No "two pass encoding" selection on 2.1.1.34 ?
Posted: Tue Aug 27, 2013 2:33 pm
Was it removed by the developer or is there a problem...
[quote="TheTinker"]Was it removed by the developer or is there a problem...[/quote]
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Postby ckhouston ยป Sun Jan 20, 2008 8:36 pm
2 pass encoding has been requested and discussed many times in these forums.
VSO has tweaked the ffmpeg encoder to obtain remarkable quality in a single pass and do it fast. I have done many tests and compared results in an objective way by looking at bitrate and quantiztion factor distributions over time and by zooming in on screenshots to look for artifacs.
I have compared with two other programs using two pass encodes and Cx2D beats both of them hands down. One example of a comparison with NeroVision is given in the last post in http://forums.vso-software.fr/multiple- ... light=nero
There are only two things I have found that a 2 pass encode in CX2D would slightly improve. One is a better estimation of the required average bitrate needed to prevent the rare overflow above tartget size. The other is better accuracy in transitions between scene changes, but these occur so fast the artifacs in them are only noticeable if you are aware they should be there and look hard for them on a very big screen TV.
I can only speculate why VSO does not add 2 pass encoding. Maybe the slight improvement is not worth complicating usage by video neophytes. Maybe the addition of that one switch mucks up the careful tweaking they have done with other switches, there are dozens of ffmpeg switches and some of them may affect others. I only know that they know their market better than any of us. They certainly know more about the program itself and about video processing than I do.
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Thanks for the help VSO. So if it ain't in your program any longer take the bloody thing out of the ONLINE GUIDE!
re: "Two-pass encoding- Blu-ray Converter encodes the video with a variable bitrate, which is best for quality, using a customized Constant Quality encoding method. This means that if a scene is "complex" (with fast movement), the encoder will reserve more space for this part of the video than for simple scenes (static) with less information (elements).
The more/longer the video you want to put on a DVD, the lower the average video bitrate must be, so it is more important to save some space during "slow" or static scenes to provide more space for "fast" action scenes. In the two pass mode, the first pass has the job of reading, analyzing and taking notes of the video file in order to get an overview of the whole video file including specific information about scenes. The second pass has the job of doing the actual encoding. When the second pass starts to encode, it has for each frame the value of the complexity (including other information such as motion vectors, ...) determined during the first pass. So, the encoder is capable of distributing the bitrate exactly where it is required, taking the whole movie as reference. Audio encoding is done in second pass.
If unticked/unchecked)then the software will use the Single pass encoding: The encoder doesn't know the complexity of the scenes because they were not yet played. So, averaging the bitrate must be done within a small portion of the video (a few seconds). Thus, it may occur that if a complex scene arrives, but to maintain the average bitrate over the slice of video considered, there is not enough bitrate available to handle the scene, thus giving artifacts."