitrate in bits per second and not bytes per second.


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Aaron Star
Re: Reduction of file size
on Aug 3, 2015 at 7:56:25 pm

One thing to keep in mind is file bitrate is overall, which includes your audio bit rate. Make sure to subtract your audio bit rate, then calculate your video bitrate.

From Vegas, I would render your finals to XDCAM-EX, then use Handbrake. Handbrake will use the best image scaler for sizes below your project setting, and a VBR codec which will minimize your storage needs.


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Norman Black
Re: Reduction of file size
on Aug 3, 2015 at 9:19:32 pm

[Aaron Star] "From Vegas, I would render your finals to XDCAM-EX, then use Handbrake. Handbrake will use the best image scaler for sizes below your project setting, and a VBR codec which will minimize your storage needs."

??? If you target a bitrate X in Vegas AVC and the same bitrate in Handbrake AVC then the file sizes will be the same.

Handbrake may have better visual quality at a given bitrate, but that really depends on the bitrate being targeted. The lower the bitrate the better x264 is in comparison the the AVC encoders in Vegas.


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