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• How play audio from a .mkv file from specific frame in python

  31 juillet 2022, par ChaseRatliff

  I would like to know how I could go about playing audio from a .mkv file. I am trying to play video. I am using opencv to display the video and ffpyplayer to play the audio. I can set the frame I want to start playing at in opencv but not in ffplayer. Any ideas or suggestions would help a ton. Here is what I have came up with.

  


  import cv2
from ffpyplayer.player import MediaPlayer

video_path=videoName

def PlayVideo(video_path):
    font = cv2.FONT_HERSHEY_SIMPLEX
    video=cv2.VideoCapture(video_path)

    video.set(cv2.CAP_PROP_POS_FRAMES, 7200)
    player = MediaPlayer(video_path)
    while True:
        font = cv2.FONT_HERSHEY_SIMPLEX
        grabbed, frame=video.read()
        audio_frame, val = player.get_frame()

    if not grabbed:
        print("End of video")
        break
        
    if cv2.waitKey(28) & 0xFF == ord("q"):
        break

    cv2.imshow("Video", frame)
    if val != 'eof' and audio_frame is not None:
        #audio
        img, t = audio_frame

video.release()
cv2.destroyAllWindows()

PlayVideo(video_path)


  


• How to use ffmpeg to play ps stream ?

  10 février 2018, par Zhang

  I use ffmpeg api to play media based on rtsp，but print log "Could not find codec parameters for stream 0 (Video : none, none) : unknown codec" . rtp payload is ps packet，how can I demux？

  if (avformat_open_input(&avFormatCtx, pathUrl, NULL, NULL) != 0) {
  
      NSLog(@"Open video file fail!!!");
  
      return NO;
  
  }
  
  
  
  // Retrieve stream information
  
  if (avformat_find_stream_info(avFormatCtx, NULL) < 0) {
  
      NSLog(@"Retrieve stream information fail!!!");
  
      return NO;
  
  }
  
  
  
  // Find the first video stream
  
  videoStream =  av_find_best_stream(avFormatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, &avCodec, 0);
  
  char *errstr =   av_err2str(videoStream);

• how to play m4s chunks downloaded from mpd file

  28 août 2015, par Mayank Agarwal

  Below i have written sample code to download first 7 chunks of mpd file of single quality alongwith base url mp4 of that particular quality.I am putting m4s chunks in queue of strings.How can i play the downloaded data.
  i have queue in which at first iteration is mp4 segment of particular quality
  and then in subsequent iterations i have m4s chunks of same quality
  Now i want to play this queue buffer using ffmpeg or gstreamer.How can i do this
  Individually i am able to play by downloading single mp4(of particular quality in mpd structure) then using cat concatenating with m4s chunks and then play.

  In open source libdash how it is done,if anyone has any idea.

  Please guide.

    #include <iostream>
  
  #include 
  
  #include <curl></curl>curl.h> 
  
  #include <queue>
  
  #include <cstdlib>
  
  
  
  using namespace std;
  
  string data; 
  
  std::queue<string> myqueue;
  
  int size =0;
  
  
  
  
  
  
  
   size_t writeCallback(char* buf, size_t size, size_t nmemb, void* up)
  
   { 
  
  
  
    printf("size  = %d\n\n\n",size);
  
    printf("size nmemb  = %d\n\n\n\n\n",nmemb);
  
    for (int c = 0; c/tell curl how many bytes we handled
  
    }
  
  
  
  
  
  
  
    int main()
  
    {
  
    CURL* curl; //our curl object
  
    char url_firstpart[80];// = NULL;
  
    char bitwide_chunk[10];
  
    char buffer[10];
  
  
  
  
  
  curl_global_init(CURL_GLOBAL_ALL); //pretty obvious
  
  curl = curl_easy_init();
  
  
  
  for(int i=0;i&lt;7;i++)
  
  {   
  
  
  
  strcpy(url_firstpart,"http://www-itec.uni- klu.ac.at/ftp/datasets/mmsys12/Valkaama/valkaama_1s/valkaama_1s_50kbit/valkaama_1s");
  
  string str = to_string(i);
  
  
  
  char * writable = new char[str.size() + 1];
  
  std::copy(str.begin(), str.end(), writable);
  
  writable[str.size()] = '\0'; 
  
  
  
  strcat(writable,".m4s"); 
  
  printf("concanated chink is %s\n",writable);
  
  
  
  strcat(url_firstpart,bitwide_chunk);
  
  puts(url_firstpart);
  
  
  
  
  
  curl_easy_setopt(curl, CURLOPT_URL,url_firstpart);
  
  curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &amp;writeCallback);
  
  curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L); 
  
  
  
  curl_easy_perform(curl);
  
  
  
  
  
  
  
  }
  
  
  
  size = myqueue.size();
  
  printf("Final size of queue = %d\n",size);
  
  cout &lt;&lt; endl &lt;&lt; data &lt;&lt; endl;
  
    cin.get();
  
  
  
    curl_easy_cleanup(curl);
  
    curl_global_cleanup();
  
  
  
    return 0;
  
   }
  
  </string></cstdlib></queue></iostream>