[FFmpeg-user] Differences between ffmpeg and ffplay

[Michael Koch]

I'm still experimenting with the ultrasonic converter. Converting from 
one file to another file works without problems:

C:\Users\mkoch\Desktop\Ultrasonic Live>c://ffmpeg/ffmpeg -i 
test_15kHz.mp3 -f la
vfi -i aevalsrc="sin(12000*2*PI*t):c=stereo:s=44100" -filter_complex 
"[0]volume=
1,highpass=f=12000,highpass=f=12000,highpass=f=12000,highpass=f=12000[sound];[so
und][1]amultiply,lowpass=f=10000,lowpass=f=10000,lowpass=f=10000,lowpass=f=10000
" -y out.mp3

(no console output, because this is working fine)

As the next step, I want to hear the output live on the speakers. I did 
use exactly the same command line as above, but I replaced ffmpeg by 
ffplay and I omitted the output file. At the end of the console output 
is an error message. Can't ffplay handle two inputs? Why doesn't ffplay 
accept the command line that works fine with ffmpeg?

C:\Users\mkoch\Desktop\Ultrasonic Live>c://ffmpeg/ffplay -i 
test_15kHz.mp3 -f la
vfi -i aevalsrc="sin(12000*2*PI*t):c=stereo:s=44100" -filter_complex 
"[0]volume=
1,highpass=f=12000,highpass=f=12000,highpass=f=12000,highpass=f=12000[sound];[so
und][1]amultiply,lowpass=f=10000,lowpass=f=10000,lowpass=f=10000,lowpass=f=10000
"
ffplay version N-92078-g179ed2d2e0 Copyright (c) 2003-2018 the FFmpeg 
developers

   built with gcc 8.2.1 (GCC) 20180813
   configuration: --enable-gpl --enable-version3 --enable-sdl2 
--enable-fontconfi
g --enable-gnutls --enable-iconv --enable-libass --enable-libbluray 
--enable-lib
freetype --enable-libmp3lame --enable-libopencore-amrnb 
--enable-libopencore-amr
wb --enable-libopenjpeg --enable-libopus --enable-libshine 
--enable-libsnappy --
enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx 
--enable-l
ibwavpack --enable-libwebp --enable-libx264 --enable-libx265 
--enable-libxml2 --
enable-libzimg --enable-lzma --enable-zlib --enable-gmp 
--enable-libvidstab --en
able-libvorbis --enable-libvo-amrwbenc --enable-libmysofa 
--enable-libspeex --en
able-libxvid --enable-libaom --enable-libmfx --enable-amf 
--enable-ffnvcodec --e
nable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec 
--enable-dxva2 --enab
le-avisynth
   libavutil      56. 19.101 / 56. 19.101
   libavcodec     58. 31.101 / 58. 31.101
   libavformat    58. 18.103 / 58. 18.103
   libavdevice    58.  4.104 / 58.  4.104
   libavfilter     7. 33.100 /  7. 33.100
   libswscale      5.  2.100 /  5.  2.100
   libswresample   3.  2.100 /  3.  2.100
   libpostproc    55.  2.100 / 55.  2.100
Argument 'aevalsrc=sin(12000*2*PI*t):c=stereo:s=44100' provided as input 
filenam
e, but 'test_15kHz.mp3' was already specified.

Michael