Rate Control

The Aurora5 encoder supports multiple rate control algorithms. Here are code snippets that demonstrate the different rate control modes using FFmpeg integrated with Aurora5.

  • 1-pass ABR, averaged bitrate (by setting -b:v or by setting -wz265-params bitrate)
  • 1-pass VBR, vbv-limited bitrate(by setting -b:v 1000k -maxrate 2000k -bufsize 4000k or by setting -wz265-params bitrate=1000:vbv-maxrate=2000:vbv-bufsize=4000)
  • 1-pass CBR, constant bitrate(by setting -b:v 1000k -maxrate 1000k -bufsize 1000k or by setting -wz265-params bitrate=1000:vbv-maxrate=1000:vbv-bufsize=1000 or by setting -wz265-params rc=3:bitrate=1000)
  • 1-pass strict CBR (by setting -wz265-params rc=3:bitrate=1000:strict-cbr=1)
  • Constant quality mode(by setting -crf)
  • 2-pass ABR

Two-pass example

For two-pass, you need to run ffmpeg twice as follows:

  • In pass 1 and 2, use the -wz265-params pass=1:statout=2pass.log and -wz265-params pass=2:statin=2pass.log options, respectively.
  • Make sure statout and statin is the same file.
  • In pass 1, output to a null file descriptor, not an actual file. (This will generate a logfile that ffmpeg needs for the second pass.)
  • In pass 1, you can leave audio out by specifying -an.

For libwz265, the -pass option is not applicable.

ffmpeg -y -i input -c:v libwz265 -b:v 2600k -wz265-params pass=1 -an -f null /dev/null && \
ffmpeg -i input -c:v libwz265 -b:v 2600k -wz265-params pass=2 -c:a aac -b:a 128k output.mp4

Note: Windows users should use NUL instead of /dev/null and ^ instead of \.