FFmpeg encoding to H265

Question

I read that the new H265 is supposed to have around twice the compression efficiency of H264 and supposed files around half the size http://x265.org/hevc-h265/ All of my results trying to encode to H265 give me larger files than H264 from the same source.

For H264 I am passing these switches to ffmpeg command line

-c:v libx264 -preset:v veryslow -profile:v high -crf 15 -pix_fmt yuvj420p -an -y -r 30

For H265 I am using these switches

-c:v libx265 -preset:v veryslow -crf 15 -an -y -r 30

In all tests using a variety of different source frames the H265 always results in a larger file size (and is also much much slower to encode).

Any tips for H265? I want the H265 to look like the same quality as H264 but not result in larger files.

Thanks.

Solution

x265 crf values are different from x264

https://trac.ffmpeg.org/wiki/Encode/H.265

The CRF of 28 should visually correspond to libx264 video at CRF 23

try adjusting the crf for x265 for a higher value , like 20

Comments

[Some1Else]

Thanks. Knowing the CRFs do not relate is the key. A CRF of 25 for H265 looks fine compared to a CRF of 15 for H264.