[FFmpeg-trac] #9077(swscale:open): Transparency wrong for yuv420 -> rgba on altivec (was: yuv420 -> rgb32 broken on altivec)

[FFmpeg]

#9077: Transparency wrong for yuv420 -> rgba on altivec
-------------------------------------+-----------------------------------
             Reporter:  pocock       |                    Owner:
                 Type:  defect       |                   Status:  open
             Priority:  normal       |                Component:  swscale
              Version:  git-master   |               Resolution:
             Keywords:  ppc altivec  |               Blocked By:
             Blocking:               |  Reproduced by developer:  1
Analyzed by developer:  0            |
-------------------------------------+-----------------------------------
Changes (by cehoyos):

 * keywords:  ppc => ppc altivec


Comment:

 The current behaviour (transparency broken) is also reproducible with
 68363b6989f3355457af90f0c568ccbae9d4deb2 (the fix seems not to work
 correctly), the output was broken differently before, this brokenness was
 fixed since, likely #7124.
 {{{
 ffmpeg -f rawvideo -s 320x240 -i out.yuv -pix_fmt rgb32_1 -vframes 1 -y -f
 image2 out.sgi
 FFmpeg version git-68363b6, Copyright (c) 2000-2009 Fabrice Bellard, et
 al.
   configuration: --enable-swscale --enable-gpl --cc=/opt/at12.0/bin/gcc
 -m32
   libavutil     49.15. 0 / 49.15. 0
   libavcodec    52.20. 0 / 52.20. 0
   libavformat   52.30. 1 / 52.30. 1
   libavdevice   52. 1. 0 / 52. 1. 0
   libswscale     0. 7. 1 /  0. 7. 1
   built on Jan 23 2021 15:48:35, gcc: 8.3.1 20190304 (Advance-Toolchain-
 at12.0) [revision 269374]
 Input #0, rawvideo, from 'out.yuv':
   Duration: N/A, start: 0.000000, bitrate: N/A
     Stream #0.0: Video: rawvideo, yuv420p, 320x240, 25 tbr, 25 tbn, 25 tbc
 [swscaler @ 0x10be1d00]ALTIVEC: Color Space RGBA
 Output #0, image2, to 'out.sgi':
     Stream #0.0: Video: sgi, rgb32_1, 320x240, q=2-31, 200 kb/s, 90k tbn,
 25 tbc
 Stream mapping:
   Stream #0.0 -> #0.0
 Press [q] to stop encoding
 frame=    1 fps=  0 q=0.0 Lsize=      -0kB time=0.04 bitrate=  -4.4kbits/s
 video:66kB audio:0kB global headers:0kB muxing overhead -100.032543%
 }}}
 Another workaround is the following command line:

--
Ticket URL: <https://trac.ffmpeg.org/ticket/9077#comment:3>
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