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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.

• FFMPEG : merging multiple audio (MP3) and single image convert them into a video [on hold]

  9 décembre 2013, par user3027136

  I'm tired of searching for this problem. I have found 2 solutions here, but both work only partially.
  What I want to do is to convert all the MP3 inside a folder (if possible subfolders, too) to avi or anything else accepted by Youtube. I have created 2 .bat that should do this (according to the other threads here). They don't, one of them creates the avi without the image (black) and the other seems to capture the screen.
  Here they are.
  If you know about ffmpeg please point me to the right direction. Thank you.

  This one uses mp3info.exe - to be honest I have no idea what mp3info does, I just guess it finds the lenght of the song to be mathed later with the length of the video.

  @echo off
  
  for %%a in (*.mp3) do (
  
  for /f "delims=" %%b in ('mp3info.exe -p %%S "%%a"') do (
  
  ffmpeg -i "%%a" -loop 1 -r 1 -i "cover.jpg" -acodec copy "%%~na.mp4" -t %%b
  
  )
  
  )

  This seems more simple, runs faster but captures the screenshot and ignores the cover.jpg file.

  @echo off
  
  for %%A IN (*.mp3) DO ffmpeg -i "%%A" -i "cover.jpg" "%%A.mpg"
  
  done

  mp2info.exe, cover.jpeg and the .bat scripts are in the same folder with the .mp3 files.

• Batch convert MP3 and static image to AVI with FFMPEG

  8 décembre 2013, par user3027136

  I'm tired of searching for this problem. I have found 2 solutions here, but both work only partially.
  What I want to do is to convert all the MP3 inside a folder (if possible subfolders, too) to avi or anything else accepted by Youtube. I have created 2 .bat that should do this (according to the other threads here). They don't, one of them creates the avi without the image (black) and the other seems to capture the screen.
  Here they are.
  If you know about ffmpeg please point me to the right direction. Thank you.

  This one uses mp3info.exe - to be honest I have no idea what mp3info does, I just guess it finds the lenght of the song to be mathed later with the length of the video.

  @echo off
  
  for %%a in (*.mp3) do (
  
  for /f "delims=" %%b in ('mp3info.exe -p %%S "%%a"') do (
  
  ffmpeg -i "%%a" -loop 1 -r 1 -i "cover.jpg" -acodec copy "%%~na.mp4" -t %%b
  
  )
  
  )

  This seems more simple, runs faster but captures the screenshot and ignores the cover.jpg file.

  @echo off
  
  for %%A IN (*.mp3) DO ffmpeg -i "%%A" -i "cover.jpg" "%%A.mpg"
  
  done

  mp2info.exe, cover.jpeg and the .bat scripts are in the same folder with the .mp3 files.