Recherche avancée

Sur d’autres sites (17430)

• VP8 for Real-time Video Applications

  15 février 2011, par noreply@blogger.com (John Luther)

  With the growing interest in videoconferencing on the web platform, it’s a good time to explore the features of VP8 that make it an exceptionally good codec for real-time applications like videoconferencing.

  VP8 Design History & Features

  Real-time applications were a primary use case when VP8 was designed. The VP8 encoder has features specifically engineered to overcome the challenges inherent in compressing and transmitting real-time video data.
  

  • Processor-adaptive encoding. 16 encoder complexity levels automatically (or manually) adjust encoder features such as motion search strategy, quantizer optimizations, and loop filtering strength.
  • Encoder can be configured to use a target percentage of the host CPU.
    Ability to measure the time taken to encode each frame and adjust encoder complexity dynamically to keep the encoding time per frame constant
  • Robust error recovery (packet retransmission, forward error correction, recovery frame/new keyframe requests)
  • Temporal scalability (i.e., a single video bitstream that can degrade as needed depending on a participant’s available bandwidth)
  • Highly efficient decoding performance on low-power devices. Conventional video technology has grown to a state of complexity where dedicated hardware chips are needed to make it work well. With VP8, software-based solutions have proven to meet customer needs without requiring specialized hardware.

  For a more information about real-time video features in VP8, see the slide presentation by WebM Project engineer Paul Wilkins (PDF file).

  Commercially Available Products

  Millions of people around the world have been using VP7/8 for video chat for years. VP8 is deployed in some of today’s most popular consumer videoconferencing applications, including Skype (group video calling), Sightspeed, ooVoo and Logitech Vid. All of these vendors are active WebM project supporters. VP8’s predecessor, VP7, has been used in Skype video calling since 2005 and is supported in the new Skype app for iPhone. Other real-time VP8 implementations are coming soon, including ooVoo, and VP8 will play a leading role in Google’s plans for real-time applications on the web platform.

  Real-time applications will be extremely important as the web platform matures. The WebM community has made significant improvements in VP8 for real-time use cases since our launch and will continue to do so in the future.

  John Luther is Product Manager of the WebM Project.

  

• The Mystery of the No such file or directory exception

  22 avril 2022, par JohnWick

  No idea what's going on here. Set a breakpoint after the for of loop in the following function. temp/concat.txt exists but the following exception is thrown :

  


  


  Uncaught Error Error : ffmpeg exited with code 1 : temp/concat.txt : No
such file or directory

  


  


  Outputting stderr gives a bit more info :

  


  


  [concat @ 000001e2e30124c0] Impossible to open
'temp/concat.txt#voiceover #funny #fall #lol.mp4' index.js:19
temp/concat.txt : No such file or directory

  


  


  And here is the contents of concat.txt, standard ffmpeg concat demuxer format :

  


  file '#voiceover #funny #fall #lol.mp4'
file 'part 2 repost 🙄 #fyp #funny @jordond262 @princemoonjq add my snap heroicdw333.mp4'
file 'This is my hair wet wet WOAHHH #GrowUpWithMe #fyp #foryoupage #love #funny #puppy #goldenretriever #cute #dog #wetwet.mp4'
file 'POV calling your friends when your 90#FootlongShuffle #GhostMode #funny #grandma  #fyp #halloween #collegegotmelike #tiktok #foryoupage.mp4'
file 'Sam Ki Singing Kaisi Lgi 😂😜 insta-samayranarula #foryou #trending #lockdown #queen_samayra #tiktokindia #funny #gharbaithoindia 🏠 #comedyindia.mp4'
file 'Reply to @juswa646  #fyp#funny #relatable.mp4'
file 'RaNdOm ViDeOs! #fy #fypシ #viral #meme #funny #xyzbca #funnyvideos #randomvideo.mp4'
file 'Reply to @bratzdoll.maya what should I do next 🙄 #fyp #foryoupage #leethe4th #memes #tall #funny #lol.mp4'
file 'Part 2 #fyp #foryou #viral #foryoupageofficiall #funny #trending.mp4'
file 'Lmfao 😂 (via @danibreezy01) #lmao #lmfao #funny #cousins #family #fyp #foryou #foryoupage.mp4'
file 'When you are a clumsy kitty #trend #joke #Khaleesi #funny #kittensoftiktok #foryou #fyp #foryoupage #cute #catsoftiktok.mp4'
file 'Tag That Friend That Always Be Falling Asleep 😂 #foryou #funny #fail #nap #sleep #pennsylvania #SHEINcares #viral #trending #meme #memes #foryoupage.mp4'
file '#funny #funnyvideos #girlfriend #crzy #Birdshit.mp4'
file 'He forgot he was a dog.                #dog #fyp #talkingdog #cute #pet #funny.mp4'
file 'Bad Day #part1 #badday #falling #funny #memes #viral #jokes #comedy #trending #fyp #foryou #share #likes #us #uk #xyzbca  #epic #pourtoi #fail #wee.mp4'
file 'I think he got offended ( #catsoftiktok #fyp #funny #catlover #MyJob #yellow #foryoupage.mp4'
file 'They took OFF today 🐶🤠🐶 #joshbutlertv #roxyandremi #funny #comedy #dogs #viral #memes.mp4'
file 'Had to make sure momma was there #funny #fyp #raccoons #love #bff #foryoupage #ThisorThatSBLV.mp4'
file 'That\'s not how you get out... #mysterymakers #escaperoom #foryou #fyp #crazystory #friends #funny #crazy #teammate.mp4'


  


  The function throwing the exception.

  


  async function makeCompilation(paths, outPath) {
  for (const filePath of paths) {
    await fs.appendFile(
      "temp/concat.txt",
      `file '${path.basename(filePath).replace("'", "\\'")}'${os.EOL}`
    );
  }
  return new Promise((resolve, reject) => {
    ffmpeg("temp/concat.txt")
      .inputOptions(["-f concat", "-safe 0"])
      .outputOption("-c copy")
      .on("stderr", (line) => console.log(line))
      .on("end", async () => {
        await fs.rm("temp/concat.txt");
        resolve();
      })
      .save(outPath);
  });
}


  


• Troll spirit

  15 juin 2013, par Mans — Law and liberty

  Last week’s announcements from the White House of steps being taken to begin fighting back against patent trolls, along with legislation passed in Vermont for the same purpose, are worthy of praise. Whether they prove effective or not, they are a sign of the problem finally having been recognised by the highest authorities. That said, only one aspect of the issue is addressed, that of non-practising entities or trolls. Little effort is being made to stymie troll-like behaviour from otherwise legitimate actors. While a stake is driven through the heart of the troll, its spirit remains free to roam the corporate world, and like a demon of darkness it possesses companies, compelling them to engage in the very practices we seek to eradicate.

  The demon

  The most damaging, when wielded by a troll, are those patents with vague or overly broad claims. These can easily be asserted against large numbers of alleged infringers, many of which likely choose to settle out of court rather than risk an expensive litigation process with uncertain outcome. Such negotiations are frequently subject to non-disclosure agreements prohibiting publication of details in any deals, or even the existence thereof. As a result, an accused has no way of assessing a fair price for a licence (assuming the patent is in fact valid), and the patent holder can thus extract from each would-be infringer precisely as much as they are willing or able to pay to avoid a lawsuit.

  At the root of this problem is the ease with which applications for the patents in question are granted. Given the volume of patent applications, it is hardly reasonable to demand a hugely more extensive examination process than currently takes place (although some improvements here are no doubt possible) ; after all, a speedy decision is in the best interest of all parties. The solution must evidently be found elsewhere.

  The exorcism

  An obvious cure to the problem is the abolishment of the patent system. As this is clearly not feasible today, more practical, albeit less effective, remedies must be sought. A few ideas follow.

  Make patent validity all or nothing

  Change the rules such that any claim being found invalid cancels the patent its entirety. With the full patent at stake in this manner, companies would be discouraged from gambling on frivolous claims and encouraged to conduct a more thorough background investigation before filing.

  Maintain a registry of licences

  Require that all patent licence agreements be filed in an open, easily searchable registry. This would hopefully increase fairness in licensing deals.

  Mandate reimbursement of licence fees for invalidated patents

  If a patent is challenged and found invalid, require that the owner reimburse any licence fees previously collected for the patent in question. Apart from being morally right, this could act as a deterrent to over-charging. The amount requested for a licence would likely be balanced against the risk of being made to pay it all back later, resulting in lower licence fees for low-confidence patents.

  These suggestions, alone or together, will not completely eradicate the problems of patent abuse. They are but small steps towards a more thorough overhaul of a system increasingly ill-suited to the nature and pace of modern technological development.