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• OpenCV ffmpeg issues when running Windows 10 app on Windows 7

  1er novembre 2016, par David G.

  I need to maintain a desktop app written in C++, using Qt and OpenCV for some video processing. As far as I understood, the decoding part of OpenCV is delegated to ffmpeg in a separate DLL for licensing reasons.

  The development environment is on Windows 10, using QT Creator and MSVC12 64-bit as compiler. OpenCV version is 3.0, the official distribution. Here, everything runs fine, I am able to decode a video using VideoCapture::open().

  Issues arise when I try to run the application in a standalone fashion with all the required DLLs in the same folder as the .exe file. All cases below are 64-bit OSes.

  On a Windows 10 computer, not the same as the developement machine and no developer libraries present, the video decoding works fine. I have tested on a Windows 8 machine as well, no issues so far.

  On Windows 7, the things get tricky. The same video files that successfully load during the previous tests are not recognized by the app at all i.e. the isOpened call on VideoCapture returns false. For further testing, I stripped the opencv_ffmpeg300_64.dll file to narrow down the issue on Windows 10 and 8 ; as expected, without this DLL the app is no more able to open the same video files.

  It seems that the DLL is simply not recognized on Windows 7.

  • Did you encounter this type of issue and, maybe, have part of a solution ?
  • I would like to monitor which DLLs are loaded as the program runs and see possible "DLL not found" errors. Is it possible, especially on a machine that does not have the entire developement environment ?
  • Can building OpenCV on my own address the issue ?
  • Even further, would it be worth to port the development environment on Windows 7 and build from there ? This requires significant work due to the project itself.

• iPhone camera live steaming

  15 juin 2012, par Inder Kumar Rathore

  I have downloaded ffmpeg lib file and complied it for armv7. I added ffmpeg lib files in my project successfully. i am able to get iphone camera live streams using AVFoundation.

  Now the problem is how will i convert iphone camera streams output as a input of ffmpeg for decode ? Check my code

  - (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
  
  
  
  
  
  CMBlockBufferRef bufferData = CMSampleBufferGetDataBuffer(sampleBuffer);
  
  size_t lengthAtOffset;
  
  size_t totalLength; char* data; 

  if(CMBlockBufferGetDataPointer(bufferData, 0, &lengthAtOffset, &totalLength, &data ) != noErr )
  NSLog(@"error !") ;
  
  

  Kindly suggested me which function of ffmpeg lib is used for decoding and how will i put CMBlockBufferRef as a input of this ??

  Thanks

• Http live streaming for ipad, iphone and safari

  23 février 2013, par Riyas Anchal

  Anyone help me to find a solution to stream a video from a mac server to iPad, iPhone and mac safari using HTTP live streaming.

  Steps taken :

  1. Installed and configured FFMPEG for encoding
  2. installed the mediasegmenter provided by the Apple.

  The ffmpeg option used is

  ffmpeg -y -i input.mp4 -acodec aac -ar 48000 -ab 128k -ac 2 -s 1024×768 -vcodec libx264 -b 1200k -flags +loop+mv4 -cmp 256 -partitions +parti4x4+partp8x8+partb8x8 -subq 7 -trellis 1 -refs 5 -coder 0 -me_range 16 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -bt 1200k -maxrate 1200k -bufsize 1200k -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 30 -aspect 4:3 -r 30 -g 90 -async 2 output.mp4

  I have tried different ffmpeg options to stream the video.In some options it works in Iphone and Safari browser in mac machine, but I didn't get an option for iPad.

  I want to stream an mp4 video for ipad, iPhone and mac safari. I also tried it with opensource segmenter .

  Have any solution for this ?

  Thanks,

  Riyas