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• Capture Video with opencv, save to ffmpeg pipe and live stream

  9 mars 2018, par Chris

  The goal is to stream an analysed live video over RTSP to some media server. To make the edits/analysis I use opencv, save the edited frames as JPEG in an FFMPEG image pipe and use the same FFMPEG to create a RTSP stream. Sorry if the terminology is not that accurate, I find it still quite confusing.

  I have the following code after quite some struggle :

  import cv2
  
  from subprocess import Popen, PIPE
  
  from PIL import Image
  
  
  
  # open pipe
  
  p = Popen('ffmpeg -y -f image2pipe -vcodec mjpeg -r 24 -i - -vcodec h264 -f rtsp -rtsp_transport tcp rtsp://localhost:8081/test.sdp', stdin=PIPE)
  
  
  
  video = cv2.VideoCapture(0)
  
  i = 0
  
  while video.isOpened():
  
      i=i+1
  
      ret, frame = video.read()
  
      if ret:
  
          #[...do some analysis stuff]
  
          im = Image.fromarray(frame)
  
          im.save(p.stdin, 'JPEG')
  
  
  
          """
  
          alternatively
  
          img_str = cv2.imencode('.jpg', frame)[1].tostring()
  
          p.stdin.write(img_str)
  
          """
  
  
  
      else:
  
          break
  
  
  
      print (i)
  
      if(i==1000):
  
          break
  
  
  
  
  
  p.stdin.close()
  
  p.wait()
  
  video.release()
  
  cv2.destroyAllWindows()
  
  print("done streaming video")

  This runs for 124 frames (i=124) then the loop hangs and I get some message from ffmpeg where I am not sure what it is about, however it does not look like an error :

  push frame
  
  122
  
  push frame
  
  123
  
  push frame
  
  124
  
  Input #0, image2pipe, from 'pipe:':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 640x480 [SAR 1:1 DAR 4:3], 24 fps, 24 tbr, 24 tbn, 24 tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mjpeg (native) -> h264 (libx264))
  
  [libx264 @ 000002076650d980] using SAR=1/1
  
  [libx264 @ 000002076650d980] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
  
  [libx264 @ 000002076650d980] profile High, level 3.0
  
  [libx264 @ 000002076650d980] 264 - core 155 r2893 b00bcaf - H.264/MPEG-4 AVC codec - Copyleft 2003-2017 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=24 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  push frame

  The webcam seems to continue running but no more frames are pushed into the pipe. It looks like some buffer is filled or something. If I write directly to a video file instead of rtsp, it works. If I open the rtsp stream simultaneously with ffplay, it also works (although with a 5 seconds lag).
  Anyone an idea where this is coming from and how to solve it ?

• SDL save screenshot on iOS

  12 avril 2018, par Law Gimenez

  I am trying to save a screen or frame from the SDL’s "window" into a PNG file and so I’m using SDL_image library. My code is below

  IMG_Init(Int32(IMG_INIT_PNG.rawValue))
  
  let screenShot = SDL_CreateRGBSurface(0, 640, 480, 32, 0, 0, 0, 0)
  
  SDL_SetRenderTarget(renderer, texture)
  
  SDL_RenderReadPixels(renderer, nil, Uint32(SDL_PIXELFORMAT_ARGB8888), screenShot?.pointee.pixels, (screenShot?.pointee.pitch)!)
  
  let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
  
  IMG_SavePNG(screenShot, "\(documentsPath)/image.png")
  
  SDL_FreeSurface(screenShot)

  But the image.png was not saved. If anyone can lead or help me. Thank you !

  Additional code, the image saved is just black

  IMG_Init(Int32(IMG_INIT_PNG.rawValue))
  
  let screenShot = SDL_CreateRGBSurface(Uint32(SDL_SWSURFACE), 640, 480, 32, 0, 0, 0, 0)
  
  // SDL_SetRenderTarget(renderer, texture)
  
  SDL_RenderReadPixels(renderer, nil, Uint32(SDL_PIXELFORMAT_ARGB8888), screenShot?.pointee.pixels, (screenShot?.pointee.pitch)!)
  
  // Save to documents directory
  
  let fileManager = FileManager.default
  
  do {
  
      let documentDirectory = try fileManager.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
  
      let fileUrl = documentDirectory.appendingPathComponent("imageLOL.png")
  
      if !fileManager.fileExists(atPath: fileUrl.path) {
  
          print("File NO exists")
  
          // Create file at path
  
          let data = Data()
  
          let createFile = fileManager.createFile(atPath: fileUrl.path, contents: data, attributes: nil)
  
          if createFile {
  
              print("Create file success")
  
          } else {
  
              print("Create file failed")
  
          }
  
      } else {
  
          print("File exists")
  
  
  
      }
  
      let result = IMG_SavePNG(screenShot, fileUrl.path)
  
      print("result = \(result)")
  
      // After saving screenshot
  
      let image = UIImage(contentsOfFile: fileUrl.path)
  
      let imageData = UIImagePNGRepresentation(image!)
  
      print("image length = \(String(describing: imageData?.count))")
  
      UIImageWriteToSavedPhotosAlbum(image!, nil, nil, nil)
  
      SDL_FreeSurface(screenShot)
  
  } catch {
  
      print("Error docs = \(error)")
  
  }

• Video Filters like Instagram and save in SDCARD

  7 mai 2018, par Harsh Bhavsar

  Color Channel Mixer (Info.)
  https://ffmpeg.org/ffmpeg-filters.html#colorchannelmixer

  I am trying to creating video filters using FFMpeg and OpenCV just like Instagram Video filters.
  So if I want to create Sepia Effect Then I have to use color channel mixer for that with RGBA values
  ex. colorchannelmixer=.393 :.769 :.189:0 :.349 :.686 :.168:0 :.272 :.534 :.131 (This code for Sepia Effect)
  Now I want to create more effects like Instagram. So need different color channel mixers for that
  How to create them ?

  Ref. — https://github.com/krazykira/VidEffects/wiki/Permanent-video-effects

  I got only 2 filters

  Sepia
  colorchannelmixer=.393 :.769 :.189:0 :.349 :.686 :.168:0 :.272 :.534 :.131

  Grayscale
  colorchannelmixer=.3 :.4 :.3:0 :.3 :.4 :.3:0 :.3 :.4 :.3

  I need more filters.

  private void initVideoRecorder(String path) { 
  
  try { 
  
  filter = new F FmpegFrameFilter("colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131", VIDEO_GRABBER.getImageWidth(), VIDEO_GRABBER.getImageHeight()); 
  
  videoRecorder = FFmpegFrameRecorder.createDefault(path, VIDEO_GRABBER.getImageWidth(), VIDEO_GRABBER.getImageHeight()); videoRecorder.start(); 
  
  } 
  
  catch (FrameRecorder.Exception e) { 
  
  e.printStackTrace(); 
  
  }
  
   }