[FFmpeg-user] facing a error/issue in compression efficiency under h.265

[USMAN AAMER]

Hi,

I am comparing the compression efficiency of H.264 and H.265 codecs.
I have studied many research papers showing that the compression efficiency
of H.265 is much better than H.264.

But I am not able to get the same results.
I am trying to compress 664 YUV 4:2:0 video sequence with ffmpeg under
H.264 and H.265 codecs and got the resultant videos of following sizes:
H.264: 5.58 MB
H.265: 6.66 MB

I am using the following commands for compression:
H.264:
ffmpeg -i video.y4m -c:v libx264 -an -strict experimental -preset slow -CRF
30 - b:v 800k -f mp4 output.mp4

and for H.265:
  ffmpeg -i video.y4m -c:v libx265 -an -strict experimental -preset slow
-CRF 30 - b:v 800k -f mp4 output1.mp4

Kindly tell me what is the issue. Waiting for the kind response.

Thank you.