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Old Sep 09, 2010, 04:02 PM
ashdec87 is offline
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Video compression question


Hi,

So i'm working on converting a video so it can be edited. Its saved on my recorder as .mpg and I'm trying out different compressions to see what's best vs file size. Well the original is about 500mb, and I've tried a .DV, .mpeg-4 and they all come out to be about 6-8 GIGS!!! How is that even possible and none are quite as good quality as the original. The 8 gig file is close, but its 16 times the size!

ideas?
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Old Sep 09, 2010, 04:28 PM
bignose13 is offline
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what software are you using
Old Sep 09, 2010, 04:40 PM
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If it starts at 500Mb and ends at 8Gigs, then there's something wrong with
your process, and it's effectively not getting compressed at all.
Also, 500Mb may be perfectly reasonable if you're talking 15-20 minutes of video.
How long is the actual video clip you're working with?

ian
Old Sep 09, 2010, 04:53 PM
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You will have to check the bitrate that your output video is using. The final size of the file is easily calculated by taking the video bitrate (bits/sec) and then multiply by the number of seconds of video -- this is irregardless of the codec in use.

A high bitrate will give best quality and you can dial it down to happy medium trading off file size versus quality. Every codec will have its own level of degredation of video for a given bitrate level. The NTSC/PAL videos we use aren't too good quality to begin with so you won't need much to maintain quality especially with a good new codec like h264.
Old Sep 09, 2010, 05:01 PM
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oh sorry I'm using MPEG streamclip to do the compressing.

I'm using the MPEG-4 setting on highest quality. My video is 15 minutes. Looks like the final video ended up being 9.something gigs.. yeesh..

Granted the quality is identical to the original, but the increase in file size is too much..
Old Sep 10, 2010, 08:44 PM
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what's a decent bit rate I should set it at?
Old Sep 10, 2010, 09:45 PM
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Depends on the resolution, the detail, level of motion, quality of the original (ironically,
the lower the quality of the original, the higher the bitrate you'll have to choose to
maintain quality) and what codec you're using. H.264 codec generally offers the highest
quality for the lowest bitrate, but sometimes struggles with high motion, and is almost always
quite slow to compress, compared to DiVX or XviD which need about 30% higher bitrate
but can be 2-3x faster.

I'm guessing, given the tool you're using that you're on a Mac, in which case I can
offer only general advice. If you're on Windows, then try WinFF and create a profile
using XviD at about 3-4Mbit/s for SD resolution (640x480@30fps).

ian
Old Sep 10, 2010, 09:54 PM
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ok so some where in the 3-4mbs range? I just need a ballpark, then I can play with it from there..
Old Sep 13, 2010, 07:44 AM
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try http://www.virtualdub.org/download.html it can edit, recode & many other features, Best of all its free
You can play for hours with your video, looking at the trade off between size and quality.
Mike
Old Sep 13, 2010, 08:02 AM
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try 3mb. virtualdub is superb but almost certain it doesn't work on a mac.
Old Sep 13, 2010, 08:47 AM
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Quote:
Originally Posted by NDw View Post
try 3mb. virtualdub is superb but almost certain it doesn't work on a mac.
using a WINE type windoze emulator?
Mike
Old Sep 13, 2010, 09:38 AM
ashdec87 is offline
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Quote:
Originally Posted by NDw View Post
try 3mb. virtualdub is superb but almost certain it doesn't work on a mac.
I'll give that a try thanks!


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