The feature to send commands to filters in filtergraphs is barely even documented. https://ffmpeg.org/ffmpeg-filters.html#Changing-options-at-runtime-with-a-command
But, what commands a filter supports is (almost) well documented. At runtime too, it does a poor job at providing quick reference. https://github.com/FFmpeg/FFmpeg/blob/master/fftools/ffmpeg.c#L3537 fprintf(stderr, "\nEnter command: <target>|all <time>|-1 <command>[ <argument>]\n"); baffled me a lot in the command-line, even though I'm using FFmpeg for five years. How are people even supposed to infer all this mess? The syntax is ambigious. And, looking source code I figured out, parenthesis should've been used to isolate possible options. Also, https://github.com/FFmpeg/FFmpeg/blob/master/fftools/ffmpeg.c#L3539 set_tty_echo(1); doesn't work with Windows console therefore makes it hard to type. IMO readline should be used instead of own techniques as there might be errors while typing. Even though I managed to send a command to multiple filters (i.e afreqshift, rubberband), it returns (-38) all the time, according to avfilter_graph_send_command() that is an error. Further verifying the meaning of (-38), av_strerror() reports, "Function not implemented." I check if that is really the case or not. But, https://github.com/FFmpeg/FFmpeg/blob/master/libavfilter/af_afreqshift.c#L383 tells me otherwise. $ ffmpeg -f lavfi -i 'sine,afreqshift,rubberband' -f null - ffmpeg version n5.1.2 Copyright (c) 2000-2022 the FFmpeg developers built with gcc 12.2.1 (GCC) 20230111 configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-amf --enable-avisynth --enable-cuda-llvm --enable-lto --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libdav1d --enable-libdrm --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libjack --enable-libmfx --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librav1e --enable-librsvg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxml2 --enable-libxvid --enable-libzimg --enable-nvdec --enable-nvenc --enable-opencl --enable-opengl --enable-shared --enable-version3 --enable-vulkan libavutil 57. 28.100 / 57. 28.100 libavcodec 59. 37.100 / 59. 37.100 libavformat 59. 27.100 / 59. 27.100 libavdevice 59. 7.100 / 59. 7.100 libavfilter 8. 44.100 / 8. 44.100 libswscale 6. 7.100 / 6. 7.100 libswresample 4. 7.100 / 4. 7.100 libpostproc 56. 6.100 / 56. 6.100 Input #0, lavfi, from 'sine,afreqshift,rubberband': Duration: N/A, start: 0.000000, bitrate: 1411 kb/s Stream #0:0: Audio: pcm_f32le, 44100 Hz, mono, flt, 1411 kb/s Stream mapping: Stream #0:0 -> #0:0 (pcm_f32le (native) -> pcm_s16le (native)) Press [q] to stop, [?] for help Output #0, null, to 'pipe:': Metadata: encoder : Lavf59.27.100 Stream #0:0: Audio: pcm_s16le, 44100 Hz, mono, s16, 705 kb/s Metadata: encoder : Lavc59.37.100 pcm_s16le size=N/A time=00:01:44.96 bitrate=N/A speed= 105x Enter command: <target>|all <time>|-1 <command>[ <argument>] afreqshift -1 shift 100^M Command reply for stream 0: ret:-38 res: size=N/A time=00:08:53.51 bitrate=N/A speed=13.5x video:0kB audio:45953kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown Exiting normally, received signal 2. _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
