How did a file meant to be made smaller wind up larger than the original?

consptheory77

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I'm trying to re-encode a movie that is about 6GB down to 4GB, I want to keep the video bitrate the same, but knock down the audio from 5.1 to 2.0, and I went to use Handbrake to do this, but I wound up with a file than was larger (13GB) than what I started with? How did this happen? I can't use a program to enhance what already is there, right?
 

consptheory77

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In other words, did I uncompress a file to full size that was already compressed?

The video bitrate for the 6GB file is 7856 Kbps, the video bit rate for the re-encode is 19.8 Mbps at 13GB.

I set the video quality to "lossless" because I thought that would ensure the re-encode would just replicate the same bit rate.
 

Snipergod87

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Lossless will basically make the file size larger (from an already encoded video) with no actual quality gain. Hence roughly doubling in bitrate and file size. Try skipping the re-encoding of the video and just change the audio settings.
 

TJ Hooker

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Most common video codecs use lossy compression, meaning you lose some info permanently when it's compressed. Lossy compression typically allows a greater degree of compression (reduction in file size) compared to lossless. Basically you decoded/decompressed the video to original size (although whatever info that was lost during compression is still gone), and then re-encoded it lossless resulting in little to no compression. As said above, lossless encoding a file that has already undergone lossy encoding is sort of pointless.
 

consptheory77

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Well, instead of Handbrake this time I used Super to re-encode. I set the video bit rate to approximately the same, and cut the audio bitrate in half (it was actually 2.0 to being with, not DD5.1). Super didn't re-encode it at exactly the same bit rate, it came in at about 1500 kbps less, enough to come in at 4GB DVD size, but I can tell a subtle difference in I guess what they call compression artifacts, so I think I'm going to stick with my original policy of retaining the best possible bitrate and just plunk down the extra 75 cents to burn it over to a BD-25.
 

randomizer

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You can tell Handbrake to encode to a target average bitrate (typically not that useful) or target file size. It will not match it exactly, but it's usually pretty close. A two pass encode will give you a better result, as will using an encoder preset that takes longer. SUPER is probably similar. They both use the x264 encoder under the hood (though SUPER has other encoders too).
 
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