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• FFMPEG trim and concat mp3 without re-encoding

  11 décembre 2017, par QuickPrototype

  Good Day,

  I would like to know if it is possible to "join" a portion of an mp3 file to another without re-encoding using ffmpeg. I need to prepend an audio mp3 file with silence to ensure it is 60 seconds long.

  i.e if my audio file a.mp3 is 40 seconds I need to prepend 20 seconds of silence without re-encoding.

  My thoughts on doing this was to have a 60 second long silence mp3 (silence.mp3) at the same CBR and sample rate of my audio (44100 and 40kbps). I then need to "trim" this file and concat/join with the audio file (a.mp3) appropriately.

  I have a linux script that computes the required seconds to prepend and I tried using the following filter_complex expression :

  ffmpeg -i silence.mp3 -i a.mp3 -filter_complex "[1]adelay=20000[b];[0][b]amix=2" out.mp3

  This works however takes too long as it performs re-encoding which takes a long to process. Im looking for a non re encoding solution that can just join the correct sized portion of silence.mp3 to a.mp3. The commands would need to include as a parameter the length of silence that must be used from the overall silence.mp3 file.

  Any advise is appreciated.

• lpc : add ff_lpc_calc_ref_coefs_f() function

  1er septembre 2015, par Rostislav Pehlivanov

  lpc : add ff_lpc_calc_ref_coefs_f() function
  This commit adds a function to get the reflection coefficients on
  
  floating point samples. It’s functionally identical to
  
  ff_lpc_calc_ref_coefs() except it works on float samples and will
  
  return the global prediction gain. The Welch window implementation
  
  which is more optimized works only on int32_t samples so a slower
  
  generic expression was used.
  Signed-off-by : Rostislav Pehlivanov <atomnuker@gmail.com>
  

  • [DH] libavcodec/lpc.c
  • [DH] libavcodec/lpc.h

• I am really confused with this kind of compilation error( C ffmpeg Qt)

  31 octobre 2016, par David Tree

  I downloaded the latest ffmpeg source code and successfully installed it on Ubuntu
  But I failed to compile a simple demo.(I did included proper headers)

  Here are the error messages ,just to name a few :

  error: unknown type name 'AVFrame'
  
  
  
  error: 'NULL' undeclared (first use in this function)
  
  
  
  error: request for member 'streams' in something not a structure or union
  
  
  
  error: 'AVMEDIA_TYPE_VIDEO' undeclared (first use in this function)
  
  
  
  error: expected expression before ')' token

  Can you help me solve this problem ?

  Contents Added :

  e.g this is my includes

  extern "C"{
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libswscale></libswscale>swscale.h>
  
  #include <libavutil></libavutil>avutil.h>
  
  }
  
  
  
  int main(int argc, char *argv[]) {
  
  AVFormatContext *pFormatCtx;
  
  int i, videoStreamIdx;
  
  AVCodecContext *pCodecCtx;
  
  AVCodec *pCodec;
  
  AVFrame *pFrame;
  
  AVFrame *pFrameRGB;

  e.g AVFormatContext is declared in /usr/include/libavformat/avformat.h
  error message box shows Unknown type name AVFormatContext
  But How could it possibly be ?