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• configure: add nvcc to CMDLINE_SET

  16 April 2018, by Timo Rothenpieler

  configure: add nvcc to CMDLINE_SET
  This was somehow forgotten and nobody noticed until now.
  

  • [DH] configure

• ffmpeg/sox audio processing: Merging files with envelope changes

  2 October 2020, by March Hare

  So I have two audio files. One is a music bed with an intro that segues into a looping music clip (let's call this *1). The second is the voice over audio track (referenced as *2, length n).

  


  Audio *1 is fixed, while the voice over (*2) is downloaded about 3 times a day, and can vary in length. *1 is longer than we ever expect *2 to be.

  


  What I need to do is

  


  

  1. Alter the overall gain of *1 to -7.5 dB

  


  2. Begin merging VO *2 at time m, while reducing the volume envelope of *1 by -11 dB. This is fixed based on the length of the intro.

  


  3. Fade everything out to -∞ dB around the end of *2

  


  4. Trim off the silence at the end.
For reference, the total length of the final track should be m+n.

  


  


  Unfortunately, I'm not versed enough with ffmpeg or sox to know exactly what I'm after here, and a lot of the examples tend to do one thing or another and aren't always clear when combining happens. I didn't get a lot of prior notice about this coming down the pipeline, so I'd like to get something relatively quick. We're able to do all of this stuff nicely in Adobe Audition (and I can do something similar in Audacity), but the idea is to automate it. For our envelope adjustments, we were just using linear ramps rather than smoothsteps, and that sounded fine.

  


  The TLDR: The VO track *2 governs how long the file winds up being, while audio bed *1 needs to be ducked when *2 begins, and the whole thing faded out right when *2 ends.

  


  We also have an automation system (radio station automation, specialized for something different than I need), so in a pinch if we have to just cut off the audio at the end of *2, we can get the fadeout from the radio automation system.

  


  I've been using the information at this link to some effect (specifically the bit about ffmpeg volumes), but it still isn't dynamic enough for the situation.
Envelope pattern in SoX (Sound eXchange) or ffmpeg

  


  Anyone have any advice on this one? I've got Sox and ffmpeg available, and if need be I can probably install other tools as well.

  


• Capturing network video using opencv

  3 September 2014, by Subhendu Sinha Chaudhuri

  I am using ffserver and ffmpeg combination to capture web camera video and transmit it through my network.

  I want to capture this video using opencv and python from another computer.
  I can see the video (cam1.asf) in the browser of another computer. But my opencv + python code could not capture any frame.

  Code for ffserver

  HTTPPort 8090
  
  HTTPBindAddress 0.0.0.0
  
  MaxHTTPConnections 2000
  
  MaxClients 1000
  
  MaxBandWidth 2000
  
  
  
  <feed>
  
     File ./tmp/feed1.ffm
  
     FileMaxSize 1G
  
     ACL allow 127.0.0.1
  
  </feed>
  
  
  
  <stream>
  
    Feed feed1.ffm
  
    Format asf
  
    VideoCodec msmpeg4v2
  
    VideoFrameRate 30
  
    VideoSize vga
  
  </stream>

  FFmpeg

  $ffmpeg -f video4linux2 -i /dev/video0 192.168.1.3 /cam1.ffm

  This stream can be seen in the browser

  But with opencv code

  import sys
  
  import cv2.cv as cv
  
  import numpy
  
  
  
  video="http://http://192.168.1.3:8090/cam1.asf"
  
  capture =cv.CaptureFromFile(video)
  
  cv.NamedWindow('Video Stream', 1 )
  
  while True:
  
    # capture the current frame
  
    frame = cv.QueryFrame(capture)
  
    #if frame is None:
  
     # break
  
    #else:
  
      #detect(frame)
  
    cv.ShowImage('Video Stream', frame)
  
    if cv.WaitKey(10) == 27:
  
      print 'ESC pressed. Exiting ...'
  
      break

  I donot get any output in the stream

  My aim is to work with the web camera video both at the base station (ie where the web camera is connected) and also at the network location