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• Is there a way to control ffplay audio volume from command line and from key commands on Mac OSX ?

  20 avril 2023, par smartblonde

  We want to use ffplay to monitor live RTMP feeds. We have a script to open an instance of ffplay for each feed. We would like to control the initial volume of the video to be around 30 out of 100. We would also like to be able to raise or lower the volume via key commands during the stream. We are referring to this doc : http://ffmpeg.org/ffplay.html

  



  We've tried the main option -volume 30, to try and start the volume at 30/100. FFplay says unrecognized option when it sees -volume on the command line.

  



  Also, we've tried using 9 and 0 to lower or raise the volume once the player is up and playing the live RTMP feed. These key commands seem to have no effect on the player's volume.

  



  Are there other shell parameters, and other key commands, that are known to work on all builds/OS's for ffplay ? If not, why change these basic functions from release and O/S ato other release ? In any case what works on MacOSX ? Thank you !

  


• how to sync video and audio in python

  15 septembre 2018, par Abhinandan Kapoor

  So, i have written the following code.it consist of three functions :
  1.Opencv(for recording video)
  2.pyaudio (for audio recording)
  3.ffmpeg(for sync audio & video

  Now the problem is that i’m able to get a single file with audio & video but they’re not sync.how to make them sync.

  Plus I need help in start/stop of the opencv.I tried to set time duration in opencv but unable to get.kindly help me in this.

  **import numpy as np
  
  import cv2
  
  import time
  
  # The duration in seconds of the video captured
  
  capture_duration = 10
  
  cap = cv2.VideoCapture(0)
  
  fourcc = cv2.VideoWriter_fourcc(*'XVID')
  
  out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
  
  start_time = time.time()
  
  while( int(time.time() - start_time) < capture_duration ):
  
      ret, frame = cap.read()
  
      if ret==True:
  
          frame = cv2.flip(frame,0)
  
          out.write(frame)
  
          cv2.imshow('frame',frame)
  
      else:
  
          break
  
  cap.release()
  
  out.release()
  
  cv2.destroyAllWindows()**

• FFplay : WASAPI can't initialize audio client (FFmpeg 3.4 binaries)

  9 juillet 2022, par fve

  I am trying to playback a stream that is multicasted over RTP using ffplay on Windows 7 64 bits.
The computer that serves the audio over RTP runs :

  



  ffmpeg -re -f dshow -audio_buffer_size 15 -ac 1 -i audio="Mic in at front Mic-in (Realtek" -ar 8k -acodec pcm_alaw -vn -f rtp rtp://127.0.0.1:5000


  



  The client runs :

  



  ffplay rtp://127.0.0.1:5000


  



  While this was working correctly in release 3.3, release 3.4 fails with this error :

  



  SDL_OpenAudio (1 channels, 8000 Hz): WASAPI can't initialize audio client: CoInitialize has not been called.

No more combinations to try, audio open failed
Failed to open file 'rtp://127.0.0.1:5000' or configure filtergraph


  



  Anyone has an idea of whats going on ?

  



  Thanks

  



  UPDATE #1 :

  



  A workaround is to specify an alternate output driver.
Set SDL_AUDIODRIVER environment variable value to the driver you want to use.
Under windows 7, directsound and winmm both solved my issue.