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• Draw FFmpeg AVFrame data with OpenGL in Go

  27 avril 2018, par nevernew

  I’m making a video player in Go (on Windows) using FFmpeg and OpenGl, with the go wrappers goav and go-gl respectively. I want to set the pixels (stored in AVFrame->data) as a texture to display with OpenGL.

  I have it drawing pixels from a test array I created in Go, but it’s not taking the AVFrame data at all. The gl wrapper is giving me an error panic: reflect: call of reflect.Value.Pointer on uintptr Value with this code, I’ve tried different ways, trying to cast the data to the right type to be accepted but to no avail.

  This is the offending code where f is of type *Frame :

  type Frame C.struct_AVFrame
  
  
  
  dataPtr := (*uint8)(unsafe.Pointer((*C.uint8_t)(unsafe.Pointer(&f.data))))
  
  dataAddr := uintptr(unsafe.Pointer(dataPtr))
  
  
  
  glPixelPointer := gl.Ptr(dataAddr) // reflect error happens here, so the pointer is wrong

  Trying to get the data from this C struct :

  #include 
  
  
  
  typedef struct AVFrame {
  
  #define AV_NUM_DATA_POINTERS 8
  
      uint8_t *data[AV_NUM_DATA_POINTERS];
  
  }

  I can provide the rest of the code if needed, but there’s a lot of it to get the example running.

• Draw FFmpeg AVFrame data with OpenGL with Go

  27 avril 2018, par nevernew

  I’m making a video player in Go (on Windows) using FFmpeg and OpenGl, with the go wrappers goav and go-gl respectively. I want to set the pixels (stored in AVFrame->data) as a texture to display with OpenGL.

  I have it drawing pixels from a test array I created in Go, but it’s not taking the AVFrame data at all. The gl wrapper is giving me an error panic: reflect: call of reflect.Value.Pointer on uintptr Value with this code, I’ve tried different ways, trying to cast the data to the right type to be accepted but to no avail.

  This is the offending code where f is of type *Frame :

  type Frame C.struct_AVFrame
  
  
  
  dataPtr := (*uint8)(unsafe.Pointer((*C.uint8_t)(unsafe.Pointer(&f.data))))
  
  dataAddr := uintptr(unsafe.Pointer(dataPtr))
  
  
  
  glPixelPointer := gl.Ptr(dataAddr) // reflect error happens here, so the pointer is wrong

  Trying to get the data from this C struct :

  #include 
  
  
  
  typedef struct AVFrame {
  
  #define AV_NUM_DATA_POINTERS 8
  
      uint8_t *data[AV_NUM_DATA_POINTERS];
  
  }

  I can provide the rest of the code if needed, but there’s a lot of it to get the example running.

• Python stream H.264 data over socket

  9 janvier 2017, par Ezra Knobloch

  I am creating a H.264 encoded stream on my Raspberry using the tool ’raspivid’ and sending that stream to stdout.
  What i want is sending that stream to another computer and feed it to ffmpeg which in turn feeds it to MPlayer.

  When i do this using netcat and pipes it does work really good, i have a clean stream without any graphic bugs.

  I try to get the raspivid stdout over the subprocess module, see code below. Im more or less sure the problem lies somewhere there cause i did something similar a while back and it worked without many problems, and the only thing i did different now is using subprocess.

  My question is : does someone see what causes my problems ?

  Some Notes :

  • Using streamObj.get_data(pcktSize) did never work until now (MPlayer and ffmpeg cant open the stream)

  • process.stdout.readline() seems to be a bit faster than just read()

  • this code seems to be slower than just piping and netcat, how would i make it faster ? (while still using python)

  i need to write this sentence cause the code formatting below would be corrupted if i would not.

  import subprocess, socket, sys, time
  
  from thread import start_new_thread
  
  
  
  class streamObject:
  
      def __init__(self):
  
          global data
  
          data = ""
  
  
  
      def start_stream(self, rot, t, w, h, fps):
  
          global data
  
  
  
          process = subprocess.Popen(['/usr/bin/raspivid', '-rot', str(rot), '-t', str(t), '-w', str(w), '-h', str(h), '-fps', str(fps), '-o', '-'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
  
  
          nodata_counter = 0
  
  
  
          while 1:
  
              if process.poll() is None:
  
                  data += process.stdout.readline()
  
                  #data += process.stdout.read(256)
  
  
  
                  sys.stdout.write("buffered %i bytes.     \r" % len(data))
  
                  sys.stdout.flush()
  
              elif nodata_counter < 200:
  
                  nodata_counter += 1
  
  
  
                  time.sleep(0.1)
  
              else:
  
                  break
  
  
  
      def get_alldata(self):
  
          global data
  
  
  
          return data
  
  
  
      def get_data(self, data_len):
  
          global data
  
  
  
          if len(data) > data_len:
  
              temp = data[0:data_len]
  
              data = data[data_len:len(data)]
  
  
  
              return temp
  
          else:
  
              return None
  
  
  
      def clear_cache(self):
  
          global data
  
  
  
          data = ""
  
  
  
      def poll(self):
  
          global data
  
  
  
          try:
  
              if len(data) != 0:
  
                  return None
  
              else:
  
                  return 0
  
          except:
  
              return 0
  
  
  
  def socket_connect(ip, port):
  
      s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  
      s.connect((ip, port))
  
  
  
      return s
  
  
  
  def socket_listen(ip, port):
  
      s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  
      s.bind((ip, port))
  
      s.listen(1)
  
  
  
      conn, addr = s.accept()
  
  
  
      return conn
  
  
  
  def socket_close(sock):
  
      sock.close()
  
  
  
  def send_stream(sock, streamObj, pcktSize):
  
      timeout = 0
  
  
  
      while 1:
  
          if streamObj.poll() is None:
  
              #data = streamObj.get_data(pcktSize)
  
  
  
              data = streamObj.get_alldata()
  
              streamObj.clear_cache()
  
  
  
              if data is not None:
  
                  sock.send(data)
  
          elif timeout < 200:
  
              timeout += 1
  
  
  
              time.sleep(0.1)
  
          else:
  
              break
  
  
  
  stream = streamObject()
  
  
  
  start_new_thread(stream.start_stream, (180, 0, 1280, 720, 20))
  
  
  
  sock = socket_connect("xxxx.xxxx.xxxx.xxxx", 7777)
  
  
  
  send_stream(sock, stream, 256)

  Here is a short video of the graphic bugs i encounter.

  I am doing this over a direct ethernet connection at this time.