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| jcsston |
| Posted: Dec 3 2002, 03:47 AM |
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Matroska Dev
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If I encode something at 100% and it comes out 900MB if I re-encode at 50% would the file size be 450MB?
Would this have less quality than a two-pass at the same avg bitrate?
This is with DivX 5.0.2 Pro
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| fccHandler |
| Posted: Dec 3 2002, 04:25 AM |
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Administrator n00b
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Hmm... Try it and see 
IMHO, "1-pass, quality-based" unquestionably produces the best quality video, especially during high-motion scenes. The disadvantage is that the file size is unpredictable, so you may wind up doing several encodings at different percentages before you find the magic setting that produces the file size you want.
If you don't have time for such nonsense, then "2-pass" gives excellent quality by spreading the bits around where it thinks they're needed. If you're really pressed for time, "1-pass" is quite good too.
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May the FOURCC be with you... |
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| ChristianHJW |
| Posted: Dec 3 2002, 06:45 AM |
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Download 'The Gordian Knot' from www.dom9.org ... its a great frontend to Vdub, and coming with a very powerful bitrate calculator, so you can find ut exactly what bitrate you have to set to achieve a certain file size ... a quality setting of 50% would not shrink your video size by 50% ( in fact it could be even bigger than before ) ...
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Support matroska as container and Gstreamer as the only truely open, x-platform multimedia platform .... |
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| jcsston |
| Posted: Dec 3 2002, 07:45 AM |
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I have Gordian Knot and I use it as a bitrate calc (I like the fact I can enter the no of frames)
But I don't like doing a two-pass because if I need a different bitrate I have to start over.
50% percent = Yuck,
the file size was reduced on my test file from 150MB at 100% to 20MB.
The quantizer setting at 4 produces half the size of 2 (100%) and the 8 setting produces 1/4 size.
I like to do a whole pass at 100% similar to what Gordian Knot for a compression check, but I process the entire file figure out exactly what bitrate to set it to.
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Use the Matroska file format |
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| fccHandler |
| Posted: Dec 3 2002, 09:03 AM |
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@jcsston:
I think I understand what you are trying to do, and your observation that doubling the quantizer halves the file size is valuable information indeed (I had never noticed that myself). It suggests a simple linear relationship between the quantizer value and the level of compression! If this is true, then only one "compression check" encoding should be necessary to determine the exact quantizer value that will produce the file size you want.
(I'll be amazed if it's that simple, but it's worth a try.)
Thanks for the tip! 
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May the FOURCC be with you... |
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| drizztcanrender |
| Posted: Dec 5 2002, 03:32 PM |
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Well quality based encoding in divx5.02 is vbr.That's why you won't have the half video size if you go down from 100% to 50%.The quantizers yes they do have a linear relation with that size,at least if we are talking about mbs and not kbs...The highest quality you can achieve is quant 2,although in some discussion, if recall correct, now quant 1 is usable....and huge. |
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| fccHandler |
| Posted: Dec 5 2002, 05:42 PM |
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| QUOTE (drizztcanrender @ Dec 5 2002, 11:32 AM) | The quantizers yes they do have a linear relation with that size,at least if we are talking about mbs and not kbs...
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 Eh? What's the difference, other than scale?
| QUOTE | | The highest quality you can achieve is quant 2,although in some discussion, if recall correct, now quant 1 is usable....and huge. |
Yes, IIRC you can get quant 1 via a neat trick: Set "1-pass" to 10000 kbps and set "minimum quantizer" = 1.
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May the FOURCC be with you... |
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| jcsston |
| Posted: Dec 6 2002, 12:50 AM |
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Matroska Dev
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The ffdshow filter doesn't seem to like the 1 quantizer.
This looks fine in VDub which uses DivX 5 to decode it
Edit: Duh  I should've updated to one of the alpha releases.
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| drizztcanrender |
| Posted: Dec 6 2002, 02:32 PM |
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Unregistered
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[QUOTE](drizztcanrender @ Dec 5 2002, 11:32 AM)
The quantizers yes they do have a linear relation with that size,at least if we are talking about mbs and not kbs...
Eh? What's the difference, other than scale?
Well it may seem strange but when we are comparing video sizes with different settings of a codec(or codecs) we always look as far as kbs resemblance. |
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