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• scipy.io.wavfile.read() the stdout from FFmpeg

  28 février 2018, par PhuckMyLife

  After searching for a long time, I still cannot find the solution to use scipy.io.wavfile.read() to read the bytes from the stdout of FFmpeg 3.3.6.

  Here is the example code working perfectly. However, it needs to save a converted file to disk.

  import subprocess
  
  import scipy.io.wavfile as wavfile
  
  
  
  command = 'ffmpeg -i in.mp3 out.wav'
  
  subprocess.run(command)
  
  
  
  with open('out.wav', 'rb') as wf:
  
      rate, signal = wavfile.read(wf)
  
  
  
  print(rate, signal)

  And here is the code I try to get the FFmpeg output from stdout and load it into scipy wavfile.

  import io
  
  import subprocess
  
  import scipy.io.wavfile as wavfile
  
  
  
  command = 'ffmpeg -i in.mp3 -f wav -'
  
  proc = subprocess.run(command, stdout=subprocess.PIPE)
  
  
  
  rate, signal = wavfile.read(io.BytesIO(proc.stdout))
  
  
  
  print(rate, signal)

  Sadly, it raises a ValueError.

  Traceback (most recent call last):
  
    File ".\err.py", line 8, in <module>
  
      rate, signal = wavfile.read(io.BytesIO(proc.stdout))
  
    File "C:\Users\Sean Wu\AppData\Local\Programs\Python\Python36\lib\site-
  
  packages\scipy\io\wavfile.py", line 246, in read
  
      raise ValueError("Unexpected end of file.")
  
  ValueError: Unexpected end of file.
  
  </module>

  Are there any methods to solve this problem ?

• How to read h264 stream as a file from the USB webcam directly in c++ without using opencv ?

  6 mars 2018, par irobo

  I am able to read a video file of h264 format and doing some machine learning inference on top of it. The code works absolutely fine for input from a file. Below code is a sample code from Deepstream SDK

  FileDataProvider(const char *szFilePath, simplelogger::Logger *logger)
  
      : logger_(logger)
  
      {
  
           fp_ = fopen(szFilePath, "rb");
  
  
  
          //fp_ = fopen("/dev/video0", "rb");
  
  
  
  
  
          if (nullptr == fp_) {
  
              LOG_ERROR(logger, "Failed to open file " << szFilePath);
  
              exit(1);
  
          }
  
          pLoadBuf_ = new uint8_t[nLoadBuf_];
  
          pPktBuf_ = new uint8_t[nPktBuf_];
  
          assert(nullptr != pLoadBuf_);
  
      }
  
      ~FileDataProvider() {
  
          if (fp_) {
  
              fclose(fp_);
  
          }
  
          if (pLoadBuf_) {
  
              delete [] pLoadBuf_;
  
          }
  
          if (pPktBuf_) {
  
              delete [] pPktBuf_;
  
          }
  
      }

  What is requirement ?

  • Read from the Logitech c920 webcam instead for video file.
  • I know How to read from webcam using opencv. But I don’t want to use opencv here.

  My Research

  • Using v4l we can get the stream and display it in vlc.
  • Camera supports below formats.

  @ubox : $ v4l2-ctl —device=/dev/video1 —list-formats

  ioctl : VIDIOC_ENUM_FMT Index : 0 Type : Video Capture
  Pixel Format : ’YUYV’ Name : YUYV 4:2:2

  Index : 1 Type : Video Capture Pixel Format : ’H264’
  (compressed) Name : H.264

  Index : 2 Type : Video Capture Pixel Format : ’MJPG’
  (compressed) Name : Motion-JPEG

  • Reading output of a USB webcam in Linux
  • vlc v4l2:///dev/video1 --v4l2-chroma=h264 - this displays the video from the webcam.

  How to do this ?
   Now how to feed this live stream into
  above sample code such that it reads from the webcam rather than file ?

  [update-1]
   In otherwords, does v4l has some options to write the video stream as h264 formant ? So that, I can read that file like before(above code) when its(v4l) writing to disk.

  [update-2]
   we can use ffmpeg instead of v4c. If any solutions for using ffmpeg to save the video stream into disk continuously, so that other programs reads that file ?

• How to read h264 stream as a file from the USB webcam directly in c/c++ without using opencv ?

  23 novembre 2022, par ajayramesh

  I am able to read a video file of h264 format and doing some machine learning inference on top of it. The code works absolutely fine for input from a file. Below code is a sample code from Deepstream SDK

  



  FileDataProvider(const char *szFilePath, simplelogger::Logger *logger)
    : logger_(logger)
    {
         fp_ = fopen(szFilePath, "rb");

        //fp_ = fopen("/dev/video0", "rb");


        if (nullptr == fp_) {
            LOG_ERROR(logger, "Failed to open file " << szFilePath);
            exit(1);
        }
        pLoadBuf_ = new uint8_t[nLoadBuf_];
        pPktBuf_ = new uint8_t[nPktBuf_];
        assert(nullptr != pLoadBuf_);
    }
    ~FileDataProvider() {
        if (fp_) {
            fclose(fp_);
        }
        if (pLoadBuf_) {
            delete [] pLoadBuf_;
        }
        if (pPktBuf_) {
            delete [] pPktBuf_;
        }
    }


  



  What is requirement ?

  



  

  • Read from the Logitech c920 webcam instead for video file.

  


  • I know How to read from webcam using opencv. But I don't want to use opencv here.

  


  



  My Research

  



  

  • Using v4l we can get the stream and display it in vlc.

  


  • Camera supports below formats.

  


  



  


  @ubox : $ v4l2-ctl —device=/dev/video1 —list-formats

  
 


  ioctl : VIDIOC_ENUM_FMT Index : 0 Type : Video Capture
 Pixel Format : 'YUYV' Name : YUYV 4:2:2

  
 


  Index : 1 Type : Video Capture Pixel Format : 'H264'
 (compressed) Name : H.264

  
 


  Index : 2 Type : Video Capture Pixel Format : 'MJPG'
 (compressed) Name : Motion-JPEG

  


  



  

  • Reading output of a USB webcam in Linux

  


  • vlc v4l2:///dev/video1 --v4l2-chroma=h264 - this displays the video from the webcam.

  


  



  How to do this ?
- Now how to feed this live stream into
 above sample code such that it reads from the webcam rather than file ?

  



  [update-1]
- In otherwords, does v4l has some options to write the video stream as h264 formant ? So that, I can read that file like before(above code) when its(v4l) writing to disk.

  



  [update-2]
- we can use ffmpeg instead of v4l. If any solutions for using ffmpeg to save the video stream into disk continuously, so that other programs reads that file ?