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Old 10th November 2009, 00:33   #1  |  Link
dbfs
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Bitrate and resolution balance

Let's start with a example... I have a lot of old 4:3 PAL and NTSC DVD's, and some newer 16:9 disc's. I'm planning to convert them to a smaller format for on my harddisk. I think it will be in WMV(vc-1) or Xvid or H264...

To the point, it is not smart to use a bitrate of 1200kbps for a full resolution encoding of a dvd from native dvd 480P DVD to 848x480P, because the bitrate is way to low for a high resolution encoding, it will result in a video with a lot of artifacts.

Resize is the best solution, but you need the best balance between bitrate and resolution, 1200kbps for video in a 16:9 resized 480x270 is too high, no artifacts in the video, but a lot of bitrate is throw away because the low resolution.

Too high resolution is not good because too much data with a too low bitrate which result in smooth video with artifacts.

My plan is to use a bitrate of 1200kbps, I've tried experimenting with different resolution's but a can't make a decision.

My question to you is:'How can I make a good decision and make a good balance between bitrate and resolution for standard def video's, and what is yours balance between resolution and bitrate?

Last edited by Guest; 10th November 2009 at 01:13. Reason: 12
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Old 10th November 2009, 00:58   #2  |  Link
MatLz
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Hi!
It depends on the complexity/compressibility of the source...
For example, an action movie is less compressible than a slow drama. Animes are generaly more compressible than regular movie.
So if you have a bitrate in mind, down the res for action movie and up for animes or drama...

Last edited by MatLz; 10th November 2009 at 01:00.
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Old 10th November 2009, 01:00   #3  |  Link
nurbs
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Quote:
Originally Posted by dbfs View Post
To the point, it is not smart to use a bitrate of 1200kbps for a full resolution encoding of a dvd from native dvd 480P DVD to 848x480P, because the bitrate is way to low for a high resolution encoding, it will result in a video with a lot of artifacts.
You can't say that. It depends on the codec you use and the complexity of the source video. If you are encoding cartoons (e.g. The Simpsons) to H.264 for instance you are probably just wasting space at that bitrate.

Quote:
My question to you is:'How can I make the best decision and make a good balance between bitrate and resolution for standard def video's, and what is yours balance between resolution and bitrate?
You don't. You pick a resolution and then you let the encoder decide for you. x264 for instance has a constant quality mode (CRF). You pick a number and your encodes will come out with more or less the same quality, but you won't know the bitrate beforehand.
Other codecs have a constant quantizer mode which can also be used for that purpose, although it's probably less optimal. Alternatively you can do a compression check by encoding say 10% of your source at a certain quantizer and then do a 2-pass encode with the resulting bitrate.
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Old 10th November 2009, 02:21   #4  |  Link
prOnorama
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Quote:
Originally Posted by MatLz View Post
Hi!
For example, an action movie is less compressible than a slow drama.
That's not always the case: a grainy drama might be harder to compress than a smooth fast moving action movie for instance, compressibility needs to be examined on a per source basis.
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Old 11th November 2009, 00:22   #5  |  Link
dbfs
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No any standard for SD web formats? I know that 704 x 396 is quite much used for sd, but is this a standard?
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Old 11th November 2009, 00:31   #6  |  Link
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There is no standard defined by any standardization organization. I'm sure the "scene," various streaming websites, etc etc have their own internal "standards," but that's probably not what you mean and I don't see why that should have any bearing on your decision.

The reason there is no standard is because you don't need one! Software players can handle whatever resolution/framerate/bitrate/etc you throw at them, so there is no need to make any standards.
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Old 11th November 2009, 15:50   #7  |  Link
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Usually it would be good idea to use multiples of original video resolution, if they are re-encoded for streaming or something else were you need lower resolution. Most videos are from standard TV broadcasts or cameras which have fixed resolutions and scaling them to arbitrary resolution can produce loss of quality instead going for multiplies like 720x576 -> 360x288 or if visible video is less than that, then divide it with half resolution.

Fixed bitrate like 1200 kbps or whatever, will produce variable quality videos because the amount of movement, noise or colors will require different amount of bitrate to look about same as original video. There is no way around that.
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