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• FFmpeg : Remux f4v cutted from stream to mp4

  13 mai 2019, par Martin

  I have a mp4 file cutted from a H.264/AAC stream with Wowza Media Server. After the cutting, the file was forced to mp4 format with the following command:

  ffmpeg -i wowza_output_file -vcodec copy -acodec copy -f mp4 -y wowza_output_file_copy
  

  From there I renamed it to test_f4v.mp4 and took ffprobe, to take a look at the file:

  ffprobe version 0.8, Copyright (c) 2007-2011 the FFmpeg developers
    built on Jul 20 2011 13:32:19 with gcc 4.4.3
    configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264
    libavutil    51.  9. 1 / 51.  9. 1
    libavcodec   53.  7. 0 / 53.  7. 0
    libavformat  53.  4. 0 / 53.  4. 0
    libavdevice  53.  1. 1 / 53.  1. 1
    libavfilter   2. 23. 0 /  2. 23. 0
    libswscale    2.  0. 0 /  2.  0. 0
    libpostproc  51.  2. 0 / 51.  2. 0
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test_f4v.mp4':
    Metadata:
      major_brand     : f4v 
      minor_version   : 0
      compatible_brands: isommp42m4v 
      creation_time   : 2012-04-23 12:36:06
    Duration: 01:00:01.84, start: 0.000000, bitrate: 2004 kb/s
      Stream #0.0(eng): Video: h264 (Baseline), yuv420p, 854x480 [PAR 1:1 DAR 427:240], 1903 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
      Metadata:
        creation_time   : 2012-04-23 12:36:06
      Stream #0.1(eng): Audio: aac, 48000 Hz, stereo, s16, 96 kb/s
      Metadata:
        creation_time   : 2012-04-23 12:36:06
  

  Now there is a problem. I need a file, which has the following meta data:

  major_brand     : mp42
  compatible_brands: isom
  

  Is there a way to remux the mp4 file to get the major_brand and compatible_brands to the described values with ffmpeg?

• look for an mp4 file inside a directory and send it to different directory after converting to mp3 in php ?

  13 mai 2019, par flash

  I have a directory called incoming_folder in which there is an mp4 file.

  What I want to achieve through php code is to scan a incoming_folder directory, look for an mp4 file and send it to outgoing_folder after converting it into mp3. Technically outgoing_folder should have mp3 version of mp4 from incoming_folder

  Tried with the following code although its scanning the incoming_folder directory but no conversion is happening through ffmpeg.

  <?php
  $dir    = 'in_folder';  /* Place where mp4 file is present */
  $files1 = scandir($dir);
  print_r($files1);    /* It lists all the files in a directory including mp4 file*/
  
  $destination = 'out_folder';  /* Place where mp3 file need to be send after conversion from mp4 */
  
  foreach($files1 as $f)
  {
    $parts = pathinfo($f);
  
    switch($parts['extension'])
    {
      case 'mp4' :
        system('ffmpeg -i '.$f.' -map 0:2 -ac 1 '.$destination.DS. $parts['filename'].'.mp3', $result);
  
        if ($result) {
          // Do something with result if you want
          // log for example
        }
        break;
  
      case 'mp3' :
        // copy($f, $destination. DS . $parts['filename']. '.' . $parts['extension']);
        copy($f, $destination.DS.$parts['filename'].'.mp3');
        break;  
    }
  }
  ?>
  

• Why does ffmpeg with libfdk_aac encoding cuts away 25ms in the beginning of an audio file ?

  13 mai 2019, par vkuzma

  I switched encoding from aac to libfdk_aac due to qaulity issues. I noticed with the new encoding a small part of the audio file will be cut in the beginning. I tested this with multiple files. This is the command i am using:

  ffmpeg -y -noaccurate_seek -i file.mp3 -b:a 260k -c:a libfdk_aac -vn -movflags +faststart output.m4a
  

  I tried different variations but alway ended up with cut file.

  Here is the output of a wave editor

  source file:

  

  ouput:

  

• FFMpeg : how to use between() to select last second ?

  13 mai 2019, par rcpinheiro

  I'm trying to apply a caption using drawtext that should disappear one second before the video end:

  ffmpeg -i input.mp4 -vf "drawtext=enable='between(t,0,5)':fontfile=font.ttf:text='Some caption':x=60:y=640:fontsize=40:fontcolor=#f0f0f0@0.9" -vcodec libx264 -crf 27 -preset ultrafast -strict -2 -acodec copy output.mp4
  

  The problem is that I don't know the video length beforehand. I've tried using 'between(t,0,-1)' but it doesn't work, the caption never shows up. Anyone knows if is there a way to do this without having to open the video first to check length and only after that draw the caption? Thanks in advance!

• Capture desktop with gdigrab and save the result to video file using ffmpeg and C++

  13 mai 2019, par Skunz

  I'm building a C++ application that is able to capture the screen and save the output to a file (.mkv, .mp4, doesn't matter).

  I tried to switch codecs and played with the AVCodecContext settings. When subsitute the gdi capture with reading from a static .mp4 file everything works fine.

  Here is my gdigrab initalization.

  _inputFormat = av_find_input_format("gdigrab");
  
      if (!_inputFormat) {
          std::cout << "Unable to open input Format" << std::endl;
          exit(1);
      }
  
      if (avformat_open_input(&_screenFormatContext, "desktop", _inputFormat, &_recordOptions) < 0) {
          std::cout << "Unable to open input stream" << std::endl;
          exit(1);
      }
  
      if (avformat_find_stream_info(_screenFormatContext, &_recordOptions) < 0) {
          std::cout << "Couldn't find input stream" << std::endl;
          exit(1);
      }
  
      av_dump_format(_screenFormatContext, 0, "GDI Capture", 0);
      for (int i = 0; i < _screenFormatContext->nb_streams; i++) {
          if (_screenFormatContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
              _videoStreamIdx = i;
              break;
          }
      }
  
      if (_videoStreamIdx == -1) {
          std::cout << "Unable to find video Stream" << std::endl;
          exit(1);
      }
  
      _codecPar = _screenFormatContext->streams[_videoStreamIdx]->codecpar;
  

  Here is my setup code for the encoder and decoder.

      /*
          Decoder
      */
      _dCodec = avcodec_find_decoder(_codecPar->codec_id);
      if (!_dCodec) {
          std::cout << "Unable to find decoder" << std::endl;
          exit(1);
      }
  
      _dCodecContext = avcodec_alloc_context3(_dCodec);
      if (avcodec_parameters_to_context(_dCodecContext, _codecPar) < 0) {
          std::cout << "Unable to copy context" << std::endl;
          exit(1);
      }
      if (avcodec_open2(_dCodecContext, _dCodec, NULL) < 0) {
          std::cout << "Unable to open dCodec" << std::endl;
          exit(1);
      }
  
      /*
          Encoder
      */
      _eCodec = avcodec_find_encoder(AV_CODEC_ID_H265);
      if (!_eCodec) {
          std::cout << "Unable to find encoder" << std::endl;
          exit(1);
      }
  
      _eCodecContext = avcodec_alloc_context3(_eCodec);
  
      //width and height have to be divisible by 2
      if (_codecPar->width % 2 != 0)
          _codecPar->width--;
      if (_codecPar->height % 2 != 0)
          _codecPar->height--;
  
      _eCodecContext->pix_fmt = AV_PIX_FMT_YUV422P;
      _eCodecContext->width = _codecPar->width;
      _eCodecContext->height = _codecPar->height;
      _eCodecContext->gop_size = 10;
      _eCodecContext->max_b_frames = 1;
  
      _eCodecContext->time_base.den = 30;
      _eCodecContext->time_base.num = 1;
  
      if (avcodec_open2(_eCodecContext, _eCodec, NULL) < 0) {
          std::cout << "Unable to open eCodec" << std::endl;
          exit(1);
      }
  

  Here is my main loop. Grabbing the packets from gdi, decoding them and encoding them.

      while (av_read_frame(_screenFormatContext, _pkt) == 0) {
          if (_pkt->stream_index == _videoStreamIdx) {
              if (_decodePacket() < 0)
                  exit(1);
              _encodeFrame();
          }
          av_packet_unref(_pkt);
  }
  
  

  And here the encoding/decoding functions

  int     ScreenRecorder::_decodePacket(void)
  {
      //send packet to decoder
      int ret = avcodec_send_packet(_dCodecContext, _pkt);
      if (ret < 0) {
          std::cout << "error while sending packet to decoder" << std::endl;
          return ret;
      }
  
      ret = avcodec_receive_frame(_dCodecContext, _frame);
      if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
          return 0;
      //Was there an error?
      else if (ret < 0) {
          std::cout << "Error with receiving frame" << std::endl;
          exit(1);
      }
      //No errors -> got frame
      std::cout << "Got frame " << _dCodecContext->frame_number << " with size " << _frame->pkt_size << std::endl;
      char frame_filename[1024];
      snprintf(frame_filename, sizeof(frame_filename), "%s-%d.pgm", "frame", _dCodecContext->frame_number);
      //_saveGrayFrame(_frame->data[0], _frame->linesize[0], _frame->width, _frame->height, frame_filename);
      return 0;
  }
  
  void    ScreenRecorder::_encodeFrame(void)
  {
      AVPacket* pkt = av_packet_alloc();
  
      // send frame to encoder - 0 on success
      int ret = avcodec_send_frame(_eCodecContext, _frame);
      if (ret < 0) {
          std::cerr << "Unable to send frame! ERRORCODE: " << ret << std::endl;
          exit(1);
      }
  
      while (ret == 0) {
          ret = avcodec_receive_packet(_eCodecContext, pkt);
          //Do I need to send more packets?
          if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
              std::cout << "Needing one more packet " << std::endl;
              av_packet_unref(pkt);
              return ;
          }
          //Was there an error?
          else if (ret < 0) {
              std::cout << "Error with receiving packet" << std::endl;
              exit(1);
          }
          //No errors -> got packet
          std::cout << "Got packet " << pkt->pts << " of size " << pkt->size << std::endl;
          if (av_write_frame(_outFormatContext, pkt) < 0) {
              std::cout << "Unable to write frame" << std::endl;
              exit(1);
          }
          av_packet_unref(pkt);
      }
  }
  

  In case you still need the header file

  #ifndef SCREENRECORDER_HPP
  # define SCREENRECORDER_HPP
  
  extern "C" {
      #include "libavcodec/avcodec.h"
      #include "libavdevice/avdevice.h"
      #include "libavformat/avformat.h"
      #include "libavformat/avio.h"
  }
  
  class ScreenRecorder
  {
  private:
      AVCodecContext      *_dCodecContext;
      AVCodecContext      *_eCodecContext;
  
      AVFormatContext     *_fileFormatContext;
      AVFormatContext     *_screenFormatContext;
      AVFormatContext     *_outFormatContext;
  
      AVInputFormat       *_inputFormat;
  
      AVCodecParameters   *_codecPar;
  
      AVStream            *_videoTrack;
  
      AVCodec             *_dCodec;
      AVCodec             *_eCodec;
  
      AVFrame             *_frame;
  
      AVPacket            *_pkt;
  
      AVDictionary        *_options;
      AVDictionary        *_recordOptions;
  
  
      int                 _videoStreamIdx;
  
      int                 _decodePacket(void);
      void                _encodeFrame(void);
      void                _openInputFile(void);
      void                _initalizeCodec(void);
      void                _initalizeOutputFile(void);
      void                _closeCodec(void);
      void                _initalizeGDI(void);
      void                _saveGrayFrame(unsigned char* buf, int wrap, int xsize, int ysize, char* filename);
  
  public:
      ScreenRecorder();
      ~ScreenRecorder();
  
      void                start();
  };
  
  #endif
  
  

  When I run my code I am getting Exception thrown at 0x00007FF819864A80 (msvcrt.dll) in Streaming.exe: 0xC0000005: Access violation reading location 0x0000000000000EF0. It comes from avcodec_send_frame function. Seems like I'm trying to access memory that wasn't allocated. I am new to the ffmpeg lib and hope that someone can get me on the right track. Thank you very much. If you have any questions please ask them.