[FFmpeg-user] FFplay, wrong output size on extended desktop

Michael Koch astroelectronic at t-online.de
Wed May 25 18:01:55 EEST 2022


we want to use FFplay in a planetarium. It's a Windows computer with an 
extended desktop. The left monitor contains the user interface 
(1920x1080) and at the right side is a 4Kx4K extended desktop, which is 
shown on two 4096x2048 monitors, upper half and lower half. The extended 
4Kx4K desktop is mirrored to the dome with 11 projectors.

We are using this 4Kx4K test image:

This is the FFplay command line:
ffplay -noborder -left 1920 -top 0 4096.png

The problem is that the image is shown twice as large as it should be, 
so that we see only the top left quadrant.
You can see a screenshot in this discord channel (in german language):

If we set the size to 2048x2048, then the output is 4096x4096:
ffplay -noborder -x 2048 -y 2048 -left 1920 -top 0 4096.png
But then we don't have the full 4K resolution.

Who has an idea what's wrong here?
The console output is below.


D:\PROJEKTE\METAVERSED\Teststream>ffplay -noborder -left 1920 -top 0 
ffplay version 2022-05-23-git-6076dbcb55-essentials_build-www.gyan.dev 
Copyright (c) 2003-2022 the FFmpeg developers
   built with gcc 11.3.0 (Rev1, Built by MSYS2 project)
   configuration: --enable-gpl --enable-version3 --enable-static 
--disable-w32threads --disable-autodetect --enable-fontconfig 
--enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp 
--enable-bzlib --enable-lzma --enable-zlib --enable-libsrt 
--enable-libssh --enable-libzmq --enable-avisynth --enable-sdl2 
--enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid 
--enable-libaom --enable-libopenjpeg --enable-libvpx 
--enable-mediafoundation --enable-libass --enable-libfreetype 
--enable-libfribidi --enable-libvidstab --enable-libvmaf 
--enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid 
--enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va 
--enable-dxva2 --enable-libmfx --enable-libgme --enable-libopenmpt 
--enable-libopencore-amrwb --enable-libmp3lame --enable-libtheora 
--enable-libvo-amrwbenc --enable-libgsm --enable-libopencore-amrnb 
--enable-libopus --enable-libspeex --enable-libvorbis --enable-librubberband
   libavutil      57. 25.100 / 57. 25.100
   libavcodec     59. 28.100 / 59. 28.100
   libavformat    59. 24.100 / 59. 24.100
   libavdevice    59.  6.100 / 59.  6.100
   libavfilter     8. 38.100 /  8. 38.100
   libswscale      6.  6.100 /  6.  6.100
   libswresample   4.  6.100 /  4.  6.100
   libpostproc    56.  5.100 / 56.  5.100
Input #0, png_pipe, from '4096.png':KB vq=    0KB sq=    0B f=0/0
   Duration: N/A, bitrate: N/A
   Stream #0:0: Video: png, rgb24(pc), 4096x4096, 25 fps, 25 tbr, 25 tbn

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