Changes between Initial Version and Version 1 of Ticket #9781


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Timestamp:
May 12, 2022, 7:29:18 PM (4 years ago)
Author:
Llyw
Comment:

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  • Ticket #9781

    • Property Cc Llyw added

  • Ticket #9781 – Description

    initial v1  
    33Take, for example, the 720p VP9 WebM version of Blender Foundation's Elephants Dream at https://upload.wikimedia.org/wikipedia/commons/transcoded/2/28/Elephants_Dream_%282006%29_1080p24.webm/Elephants_Dream_%282006%29_1080p24.webm.720p.vp9.webm.
    44
    5 At roughly 7 minutes, 2 seconds a stills image of this video looks like this in VLC 3.0.17.4: (See first attachment)
     5At roughly 7 minutes, 2 seconds a stills image of this video looks like this in VLC 3.0.17.4:
     6[[Image(https://trac.ffmpeg.org/attachment/ticket/9781/Original.png)]]
    67
    78
    … …  
    1011ffmpeg -i 'Elephants_Dream_(2006)_1080p24.webm.720p.vp9.webm' -vf 'zscale=w=480:h=272:f=lanczos,setdar=dar=16/9' -pix_fmt yuv420p Output_Distorted.mp4
    1112}}}
    12 The corresponding stills image will look like this when resizing the video port to show a 720p resolution: (See second attachment)
     13The corresponding stills image will look like this when resizing the video port to show a 720p resolution:
     14[[Image(https://trac.ffmpeg.org/attachment/ticket/9781/Output_Distorted.png)]]
    1315
    1416I understand that there is some movement in this scene but if you look at the background you should clearly see the distortion I was talking about.
    … …  
    1921ffmpeg -i 'Elephants_Dream_(2006)_1080p24.webm.720p.vp9.webm' -vf 'scale=w=480:h=272:flags=lanczos+accurate_rnd,setdar=dar=16/9' -pix_fmt yuv420p Output_Undistorted.mp4
    2022}}}
    21 Here, the corresponding stills image looks like this and does not show significant distortion when comparing with the stills image of the input video (some minor mismatch is obviously expected due to the strong resampling and movement in the scene): (See third attachment)
     23Here, the corresponding stills image looks like this and does not show significant distortion when comparing with the stills image of the input video (some minor mismatch is obviously expected due to the strong resampling and movement in the scene):
     24[[Image(https://trac.ffmpeg.org/attachment/ticket/9781/Output_Undistorted.png)]]
    2225
    2326I am assuming that this might have something to do with the recent-ish efforts to parallelize the `zscale` filter and would appreciate it, if this behavior is investigated.