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• Why I became a HTML5 co-editor

  15 août 2012, par silvia

  A few weeks ago, I had the honor to be appointed as part of the editorial team of the W3C HTML5 specification.

  Since Ian Hickson had recently decided to focus solely on editing the WHATWG HTML living standard specification, the W3C started looking for other editors to take the existing HTML5 specification to REC level. REC level is what other standards organizations call a “ratified standard”.

  But what does REC level really mean for HTML ?

  In my probably somewhat subjective view, recommendation level means that a snapshot is taken of the continuously evolving HTML spec, which has a comprehensive feature set, that is implemented in a cross-browser interoperable way, has a complete test set for the features, and has received wide review. The latter implies that other groups in the W3C have had a chance to look at the specification and make sure it satisfies their basic requirements, which include e.g. applicability to all users (accessibility, internationalization), platforms, and devices (mobile, TV).

  Basically it means that we stop for a “moment”, take a deep breath, polish the feature set that we’ve been working on this far, and make sure we all agree on it, before we get back to changing the world with cool new stuff. In a software project we would call it a release branch with feature freeze.

  Now, as productive as that may sound for software – it’s not actually that exciting for a specification. Firstly, the most exciting things happen when writing new features. Secondly, development of browsers doesn’t just magically stop to get the release (REC) happening. And lastly, if we’ve done our specification work well, there should be only little work to do. Basically, it’s the unthankful work of tidying up that we’re looking at here.

  So, why am I doing it ? I am not doing this for money – I’m currently part-time contracting to Google’s accessibility team working on video accessibility and this editor work is not covered by my contract. It wasn’t possible to reconcile polishing work on a specification with the goals of my contract, which include pushing new accessibility features forward. Therefore, when invited, I decided to offer my spare time to the W3C.

  I’m giving this time under the condition that I’d only be looking at accessibility and video related sections. This is where my interest and expertise lie, and where I’m passionate to get things right. I want to make sure that we create accessibility features that will be implemented and that we polish existing video features. I want to make sure we don’t digress from implementations which continue to get updated and may follow the WHATWG spec or HTML.next or other needs.

  I am not yet completely sure what the editorship will entail. Will we look at tests, too ? Will we get involved in HTML.next ? This far we’ve been preparing for our work by setting up adequate version control repositories, building a spec creation process, discussing how to bridge to the WHATWG commits, and analysing the long list of bugs to see how to cope with them. There’s plenty of actual text editing work ahead and the team is shaping up well ! I look forward to the new experiences.

• 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 ?