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• How can I use avformat_open_input function (ffmpeg)

  5 mai 2016, par johncarrie

  I have bought a HD HDMI to UVC device which has HDMI video source input and UVC for video output here.
  I connect it from laptop A (input source HDMI) to laptop B (output USB).
  I have installed Ubuntu 14.04 desktop on Laptop B and Win 8.1 on Laptop A.
  B also have ffmpeg, opencv and sdl library installed.
  My target is to capture video and audio from A via HD HDMI to UVC on B.
  So I have decided to use libav of ffmpeg.
  I saw this and used avformat_open_input function but this function returned error.
  I thought that the error was occurred because the second parameter of avformat_open_input (const char * url) was invalid.
  I know that the url should be like video:video device name:audio:audio card name.
  How can I indicate the device names ?

  Here’s the result of v4l2-ctl --list-devices command in terminal.

  HD WebCam (usb-0000:02:03.0-1):   
  
      /dev/video0
  
  HD TV CAM (usb-0000:03:00.0-2.1):   
  
      /dev/video1

  And the result of arecord -l in terminal.

  **** List of CAPTURE Hardware Devices ****  
  
  card 0: AudioPCI [Ensoniq AudioPCI], device 0: ES1371/1 [ES1371 DAC2/ADC]  
  
  Subdevices: 1/1  
  
  Subdevice #0: subdevice #0    
  
  card 1: CAM [HD TV CAM], device 0: USB Audio [USB Audio]    
  
  Subdevices: 1/1  
  
  Subdevice #0: subdevice #0  

  Thank you.

• ffmpeg : how to resample audio file

  9 juin 2021, par xrfang

  I need to convert a 44KHz stero m4a audio file to 22KHz mono mp3 VBR file, how can I do that with ffmpeg on linux terminal ? Thanks.

  


• Live stream is gets delayed while processing frame in opencv + python

  18 mars 2021, par Himanshu sharma

  I capture and process an IP camera RTSP stream in a OpenCV 4.4.0.46 on Ubuntu.
Unfortunately the processing takes quite a lot of time, roughly 0.2s per frame, and the stream quickly gets delayed.
Video file have to save for 5 min but by this delaying video file is saved for 3-4 min only.

  


  Can we process faster to overcome delays ?

  


  I have two IP camera which have two diffrent fps_rate(Camera 1 have 18000 and camera 2 have 20 fps)

  


  I am implementing this code in difference Ubuntu PCs

  


  

  • Python 3.8.5 (default, Jul 28 2020, 12:59:40) [GCC 9.3.0] on linux

  


  • Django==3.1.2

  


  • Ubuntu = 18.04 and 20.04

  


  • opencv-contrib-python==4.4.0.46

  


  • opencv-python==4.4.0.46

  


  


  input_stream = 'rtsp://'+username+':'+password+'@'+ip+'/user='+username+'_password='+password+'_channel=0channel_number_stream=0.sdp'
input_stream---> rtsp://admin:Admin123@192.168.1.208/user=admin_password=Admin123_channel=0channel_number_stream=0.sdp

input_stream---> rtsp://Admin:@192.168.1.209/user=Admin_password=_channel=0channel_number_stream=0.sdp

vs = cv2.VideoCapture(input_stream)
fps_rate = int(vs.get(cv2.CAP_PROP_FPS))
I have two IP camera which have two diffrent fps_rate(Camera 1 have 18000 and camera 2 have 20 fps)

video_file_name = 0
start_time = time.time()
while(True):
    ret, frame = vs.read()
    time.sleep(0.2)     # <= Simulate processing time (mask detection, face detection and many detection is hapning)


    ###  Start of  writing a video to disk          
    minute = 5  ## saving a file for 5 minute only then saving another file for 5 min
    second  = 60
    minite_to_save_video = int(minute) * int(second)


    # if we are supposed to be writing a video to disk, initialize
    if time.time() - start_time >= minite_to_save_video or  video_file_name == 0 :
        ## where H = heigth, W = width, C = channel 
        H, W, C = frame.shape
        
        print('time.time()-->',time.time(),'video_file_name-->', video_file_name,  ' #####')
        start_time = time.time()

        video_file_name = str(time.mktime(datetime.datetime.now().timetuple())).replace('.0', '')
        output_save_directory = output_stream+str(int(video_file_name))+'.mp4'


        fourcc = cv2.VideoWriter_fourcc(*'avc1')
        
        writer = cv2.VideoWriter(output_save_directory, fourcc,20.0,(W, H), True)

    # check to see if we should write the frame to disk
    if writer is not None:
        
        try:
            writer.write(frame)

        except Exception as e:
            print('Error in writing video output---> ', e)