Solid gray output

[ways]

Hi

When I run this I only get a solid gray image. Output from terminal:

~/Downloads/libseek-master
○ sudo ./build/seek-test| ffplay -i - -f rawvideo -video_size 208x156 -pixel_format gray16le
ffplay version 2.8.6-1ubuntu2 Copyright (c) 2003-2016 the FFmpeg developers
built with gcc 5.3.1 (Ubuntu 5.3.1-11ubuntu1) 20160311
configuration: --prefix=/usr --extra-version=1ubuntu2 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
libavutil 54. 31.100 / 54. 31.100
libavcodec 56. 60.100 / 56. 60.100
libavformat 56. 40.101 / 56. 40.101
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 40.101 / 5. 40.101
libavresample 2. 1. 0 / 2. 1. 0
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 2.101 / 1. 2.101
libpostproc 53. 3.100 / 53. 3.100
Status byte: 4.000 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 9.000 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 9
Status byte: 8.000 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 8
Status byte: 7.000 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 7
Status byte: a.000 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 10
Status byte: 5.000 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 5
Status byte: 1.000 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.000 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Input #0, rawvideo, from 'pipe:':
Duration: N/A, start: 0.000000, bitrate: 12979 kb/s
Stream #0:0: Video: rawvideo (Y1[0][16] / 0x10003159), gray16le, 208x156, 12979 kb/s, 25 tbr, 25 tbn, 25 tbc
Status byte: 3.000 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.072 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 6.153 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 6
Status byte: 1.153 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.153 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.628 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.709 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.800 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.882 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 6.963 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 6
Status byte: 1.963 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.963 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.458 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.539 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.621 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.702 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 6.793 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 6
Status byte: 1.793 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.793 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.278 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.360 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.451 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.533 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 6.614 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 6
Status byte: 1.614 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.614 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.109 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.192 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.273 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.355 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.446 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.527 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.609 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.690 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.781 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.863 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.944 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.035 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.116 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.198 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.279 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.371 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.462 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.533 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.624 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.705 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 6.787 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 6
Status byte: 1.787 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.787 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.282 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.363 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.444 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.526 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.617 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.698 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.779 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.871 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.952 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.034 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.125 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.206 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.287 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.368 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.459 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.541 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.622 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.713 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.794 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 3.875 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Status byte: 6.967 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
Ignore 6
Status byte: 1.967 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0
^C 9.74 M-V: 6.967 fd= 0 aq= 0KB vq= 0KB sq= 0B f=0/0

[ways]

If i run it without "-pixel_format gray16le" I get lots of colors, so there's definitely some data there.

[ways]

The former command still gives a gray picture, but sudo ./test-viewer.py gives me a working video.

Is there a way to only dump one picture?