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• WebRTC books – a brief review

  30 décembre 2013, par silvia

  I just finished reading Rob Manson’s awesome book “Getting Started with WebRTC” and I can highly recommend it for any Web developer who is interested in WebRTC.

  Rob explains very clearly how to create your first video, audio or data peer-connection using WebRTC in current Google Chrome or Firefox (I think it also now applies to Opera, though that wasn’t the case when his book was published). He makes available example code, so you can replicate it in your own Web application easily, including the setup of a signalling server. He also points out that you need a ICE (STUN/TURN) server to punch through firewalls and gives recommendations for what software is available, but stops short of explaining how to set them up.

  Rob’s focus is very much on the features required in a typical Web application :

  • video calls
  • audio calls
  • text chats
  • file sharing

  In fact, he provides the most in-depth demo of how to set up a good file sharing interface I have come across.

  Rob then also extends his introduction to WebRTC to two key application areas : education and team communication. His recommendations are spot on and required reading for anyone developing applications in these spaces.

  —

  Before Rob’s book, I have also read Alan Johnson and Dan Burnett’s “WebRTC” book on APIs and RTCWEB protocols of the HTML5 Real-Time Web.

  Alan and Dan’s book was written more than a year ago and explains that state of standardisation at that time. It’s probably a little out-dated now, but it still gives you good foundations on why some decisions were made the way they are and what are contentious issues (some of which still remain). If you really want to understand what happens behind the scenes when you call certain functions in the WebRTC APIs of browsers, then this is for you.

  Alan and Dan’s book explains in more details than Rob’s book how IP addresses of communication partners are found, how firewall holepunching works, how sessions get negotiated, and how the standards process works. It’s probably less useful to a Web developer who just wants to implement video call functionality into their Web application, though if something goes wrong you may find yourself digging into the details of SDP, SRTP, DTLS, and other cryptic abbreviations of protocols that all need to work together to get a WebRTC call working.

  —

  Overall, both books are worthwhile and cover different aspects of WebRTC that you will stumble across if you are directly dealing with WebRTC code.

• Live Streaming WebM with Wowza Server

  2 décembre 2010, par noreply@blogger.com (John Luther)

  Guest blogger Charlie Good is CTO and co-founder of Wowza Media Systems

  As a company, we at Wowza move fast and like to tinker. When WebM was announced in May, we saw it as a promising new approach to HTML5 video and decided to do an experiment with live WebM streaming over http.

  Adding WebM VP8 video and Vorbis audio to the other encoding formats that our server supported was easy (we designed the Wowza server to be codec-agnostic). We then created a WebMfile and implemented WebM HTTP streaming.

  We originally created the demo as a proof-of-concept for the IBC show in September, 2010 but have made it available to watch on our web site.

  The file is streamed live (more precisely, "pseudo-live") over http using the Wowza server-side publishing API (PDF). The result is very impressive ; playback starts fast and the VP8 image quality is fantastic.

  You will need a WebM-enabled browser or VLC media player 1.1.5 to view the live stream.

  If you’re interested in keeping up with Wowza’s WebM progress, visit Wowza Labs or drop us a note at info@wowzamedia.com.

  

• how to scale video using ffmpeg with -filter_complex

  7 juillet 2020, par JuraganFilm

  im trying to encode my video with watermark and subtitles , i and i have this codes that work for watermark and subtitles

  


  ffmpeg -hide_banner -i $video -i $TITLE.ass -loop 1 -i $WATERMARK -loop 1 -i $LOGO -filter_complex "[${videomap}]drawtext=text='${TEXT}':fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf:y=h-line_h-100:x=w-(t-${MARQUE})*w/15:y='10':enable='lt(mod(t\,1000)\,100)':fontcolor=orange:fontsize=${FONT}:shadowx=${SHADOWX}:shadowy=${SHADOWY},ass=$TITLE.ass[FID1];[FID1][2:v]overlay=10:${WATERMARKPOSITION}:repeatlast=0:enable='between(t,300,600)'[FID3];[3:v]fade=in:st=1200:d=1.6:alpha=1,fade=out:st=107998:d=1.6:alpha=1[FID6];[FID3][FID6]overlay=10:5:repeatlast=0:enable='between(t,1200,187922)'" -c:v libx264 -x264-params "no-deblock=0:ref=2:weightp=2:chroma_qp_offset=0:keyint=50:keyint_min=5:bframes=3:b_pyramid=1:b-adapt=2:subme=7:b_bias=0:direct=1:weightb=1:open_gop=0:scenecut=40::threads=7:lookahead_threads=1" -b:v 500k -minrate 500k -maxrate 600k -bufsize 1200k -pix_fmt yuv420p -preset ultrafast -profile:v baseline -level:v 3.0 -c:a copy -vf "scale=trunc(oh*a/2)*2:480:flags=bicubic" -use_editlist 0 -movflags faststart -metadata title="${INFOVID} - Visit us @ ${WEBSITE}" -strict -2 -f mp4 -y "${output}/$TITLE-480p.mp4"


  


  and now im trying to scale the video to 480p quality , i've tried using

  


  -vf "scale=trunc(oh*a/2)*2:480"


  


  and also add :flags=bicubic but still i got error .

  


  how to scale video with -filter_complex from those code above ?

  


  thank you before !