IFF ANIM: support decoding of interlaced Scala's anims

[ami_stuff]

plays with:

​http://www.morguesoft.eu/Contenido/Programs/Windows/AWC-WIN.zip

(but interlaced decoding is buggy atm - may crash due to invalid memory accesses)

​https://www.datafilehost.com/d/4e926a5f

ANIM 16i/ANIM32i 

These two formats are well worth experi- 
menting with if you have the time. They are 
only useful H you are going to play back ani- 
mations at maximum speed all the time, but 
the advantage is a 50% drop in file size. The 
format works by taking advantage of the 
Amiga's interlaced mode, which doubles the 
resolution by using two screen refreshes. 
Ordinarily this can appear as a form of flicker- 
ing when used to display the largely- static 
Workbench, but fast moving animations can 
benefit. The original animation must have 
been created in interlaced mode, and when 
saved the new file will discard every second 
line - which would not have been seen 
anyway."

https://archive.org/stream/CUAmigaIssue101Jul98/CU_Amiga_Issue_101_Jul_98_djvu.txt

C:\>ffmpegx -i at2.anim32i -f null -
ffmpeg version N-80343-geaa1143 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.5.0 (GCC) 20100414 (Fedora MinGW 4.5.0-1.fc14)
  configuration: --prefix=/var/www/users/research/ffmpeg/snapshots/build --arch=
x86 --target-os=mingw32 --cross-prefix=i686-pc-mingw32- --cc='ccache i686-pc-min
gw32-gcc' --enable-pthreads --enable-memalign-hack --enable-runtime-cpudetect --
enable-cross-compile --enable-static --disable-shared --extra-libs='-lws2_32 -lw
inmm -lpthread' --extra-cflags='--static -I/var/www/users/research/ffmpeg/snapsh
ots/build/include' --extra-ldflags='-static -L/var/www/users/research/ffmpeg/sna
pshots/build/lib' --enable-bzlib --enable-zlib --enable-gpl --enable-version3 --
enable-nonfree --enable-libx264 --enable-libspeex --enable-libtheora --enable-li
bvorbis --enable-libfaac --enable-libxvid --enable-libopencore-amrnb --enable-li
bopencore-amrwb --enable-libmp3lame --enable-libfreetype --enable-libvpx --disab
le-decoder=libvpx
  libavutil      55. 24.100 / 55. 24.100
  libavcodec     57. 46.100 / 57. 46.100
  libavformat    57. 38.100 / 57. 38.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 46.101 /  6. 46.101
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  1.100 /  2.  1.100
  libpostproc    54.  0.100 / 54.  0.100
Input #0, iff, from 'at2.anim32i':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: iff_ilbm (ANIM / 0x4D494E41), pal8, 640x256, 60 fps, 60
tbr, 60 tbn, 60 tbc
[null @ 0x28d73a0] Using AVStream.codec to pass codec parameters to muxers is de
precated, use AVStream.codecpar instead.
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf57.38.100
    Stream #0:0: Video: wrapped_avframe, pal8, 640x256, q=2-31, 200 kb/s, 60 fps
, 60 tbn, 60 tbc
    Metadata:
      encoder         : Lavc57.46.100 wrapped_avframe
Stream mapping:
  Stream #0:0 -> #0:0 (iff_ilbm (iff) -> wrapped_avframe (native))
Press [q] to stop, [?] for help
[iff @ 0x28d4b80] bitmap (compression 0x6401, bpp 8, ham 0, interlaced 1) is not
 implemented. Update your FFmpeg version to the newest one from Git. If the prob
lem still occurs, it means that your file has a feature which has not been imple
mented.
[iff @ 0x28d4b80] If you want to help, upload a sample of this file to ftp://upl
oad.ffmpeg.org/incoming/ and contact the ffmpeg-devel mailing list. (ffmpeg-deve
l@ffmpeg.org)
Error while decoding stream #0:0: Invalid data found when processing input
[iff @ 0x28d4b80] bitmap (compression 0x6401, bpp 8, ham 0, interlaced 1) is not
 implemented. Update your FFmpeg version to the newest one from Git. If the prob
lem still occurs, it means that your file has a feature which has not been imple
mented.
[iff @ 0x28d4b80] If you want to help, upload a sample of this file to ftp://upl
oad.ffmpeg.org/incoming/ and contact the ffmpeg-devel mailing list. (ffmpeg-deve
l@ffmpeg.org)
Error while decoding stream #0:0: Invalid data found when processing input
[iff @ 0x28d4b80] bitmap (compression 0x6401, bpp 8, ham 0, interlaced 1) is not
 implemented. Update your FFmpeg version to the newest one from Git. If the prob
lem still occurs, it means that your file has a feature which has not been imple
mented.
[iff @ 0x28d4b80] If you want to help, upload a sample of this file to ftp://upl
oad.ffmpeg.org/incoming/ and contact the ffmpeg-devel mailing list. (ffmpeg-deve
l@ffmpeg.org)
Error while decoding stream #0:0: Invalid data found when processing input
[iff @ 0x28d4b80] bitmap (compression 0x6401, bpp 8, ham 0, interlaced 1) is not
 implemented. Update your FFmpeg version to the newest one from Git. If the prob
lem still occurs, it means that your file has a feature which has not been imple
mented.
[iff @ 0x28d4b80] If you want to help, upload a sample of this file to ftp://upl
oad.ffmpeg.org/incoming/ and contact the ffmpeg-devel mailing list. (ffmpeg-deve
l@ffmpeg.org)
Error while decoding stream #0:0: Invalid data found when processing input
frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.01 bitrate=N/A speed=N/A
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing ove
rhead: unknown
Exiting normally, received signal 2.

[ami_stuff]

this is already supported in iffanimplay

​https://github.com/murkymark/iffanimplay/blob/master/docs/iffanimplay.txt

​https://github.com/murkymark/iffanimplay/blob/master/docs/format_description_(partly_from_internet)/iff_anim/scala_anim16_anim32.txt

​https://github.com/murkymark/iffanimplay/blob/master/iffanimplay.exe

[ami_stuff]

​https://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket5650/

also plays fine with (linux build available):

​https://github.com/BlitterStudio/AnimPlayer/releases