spv1: support 16bpp color mode

[ami_stuff]

decodes correctly with original codec

​http://www.datafilehost.com/d/e732e57d

C:\>ffmpeg -i C:\spv1_16bpp_555.avi -f null -
ffmpeg version N-76741-g8eadabf Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 5.2.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --
enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-l
ibilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --en
able-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --ena
ble-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc
 --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enabl
e-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --
enable-lzma --enable-decklink --enable-zlib
  libavutil      55.  7.100 / 55.  7.100
  libavcodec     57. 15.100 / 57. 15.100
  libavformat    57. 16.100 / 57. 16.100
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 15.100 /  6. 15.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, avi, from 'C:\spv1_16bpp_555.avi':
  Duration: 00:00:02.34, start: 0.000000, bitrate: 10263 kb/s
    Stream #0:0: Video: screenpresso (SPV1 / 0x31565053), bgr24, 320x240, 10417
kb/s, 23.97 fps, 23.97 tbr, 23.97 tbn, 23.97 tbc
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf57.16.100
    Stream #0:0: Video: wrapped_avframe, bgr24, 320x240, q=2-31, 200 kb/s, 23.97
 fps, 23.97 tbn, 23.97 tbc
    Metadata:
      encoder         : Lavc57.15.100 wrapped_avframe
Stream mapping:
  Stream #0:0 -> #0:0 (screenpresso (native) -> wrapped_avframe (native))
Press [q] to stop, [?] for help
[screenpresso @ 03833400] Unknown header 0x7304
[screenpresso @ 03833400] Unknown header 0x7204
    Last message repeated 54 times
frame=   56 fps=0.0 q=-0.0 Lsize=N/A time=00:00:02.33 bitrate=N/A
video:21kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing ov
erhead: unknown

[ami_stuff]

Fixed in some merge from libav.

[Carl Eugen Hoyos]

Fixed since 5d31074daf0e448a636fbb0436f04ed54c20eab1