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• Ffprobe with print json doesn't print anything

  10 septembre 2012, par Richard Knop

  I am trying to get information about a movie (resolution, frame rate, bit rate, codecs, duration etc) in a human readable way. I found this commnad :

  ffprobe -v quiet -print_format json -show_format -show_streams somefile.asf

  In this Stack Overflow question : Get ffmpeg information in friendly way

  But it doesn't work for me. When I try it in a terminal, the output is empty :

  richard@richard-desktop:~/projects/hello-python$ ffprobe -v quiet -print_format json -show_format -show_streams tests/test_1.mpg 
  
  richard@richard-desktop:~/projects/hello-python$ 

• FFMPEG API (compiling with specific formats)

  14 janvier 2012, par JS.

  I am trying to compile FFMPEG to support a single video type (*.mp4).

  I have everything working when I compile for all, but I do not want the extra over-head when I will only use a single format.

  Here's my compile FLAGS now (non-working for MP4). I am sure there are other codecs/decoders I need to specifically enable, but am just having a hard time finding them.

  Compiler directives showing the build flags below :

  FLAGS="$FLAGS --disable-everything"
  
  FLAGS="$FLAGS --enable-encoder=mpeg4video" ## This is the question, what all needs enabling?

  I just do not know video standards well enough to know exactly which codecs / encoders / etc. to turn on.

  av_register_all();
  
  avdevice_register_all();
  
  
  
  byteCtx = av_alloc_put_byte(buffer, BUFFER_SIZE, 0, f, ReadFunc, NULL, SeekFunc);
  
  if (!byteCtx) {
  
      return;
  
  }
  
  // Open video file (here's the failure, doesn't happen when compiled for all)
  
  inputFormat = av_find_input_format("MP4");
  
  if (!inputFormat) {
  
      LOGE(ANDROID_LOG_ERROR, "NDK:", "Null inputformat!");
  
      return;
  
  }

• Webcam stream with FFMpeg on iPhone

  6 décembre 2011, par Saphrosit

  I'm trying to send and show a webcam stream from a linux server to an iPhone app. I don't know if it's the best solution, but I downloaded and installed FFMpeg on the linux server (following, for those who want to know, this tutorial).
  FFMpeg is working fine. After a lots of wandering, I managed to send a stream to the client launching

  ffmpeg  -s 320x240 -f video4linux2 -i /dev/video0 -f mpegts -vcodec libx264 udp://192.168.1.34:1234

  where 192.168.1.34 is the address of the client. Actually the client is a Mac, but it is supposed to be an iPhone. I know the stream is sent and received correctly (tested in different ways).
  However I didn't managed to watch the stream directly on the iPhone.
  I thought of different (possible) solutions :

  • first solution : store incoming data in a NSMutableData object. Then, when the stream ends, store it and then play it using a MPMoviePlayerController. Here's the code :

    [video writeToFile:@"videoStream.m4v" atomically:YES];
    
    NSURL *url = [NSURL fileURLWithPath:@"videoStream.m4v"];
    
    
    
    MPMoviePlayerController *videoController = [[MPMoviePlayerController alloc] initWithContentURL:url];
    
    
    
    [videoController.view setFrame:CGRectMake(100, 100, 150, 150)];
    
    
    
    [self.view addSubview:videoController.view];
    
    
    
    [videoController play];

    the problem of this solution is that nothing is played (I only see a black square), even if the video is saved correctly (I can play it directly from my disk using VLC). Besides, it's not such a great idea. It's just to make things work.

  • Second solution : use CMSampleBufferRef to store the incoming video. Much more problems comes with this solution : first of all, there's no CoreMedia.framework in my system. Besides I do not get well what does this class represents and what should I do to make it works : I mean if I start (somehow) filling this "SampleBuffer" with bytes I receive from UDP connection, then it will automatically call the CMSampleBufferMakeDataReadyCallback function I set during creation ? If yes, when ? When the single frame is completed or when the whole stream is received ?

  • Third solution : use AVFoundation framework (neither this is actually available on my Mac). I did not understand if it's actually possible to start recording from a remote source or even from a NSMutableData, a char* or something like that. On AVFoundation Programming Guide I didn't find any reference that say if it's possible or not.

  I don't know which one of this solution is the best for my purpose. ANY suggestion would be appreciate.

  Besides, there's also another problem : I didn't use any segmenter program to send the video. Now, if I'm not getting wrong, segmenter needs to split the source video in smaller/shorter video easier to send. If it is right, then maybe it's not strictly necessary to make things work (may be added later). However, since the server is running under linux, I cannot use Apple's mediastreamsegmeter. May someone suggest an opensource segmenter to use in association with FFMpeg ?

  ---

  UPDATE : I edited my question adding more informations on what I did since now and what my doubts are.