Newest 'ffmpeg' Questions - Stack Overflow

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• possible C code implementation ideas for a given shell script(related to ffmpeg)

  21 août 2011, par Ted

  The shell script i'm trying to implement goes like this,

      #!/bin/bash
      while [ 1 ]
      do
         nc -l 1234 | ffmpeg -i pipe:0 -vcodec mpeg4 -s qcif -f m4v -y pipe:1 | nc localhost 1235
      done 
  

  what it does is to simply take in a stream of video input through network and do live video transcoding(with ffmpeg of course!) and streaming back the video through the net. my question is how should i go by to implement this functionality in a clean C code. i know i can use popen() to pipe such a command from a c code but i would like to do better. may be with sockets and staff... any pointers are appreciated.

  AskLearnDo.

• Iphone Streaming and playing Audio Problem

  20 août 2011, par KayKay

  I am trying to make an app that plays audio stream using ffmpeg, libmms.
  I can open mms server, get stream, and decode audio frame to raw frame using suitable codec.
  However I don't know how to do next.
  I think I must use AudioToolbox/AudioToolbox.h and make audioqueue.
  but however when I give audioqueuebuffer decode buffer's memory and play, Only plays the white noise.
  Here is my code.

  What am i missing?
  Any comment and hint is very appreciated.
  Thanks very much.

  while(av_read_frame(pFormatCtx, &pkt)>=0)
  {
      int pkt_decoded_len = 0;
      int frame_decoded_len;
      int decode_buff_remain=AVCODEC_MAX_AUDIO_FRAME_SIZE * 5;
      if(pkt.stream_index==audiostream)
      {
          frame_decoded_len=decode_buff_remain;
          int16_t *decode_buff_ptr = decode_buffer;
          int decoded_tot_len=0;
          pkt_decoded_len = avcodec_decode_audio2(pCodecCtx, decode_buff_ptr, &frame_decoded_len,
                                                  pkt.data, pkt.size);
          if (pkt_decoded_len <0) break;
          AudioQueueAllocateBuffer(audioQueue, kBufferSize, &buffers[i]);
          AQOutputCallback(self, audioQueue, buffers[i], pkt_decoded_len);
  
          if(i == 1){
              AudioQueueSetParameter(audioQueue, kAudioQueueParam_Volume, 1.0);
              AudioQueueStart(audioQueue, NULL);
          }
          i++;
      }
  }
  
  
  void AQOutputCallback(void *inData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer, int copySize)
  {
      mmsDemoViewController *staticApp = (mmsDemoViewController *)inData;
      [staticApp handleBufferCompleteForQueue:inAQ buffer:inBuffer size:copySize];
  }
  
  - (void)handleBufferCompleteForQueue:(AudioQueueRef)inAQ
                            buffer:(AudioQueueBufferRef)inBuffer
                              size:(int)copySize
  {
      inBuffer->mAudioDataByteSize = inBuffer->mAudioDataBytesCapacity;
      memcpy((char*)inBuffer->mAudioData, (const char*)decode_buffer, copySize);
  
      AudioQueueEnqueueBuffer(inAQ, inBuffer, 0, NULL);
  }
  

• Where is the documentation for the Mjpeg codec used in mencoder, VLC and FFMpeg ?

  18 août 2011, par Sugrue

  Mencoder has a lovely option for converting a mjpeg file into an avi file with an 'MJPG' codec that plays in VLC.

  The command line to do this is:

  mencoder filename.mjpeg -oac copy -ovc copy -o outputfile.avi -speed 0.3

  where 0.3 is the ratio of the desired play framerate to the default 25 fps. All this does is make a copy of the mjpeg file, put an avi header on top and at the end, what seems to be an index of the frame positions in the file.

  I want to replicate this in my own code, but I can't find documentation anywhere. What is the exact format of the index section? The header has extra filler bytes in it for some reason - whats this about?

  Anyone know where I can find documentation? Both mencoder and vlc seem to have this codec built in.

• Ffmpeg compilation fails due to undefined symbol _x264_encoder_open_112 for architecture x86_64

  18 août 2011, par Saptarshi Biswas

  I am compiling ffmpeg on Snow Leopard from source. Using Macport is not an option since I have some custom modification in ffmpeg. The make commands are:

  $ ./configure --enable-gpl --enable-libmp3lame --enable-static \
              --disable-shared --enable-libx264 --enable-pthreads \
              --disable-doc --enable-avfilter
  $ make
  

  The error:

  CC  ffplay.o
  ffplay.c: In function ‘SDL_main’:
  ffplay.c:3157: warning: assignment discards qualifiers from pointer target type
  LD  ffplay_g
  Undefined symbols for architecture x86_64:
    "_x264_encoder_open_112", referenced from:
        _X264_init in libavcodec.a(libx264.o)
  ld: symbol(s) not found for architecture x86_64
  collect2: ld returned 1 exit status
  make: *** [ffplay_g] Error 1
  

  ---

  I have compiled libx264 from source, which went fine.

  $ cd x264-snapshot-20101228-2245; ./configure && make && sudo make install
  

  ... and it contains the symbol "_x264_encoder_open_112"

  $ nm ./libx264.a | grep _x264_encoder_open_112
  0000000000003ef0 T _x264_encoder_open_112
  000000000000d7b0 S _x264_encoder_open_112.eh
  

  What might be going wrong?