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| Munemasa Katagiri |
| Posted: Dec 18 2002, 07:06 PM |
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Ok, guys.... I have this problem, I must make a small file but I keep getting those little squares all over! 
I went to a lot of sites but I can't learn a way to configure DivX 5 fast and nice.
Thanks a lot! 
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| jac_goudsmit |
| Posted: Dec 18 2002, 08:59 PM |
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Video compressors and decompressors (codecs) compress the picture in small blocks of e.g. 8x8 pixels called macroblocks.
When you ask the codec to generate a heavily compressed output, the codec has to drop a lot of information which results in "compression artefacts" such as macroblocks becoming visible. If you allow the codec to compress less heavily, the picture should improve dramatically.
Let's say you have a movie at 640x480 at 30fps (similar to NTSC). When you want to encode this with DivX 5, you will get acceptable quality at about 800kbits/sec. The quality is better at higher bitrates of course, and quality is a subjective matter, but let's use this for an example. Also I assume that the source material that you are using is of perfect quality i.e. little noise and no compression artefacts from other encoders (if you grab with MJPEG, don't set the bitrate any lower than 3kbytes/sec)
At 800kbits/sec video and 128kbits/sec for audio, one CD-R will be enough to fit most movies (there are bitrate calculators to figure this out). But if you want to fit your movie in less space, you can either lower the bitrate of the compressor or you can resize the movie. If you go from 640x480 to 320x240, you are reducing the total number of pixels by a factor of 4, so you can probably safely reduce the video bitrate to 200kbits/sec. That way the only visible difference in video quality is the size of the picture.
You may also want to reduce the audio bitrate by changing the audio encoder's parameters or by resampling the audio or reducing the number of audio channels. E.g. changing the audio from 44.1kHz stereo to 22.05kHz mono will reduce the audio data by a factor of 4 and you can encode it at a lower bitrate e.g. 32kbits/sec instead of 128.
===Jac |
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| Munemasa Katagiri |
| Posted: Dec 18 2002, 09:06 PM |
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Thanks for the advice. I'll see what I can do to improve my encodes! |
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