ClearVideo: support P-frames

[ami_stuff]

there is also something like fif (fractal image format) from the same company
maybe it would be easier to re/implement it and reuse part of the code for clv1 decoder?

​http://users.senet.com.au/~mjbone/Fractals.html
​http://www.drdobbs.com/tools/inside-iterated-systems-fractal-developm/184410115

some more clv1 samples:

​https://files.fm/u/dccwwnyy

C:\>ffmpeg -i clv1_50kbps.rm out.avi
ffmpeg version 3.4.git Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 4.6.2 (GCC)
  configuration: --enable-gpl --disable-ffprobe
  libavutil      56.  0.100 / 56.  0.100
  libavcodec     58.  1.100 / 58.  1.100
  libavformat    58.  0.102 / 58.  0.102
  libavdevice    58.  0.100 / 58.  0.100
  libavfilter     7.  0.101 /  7.  0.101
  libswscale      5.  0.101 /  5.  0.101
  libswresample   3.  0.101 /  3.  0.101
  libpostproc    55.  0.100 / 55.  0.100
[clearvideo @ 0236d4e0] Warning: not compiled with thread support, using thread
emulation
Input #0, rm, from 'clv1_50kbps.rm':
  Metadata:
    title           :
    author          :
    copyright       :
    comment         :
  Duration: 00:00:03.20, start: 0.000000, bitrate: 41 kb/s
    Stream #0:0: Video: clearvideo (CLV1 / 0x31564C43), yuv420p, 320x240, 50 kb/
s, 15 fps, 15 tbr, 1k tbn, 1k tbc
[clearvideo @ 024d8d00] Warning: not compiled with thread support, using thread
emulation
Stream mapping:
  Stream #0:0 -> #0:0 (clearvideo (native) -> mpeg4 (native))
Press [q] to stop, [?] for help
[mpeg4 @ 023651a0] Warning: not compiled with thread support, using thread emula
tion
Output #0, avi, to 'out.avi':
  Metadata:
    INAM            :
    author          :
    ICOP            :
    ICMT            :
    ISFT            : Lavf58.0.102
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 320x240, q=2-31, 200
 kb/s, 15 fps, 15 tbn, 15 tbc
    Metadata:
      encoder         : Lavc58.1.100 mpeg4
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
[clearvideo @ 024d8d00] Non-I-frames in Clearvideo is not implemented. Update yo
ur FFmpeg version to the newest one from Git. If the problem still occurs, it me
ans that your file has a feature which has not been implemented.
Error while decoding stream #0:0: Not yet implemented in FFmpeg, patches welcome

    Last message repeated 29 times
frame=    2 fps=0.0 q=2.0 Lsize=      17kB time=00:00:00.86 bitrate= 159.2kbits/
s speed=2.64x
video:11kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing ov
erhead: 53.329185%
Conversion failed!

[Elon Musk]

The links you provided are useless. I guess relevant fdk from iterated systems is lost.

[Elon Musk]

Fixed in a8745869946d6a5da3cbb1dfcb1a9d3109c49dc1.