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• writing mp4 file from binary string python

  29 juin 2019, par Irakli Mchedlishvili

  I have a Binary string of mp4 video file and want to convert it back to mp4 file, to get single frame out of there with openCV library

  import cv2
  
  import tempfile
  
  
  
  temp_path = tempfile.gettempdir()
  
  video_binary_string = 'AAAAIGZ0eXBpc29tAAACAGlzb21pc28yYXZjMW1wNDEAAAAIZnJlZQAQC0ttZGF0AQIUGRQmM...'
  
  
  
  with open(temp_path+'/video.mp4', 'wb') as wfile:
  
     wfile.write(video_binary_string)
  
  cap = cv2.VideoCapture(temp_path+'/video.mp4')
  
  success, frame = cap.read()
  
  
  
  print success
  
  >>> False

  If frame was read correctly, it would be True

  I understand that this is not the correct way of writing video file. I tried to do it with FFMPEG but I can’t understand it’s documentation.

  Please give an example with simple explanations how to convert binary string back to video, with this or other way.

• Playback of FFMPEG Audio Using NAudio Has Lots of Noise

  28 août 2018, par Hrethric

  I have a video that I’m trying to play back using the FFMPEG framework, and NAudio to playback the audio frames. The video plays back just fine, but when I play back the audio using a BufferedWaveProvider while the underlying audio sounds correct, it has a ton of static/noise. What’s important to note in the attached code is when the events fire off from the managed C++ class, a C# class receives the event and then grabs the latest relevant AVFrame data. This works flawlessly for video, but like I said, when I try to play back the audio I have a bunch of noise. For now I’ve hardcoded the NAudio WaveFormat settings, but they should match the video’s audio.

      ///////////////////////// C# /////////////////////////////
  
  
  
      // Gets the size of the data from the audio AVFrame (audioFrame->linesize[0])
  
      int size = _Decoder.GetAVAudioFrameSize();
  
  
  
      if (!once)
  
      {
  
          managedArray = new byte[size];
  
          once = true;
  
      }
  
  
  
      // Gets the data array from the audio AVFrame
  
      IntPtr data = _Decoder.GetAVAudioFrameData();
  
  
  
      Marshal.Copy(data, managedArray, 0, size);
  
  
  
      if (_waveProvider == null)
  
      {
  
          _waveProvider = new BufferedWaveProvider(new WaveFormat(44100, 16, 2));
  
          _waveOut.NumberOfBuffers = 2;
  
          _waveOut.DesiredLatency = 300;
  
          _waveOut.Init(_waveProvider);
  
          _waveOut.Play();
  
      }
  
  
  
      _waveProvider.AddSamples(managedArray, 0, size);
  
  
  
  
  
      //////////////////////// Managed C++ /////////////////////////
  
      while (_shouldRead)
  
      {
  
          // if we're not initialized, sleep
  
          if (!_initialized || !_FFMpegObject->AVFormatContextReady())
  
          {
  
              Thread::Sleep(READ_INIT_WAIT_TIME);
  
          }
  
          else if (_sequentialFailedReadCount > MAX_SEQUENTIAL_READ_FAILS)
  
          {
  
              // we've failed a lot and probably lost the stream, try to reconnect.
  
              _sequentialFailedReadCount = 0;
  
              _initialized = false;
  
              StartInitThread();
  
              Thread::Sleep(READ_INIT_WAIT_TIME << 1);
  
          }
  
          else // otherwise, try reading one AV packet 
  
          {
  
              if (_FFMpegObject->AVReadFrame())
  
              {
  
                  if (_FFMpegObject->GetAVPacketStreamIndex() == _videoStreamIndex)
  
                  {
  
                      _sequentialFailedReadCount = 0;
  
  
  
                      // decode the video packet
  
                      _frameLock->WaitOne();
  
                      frameFinished = _FFMpegObject->AVCodecDecodeVideo2();
  
                      _frameLock->ReleaseMutex();
  
  
  
                      if (frameFinished)
  
                      {
  
                          _framesDecoded++;
  
  
  
                          if (!_isPaused) // If paused and AFAP playback, just don't call the callback
  
                          {
  
                              FrameFinished(this, EventArgs::Empty);
  
  
  
                              Thread::Sleep((int)(1000 / (GetFrameRate() * _speed)));
  
                          }
  
                      }
  
                  }
  
                  else if (_FFMpegObject->GetAVPacketStreamIndex() == _audioStreamIndex)
  
                  {
  
                      // decode the audio packet.
  
                      _frameLock->WaitOne();
  
                      audioFrameFinished = _FFMpegObject->AVCodecDecodeAudio4();
  
                      _frameLock->ReleaseMutex();
  
  
  
                      if (audioFrameFinished)
  
                      {
  
                          if (!_isPaused) // If paused and AFAP playback, just don't call the callback
  
                          {
  
                              // Fire the event - leaving it up to video to do the sleeps -- not sure if that will work or not
  
                              AudioFrameFinished(this, EventArgs::Empty);
  
                          }
  
                      }
  
                  }
  
  
  
                  _FFMpegObject->AVFreeFramePacket();
  
  
  
              }
  
              else // failed to read an AV packet
  
              {
  
                  _sequentialFailedReadCount++;
  
                  _failedReadCount++;
  
                  Thread::Sleep(READ_FAILED_WAIT_TIME);
  
              }
  
          }
  
      }

• writting mp4 file from binary string python

  25 avril 2016, par Irakli Mchedlishvili

  I have a Binary string of mp4 video file and want to convert it back to mp4 file, to get single frame out of there with openCV library

  import cv2
  
  import tempfile
  
  
  
  temp_path = tempfile.gettempdir()
  
  video_binary_string = 'AAAAIGZ0eXBpc29tAAACAGlzb21pc28yYXZjMW1wNDEAAAAIZnJlZQAQC0ttZGF0AQIUGRQmM...'
  
  
  
  with open(temp_path+'/video.mp4', 'wb') as wfile:
  
     wfile.write(video_binary_string)
  
  cap = cv2.VideoCapture(temp_path+'/video.mp4')
  
  success, frame = cap.read()
  
  
  
  print success
  
  >>> False

  If frame was read correctly, it would be True

  I understand that this is not the correct way of writing video file. I tried to do it with FFMPEG but I can’t understand it’s documentation.

  Please give an example with simple explanations how to convert binary string back to video, with this or other way.