[FFmpeg-user] concat audio files

[Michael Koch]

I want to concat two audio files. What's wrong with this command line?

ffmpeg -i birds1.wav -i birds1.wav -lavfi [0][1]concat=n=2:a=1 -c:a aac 
-y sound.mp4

I always get this error message:
Stream specifier '' in filtergraph description [0][1]concat=n=2:a=1 
matches no streams.

The console output is below.

Michael



D:\Bochum\audio>ffmpeg -i birds1.wav -i birds1.wav -lavfi 
[0][1]concat=n=2:a=1 -c:a aac -y sound.mp4
ffmpeg version 2022-06-06-git-73302aa193-essentials_build-www.gyan.dev 
Copyright (c) 2000-2022 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. 26.100 / 57. 26.100
   libavcodec     59. 33.100 / 59. 33.100
   libavformat    59. 24.100 / 59. 24.100
   libavdevice    59.  6.100 / 59.  6.100
   libavfilter     8. 40.100 /  8. 40.100
   libswscale      6.  6.100 /  6.  6.100
   libswresample   4.  6.100 /  4.  6.100
   libpostproc    56.  5.100 / 56.  5.100
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, wav, from 'birds1.wav':
   Duration: 00:02:01.97, bitrate: 2116 kb/s
   Stream #0:0: Audio: pcm_s24le ([1][0][0][0] / 0x0001), 44100 Hz, 
stereo, s32 (24 bit), 2116 kb/s
Guessed Channel Layout for Input Stream #1.0 : stereo
Input #1, wav, from 'birds1.wav':
   Duration: 00:02:01.97, bitrate: 2116 kb/s
   Stream #1:0: Audio: pcm_s24le ([1][0][0][0] / 0x0001), 44100 Hz, 
stereo, s32 (24 bit), 2116 kb/s
Stream specifier '' in filtergraph description [0][1]concat=n=2:a=1 
matches no streams.