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• Compiling tutorial programs on FFMPEG

  29 janvier 2012, par iwant2learn

  How do i compile the sample programs given in FFMPEG. i am not able to compile as i get
  error as CODEC_TYPE_VIDEO undeclared. Can any one please suggest me how to compile the programs. I am using ubuntu 11.

  This is the first example :

  $ gcc -o tutorial01 tutorial01.c -lavutil -lavformat -lavcodec -lz

  This is the output I got :

  tutorial01.c: In function ‘main’: tutorial01.c:77:3: warning: ‘dump_format’ is deprecated (declared at /usr/local/include/libavformat/avformat.h:1462)
  
  tutorial01.c:82:51: error: ‘CODEC_TYPE_VIDEO’ undeclared (first use in this function)
  
  tutorial01.c:82:51: note: each undeclared identifier is reported only once for each function it appears in

  Version info :

  ffmpeg version git-N-30430-ga52f598, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on May 31 2011 14:21:08 with gcc 4.5.2
  
    configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-x11grab
  
    libavutil    51.  3. 0 / 51.  3. 0
  
    libavcodec   53.  6. 1 / 53.  6. 1
  
    libavformat  53.  2. 0 / 53.  2. 0
  
    libavdevice  53.  1. 0 / 53.  1. 0
  
    libavfilter   2. 11. 0 /  2. 11. 0
  
    libswscale    0. 14. 0 /  0. 14. 0
  
    libpostproc  51.  2. 0 / 51.  2. 0

• YouTube's HD Video Streaming Server Technology ?

  30 septembre 2013, par bgentry

  Lately I've been researching different methods for streaming MP4s to the browser. Flash Media Server is an obvious choice here (using Cloudfront), and most solutions I've seen use the RTMP protocol.

  However, I spent some time on YouTube with Firebug and Chrome debugger figuring out how their streaming worked and I discovered some interesting differences between some of their videos and quality rates.

  My two sample videos are A and B. A is available up to 480p and B is available up to 1080p. For both videos, all rates up to 480p are served in an FLV container with H.264 video and AAC audio, over HTTP. What's interesting here is that if you have not yet downloaded (cached) the entire video, and you try to skip forward to an uncached part of the video, a new request will be made with a 'begin' parameter equal to the target offset in milliseconds. Example from Video A at 480p :

  http://v11.lscache8.c.youtube.com/videoplayback?ip=0.0.0.0&sparams=id%2Cexpire%2Cip%2Cipbits%2Citag%2Calgorithm%2Cburst%2Cfactor%2Coc%3AU0dWTldQVF9FSkNNNl9PSlhJ&fexp=904806%2C902906%2C903711&algorithm=throttle-factor&itag=35&ipbits=0&burst=40&sver=3&expire=1279756800&key=yt1&signature=D2D704D63C242CF187CAA5B5D5BAFB8DFACAC5FF.39180C01559C976717B651A7EB1D0C6249231EB7&factor=1.25&id=8568eb3135971f6f&begin=111863
  
  
  
  Response Headers:
  
  Cache-Control:public,max-age=23472
  
  Connection:close
  
  Content-Length:14320637
  
  Content-Type:video/x-flv
  
  Date:Wed, 21 Jul 2010 17:23:48 GMT
  
  Expires:Wed, 21 Jul 2010 23:55:00 GMT
  
  Last-Modified:Wed, 19 May 2010 12:31:41 GMT
  
  Server:gvs 1.0
  
  X-Content-Type-Options:nosniff

  The file returned by this URL is a fully valid FLV containing only the portion of the video after the requested offset.

  I did the same kind of test on the higher resolution versions of Video B. At 720p and 1080p, YouTube will return a video in an MP4 container, also with H.264 video and AAC audio. What's impressive to me is that their server takes the same type of offset for an MP4 video (via the 'begin' parameter) and returns a valid, streamable MP4 (moov atom at the front of the file with correct offsets) that also only includes the requested portion of the video.

  So, how does YouTube do this ? How do they generate the FLV or MP4 container on the fly with the correct headers and only the desired segment of the requested video ? I know this can be accomplished using FFMPEG to seek to the desired start point and the qt-faststart script to reposition the moov atom to the front of the stream, but it seems like this would be too slow to handle on-demand for millions of YouTube viewers.

  Ideas ?

  Thanks in advance !

  Footnote : I am not allowed to include more than 1 link at this point, so here is Video A's URL : http:// www.youtube .com/watch ?v=hWjrMTWXH28 "Video available up to 480p"

• Revision 55040 : Et toujours sur une idée trouvée sur ...

  1er décembre 2011, par real3t@… — Log

  Et toujours sur une idée trouvée sur ​http://www.ghacks.net/2011/11/30/embed-facebook-twitter-google-plus-without-javascript/ : la forme la plus basique de l’interaction sociale : imprimer la page.