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• Dynamic volume mixing with FFMPeg

  1er juin 2021, par jvhang

  I am streaming audio using FFMPeg and need to mix two audio sources using FFMpeg and set the volume level dynamically. I.e. once the stream starts, I need to be able update the ratio of the two volumes.

  


  Currently, I have the volume mixing and streaming working using the CLI version of FFMPeg but the volume mix ratio is static.

  


  Is there a way to dynamically set the volume ratio using the CLI tool ? Perhaps something with an FFMpeg expression ?

  


  Or is using the API the only option ? If so, can anyone point me towards an example of dynamically mixing audio ? I haven't been able to find one.

  


  Edit : here are the params I currently pass to mix audio. Again, this works fine, so not including the log as there is no error to fix. The question is how can I adjust the ratio of the amix mix after the process has launched. Willing to use the API if need be.

  


                  "-f rawvideo" + // container
                " -vcodec rawvideo" + // codec
                " -s " + width + "x" + height + // input video size, must be correct
                " -pix_fmt rgba" + // pixel format
                " -framerate " + frameRate +
                " -i pipe:0" + // from stdin in via pipe
               " -f dshow" +
                " -i audio=\"Stereo Mix (Realtek(R) Audio)\"" + //
                " -f dshow" +
                " -i audio=\"Microphone Array (Xbox NUI Sensor)\"" + // 
                " -filter_complex \"amix\"" +  // mix the two inputs, can added ratio if needed
                " -c:v libx264" + // x264 software encoder
                " -g " + frameRate *2 +
                " -keyint_min " + frameRate +
                " -c:a aac" + // audio format
                " -b:v 6M -maxrate 2M -bufsize 1M" + // constrain bitrate per twitch
                " -f flv" +
                " " + address 
            );


  


• lavu/video_enc_params : Avoid relying on an undefined C construct

  15 janvier 2023, par Martin Storsjö

  lavu/video_enc_params : Avoid relying on an undefined C construct
  The construct of using offsetof on a (potentially anonymous) struct
  
  defined within the offsetof expression, while supported by all
  
  current compilers, has been declared explicitly undefined by the
  
  C standards committee [1].
  Clang recently got a change to identify this as an issue [2] ;
  
  initially it was treated as a hard error, but it was soon after
  
  softened into a warning under the -Wgnu-offsetof-extensions option
  
  (not enabled automatically as part of -Wall though).
  Nevertheless - in this particular case, it's trivial to fix the
  
  code not to rely on the construct that the standards committee has
  
  explicitly called out as undefined.
  [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm
  
  [2] https://reviews.llvm.org/D133574
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavutil/video_enc_params.c

• Use ffmpeg to stream live content to azure media services

  9 juin 2016, par Dadicool

  I’ve been trying to stream content to azure media services using ffmpeg as it’s one of the options described here : http://azure.microsoft.com/blog/2014/09/18/azure-media-services-rtmp-support-and-live-encoders/

  My command is :

  ffmpeg -v verbose -i 300.mp4 -strict -2 -c:a aac -b:a 128k -ar 44100 -r 30 -g 60 -keyint_min 60 -b:v 400000 -c:v libx264 -preset medium -bufsize 400k -maxrate 400k -f flv rtmp://nessma-****.channel.mediaservices.windows.net:1935/live/584c99f5c47f424d9e83ac95364331e7

  I have made sure that the streaming endpoint has one active streaming unit, I also made sure that the channel is actually Ready and I even get it to start streaming (which makes a PublishURL available).

  When I execute the ffmpeg command to start streaming, I keep getting the following error :

  ffmpeg version 2.5.2 Copyright (c) 2000-2014 the FFmpeg developers
 built on Dec 30 2014 11:31:18 with llvm-gcc 4.2.1 (LLVM build 2336.11.00)
 configuration: --prefix=/Volumes/Ramdisk/sw --enable-gpl --enable-pthreads --enable-version3 --enable-libspeex --enable-libvpx --disable-decoder=libvpx --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libx264 --enable-avfilter --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-filters --enable-libgsm --enable-libvidstab --enable-libx265 --arch=x86_64 --enable-runtime-cpudetect
 libavutil      54. 15.100 / 54. 15.100
 libavcodec     56. 13.100 / 56. 13.100
 libavformat    56. 15.102 / 56. 15.102
 libavdevice    56.  3.100 / 56.  3.100
 libavfilter     5.  2.103 /  5.  2.103
 libswscale      3.  1.101 /  3.  1.101
 libswresample   1.  1.100 /  1.  1.100
 libpostproc    53.  3.100 / 53.  3.100
Routing option strict to both codec and muxer layer
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f9a0a002c00] overread end of atom 'colr' by 1 bytes
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f9a0a002c00] stream 0, timescale not set
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f9a0a002c00] max_analyze_duration 5000000 reached at 5003637 microseconds
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '300.mp4':
 Metadata:
   major_brand     : mp42
   minor_version   : 0
   compatible_brands: mp42isomavc1
   creation_time   : 2014-01-11 05:39:32
   genre           : Trailer
   artist          : Warner Bros.
   title           : 300: Rise of an Empire - Trailer 2
   encoder         : HandBrake 0.9.9 2013051800
   date            : 2014
 Duration: 00:02:33.24, start: 0.000000, bitrate: 7377 kb/s
   Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 (1920x1088), 7219 kb/s, 23.98 fps, 23.98 tbr, 90k tbn, 47.95 tbc (default)
   Metadata:
     creation_time   : 2014-01-11 05:39:32
     encoder         : JVT/AVC Coding
   Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 157 kb/s (default)
   Metadata:
     creation_time   : 2014-01-11 05:39:32
   Stream #0:2: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 101x150 [SAR 72:72 DAR 101:150], 90k tbr, 90k tbn, 90k tbc
rtmp://nessma-****.channel.mediaservices.windows.net:1935/live/584c99f5c47f424d9e83ac95364331e7: Input/output error

  The Azure blog post clearly states that this should be possible but I can’t find a working example anywhere.

  Environment :

  • MacOS Maverick
  • FFMPEG installed from official build
  • 300.mp4 : 1080p trailer of the latest 300 movie