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• copy step written on stackoverflow to install FFMPEG on wamp not working

  18 novembre 2016, par user3833682

  I’m working on project for converting youtube videos into mp3 format and found this also to install ffmpeg on wamp server Install FFMPEG on WAMP and try other links also but ffmpeg extension is not installing so I also checked it at phpinfo to confirm its installed or not but not installed and I’ve windows 7 64, wampserver 2.4, apache 2.4.4 and php version is 5.4.12 I don’t know what am I missing, I spent my 6 hours to figure out but extension of ffmpeg is not installed yet please tell me what am I doing wrong ?

  Now after that I’m getting popup message twice when I start wamp server `PHP Startup : Unable to load dynamic library

  c :/wamp/bin/php/php5.4.12/ext/php_ffmpeg.dll’ - %1 is not a valid
  Win32 application.

  

• How can I encode a real-time video from dynamically spaced frames ?

  7 mai 2019, par Ujuf66

  I’m trying to create a video from a series of screenshots. The screenshots are in a database and have dynamic FPS (1-3 FPS). How can I create a video file with constant FPS ?

  Before performing av_packet_rescale_ts I tried to change the st^.codec.time_base.den value on the fly between 1 and 3.

  This is the basic cycle of encoding of one picture :

  repeat
  
    fillchar(pkt, sizeof(TAVPacket), #0);
  
    av_init_packet(@pkt);
  
  
  
    (* encode the image *)
  
    ret := avcodec_encode_video2(st^.codec, @pkt, frame, got_packet);
  
    if (ret < 0) then
  
    begin
  
      writeln(format('Error encoding video frame: %s', [av_err2str(ret)]));
  
      exit;
  
    end;
  
  
  
    if (got_packet > 0) then
  
    begin
  
      (* rescale output packet timestamp values from codec to stream timebase *)
  
      av_packet_rescale_ts(@pkt, st^.codec.time_base, st^.time_base);
  
      pkt.stream_index := st^.index;
  
  
  
      log_packet(oc, @pkt);
  
      (* Write the compressed frame to the media file. *)
  
      av_interleaved_write_frame(oc, @pkt);
  
    end;
  
    inc(frame.pts);
  
  
  
  until (av_compare_ts(frame.pts, st^.codec^.time_base, 1, av_make_q(1, 1)) >= 0);

  Changing the FPS on the fly causes the video output to fail. If I don’t change the st^.codec.time_base.den value the video speeds up and slows down.

• How the ffmpeg astats crest factor is calculated

  30 août 2017, par FranGar

  I’m scripting a ffmpeg chain process for my work. The aim is normalizing/compressing lot of audio files (mp3’s).
  It’s done in Python and the critical part is the line :

  ffmpeg -y -i "Input.mp3" -codec:a libmp3lame -b:a 96k -af acompressor=threshold=-15dB:ratio=5:attack=0.01:release=1000:knee=2,dynaudnorm=g=3:m=2:p=0.95 "Output.mp3"

  The python script it’s complete and working BUT the nature of the audios (voice recordings) are very different so I can’t use the same params for all of them.

  I make some experimenting with the values of the ffmpeg filter astats and i discovered that the crest factor (Standard ratio of peak to RMS level ) gave a good reference to programatically get the better params.

  In fact I saw that a recording with a nice dynamic range sound and smooth in shape, get crest values around 9-15 (the compress/normlz params will be somehow conservative). But audios with crest around 22-30 need more aggressive processing.
  (All empirically)

  Somebody can clarify how the crest values are really calculated ? Which are the peaks taken to account ? (Why the flat factor is always 0 ?)
  Or if somebody knows how to get a value representing the sound ’smoothness’ will be nice also.

  Thanks for the ideas.