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When encoding videos with H.264, I'm used to the constant rate factor compression setting. However I don't see anything like it in blender's options:

enter image description here

Is there a way to set the constant rate factor from the GUI? If not, what do these settings do? I can only assume they are for the two-pass method, but I'm not sure which ones correspond to the descriptions in the wiki.

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Further down the page you refer to you, under additional information you will find ABR (Average Bit Rate) where you will find the -bitrate, -minrate, -maxrate and -bufsize that correspond to blender's settings.

The bitrate is the target rate (average over the length of video) that you want to achieve. The minimum and maximum define how far from the average it is allowed to deviate.

Video compression works by only updating areas of video that change and compressing those areas. Like jpeg the amount of compression can vary depending on the quality you want in the final image. If high quality compression pushes the bitrate higher than the maximum limit then it needs to lower the quality to stay in the range.

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Prior to version 2.79 blender did not support CRF-style encodings. 2.79 added this, although the mapping from labels to numbers isn't obvious. Hopefully an answer to What numerical CRF values do the assorted output qualities correspond to in the ffmpeg video encoding options will clear that up.

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