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Old May 21st, 2008, 03:36 AM   #1
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Decent compression settings?

I seem to be having issues getting a grip on compression settings.

I have HD footage from several sources, and in general what I want is a proxy and a smaller compressed file, but at full HD size lets say.

The proxy can be smaller in dimension as I have been doing, but where my issue lies is when I take the hd footage and render as I keep trying different things and its kind of giving me either a very compressed video or uncompressed, and no matter what settings I change (keeping dimensions stable) the file is usually very small and very compressed.

Lets say I want to take some avchd files and convert them so someone has the full hd size to see on an hd tv but I want a much smaller compressed file, what are good settings?

if it would be 1 gig file uncompressed I want something like 200 megs (as a ratio) currently it just seems like I end up with a 70meg file that is so way over compressed at full res that I woudl not give it to someone to watch.

I think I would like WMV or quicktime since they are very widely used and most all computers can see them, and really I think WMV may be overall more what I want because of this post/question http://dvinfo.net/conf/showthread.ph...892#post880892 but quicktime is what I want to figure out just so I have that option.

Thanks for any help/advice
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Old May 21st, 2008, 10:27 AM   #2
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Quote:
Originally Posted by Stephen Eastwood View Post
...I have HD footage from several sources, and in general what I want is a proxy and a smaller compressed file, but at full HD size lets say.

The proxy can be smaller in dimension as I have been doing, but where my issue lies is when I take the hd footage and render as I keep trying different things and its kind of giving me either a very compressed video or uncompressed, and no matter what settings I change (keeping dimensions stable) the file is usually very small and very compressed.

Lets say I want to take some avchd files and convert them so someone has the full hd size to see on an hd tv but I want a much smaller compressed file, what are good settings?

if it would be 1 gig file uncompressed I want something like 200 megs (as a ratio) currently it just seems like I end up with a 70meg file that is so way over compressed at full res that I woudl not give it to someone to watch.

I think I would like WMV or quicktime...
If I understand, you are looking for a proxy format and a compressed format for computer distribution? What is it that you would do with the proxy format?

First, you need to get away from evaluating compression ratios based on file size, and develop an understanding of bitrate. The combination of image dimensions and bitrate determine the look for a given codec.

For example, DV uses intraframe compression (each frame is compressed separately) of 5:1 pixel dimensions of 720x480, and a bitrate of 25Mbps (megabits per second... watch that "b", if it is a "B" that stands for Bytes).

Using amazing interframe compression tricks (15 frames are taken as a group and compressed), HDV is (usually) 1440x1080 pixels and still 25Mbps.

If you multiply it out, there are 4.5 times as many pixels in HDV as DV, at the same bitrate.

A distribution format can be more highly compressed. For example, the combined video/audio/subs bitrate on a DVD can be up to 10.08Mbps at 720x480.

The purpose of reiterating these standards is to emphasize bitrate.

OK, now we go into Vegas and we're ready to compress to Windows Media V9, for example. Skip the presets and go to the custom dialogs. Choose a pixel size, let's say 320x240. Choose an audio resolution/bitrate, don't go higher than you need to because this takes away bitrate from video. Go to the last tab and choose a single bitrate of 300Kbps.

Test this out with some well-lit head and shoulders video shot on a tripod. Test again with some hand-held video with moving subjects and fine detail. You'll quickly see there are substantial differences in how the codec handles these two types of content.

Select full screen playback in Windows Media Player. Select 200%. Select original size.

Do some more renders with the same content:
240x180 56Kbps (this is where we started with online video!!!)
320x240 300Kbps
320x240 450Kbps
640x480 300Kbps
640x480 800Kbps
640x480 1.3Mbps
640x480 1.8Mbps

If you spend an afternoon doing these tests and benchmarking, evaluating the results for yourself, you'll know more about practical video compression than 99% of working pros, and can apply that knowledge to Quicktime as well as any other compressed format (hint: WMV is an outstanding codec!).

You may wish to keep going to HD in your benchmarking, you'll want to test bitrates from 1.2 to 7Mbps.

Useful references:
Adam Wilt's website
Videohelp, great dvd reference, but compression is compression.
Unfortunately, there's no similar web site I know of for more compressed formats like WMV and QT.
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