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• split video (avi/h264) on keyframe

  30 novembre 2012, par m.sr

  Hallo.

  I have a big video file. ffmpeg, tcprobe and other tool say, it is an h264-stream in an AVI-container.

  Now i'd like to cut out small chunks form the video.

  1. Problem : The index of the video seam corrupted/destroyed. I kind of fixed this via mplayer -forceidx -saveidx <indexfile> <bigvideofile></bigvideofile></indexfile>. The Problem here is, that I'm now stuck with mplayer/mencoder which can use this index file via -loadidx <indexfile></indexfile>. I have tried correcting the index like described in man aviindex (mplayer -frames 0 -saveidx mpidx broken.avi ; aviindex -i mpidx -o tcindex ; avimerge -x tcindex -i broken.avi -o fixed.avi), but this didn't fix my video - meaning that most tools i've tested couldn't search in the video file.

  2. Problem : I cut out parts of the video via following command : mencoder -loadidx in.idx -ss 8578 -endpos 20 -oac faac -ovc x264 -sws 9 -lavfopts format=mp4 -x264encopts <lotsofopts> -of lavf -vf scale=800:-10,harddup in.avi -o out.mp4</lotsofopts>. Now here the problem is, that some videos are corrupted at the beginning. I think this is because the fact, that i do not necessarily cut at keyframe.

  Questions :

  1. What is the best way to fix the index of an avi "inline" so that every tool can again work as expected with it ?

  2. How can i split at the keyframes ? Is there an mencoder-option for this ?

  3. Are Keyframes coming in a frequency ? How to find out this frequency ? (So with a bit of math it should be possible to calculate the next keyframe and cut there)

  4. Is ther perhaps some completely other way to split this movie ? Doing it by hand is no option, i've to cut out 1000+ chunks ...

  Thanks a lot !

• Video Concatenation or Merging

  19 juin 2013, par 2vision2

  I need to join/merge/concatenate more than two different video files (Eg :3gp, mp4 ) in android platform and need to store them as mp4 file.

  So far from my analysis, I’ve seen people referring FFMPEG for these purposes.

  Is FFMPEG available for android ? Or any other alternative packages available for video concatenation ?

  Can FFMPEG concatenate two different kinds of Video files ?(Eg : Combination of mp4 and 3gp)

  Update : Can OpenGL be helpful for merging more than two videos along with audio ?

• How to publish selfmade stream with ffmpeg and c++ to rtmp server ?

  25 octobre 2013, par Alexandr R

  Have a nice day to you, people !

  I am writing an application for Windows that will capture the screen and send the stream to Wowza server by rtmp (for broadcasting). My application use ffmpeg and Qt.
  I capture the screen with WinApi, convert a buffer to YUV444(because it's simplest) and encode frame as described at the file decoding_encoding.c (from FFmpeg examples) :

  ///////////////////////////
  
  //Encoder initialization
  
  ///////////////////////////
  
  avcodec_register_all();
  
  codec=avcodec_find_encoder(AV_CODEC_ID_H264);
  
  c = avcodec_alloc_context3(codec);
  
  c->width=scr_width;
  
  c->height=scr_height;
  
  c->bit_rate = 400000;
  
  int base_num=1;
  
  int base_den=1;//for one frame per second
  
  c->time_base= (AVRational){base_num,base_den};
  
  c->gop_size = 10;
  
  c->max_b_frames=1;
  
  c->pix_fmt = AV_PIX_FMT_YUV444P;
  
  av_opt_set(c->priv_data, "preset", "slow", 0);
  
  
  
  frame = avcodec_alloc_frame();
  
  frame->format = c->pix_fmt;
  
  frame->width  = c->width;
  
  frame->height = c->height;
  
  
  
  for(int counter=0;counter<10;counter++)
  
  {
  
  ///////////////////////////
  
  //Capturing Screen
  
  ///////////////////////////
  
      GetCapScr(shotbuf,scr_width,scr_height);//result: shotbuf is filled by screendata from HBITMAP
  
  ///////////////////////////
  
  //Convert buffer to YUV444 (standard formula)
  
  //It's handmade function because of problems with prepare buffer to swscale from HBITMAP
  
  ///////////////////////////
  
      RGBtoYUV(shotbuf,frame->linesize,frame->data,scr_width,scr_height);//result in frame->data
  
  ///////////////////////////
  
  //Encode Screenshot
  
  ///////////////////////////
  
      av_init_packet(&pkt);
  
      pkt.data = NULL;    // packet data will be allocated by the encoder
  
      pkt.size = 0;
  
      frame->pts = counter;
  
      avcodec_encode_video2(c, &pkt, frame, &got_output);
  
      if (got_output) 
  
      {
  
          //I think that  sending packet by rtmp  must be here!
  
          av_free_packet(&pkt);             
  
  
  
      }
  
  
  
  }
  
  // Get the delayed frames
  
  for (int got_output = 1,i=0; got_output; i++)
  
  {
  
      ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
  
      if (ret < 0)
  
          {
  
              fprintf(stderr, "Error encoding frame\n");
  
              exit(1);
  
          }
  
          if (got_output)
  
          {
  
          //I think that  sending packet by rtmp  must be here!
  
          av_free_packet(&pkt);      
  
          }
  
  }
  
  
  
  ///////////////////////////
  
  //Deinitialize encoder
  
  ///////////////////////////
  
  avcodec_close(c);
  
  av_free(c);
  
  av_freep(&frame->data[0]);
  
  avcodec_free_frame(&frame);

  I need to send video stream generated by this code to RTMP server.
  In other words, I need c++/c analog for this command :

  ffmpeg -re -i "sample.h264" -f flv rtmp://sample.url.com/screen/test_stream

  It's useful, but I don't want to save stream to file, I want to use ffmpeg libraries for realtime encoding screen capture and sending encoded frames to RTMP server inside my own application.
  Please give me a little example how to initialize AVFormatContext properly and to send my encoded video AVPackets to server.

  Thanks.