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• 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"

• How to solve libx264 not found when building ffmpeg-with-libx264-enabled for android ?

  6 mars 2012, par newentry

  i am trying build android-ffmpeg-x264 downloaded from git. Link https://github.com/halfninja/android-ffmpeg-x264

  After running ./config_make_everything.sh i am getting following error

  ERROR : libx264 not found

  If you think configure made a mistake, make sure you are using the latest
  version from Git. If the latest version fails, report the problem to the
  ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net.
  Include the log file "config.log" produced by configure as this will help
  solving the problem.

  <pre>
  
  Makefile:1: config.mak: No such file or directory
  
  libavutil/Makefile:1: libavutil/../config.mak: No such file or directory
  
  libavutil/../subdir.mak:96: warning: overriding commands for target `libavutil/&#39;
  
  libavutil/../subdir.mak:26: warning: ignoring old commands for target `libavutil/&#39;
  
  libavutil/../subdir.mak:96: warning: overriding commands for target `libavutil/&#39;
  
  libavutil/../subdir.mak:96: warning: ignoring old commands for target `libavutil/&#39;
  
  
  
  tests/Makefile:44: /tests/fate.mak: No such file or directory
  
  tests/Makefile:45: /tests/fate2.mak: No such file or directory
  
  tests/Makefile:47: /tests/fate/aac.mak: No such file or directory
  
  tests/Makefile:48: /tests/fate/als.mak: No such file or directory
  
  tests/Makefile:49: /tests/fate/fft.mak: No such file or directory
  
  tests/Makefile:50: /tests/fate/h264.mak: No such file or directory
  
  tests/Makefile:51: /tests/fate/mp3.mak: No such file or directory
  
  tests/Makefile:52: /tests/fate/vorbis.mak: No such file or directory
  
  tests/Makefile:53: /tests/fate/vp8.mak: No such file or directory
  
  make: *** No rule to make target `/tests/fate/vp8.mak&#39;.  Stop.
  
  </pre>

  config.log contains

  <pre>
  
      ratecontrol.c:(.text+0xa400): undefined reference to `memset&#39;
  
  ratecontrol.c:(.text+0xa41c): undefined reference to `memset&#39;
  
  ratecontrol.c:(.text+0xa448): undefined reference to `__aeabi_l2d&#39;
  
  ratecontrol.c:(.text+0xa49c): undefined reference to `__aeabi_ldivmod&#39;
  
  ratecontrol.c:(.text+0xa4a0): undefined reference to `__aeabi_l2d&#39;
  
  ratecontrol.c:(.text+0xa4f8): undefined reference to `__aeabi_idivmod&#39;
  
  ratecontrol.c:(.text+0xa794): undefined reference to `__aeabi_l2d&#39;
  
  ../x264/libx264.a(set.o): In function `x264_validate_levels&#39;:
  
  set.c:(.text+0x200): undefined reference to `__aeabi_ldivmod&#39;
  
  set.c:(.text+0x334): undefined reference to `__aeabi_idiv&#39;
  
  ../x264/libx264.a(set.o): In function `x264_sei_version_write&#39;:
  
  set.c:(.text+0xeec): undefined reference to `strlen&#39;
  
  set.c:(.text+0xf10): undefined reference to `memcpy&#39;
  
  set.c:(.text+0xf3c): undefined reference to `sprintf&#39;
  
  set.c:(.text+0xf44): undefined reference to `strlen&#39;
  
  ../x264/libx264.a(set.o): In function `scaling_list_write&#39;:
  
  set.c:(.text+0x20b0): undefined reference to `memcmp&#39;
  
  set.c:(.text+0x2138): undefined reference to `memcmp&#39;
  
  set.c:(.text+0x2158): undefined reference to `memcmp&#39;
  
  ../x264/libx264.a(set.o): In function `x264_pps_write&#39;:
  
  set.c:(.text+0x5870): undefined reference to `memcmp&#39;
  
  set.c:(.text+0x5a7c): undefined reference to `memcmp&#39;
  
  ../x264/libx264.a(set.o):set.c:(.text+0x5a9c): more undefined references to `memcmp&#39; follow
  
  ../x264/libx264.a(macroblock.o): In function `x264_noise_reduction_update&#39;:
  
  macroblock.c:(.text+0xe10): undefined reference to `__aeabi_uldivmod&#39;
  
  ../x264/libx264.a(macroblock.o): In function `x264_predict_lossless_8x8_chroma&#39;:
  
  macroblock.c:(.text+0x3224): undefined reference to `memcpy&#39;
  
  macroblock.c:(.text+0x323c): undefined reference to `memcpy&#39;
  
  ../x264/libx264.a(cabac.o): In function `x264_macroblock_write_cabac&#39;:
  
  cabac.c:(.text+0x2c58): undefined reference to `__assert2&#39;
  
  cabac.c:(.text+0x2dd8): undefined reference to `__assert2&#39;
  
  cabac.c:(.text+0x2f80): undefined reference to `__assert2&#39;
  
  cabac.c:(.text+0x3020): undefined reference to `__assert2&#39;
  
  ../x264/libx264.a(rectangle.o): In function `x264_macroblock_cache_ref_1_1&#39;:
  
  rectangle.c:(.text+0x1e4): undefined reference to `__assert2&#39;
  
  ../x264/libx264.a(rectangle.o):rectangle.c:(.text+0x210): more undefined references to `__assert2&#39; follow
  
  ERROR: libx264 not found
  
  </pre>

  1.I am using fedora to build both ffmpeg and x264
  2.NDK r7

  Any solution to successfully build the code ?

• getting very bad image after encoding

  20 avril 2012, par user1310596

  I am encoding images using avcodec_encode_video method and displaying them on subscriber demo of the Red5 media server.

  The problem i am facing is that all the images which are being displayed are totally distorted and nothing is clearly visible. I think something might be wrong with the pix_fmt set in avcodec context.
  Moreover image size is also quite large as 64000 bytes after encoding which I think is little weird
  Please give me solution of this problem. Any help is appreciated.