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I converted an avc (h264) file to an hevc (h265) file and an av1 file.

Relative to the hevc (h265) file, the av1 file is far larger in size, and the av1 file has worse psnr and ssim results too.

With the hevc (h265) file, i used the default crf setting (28)

av1 doesn't have a default crf amount, but i used the ffmpeg recommendation of 30

Here's the command i used to do the hevc (h265) conversion

C:\Users\l\Desktop\6-app\ffmpeg -i y.mp4 -c:v libx265 -preset 8 -vf scale=1920:1080 -r 60 -ab 192k -ar 48k -map_chapters -1 -map_metadata -1 z.mp4

Here's the command i used to do the av1 conversion

C:\Users\l\Desktop\6-app\ffmpeg -i y.mp4 -c:v libaom-av1 -crf 30 -b:v 0 -strict experimental -vf scale=1920:1080 -r 60 -ab 192k -ar 48k -map_chapters -1 -map_metadata -1 z.mkv

Here are the psnr and ssim results of the hevc (h265) file

ssim

Y:0.981764 (17.390662)
U:0.992258 (21.111573)
V:0.992246 (21.104816)
All:0.985260 (18.315015)

psnr

y:41.620801
u:48.257839
v:47.699066
average:42.905441
min:38.873493
max:58.862531

Here are the psnr and ssim results of the av1 file

ssim

Y:0.923286 (11.151250)
U:0.991684 (20.800862)
V:0.987425 (19.004970)
All:0.945376 (12.626126)

psnr

y:27.332443
u:44.955360
v:41.569108
average:29.034062
min:8.783696
max:59.518112

Here are the size results of the files

avc

3.9 mb

hevc (h265)

4.6 mb

av1

9.59 mb

I know i'm compressing an already well-compressed file, I didn't necessarily expect a smaller file size - but i did expect av1 to outperform hevc (h265))

Here are the actual files

combo-3-avc-original.mp4

combo-3-hevc.mp4

combo-3-av1.mkv

Why would such poor results occur?

edit:

· here are the versions of the tools

ffmpeg version N-93389-gd15117c996
[libaom-av1 @ 0000025b4839bf40] 1.0.0-1458-ge40c226a6
libavutil      56. 26.100 / 56. 26.100
libavcodec     58. 47.103 / 58. 47.103
libavformat    58. 26.101 / 58. 26.101
libavdevice    58.  6.101 / 58.  6.101
libavfilter     7. 48.100 /  7. 48.100
libswscale      5.  4.100 /  5.  4.100
libswresample   3.  4.100 /  3.  4.100
libpostproc    55.  4.100 / 55.  4.100
  • libaom is still an experimental encoder - performance will remain in flux for the time being. Which build are you using? – Gyan Mar 21 at 6:49
  • @gyan · i edited my post with version details at the bottom – abcjme Mar 21 at 7:45
  • libaom version? – Gyan Mar 21 at 7:48
  • @gyan ? how do i check libaom version – abcjme Mar 21 at 8:27
  • When you encode using libaom, ffmpeg log will have a line like this, [libaom-av1 @ 0000000003990500] 1.0.0-1475-g7c64a0dca – Gyan Mar 21 at 8:39

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