What is the difference between 2-pass and 1-pass encoding?
If you read above about VBR vs. CBR encoding, youll recall that a VBR encoder will from time to time make mistakes when throttling the bitrate. If it goes too low, you can get some nasty artifacts. One feature found on professional encoders that helps reduce this problem is 2-pass VBR. In a nutshell, the encoder will make a first pass at encoding the video, then rewind and do it again. When finished, the encoder analyzes the results before finalizing. By using 2 passes and analysis, the encoder is less likely to err in choosing the bitrates. For the really picky compressionist, he can then use segment re-encoding to fix any errors.
