h263: some L263 files decodes with wrong colors

[ami_stuff]

for example this one (decodes ok with lead h263 codec):

​https://web.archive.org/web/20060206015400/http://www.leadcodecs.com/Download/h263/WhatBox_H263_720x480_Quality%20and%20size%20equaly%20Important.avi

​https://web.archive.org/web/20060206015400/http://www.leadcodecs.com/Download/H263-Videos.htm

"-vf swapuv" fixes the problem

C:\>ffmpeg -i "C:\WhatBox_H263_720x480_Quality and size equaly Important.avi" out.avi
ffmpeg version 3.2.git Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 4.6.2 (GCC)
  configuration: --disable-pthreads --disable-ffprobe --enable-gpl
  libavutil      55. 48.100 / 55. 48.100
  libavcodec     57. 83.100 / 57. 83.100
  libavformat    57. 66.104 / 57. 66.104
  libavdevice    57.  3.100 / 57.  3.100
  libavfilter     6. 76.100 /  6. 76.100
  libswscale      4.  3.101 /  4.  3.101
  libswresample   2.  4.100 /  2.  4.100
  libpostproc    54.  2.100 / 54.  2.100
[avi @ 02383da0] non-interleaved AVI
[h263 @ 0238d720] Warning: not compiled with thread support, using thread emulat
ion
[pcm_s16le @ 0238c4c0] Warning: not compiled with thread support, using thread e
mulation
Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0, avi, from 'C:\WhatBox_H263_720x480_Quality and size equaly Important.a
vi':
  Duration: 00:00:39.17, start: 0.000000, bitrate: 3208 kb/s
    Stream #0:0: Video: h263 (L263 / 0x3336324C), yuv420p, 720x480 [SAR 12:11 DA
R 18:11], 1643 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn, 29.97 tbc
    Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, stereo, s16
, 1536 kb/s
[h263 @ 02770020] Warning: not compiled with thread support, using thread emulat
ion
[pcm_s16le @ 02771800] Warning: not compiled with thread support, using thread e
mulation
Stream mapping:
  Stream #0:0 -> #0:0 (h263 (native) -> mpeg4 (native))
  Stream #0:1 -> #0:1 (pcm_s16le (native) -> ac3 (native))
Press [q] to stop, [?] for help
[mpeg4 @ 027729c0] Warning: not compiled with thread support, using thread emula
tion
[ac3 @ 0271ccc0] Warning: not compiled with thread support, using thread emulati
on
Output #0, avi, to 'out.avi':
  Metadata:
    ISFT            : Lavf57.66.104
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p(progressive), 720x480
 [SAR 12:11 DAR 18:11], q=2-31, 200 kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc
    Metadata:
      encoder         : Lavc57.83.100 mpeg4
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
    Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, stereo, fltp, 192 k
b/s
    Metadata:
      encoder         : Lavc57.83.100 ac3
frame=   32 fps=0.0 q=22.6 size=     124kB time=00:00:01.10 bitrate= 921.2kbits/
frame=  197 fps=0.0 q=31.0 size=     482kB time=00:00:06.60 bitrate= 597.9kbits/
frame=  372 fps=248 q=31.0 size=     855kB time=00:00:12.44 bitrate= 563.0kbits/
frame=  536 fps=268 q=31.0 size=    1280kB time=00:00:17.91 bitrate= 585.3kbits/
frame=  699 fps=280 q=31.0 size=    1681kB time=00:00:23.39 bitrate= 588.8kbits/
frame=  864 fps=288 q=31.0 size=    2093kB time=00:00:28.89 bitrate= 593.3kbits/
frame= 1034 fps=295 q=31.0 size=    2507kB time=00:00:34.56 bitrate= 594.1kbits/
frame= 1172 fps=302 q=31.0 Lsize=    2821kB time=00:00:39.17 bitrate= 589.9kbits
/s speed=10.1x
video:1837kB audio:917kB subtitle:0kB other streams:0kB global headers:0kB muxin
g overhead: 2.413010%

[ami_stuff]

unrelated: also there are some artefacts for example around 6.3s which are not visible while decoding the file with lead codec

[Carl Eugen Hoyos]

Attached patch breaks the files attached to ticket #925.