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• Use specific channels from specific streams for the final stream using FFMPEG [closed]

  9 juin 2024, par Kazu-kun

  I want to create a 5.1ch audio stream from a 2ch audio stream. However I want to put a negative delay to LFE, SL and SR channels since they will be played from my bluetooth speaker, so I want to make up for the delay by giving it a negative delay.

  


  


  ffmpeg -itsoffset 0.1 -i input.mkv -i input.mkv

  


  -filter_complex “

  


  [1:a]pan=5.1(side)|FL=FL|FR=FR|LFEp>


  [0:a]pan=5.1(side)|FL=FL|FR=FR|LFEp>


  [orig5_1][delayed5_1]amerge=inputs=2,pan=5.1(side)|FL=c6|FR=c7|LFE=c2|SL=c3|SR=c4[a]”

  


  -map "[a]" -map 0:v -map 0:s -c:v copy -c:a flac -c:s copy output.mkv

  


  


  I tried taking the same input twice with the first one being delayed by 0.1 secs. With the delayed input a 5.1 audio is created and with the original another 5.1 audio is created as well. Then the two audio streams are merged with amerge and combined into a single 5.1 audio by taking delayed channels for FL and FR(These will be played from my MacBook) and by taking original channels for LFE, SL and SR(These will be played from my bluetooth JBL). Finally the video and subs streams are taken from the delayed.

  


  The above command gave a "pipe pipe pipe dqoute" error and when I entered the command again it said :

  


  


  zsh : unknown file attribute : i

  


  zsh : no such file or directory : FL+FR

  


  zsh : unknown file attribute : i

  


  zsh : no such file or directory : FL+FR

  


  zsh : unknown file attribute : i

  


  zsh : command not found : -map

  


  


  Please give me a command for my requirement !

  


• avstring-test : Mark pointer passed to av_free() as non-const

  19 octobre 2013, par Diego Biurrun

  avstring-test : Mark pointer passed to av_free() as non-const
  libavutil/avstring.c:278:9 : warning : passing argument 1 of ‘av_free’ discards ‘const’ qualifier from pointer target type
  

  • [DH] libavutil/avstring.c

• C pointer casting to and from Golang

  26 avril 2018, par nevernew

  I’m writing an app for the windows platform using FFmpeg and it’s golang wrapper goav, but I’m having trouble understanding how to pass the C pointers between C and Golang.

  I’ve stripped out all the relevant parts of the C code, the wrapper and my code, shown below :

  C code - libavutil/frame.h

  #include 
  
  
  
  typedef struct AVFrame {
  
  #define AV_NUM_DATA_POINTERS 8
  
      uint8_t *data[AV_NUM_DATA_POINTERS];
  
  }

  Golang goav wrapper

  package avutil
  
  
  
  /*
  
      #cgo pkg-config: libavutil
  
      #include <libavutil></libavutil>frame.h>
  
      #include 
  
  
  
      // C code I added:
  
      #include 
  
  
  
      void SaveFrame(const char* location, uint8_t *data, int width, int height) {
  
          FILE *pFile;
  
          int  y;
  
  
  
          // Open file
  
          pFile=fopen(location, "wb");
  
          if(pFile==NULL)
  
              return;
  
  
  
          // Write header
  
          fprintf(pFile, "P6\n%d %d\n255\n", width, height);
  
  
  
          // Write pixel data
  
          for(y=0; y/ Close file
  
          fclose(pFile);
  
      }
  
  */
  
  import "C"
  
  import (
  
      "unsafe"
  
  )
  
  
  
  type Frame C.struct_AVFrame
  
  
  
  func Data(f *Frame) *uint8 {
  
      // i think this is the function thats not working?
  
      return (*uint8)(unsafe.Pointer((*C.uint8_t)(unsafe.Pointer(&amp;f.data))))
  
  }
  
  func SaveFrame(location string, data *uint8, width int, height int) {
  
      C.SaveFrame(C.CString(location), unsafe.Pointer(data), C.int(width), C.int(height))
  
  }

  My Golang code

  package main
  
  
  
  import "github.com/giorgisio/goav/avutil"
  
  
  
  func main() {
  
      var frame *avutil.Frame
  
      var data *uint8
  
  
  
      //... initialize frame
  
  
  
      data = avutil.Data(frame)
  
      avutil.SaveFrame("frame0.ppm", data, 1920, 1080)
  
  }

  When I try to save the frame, the resulting image is garbled because the pointer is wrong, how do i fix this ?