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#1 ashdec87 Sep 09, 2010 03:02 PM

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?

#2 bignose13 Sep 09, 2010 03:28 PM

what software are you using

#3 Daemon Sep 09, 2010 03:40 PM

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

#4 WEREE Sep 09, 2010 03:53 PM

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.

#5 ashdec87 Sep 09, 2010 04:01 PM

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..

#6 ashdec87 Sep 10, 2010 07:44 PM

what's a decent bit rate I should set it at?

#7 Daemon Sep 10, 2010 08:45 PM

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

#8 ashdec87 Sep 10, 2010 08:54 PM

ok so some where in the 3-4mbs range? I just need a ballpark, then I can play with it from there..

#9 empeabee Sep 13, 2010 06:44 AM

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

#10 NDw Sep 13, 2010 07:02 AM

try 3mb. virtualdub is superb but almost certain it doesn't work on a mac.

#11 empeabee Sep 13, 2010 07:47 AM

Quote:

Originally Posted by NDw (Post 16035003)
try 3mb. virtualdub is superb but almost certain it doesn't work on a mac.

using a WINE type windoze emulator?
Mike

#12 ashdec87 Sep 13, 2010 08:38 AM

Quote:

Originally Posted by NDw (Post 16035003)
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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