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Revision 3 - (view) (download)
| 1 : | Isibaar | 3 | xvid vfw help |
| 2 : | 20/jan/02 | ||
| 3 : | |||
| 4 : | *** rate control *** | ||
| 5 : | |||
| 6 : | xvid offers a number of different rate control modes | ||
| 7 : | |||
| 8 : | - 1pass-cbr: constant-bitrate | ||
| 9 : | use the bitrate slider to select the desired bitrate; refer to 'cbr constants' for advanced options. note: we actually use an average-bitrate algorithm, so the instaneous bitrate will fluxuate. | ||
| 10 : | |||
| 11 : | - 1pass-quality | ||
| 12 : | use the quality slider to select a desired quality percentile. the quality% is then used to calculate an average-quantizer. | ||
| 13 : | |||
| 14 : | - 1pass-quantizer | ||
| 15 : | force the codec to use a fixed quantizer for all frames. valid range: [1,31]. | ||
| 16 : | |||
| 17 : | - 2pass | ||
| 18 : | a detailed explaination of 2pass can be found here: http://www.research.ibm.com/journal/rd/434/westerink.html | ||
| 19 : | our implementation of two pass encoding requires three steps | ||
| 20 : | 1) 1stpass: collect compression statisics to a stats file. | ||
| 21 : | 2) process the stats using gordian knot, xihprom, etc. | ||
| 22 : | 3) 2ndpass: compress the video using both the original 1stpass stats file, and the normalized stats file. | ||
| 23 : | |||
| 24 : | |||
| 25 : | *** encoder tuning *** | ||
| 26 : | |||
| 27 : | - max keyframe interval | ||
| 28 : | the maximum interval between keyframes. | ||
| 29 : | |||
| 30 : | - motion search precision | ||
| 31 : | controls the speed/quality of the motion search algorithm. range [0,6]. | ||
| 32 : | lower values are faster but reduce compressibility. | ||
| 33 : | higher values are slower but increase compressibility. | ||
| 34 : | |||
| 35 : | - quantization type | ||
| 36 : | quantization is the process of removing detail. there are two types: | ||
| 37 : | h.263: used by divx4.x and h263 encoders. | ||
| 38 : | mpeg: used by the microsoft mpeg-4 encoder, mpeg-1/2. | ||
| 39 : | |||
| 40 : | mpeg quantization gives sharper looking images, but can introduce grain/noise. while h.263 gives softer looking images, removes noise (but sometimes too much) and is slightly faster. | ||
| 41 : | |||
| 42 : | |||
| 43 : | *** cbr constants *** | ||
| 44 : | |||
| 45 : | these apply only to 1pass-cbr mode. | ||
| 46 : | |||
| 47 : | - average peroid | ||
| 48 : | the number of frames over which the average bitrate is maintained. | ||
| 49 : | |||
| 50 : | - reaction peroid | ||
| 51 : | (?) the number of frames inwhich we react to sudden change in bitrate. | ||
| 52 : | |||
| 53 : | - up/down ratio | ||
| 54 : | (?) a percentile representing how fast/much we react. | ||
| 55 : | |||
| 56 : | |||
| 57 : | *** debug *** | ||
| 58 : | |||
| 59 : | - min/max quantizer. | ||
| 60 : | lets you limit the flexibility of the encoder. | ||
| 61 : | a minquant=1 can sometimes cause problems with 1pass-cbr and 2pass. | ||
| 62 : | |||
| 63 : | - luminance masking | ||
| 64 : | enabled per-macroblock quantizer decision. very experimental | ||
| 65 : | |||
| 66 : | - discard encoded bitstream on 1st-pass | ||
| 67 : | by default xvid discards the compressed bitstream during the the 1st pass of a two pass encoding session. example: in windows you end up with an empty .avi file. if this box is unchecked the bitstream is kept. | ||
| 68 : | note: the 1st compressed bitstream can large. | ||
| 69 : | |||
| 70 : | this can be used to perform a 'fast 2pass' encoding. | ||
| 71 : | 1) perform 1st pass encoding of your source material with discard unchecked. | ||
| 72 : | 2) process the stats file | ||
| 73 : | 3) open the bitstream created in the first pass, and perform the 2nd pass on it. | ||
| 74 : | note: there is some quality loss. judge it for yourself. | ||
| 75 : | |||
| 76 : | - perform dummy 2nd-pass | ||
| 77 : | this can be used to check the accuracy of your stats file processor/calculator. it instructs xvid to create a dummy/junk bitstream exactly to the size described in the processed stats file. | ||
| 78 : | |||
| 79 : | *** cpu *** | ||
| 80 : | |||
| 81 : | provides auto/manual control over cpu-feature optimizations. | ||
| 82 : | |||
| 83 : | |||
| 84 : | *** about *** | ||
| 85 : | |||
| 86 : | build timestamp, etc. |
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