Newest 'ffmpeg' Questions - Stack Overflow

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• How to play a part of the MP4 video stream ?

  14 novembre 2014, par AgentFire

  I have a URL (/ipcam/mpeg4.cgi) which points to my IP camera which is connected via Ethernet. Accessing the URL resuls in a infinite stream of video (possibly with audio) data.

  I would like to store this data into a video file and play it later with a video player (HTML5's video tag is preferred as the player).

  However, a straightforward approach, which is simple saving the stream data into .mp4 file, didn't work.

  I have looked into the file and here is what I saw (click to enlarge):

  

  It turned out, there are some HTML headers, which I further on manually excluded using the binary editing tool, and yet no player could play the rest of the file.

  The HTML headers are:

  --myboundary
  Content-Type: image/mpeg4
  Content-Length: 76241
  X-Status: 0
  X-Tag: 1693923
  X-Flags: 0
  X-Alarm: 0
  X-Frametype: I
  X-Framerate: 30
  X-Resolution: 1920*1080
  X-Audio: 1
  X-Time: 2000-02-03 02:46:31
  alarm: 0000
  

  My question is pretty clear now, and I would like any help or suggestion. I suspect, I have to manually create some MP4 headers myself based on those values above, however, I fail to understand format descriptions such as these.

  I have the following video stream settings on my IP camera (click to enlarge):

  

  I could also use the ffmpeg tool, but no matter how I try and mix the arguments to the program, it keeps telling me this error:

  

• ffmpeg - add logo in a specific time interval

  14 novembre 2014, par Kåre Brøgger Sørensen

  Is there a way - in a one liner - where I do not have to use ffmpeg to calculate the duration of the whole video before i render ..

  I would like something like:

  ffmpeg -i ny_video_no_logo.mp4 -i ~/Pictures/home_logo_roed_new.png -filter_complex "[0:v][1:v]overlay=main_w-overlay_w-10:main_h-overlay_h-10:enable='between(t,5.50,FULl_LENGTH - 10)'" -codec:a copy out.mp4

  I there a simple way like the "main_w" to get the video length inserted - I am using a non existing variable FULL_LENGTH in the above?

  Or do i have to make a ffmpeg -i and extract the time from this?

• How to add meta data into a video frame and how to read it ?

  14 novembre 2014, par Asanga Ranasinghe

  I am using AForge.FFmpeg to create a video using a sequence of images. What I want is to add some meta data with each frame when I am making the video. Is there a possible way to do that? If it is, I want to know how to read it again after creating the video. Please help me with this.

  Code I used to create the video. (Using AFroge.ffmpeg)

  VideoFileWriter writer = new VideoFileWriter();
  writer.Open(String.Format("D:\\test.avi", DateTime.Now), 640, 480, 10, VideoCodec.MPEG4);
  while (Condition){
  //I want a method to add meta data into the frame
  writer.WriteVideoFrame(current);//Adding frames into the video using a loop    
  }
  writer.Close();
  

• FFMPEG : Set output res and bitrate depending upon input video

  13 novembre 2014, par Jegschemesch

  I'm processing user videos with differing aspect ratios. It seems FFMPEG only allows you to specify a fixed resolution. I want the output res to be appropriate for the input res. Similarly, I'd like FFMPEG to intelligently set the output bitrate based on the input video: obviously it shouldn't be any bigger than the input.

  I can get the properties of a video with,

  ffmpeg -i example.flv
  

  But this requires some ugly parsing of the output, so I'm wondering if FFMPEG or some other tool has a more direct facility.

  Basically, I have the Youtube problem: crap comes in, reasonably uniform quality should come out.

• Process AVFrame using opencv mat causing encoding error

  13 novembre 2014, par user2789801

  I'm trying to decode a video file using ffmpeg, grab the AVFrame object, convert it to opencv mat object, do some processing then convert it back to AVFrame object and encode it back to a video file.

  Well, the program can run, but it produces bad result.

  I Keep getting errors like "top block unavailable for requested intra mode at 7 19", "error while decoding MB 7 19, bytestream 358", "concealing 294 DC, 294AC, 294 MV errors in P frame" etc.

  And the result video got glithes all over it. like this,

  I'm guessing it's because my AVFrame to Mat and Mat to AVFrame methods, and here they are

  //unspecified function
  temp_rgb_frame = avcodec_alloc_frame(); 
  int numBytes = avpicture_get_size(PIX_FMT_RGB24, width, height); 
  uint8_t * frame2_buffer = (uint8_t *)av_malloc(numBytes * sizeof(uint8_t)); 
  avpicture_fill((AVPicture*)temp_rgb_frame, frame2_buffer, PIX_FMT_RGB24, width, height);
  
  void CoreProcessor::Mat2AVFrame(cv::Mat **input, AVFrame *output)
  {
      //create a AVPicture frame from the opencv Mat input image
      avpicture_fill((AVPicture *)temp_rgb_frame,
          (uint8_t *)(*input)->data,
          AV_PIX_FMT_RGB24,
          (*input)->cols,
          (*input)->rows);
  
      //convert the frame to the color space and pixel format specified in the sws context
  
      sws_scale(
          rgb_to_yuv_context, 
          temp_rgb_frame->data,
          temp_rgb_frame->linesize,
          0, height, 
          ((AVPicture *)output)->data, 
          ((AVPicture *)output)->linesize);
  
      (*input)->release();
  
  }
  
  void CoreProcessor::AVFrame2Mat(AVFrame *pFrame, cv::Mat **mat)
  {
      sws_scale(
          yuv_to_rgb_context, 
          ((AVPicture*)pFrame)->data, 
          ((AVPicture*)pFrame)->linesize, 
          0, height, 
          ((AVPicture *)temp_rgb_frame)->data,
          ((AVPicture *)temp_rgb_frame)->linesize);
  
      *mat = new cv::Mat(pFrame->height, pFrame->width, CV_8UC3, temp_rgb_frame->data[0]);
  }
  
  void CoreProcessor::process_frame(AVFrame *pFrame)
  {
      cv::Mat *mat = NULL;
      AVFrame2Mat(pFrame, &mat);
      Mat2AVFrame(&mat, pFrame);
  }
  

  Am I doing something wrong with the memory? Because if I remove the processing part, just decode and then encode the frame, the result is correct.