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• iPAD Streaming video to a ffmpeg server. front facing camera

  6 décembre 2011, par IrishGringo

  This is a video chat type program.
  My project is to write a native ObjC app that will stream video from the front facing camera to a server. This server will format and relay to be sent to another location.
  In a related question, I want to display video streaming from the server. The video server will probably be running ffmpeg for formating.
  But this question is just asking advice for the iPAD project. I wanted to get comments about issues I need to be thinking about.

  This is my strategy :
  I was thinking of using AVFoundation framework to stream from the cam to a URL server. I don't know if I will be formatting on the client or no, so some comment there would be interesting. http://developer.apple.com/library/mac/#documentation/AVFoundation/Reference/AVFoundationFramework/_index.html

  For streaming the video, I was going to be using :
  http://developer.apple.com/library/IOs/#documentation/AVFoundation/Reference/AVCaptureSession_Class/Reference/Reference.html#//apple_ref/occ/cl/AVCaptureSession

  so if someone has some ideas/suggestions... extra code I can look at. I would appreciate it.

• Recommendations for real-time pixel-level analysis of television (TV) video

  6 décembre 2011, par Randall Cook

  [Note : This is a rewrite of an earlier question that was considered inappropriate and closed.]

  I need to do some pixel-level analysis of television (TV) video. The exact nature of this analysis is not pertinent, but it basically involves looking at every pixel of every frame of TV video, starting from an MPEG-2 transport stream. The host platform will be server-class, multiprocessor 64-bit Linux machines.

  I need a library that can handle the decoding of the transport stream and present me with the image data in real-time. OpenCV and ffmpeg are two libraries that I am considering for this work. OpenCV is appealing because I have heard it has easy to use APIs and rich image analysis support, but I have no experience using it. I have used ffmpeg in the past for extracting video frame data from files for analysis, but it lacks image analysis support (though Intel's IPP can supplement).

  In addition to general recommendations for approaches to this problem (excluding the actual image analysis), I have some more specific questions that would help me get started :

  1. Are ffmpeg or OpenCV commonly used in industry as a foundation for real-time
     video analysis, or is there something else I should be looking at ?
  2. Can OpenCV decode video frames in real time, and still leave enough
     CPU left over to do nontrivial image analysis, also in real-time ?
  3. Is sufficient to use ffpmeg for MPEG-2 transport stream decoding, or
     is it preferable to just use an MPEG-2 decoding library directly (and if so, which one) ?
  4. Are there particular pixel formats for the output frames that ffmpeg
     or OpenCV is particularly efficient at producing (like RGB, YUV, or YUV422, etc) ?

• How to create a video from png images using ffmpeg

  28 décembre 2011, par Rajat

  I want to create a video from different png images. My code is :

  ffmpeg -r 20 -f image2 -i slideshow/%d.png -y -s 320x240 -aspect 4:3 out.mp4

  and i receive output :

  FFmpeg version SVN-r26400, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on Sep 27 2011 00:47:07 with gcc 4.1.2 20080704 (Red Hat 4.1.2-50)
  
    configuration: --enable-avfilter --enable-filter=fade
  
    libavutil     50.36. 0 / 50.36. 0
  
    libavcore      0.16. 1 /  0.16. 1
  
    libavcodec    52.108. 0 / 52.108. 0
  
    libavformat   52.93. 0 / 52.93. 0
  
    libavdevice   52. 2. 3 / 52. 2. 3
  
    libavfilter    1.74. 0 /  1.74. 0
  
    libswscale     0.12. 0 /  0.12. 0
  
  Input #0, image2, from 'slideshow/%d.png':
  
    Duration: 00:00:00.25, start: 0.000000, bitrate: N/A
  
      Stream #0.0: Video: png, rgb24, 720x471, 20 fps, 20 tbr, 20 tbn, 20 tbc
  
  [buffer @ 0x9687230] w:720 h:471 pixfmt:rgb24
  
  [scale @ 0x9687600] w:720 h:471 fmt:rgb24 -> w:320 h:240 fmt:yuv420p flags:0xa0000004
  
  Output #0, mp4, to 'out.mp4':
  
    Metadata:
  
      encoder         : Lavf52.93.0
  
      Stream #0.0: Video: mpeg4, yuv420p, 320x240 [PAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 20 tbn, 20 tbc
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
  Press [q] to stop encoding
  
  Segmentation fault

  What might be the problem ? Please help...
  Currently i am using centos 5 server.