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• MacOS - how to choose audio device from terminal

  9 octobre 2024, par jon_two

  I've been working on a Python program to create audio and also play back existing sound files. I can spawn multiple processes and have them all play to the laptop speakers, but I was wondering if it was possible to send each signal to a separate sound device. This is so I can apply effects to some processes but not all together.

  


  I'm using a MacBook and python simpleaudio, which calls AudioToolbox to connect to the output device. I've also got ffmpeg installed, so could use ffplay if that is easier. The pydub library uses this - it exports the current wave to a temp file then uses subprocess and ffplay to play it back.

  


  I can get a list of devices, but am not sure how to use this list to choose a device.

  


  % ffplay -devices
Devices:
 D. = Demuxing supported
 .E = Muxing supported
 --
  E audiotoolbox    AudioToolbox output device
 D  avfoundation    AVFoundation input device
 D  lavfi           Libavfilter virtual input device
  E sdl,sdl2        SDL2 output device
 D  x11grab         X11 screen capture, using XCB


  


  I did see a post that suggested using ffmpeg to list devices, again I can't figure out how to use this list.

  


  % ffmpeg -f lavfi -i sine=r=44100 -f audiotoolbox -list_devices true -
Input #0, lavfi, from 'sine=r=44100':
  Duration: N/A, start: 0.000000, bitrate: 705 kb/s
  Stream #0:0: Audio: pcm_s16le, 44100 Hz, mono, s16, 705 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
[AudioToolbox @ 0x135e3f230] CoreAudio devices:
[AudioToolbox @ 0x135e3f230] [0]               Background Music, (null)
[AudioToolbox @ 0x135e3f230] [1]   Background Music (UI Sounds), BGMDevice_UISounds
[AudioToolbox @ 0x135e3f230] [2]         MacBook Air Microphone, BuiltInMicrophoneDevice
[AudioToolbox @ 0x135e3f230] [3]           MacBook Air Speakers, BuiltInSpeakerDevice
[AudioToolbox @ 0x135e3f230] [4]               Aggregate Device, ~:AMS2_Aggregate:0
Output #0, audiotoolbox, 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=00:00:05.06 bitrate=N/A speed=0.984x    
video:0kB audio:436kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Exiting normally, received signal 2.


  


  This does at least give me a recognisable list of devices. If I add more Aggregate Devices, can I play back different files to each device ?

  


• How do i get ffprobe to parse 'TAG : timecode' into ffmpeg 'drawtext' command ? (Bash Terminal)

  4 juin 2019, par Myles

  I have a .mov file that contains original source timecode metadata but i can’t figure out a way to get ffmpeg to burn the original timecode into the picture.

  If i open the original file in QuickTime Player we can see it displays the true timecode on the far left :
  

  I can also see that ffprobe is able to see the metadata when i run the following :

  Command :

  ffprobe -i test.mov -show_streams

  Abbreviated Result :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 537199360
  
      compatible_brands: qt  
  
      creation_time   : 2018-11-05T14:20:51.000000Z
  
      timecode        : 09:59:53:00
  
    Duration: 00:16:37.64, start: 0.000000, bitrate: 1680 kb/s

  So i can see that ffprobe is able to determine the start timecode of the file in its metadata results. The question is how to i pass that information into an ffmpeg command so that the timecode seen by ffprobe is what gets used when i convert the file for timecode burn-in ?

  An example of a standard burnt in timecode command would be this :

  ffmpeg -i test.mov -vcodec libx264 -cmp 22 -vf
  "drawtext=fontfile=DroidSansMono.ttf : timecode=’09:59:53:00’ : r=25 :
  x=(w-tw)/2 : y=h-(2*lh) : fontcolor=white : box=1 : boxcolor=0x00000099"
  -y test_bitc.mov

  The only problem there though is that i’ve had to manually put the timecode in myself. I want the command to use the existing timecode metadata as the timecode input value so the same command can be used on multiple files.

  Does anyone know how to do this ?

• Terminal : How to extract image-based subtitles from mp4 ?

  4 août 2022, par DevonDahon

  How to extract image-based subtitles from mp4 video ?

  


  $ ffmpeg -i myvideo.mp4
ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
  built with Apple clang version 13.1.6 (clang-1316.0.21.2.5)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/5.0.1_3 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox
  libavutil      57. 17.100 / 57. 17.100
  libavcodec     59. 18.100 / 59. 18.100
  libavformat    59. 16.100 / 59. 16.100
  libavdevice    59.  4.100 / 59.  4.100
  libavfilter     8. 24.100 /  8. 24.100
  libswscale      6.  4.100 /  6.  4.100
  libswresample   4.  3.100 /  4.  3.100
  libpostproc    56.  3.100 / 56.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'myvideo.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 512
    compatible_brands: mp42iso2avc1mp41
    creation_time   : 2022-08-03T21:58:07.000000Z
    encoder         : HandBrake 1.5.1 2022011000
  Duration: 00:11:05.40, start: 0.000000, bitrate: 1635 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, smpte170m/bt470bg/bt470bg, progressive), 712x576 [SAR 16:15 DAR 178:135], 1454 kb/s, 25 fps, 25 tbr, 90k tbn (default)
    Metadata:
      creation_time   : 2022-08-03T21:58:07.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](bre): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 162 kb/s (default)
    Metadata:
      creation_time   : 2022-08-03T21:58:07.000000Z
      handler_name    : Stereo
      vendor_id       : [0][0][0][0]
  Stream #0:2[0x3](bre): Subtitle: dvd_subtitle (mp4s / 0x7334706D), 720x576, 6 kb/s (default)
    Metadata:
      creation_time   : 2022-08-03T21:58:07.000000Z
      handler_name    : Brezhoneg
  Stream #0:3[0x4](fra): Subtitle: dvd_subtitle (mp4s / 0x7334706D), 720x576, 6 kb/s
    Metadata:
      creation_time   : 2022-08-03T21:58:07.000000Z
      handler_name    : Français
At least one output file must be specified