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• Record video with Xvfb + FFmpeg using Selenium in headless mode

  12 mars 2024, par ifdef14

  I am trying to record video using Selenium in headless mode. I am using Xvfb and FFmpeg bindings for Python. I've already tried :

  


  import subprocess
import threading
import time

from chromedriver_py import binary_path
from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from xvfbwrapper import Xvfb


def record_video(xvfb_width, xvfb_height, xvfb_screen_num):
    subprocess.call(
        [
            'ffmpeg',
            '-f',
            'x11grab',
            '-video_size',
            f'{xvfb_width}x{xvfb_height}',
            '-i',
            xvfb_screen_num,
            '-codec:v',
            'libx264',
            '-r',
            '12',
            'videos/video.mp4',
        ]
    )


with Xvfb() as xvfb:
    '''
    xvfb.xvfb_cmd[1]) returns scren num
    :217295622
    :319294854
    :
    '''
    xvfb_width, xvfb_height, xvfb_screen_num = xvfb.width, xvfb.height, xvfb.xvfb_cmd[1]
    thread = threading.Thread(target=record_video, args=(xvfb_width, xvfb_height, xvfb_screen_num))
    thread.start()
    opts = webdriver.ChromeOptions()
    opts.add_argument('--headless')
    try:
        driver = webdriver.Chrome(service=Service(executable_path=binary_path), options=opts)
    finally:
        driver.close()
        driver.quit()



  


  As much as I understand xvfb.xvfb_cmd[1] returns an information about virtual display isn't it ? When I executed this script, I got the error message :

  


  [x11grab @ 0x5e039cfe2280] Failed to query xcb pointer0.00 bitrate=N/A speed=N/A    
:1379911620: Generic error in an external library


  


  I also tried to use the following commands :

  


  xvfb-run --listen-tcp --server-num 1 --auth-file /tmp/xvfb.auth -s "-ac -screen 0 1920x1080x24" python main.py &

  


  ffmpeg -f x11grab -video_size 1920x1080 -i :1 -codec:v libx264 -r 12 videos/video.mp4

  


  In the commands above, there are used xvfb-run --server-num 1 and ffmpeg -i :1, why ?

  


  Overall, when Selenium is running in the headless mode what's going on behind the scenes ? Is it using virtual display ? If yes, how can I detect display id of this, etc. Am I on the right path ?

  


  I am not using Docker or any kind of virtualization. All kind of tests are running on my local Ubuntu machine.

  


• How to convert sequence of image file to video using c programming ?

  4 avril 2021, par Rahul Chandran

  I am working on a V4L2 camera driver.The webcam taking number of sequence of image files.Now I want to convert it into video (mp4) file.How it is possible using FFMPEG/GSTREAM using pure c source code instead of ubuntu terminal command ?

  


• avcodec : disallow hwaccel with frame threads

  23 octobre 2015, par Hendrik Leppkes

  avcodec : disallow hwaccel with frame threads
  HWAccels with frame threads are fundamentally flawed in avcodecs current
  
  design, and there are several known problems ranging from image corruption
  
  to driver crashes.
  These problems come down to two design problems in the interaction of
  
  threads and HWAccel decoding :
  (1)
  
  While avcodec prevents parallel decoding and as such simultaneous access
  
  to the hardware accelerator from the decoding threads, it cannot account
  
  for the user code and its access to the hardware surfaces and the hardware
  
  itself.
  This can result in image corruption or even driver crashes if the
  
  user code locks image surfaces while they are being used by the decoder
  
  threads as reference frames.
  The current HWAccel API does not offer any way to ensure exclusive access
  
  to the hardware or the surfaces if frame threading is used.
  (2)
  
  Initialization of the HWAccel with frame threads is non-trivial, and many
  
  decoders had and still have issues that cause excess calls to the
  
  get_format callback.
  This will potentially cause duplicate HWAccel initialization, which in
  
  extreme cases can even lead to driver crashes if the HWAccel is
  
  re-initialized while the user code is actively accessing the hardware
  
  surfaces associated with it, or lead to image corruption due to lost
  
  reference frames.
  While both of these issues are solvable, fixing (1) would at least require
  
  a huge API redesign which would move a lot of complexity into the user
  
  code.
  The only reason the combination of frame threads and HWAccel was
  
  considered useful is to allow a seamless fallback to multi-threaded
  
  software decoding if the HWAccel is not available, however the issues
  
  outlined above far outweigh this.
  The proper solution for a fallback is to re-open the AVCodecContext with
  
  threading enabled if the HWAccel failed, which is a practice commonly used
  
  by various user applications using avcodec today already.
  Reviewed-by : Gwenole Beauchesne <gb.devel@gmail.com>
  
  Reviewed-by : wm4 <nfxjfg@googlemail.com>
  
  Signed-off-by : Hendrik Leppkes <h.leppkes@gmail.com>
  

  • [DH] libavcodec/utils.c