Recherche avancée

Sur d’autres sites (7790)

• Can -axcorrelate be used for time delay analysis ?

  31 octobre 2020, par koral

  I'm trying to find a way to easily automatically synchronize two audio tracks. I've found the axcorrelate filter in ffmpeg's documentation, and I'm curious if it can be used for time delay analysis with cross-correlation.

  


  I've been playing around with correlating different audio files and opening them in Audacity to see some sort of a pattern that can be detected in the output file, but I wasn't able to see anything that stands out to me.

  


  My observations :

  


  

  • correlating two same tracks results in mostly empty output

  


  • if I delay one of the input files by one second, the correlation start (time in wav file when for the first time a sound is output) is moved by one second forward, but the delay cannot be calculated since the original start time is unknown

  


  • correlating some original file with that original file delayed by some amount results in gibberish data, that seems random to me

  


  


  Any help would be appreciated. I found this pdf that uses Praat to detect the cross correlation, but I'd like to keep this FFmpeg only to not ship multiple dependencies to my users.

  


• Have ffplay output current time in millisecond resolution

  21 août 2020, par 12.yakir

  What are the arguments for ffplay to output the duration/time-stamp of the current frame in millisecond resolution (dumping it to stderr or stdout, not embedding or overlaying it into the video) ?

  


  Right now playing a video (and pausing it) will look like this :

  


  ~$ ffplay -i video.mp4 -hide_banner -loglevel 8 -stats
   2.09 A-V: -0.004 fd=   6 aq=   31KB vq=   84KB sq=    0B f=0/0


  


  Note that the current time, 2.09, is in "centi-seconds" (one hundredth of a second), not millisecond (one thousandeth of a second).

  


  Ideally, it would output only the current time in millisecond resolution :

  


  ~$ ffplay -i video.mp4 -hide_banner -loglevel 8 -stats <enter magic="magic" arguments="arguments" here="here">&#xA;   2.093&#xA;</enter>

  


• Recording Video and Voice at the same time to .mp4 on raspbarry pi

  18 juin 2014, par SunBae Yim

  I tried for 3 months, But can’t resolved it.
  on Raspberry Pi.

  I want to recording video and voice to mp4, And Realtime streaming(Mjpeg) no delay.

  Of course, It has Pi Camera Module.
  And I installed a soundcard as below.

  pi@raspberrypi ~ $ aplay -l
  
  **** List of PLAYBACK Hardware Devices ****
  
  card 0: sndrpiproto [snd_rpi_proto], device 0: WM8731 HiFi wm8731-hifi-0 []
  
    Subdevices: 1/1
  
    Subdevice #0: subdevice #0

  First Goal is :

  Recording voice(aac or mp3) and video(h264) at the same time to .mp4.
  h264 and aac are combined into mp4 container.
  I failed make it using ffmpeg. too difficult.

  Sencond Goal is :

  Realtime Streaming for MJPEG.
  I receive stream using Safari, Chrome, FireFox, Explorer on Windows & Android.
  And using IP CAM VIEWER of Android App.

  I tried various solution,
  But most solutions are only video no voice.

  Third Goal is :

  Above Functions are run at the same time on Raspberry Pi.
  Maybe I will make Python and Shell Scripts files for run above solution at the same time.

  Please Help me !

  Thanks,
  SB YIM