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• when audioqueue play lpcm decoded from ffmpeg, the elapsed time of audio queue exceeds the duraion of the media

  15 août 2012, par zhzhy

  When play the lpcm data decoded from ffmpeg with audioqueue, the elapsed time got by AudioQueueGetCurrentTime exceeds the duration of media. But when decode the same media with AVFoundation framework, the elapsed time equals duration of the media, and so when read media by ffmpeg with no decoded, then send the compressed media data to audioqueue, the elapsed time also equals duration of the media. The AudioStreamBasicDescription set as following :

      asbd.mSampleRate = 44100;
  
      asbd.mFormatID = kAudioFormatLinearPCM;
  
      asbd.mFormatFlags = kAudioFormatFlagsCanonical;
  
      asbd.mBytesPerPacket = 4;
  
      asbd.mFramesPerPacket = 1;
  
      asbd.mBytesPerFrame = 4;
  
      asbd.mChannelsPerFrame = 2;
  
      asbd.mBitsPerChannel = 16;
  
      asbd.mReserved = 0;

  When playing with data decoded from AVFoundation, the setting of AudioStreamBasicDescription is the same as above. By my test found that AudioTimeStamp.mSampleTime got by AudioQueueGetCurrentTime is different between ffmpeg and AVFoundation, the value of ffmpeg is greater than AVFoundation. So I want to know how this happen, and how to fix it ?
  Thanks !

• ffmpeg stream Raspberry pi

  2 décembre 2020, par Matt85

  I use a rasberry pI4 with usb camera to stream on our server in rtmp

  


  we would like to use the native resolution of the cam

  


  I use video4linux and ffmpeg

  


  here the formats you see :

  


  [video4linux2, v4l2 @ 0x17641c0] Compressed : mjpeg : Motion-JPEG : 1600x1200 3264x2448 2592x1944 2048x1536 1280x960 1024x768 800x600 640x480 320x240 1600x1200
[video4linux2, v4l2 @ 0x17641c0] Raw : yuyv422 : YUYV 4 : 2 : 2 : 1600x1200 3264x2448 2592x1944 2048x1536 1280x960 1024x768 800x600 640x480 320x240 1600x1200

  


  this are the result supported by the usb cam in 2 formats (YUY and MJPEG)

  


  our server accepts incoming RTMP

  


  we would like to stream in RTMP at 1280x960 with output at 20fps (supported for mjpeg)

  


  what is the correct string we need to use in ffmpeg

  


  we tried many variations, but the frame rate is not correct it comes out very low.

  


  the string we use is this :

  


  # ! /bin/bash
ffmpeg
  
-f v4l2 -i /dev/video0
  
-c : v libx264 -pix_fmt yuv420p -preset ultrafast -b 3000k -g 40 -b : v 2000k
  
-bufsize 512k
  
-threads 1 -qscale 0
  
-r 20
  
-s 1280x960
  
-f flv rtmp ://login:password@xxx.xxx.xxx.xxx:1935/xxxx/xxxx

  


  comes out at 10 / 12fps

  


  and gives us this :

  


  Please use -b : a or -b : v, -b is ambiguous
Please use -q : a or -q : v, -qscale is ambiguous

  


  Help from the most experienced of ffmpeg, thanks

  


• How to read a text file in c++ ?

  16 mai 2017, par Sanduni Wickramasinghe

  I want to detect a predefined specific content in a video. For this I use an already identified piece of video separately and another input video. I have read the data in the identified video and bite array was saved in a text file. Now I want to compare the content of saved text file with the input video content.

  This is my code

      void CFfmpegmethods::VideoRead(){
  
      av_register_all();
  
      avformat_network_init();
  
      ifstream inFile;
  
      inFile.open("H:\\Sanduni_projects\\sample_ad.txt");
  
      const char *url = "H:\\Sanduni_projects\\ad_1.mp4";
  
      AVDictionary *options = NULL;
  
      AVFormatContext *s = avformat_alloc_context();
  
  
  
      AVPacket *pkt = new AVPacket(); //this structure stores compressed data
  
  
  
      //open an input stream and read the header
  
      int ret = avformat_open_input(&s, url, NULL,NULL);
  
  
  
      //avformat_find_stream_info(s, &options); //finding the missing information 
  
  
  
      if (ret < 0)
  
          abort();
  
  
  
      if (!inFile) {
  
          cerr << "Unable to open file datafile.txt";
  
          exit(1);   // call system to stop
  
      }
  
  
  
      av_dict_set(&options, "video_size", "640x480", 0);
  
      av_dict_set(&options, "pixel_format", "rgb24", 0);
  
  
  
      if (avformat_open_input(&s, url, NULL, &options) < 0){
  
          abort();
  
      }
  
      av_dict_free(&options);
  
      AVDictionaryEntry *e;
  
  
  
      if (e = av_dict_get(options, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
  
          fprintf(stderr, "Option %s not recognized by the demuxer.\n", e->key);
  
          abort();
  
      }
  
  
  
      int i = 1;
  
      int64_t duration = 0;
  
      int size = 0;
  
      uint8_t *data; //Unsigned integer type with a width of exactly 8 bits.
  
      int sum = 0;
  
  
  
      int total_size = 0;
  
      int64_t total_duration = 0;
  
      int packet_size = 0;
  
      int64_t stream_index = 0;
  
      int64_t bit_rate = 0;
  
      AVBufferRef *buf;
  
  
  
      //writing data to a file
  
      outdata.open("H:\\Sanduni_projects\\sample_ad.txt");
  
      //outdata.open("H:\\Sanduni_projects\\log.txt");
  
  
  
      if (!outdata){
  
          cerr << "Error: file could not be opened" << endl;
  
          exit(1);
  
      }
  
  
  
      //Split what is stored in the file into frames and return one for each call
  
      //returns the next frame of the stream
  
  
  
      while(1){
  
          int frame = av_read_frame(s, pkt); //one frame is readed.
  
          if (frame < 0) break;
  
          size = pkt->size;
  
          data = pkt->data;
  
  
  
          for (int j = 0; j < size; j++){
  
              for (int k = 0; k < 12; k++){
  
                  while (!inFile.eof){
  
  
  
  
  
                  }
  
                  //if (data[j] != ) break;
  
              }
  
          }
  
  
  
          //int decode = avcodec_send_packet(avctx, pkt);
  
      }
  
  
  
      //make the packet free
  
      av_packet_unref(pkt);
  
      delete pkt;
  
  
  
      cout << "total size: " << total_size << endl;
  
      cout << "total duration:" << total_duration << endl;
  
  
  
      outdata.close();
  
  
  
      //Close the file after reading
  
      avformat_close_input(&s);
  
  }
  
  
  
  
  
  void CFfmpegmethods::SampleAdCreation(){
  
      av_register_all();
  
      const char *url_ref = "H:\\Sanduni_projects\\sample_ad.mp4";
  
      AVDictionary *options = NULL;
  
      AVDictionary *options_ref = NULL;
  
      AVFormatContext *s = avformat_alloc_context();
  
      AVPacket *pkt = new AVPacket(); //this structure stores compressed data
  
  
  
  
  
      //open an input stream and read the header
  
      int ret = avformat_open_input(&s, url_ref, NULL, NULL);
  
  
  
      if (ret < 0)
  
          abort();
  
  
  
      av_dict_set(&options, "video_size", "640x480", 0);
  
      av_dict_set(&options, "pixel_format", "rgb24", 0);
  
  
  
      if (avformat_open_input(&s, url_ref, NULL, &options) < 0){
  
          abort();
  
      }
  
  
  
      av_dict_free(&options);
  
      AVDictionaryEntry *e;
  
  
  
      if (e = av_dict_get(options, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
  
          fprintf(stderr, "Option %s not recognized by the demuxer.\n", e->key);
  
          abort();
  
      }
  
  
  
      uint8_t *data; 
  
  
  
      //writing data to a file
  
      outdata.open("H:\\Sanduni_projects\\sample_ad.txt");
  
  
  
      if (!outdata){
  
          cerr << "Error: file could not be opened" << endl;
  
          exit(1);
  
      }
  
  
  
      for (int m = 0; m < 12; m++){
  
          int size = pkt->size;
  
          int frame = av_read_frame(s, pkt); 
  
          if (frame < 0) break;
  
  
  
          data = pkt->data;
  
  
  
          for (int j = 0; j < size; j++){
  
              outdata << data[j];
  
          } outdata</make the packet free
  
      av_packet_unref(pkt);
  
      delete pkt;
  
  
  
      outdata.close();
  
  
  
      //Close the file after reading
  
      avformat_close_input(&s);
  
  }