what does -crf mean in ffmpeg resize video file command?

问题

Could someone explain what -crf means in the following command:

ffmpeg -i input.mp4 -c:v libx264 -crf 65 -b:v 1M -c:a aac output.mp4

What does -crf stand for?

回答1:

CRF (Constant Rate Factor) is the default quality setting for the x264 and x265 encoders. You can set the values between 0 and 51, where :

1. lower values would result in better quality, at the expense of higher file sizes.
2. Higher values mean more compression, but at some point, you will notice the quality degradation.

You can also read about the Quantization Parameter which controls the amount of compression for every Macroblock in a frame

来源：https://stackoverflow.com/questions/54985523/what-does-crf-mean-in-ffmpeg-resize-video-file-command