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• 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.

  

• Is it possible to merge two or more videos in real-time like this ?

  25 février 2015, par Marko

  Is it possible to play video online that’s made of two or more video files ?

  Since my original post wasn’t clear enough, here’s expanded explanation and question.

  My site is hosted on Linux/Apache/PHP server. I have video files in FLV/F4V format. I can also convert them to other available formats if necessary. All videos have same aspect ratio and other parameters.

  What I want is to build (or use if exist) online video player that plays video composed of multiple video files concatenated together in real-time, i.e. when user clicks to see a video.

  For example, visitor comes to my site and sees video titled "Welcome" available to play. When he/she clicks to play that video, I take video files "Opening.f4v", "Welcome.f4v" and "Ending.f4v" and join/merge/concatenate them one after another to create one continuous video on the fly.

  Resulting video looks like one video, with no visual clues, lags or even smallest observable delay between video parts. Basically what is done is some form of on-the-fly editing or pre-editing, and user sees the result. This resulting video is not saved on the server, it’s just composed and played that way real-time.

  Also, if possible, user shouldn’t be made to wait for this merging to be over before he/she sees resulting video, but to be able to get first part of the video playing immediately, while merging is done simultaneously.

  Is this possible with flash/actionscript, ffmpeg, html5 or some other online technology ? I don’t need explanation how it’s possible, just a nod that it’s possible and some links to further investigate.

  Also, if one option is to use flash, what are alternatives for making this work when site is visited from iphone/ipad ?

• Streaming video segments uploaded in real time

  3 avril 2013, par HaneTV

  I have an application that send quicktime video segments (5s) to a nodejs server that convert them into mpeg-ts in order to stream them to a wowza server in real time :

  ffmpeg -i tempPath -c copy -bsf:v h264_mp4toannexb -f mpegts uploadDir/file.ts

  I want to know if there is a way to stream those segments in real time as they come on my nodejs server to a wowza server without interruption (assuming I can get the segments in time).
  I tried an Http live streaming style by making a playlist like this (updated when segments are uploaded)

  #EXTM3U
  
  #EXT-X-PLAYLIST-TYPE:EVENT
  
  #EXT-X-TARGETDURATION:5
  
  #EXT-X-VERSION:3
  
  #EXT-X-MEDIA-SEQUENCE:0
  
  #EXTINF:5,
  
  movie0.ts
  
  #EXTINF:5,
  
  movie1.ts
  
  #EXTINF:5,
  
  movie2.ts

  And calling ffmpeg to send it to wowza :

  ffmpeg -re -i hls+file://mypath/uploadDir/playlist.m3u8 -c copy -f flv rtmp://127.0.0.1/live/stream

  but without any success : ffmpeg doesn't want to stream without #EXT-X-ENDLIST tag and removing the 'hls+' produces lots of errors st:0 PTS: 0 DTS: 0 < 4997 invalid, clipping

  Is there a way to accomplish that ?