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tutorial:guide_to_encoding_types

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tutorial:guide_to_encoding_types [2010/04/13 00:05]
j.m created
tutorial:guide_to_encoding_types [2012/11/11 08:51] (current)
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 Why are two passes needed? Because the codec cannot see in the future. So it cannot know how much bits to give to the current images. Why are two passes needed? Because the codec cannot see in the future. So it cannot know how much bits to give to the current images.
  
-Let's assume that Quantizer*Encoded size is more or less constant. If you do the 1st pass encoding with quantizer=2,​ you will get a size S. Now, you know the wanted final size (F) that should be less than S, else you just wasted your time. :)+Let's assume that Quantizer*Encoded size is more or less constant. If you do the 1st pass encoding with quantizer=2,​ you will get a size S. Now, you know the wanted final size (F) that should be less than S, else you just wasted your time.(nbsp):-)
  
 The average quantizer is then Q=(2*S)/F. It is then tuned all along to give more bits to scenes where it will make a big difference, and less to the scenes where giving bits will not increase the quality noticably. The average quantizer is then Q=(2*S)/F. It is then tuned all along to give more bits to scenes where it will make a big difference, and less to the scenes where giving bits will not increase the quality noticably.
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   * **Recommended:​** Only useful for modifying an existing encoded file.    * **Recommended:​** Only useful for modifying an existing encoded file. 
  
-===== Single pass bitrate =====+===== Single pass – bitrate =====
  
 This encodes the video one time, using a limited video bitrate range on all scenes, regardless of whether or not they need less, equal or more bitrate. Note that this is not constant bitrate encoding. This encodes the video one time, using a limited video bitrate range on all scenes, regardless of whether or not they need less, equal or more bitrate. Note that this is not constant bitrate encoding.
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   * **Time:** Requires the least amount time of encode.   * **Time:** Requires the least amount time of encode.
   * **Video size:** Size of videos will vary and cannot be accurately predicted.   * **Video size:** Size of videos will vary and cannot be accurately predicted.
-  * **Recommended:​** ​this method is not recommended because it produces the lowest quality videos. //​Two-pass//​ is recommended.+  * **Recommended:​** ​This method is not recommended because it produces the lowest quality videos. //​Two-pass//​ is recommended.
  
-===== Single pass quantizer =====+===== Single pass – quantizer =====
  
 Also known as constant quantizer or constant quality mode. By selecting a number, each frame will get the same level of compression based on the chosen level. Good for quick and simple compression,​ at the sacrifice of possibly not achieving the large or small size of video desired. Low levels equal less compression,​ and therefore result in higher video quality. High levels equal more compression,​ and therefore result in lower video quality. This is very useful for quickly compressing something based on a simple value system. Also known as constant quantizer or constant quality mode. By selecting a number, each frame will get the same level of compression based on the chosen level. Good for quick and simple compression,​ at the sacrifice of possibly not achieving the large or small size of video desired. Low levels equal less compression,​ and therefore result in higher video quality. High levels equal more compression,​ and therefore result in lower video quality. This is very useful for quickly compressing something based on a simple value system.
tutorial/guide_to_encoding_types.txt · Last modified: 2012/11/11 08:51 (external edit)