ShareX Download FFmpeg: Understanding CRF Encoding for Optimal Video Quality

When it comes to video encoding, there are several technical terms that can be overwhelming, especially for those who are new to the field. One such term is CRF (Constant Rate Factor), which is often confused with Constant Bitrate (CBR). In this article, we will delve into the world of CRF encoding and explore how it works, its benefits, and how to use it effectively using ShareX download FFmpeg.

In tech terminology, you maintain a constant QP (quantization parameter) by compressing every frame of the same type the same amount. This is achieved by throwing away the same relative amount of information. CRF is a 'constant quality' encoding mode, as opposed to CBR. You can clearly see the logarithmic relationship between CRF and bitrate.

To give you an estimation of the bitrates to be expected for clips with different resolutions, here's a figure showing the average bitrate in MBit/s for four one-minute video clips with different encoding complexity, encoded with x264 and different CRF values. As you can see, the maximum rate can range between 10 and 25 MBit/s for a 2160p encode at CRF 23.

In video streaming, CRF can be used in a constrained/capped mode to prevent bitrate spikes. For other applications, other rate control modes are recommended. You should use CRF encoding primarily for offline file storage, in order to achieve the most optimal encodes.

A change of CRF value should result in about half/double the file size, although your results might vary. If the file size is too high, choose a higher CRF. Is the quality good enough? No? Then set a lower CRF. If you're unsure about what CRF to use, begin with the default and change it according to your subjective impression of the output.

In practice, using ShareX download FFmpeg, you can encode video files with the following command: ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 31 -b:v 0 output.mkv. This command will use the CRF encoding mode with a value of 31 to achieve optimal quality.

In conclusion, CRF encoding is a powerful tool for achieving optimal video quality while minimizing file size. By understanding how it works and how to use it effectively using ShareX download FFmpeg, you can take your video encoding skills to the next level.

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