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Web Video Creation and Optimization Forum

    
Gigs per minute of video rules of thumb
for high compressuib and speed videos
4thePegeh




msg:3655446
 4:14 pm on May 21, 2008 (gmt 0)


So I guess the real question is, how many gigs should be used up per minute of video each time I send out a video that is in the "sacrificing quality for compression and speed" rather than "improving quality" category. I want viewers to see what is happening (see a figure about 40 - 60 feet away from camera doing creative dance for example - details of costume and makeup not relevant). View of body movements, foot positioning, hand positioning and the flowing ribbons or balls required.

With that information I could look again at my hosts, and at my expected number of downloads and figure out what sort or revenues I require to keep my shirt on my back.

 

4thePegeh




msg:3655718
 8:24 pm on May 21, 2008 (gmt 0)

For my purposes they could even be offered in black and white. I guess I would have to find a way to automate the conversion from the submitted color originals. But if something converted to black and white would be much less bandwidth than color, perhaps it would be a net gain.

thecoalman




msg:3655728
 8:40 pm on May 21, 2008 (gmt 0)

There is no rule of thumb because there is too many factors involved. The bitrate required for a video depends on a few factors, most notably codec used, resolution, content of the video, quality of the source video.

Codec
Codecs are not equal, for example a DV-AVI is 14 gigs per hour, for comparable quality you'd need about 4 gigs for MPEG or 1.5 gigs for something like WMV or Divx. They each have their purpose though...

Resolution
The bitrate required is largely dependent on the resolution. Each codec has sweet spot for a specific resolution. For example if you're using DVD compliant MPEG2 at 720X480 if you get above 8000kbps generally you're not deriving any benefit but just creating a larger file. Once you get below 4000kbps macroblocking will become an issue. At that point you are better off using a lower resolution. The sweet spot for MPEG2 is around 6000kbps, provides the smallest file while not degrading video with a lot of action.

Content
Video of some guy sitting at a desk will require much less bitrate than something with a lot of action and movement.

Quality
Poorly shot video such as hand held footage, fast pans or zooms, lots of noise... etc. requires much more bitrate than steady footage shot on a tripod that is a very clean source.

Edit: FYI "gigs per minute" is well beyond full HD.

4thePegeh




msg:3655945
 1:18 am on May 22, 2008 (gmt 0)

Thanks thecoalman

Looks like I have a lot more reading to do.

thecoalman




msg:3656024
 4:37 am on May 22, 2008 (gmt 0)

There's other things you do to reduce bitrate too, for example I have WMV profile I created that will almost stream on 56k dial-up and it doesn't look bad at all and is not a postage stamp.

The properties are:

Resolution: 320X180 (for 16:9 video)
Total bitrate: 70kbps
Length: 7min22sec
File Size: 4MB

This was achieved by combining the stereo audio tracks and making them mono at 20kbps. It's not fabulous but WMA audio excels past other codecs at really low bitrates. This leaves 50kbps for the video which is very low for that resolution, the only reason it works is because the framerate was changed from 30fps to 10fps, by doing this you are removing 2/3's of the bitrate you need. This leaves it slightly choppy but overall considering the audience it was intended for its the best damn video they will ever see without having to wait for it. On a side note 15fps is not that bad at all and most people would never notice it.

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