[FFmpeg-trac] #5734(undetermined:reopened): Coherent support to VP8 with alpha channel

[FFmpeg]

#5734: Coherent support to VP8 with alpha channel
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             Reporter:  cdlvcdlv     |                    Owner:
                 Type:  defect       |                   Status:  reopened
             Priority:  normal       |                Component:
              Version:  unspecified  |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
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Changes (by cdlvcdlv):

 * status:  closed => reopened
 * resolution:  needs_more_info =>


Comment:

 1.- Generate webm with alpha.
 % ffmpeg -i
 https://upload.wikimedia.org/wikipedia/commons/1/14/Animated_PNG_example_bouncing_beach_ball.png
 -c:v libvpx -pix_fmt yuva420p -metadata:s:v:0 alpha_mode="1"
 bouncing_ball_with_alpha.webm
 2.- Generate qtrle with alpha.
 % ffmpeg -i
 https://upload.wikimedia.org/wikipedia/commons/1/14/Animated_PNG_example_bouncing_beach_ball.png
 -c:v qtrle bouncing_ball_with_alpha.mov
 3.- Generate huffyuv with alpha.
 % ffmpeg -i
 https://upload.wikimedia.org/wikipedia/commons/1/14/Animated_PNG_example_bouncing_beach_ball.png
 -c:v huffyuv bouncing_ball_with_alpha.avi
 4.- Create a background video.
 % ffmpeg -i
 https://upload.wikimedia.org/wikipedia/commons/e/e6/Typing_example.ogv -ss
 0 -t 5 -c copy -map 0 background.ogv
 5.- Test the three videos over background:
 % ffplay -i background.ogv -vf "movie=bouncing_ball_with_alpha.mov[ov];
 [in][ov]overlay"
 % ffplay -i background.ogv -vf "movie=bouncing_ball_with_alpha.avi[ov];
 [in][ov]overlay"
 % ffplay -i background.ogv -vf "movie=bouncing_ball_with_alpha.webm[ov];
 [in][ov]overlay"

 Results:
 Qtrle: right
 https://i.imgsafe.org/6535b63d1d.png
 Huffyuv: right
 https://i.imgsafe.org/6527f9c1ce.png
 Webm: wrong
 https://i.imgsafe.org/6538bf089a.png

 Version used: Zeranoe build N-80999-gf41e37b

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Ticket URL: <https://trac.ffmpeg.org/ticket/5734#comment:4>
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