On 2/26/21 9:52 PM, pdr0 wrote:
Different timebase means there is potential to compare different frames.
Use settb
ffmpeg -framerate 60000/1001 -i lossless.mkv -start_number 0 -framerate
60000/1001 -i source/%06d.tif -t 00:01:00 -lavfi
"[0:v]settb=1/AVTB,setpts=PTS-STARTPTS[main];[1:v]settb=1/AVTB,setpts=PTS-STARTPTS[ref];[main][ref]ssim"
-f null -
That seems to work. It gets rid of the "not matching timebases"
warning. It does cause the duration option (-t 00:01:00) to not work,
but I was able to use the "-frames:v" option instead. (In fact, I don't
need specify the framerate of the image sequence at all.)
$ ffmpeg -i lossless.mkv -start_number 0 -i source/%06d.tif -frames:v
3596 -lavfi
"[0:v]settb=1/AVTB,setpts=PTS-STARTPTS[main];[1:v]settb=1/AVTB,setpts=PTS-STARTPTS[ref];[main][ref]ssim"
-f null -
...
Input #0, matroska,webm, from 'lossless.mkv':
Metadata:
ENCODER : Lavf58.45.100
Duration: 00:00:59.99, start: 0.000000, bitrate: 1223104 kb/s
Stream #0:0: Video: huffyuv (HFYU / 0x55594648), bgr0, 1440x1080,
59.94 fps, 59.94 tbr, 1k tbn, 1k tbc (default)
Metadata:
ENCODER : Lavc58.91.100 huffyuv
DURATION : 00:00:59.994000000
Input #1, image2, from 'source/%06d.tif':
Duration: 04:17:10.96, start: 0.000000, bitrate: N/A
Stream #1:0: Video: tiff, rgb24, 1440x1080, 25 tbr, 25 tbn, 25 tbc
...
[Parsed_ssim_4 @ 0x562a600ac780] SSIM R:0.999888 (39.506142)
G:0.999889 (39.531716) B:0.999887 (39.466715) All:0.999888 (39.501442)
So this gets me to the same result that I got when I compared the
derived PNG image sequence to the original TIFF sequence.
$ ffmpeg -start_number 0 -i lossless/%06d.png -start_number 0 -i
source/%06d.tif -frames:v 3596 -filter_complex ssim -f null -
...
[Parsed_ssim_0 @ 0x5630c77ad440] SSIM R:0.999888 (39.506142)
G:0.999889 (39.531716) B:0.999887 (39.466715) All:0.999888 (39.501442)
Now that I know about the -frames:v option, I decided to try omitting
the last frame from the comparison.
$ ffmpeg -start_number 0 -i lossless/%06d.png -start_number 0 -i
source/%06d.tif -frames:v 3595 -filter_complex ssim -f null -
...
[Parsed_ssim_0 @ 0x560797482440] SSIM R:1.000000 (inf) G:1.000000
(inf) B:1.000000 (inf) All:1.000000 (inf)
$ ffmpeg -i lossless.mkv -start_number 0 -i source/%06d.tif -frames:v
3595 -lavfi
"[0:v]settb=1/AVTB,setpts=PTS-STARTPTS[main];[1:v]settb=1/AVTB,setpts=PTS-STARTPTS[ref];[main][ref]ssim"
-f null -
...
[Parsed_ssim_4 @ 0x5571f0a97780] SSIM R:1.000000 (inf) G:1.000000
(inf) B:1.000000 (inf) All:1.000000 (inf)
That gets me the expected score.
I don't understand why I have to omit the final frame. Both ImageMagick
and ffmpeg show the images as identical.
$ compare -metric AE lossless/003595.png source/003595.tif /tmp/diff.png
0
$ ffmpeg -i lossless/003595.png -i source/003595.tif -filter_complex
ssim -f null -
...
[Parsed_ssim_0 @ 0x561a6aae1540] SSIM R:1.000000 (inf) G:1.000000
(inf) B:1.000000 (inf) All:1.000000 (inf)
This is definitely good enough for my purposes, however. I'm going to
declare victory and move on.
Thanks for your help!
--
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