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• Why I became a HTML5 co-editor

  15 août 2012, par silvia

  A few weeks ago, I had the honor to be appointed as part of the editorial team of the W3C HTML5 specification.

  Since Ian Hickson had recently decided to focus solely on editing the WHATWG HTML living standard specification, the W3C started looking for other editors to take the existing HTML5 specification to REC level. REC level is what other standards organizations call a “ratified standard”.

  But what does REC level really mean for HTML ?

  In my probably somewhat subjective view, recommendation level means that a snapshot is taken of the continuously evolving HTML spec, which has a comprehensive feature set, that is implemented in a cross-browser interoperable way, has a complete test set for the features, and has received wide review. The latter implies that other groups in the W3C have had a chance to look at the specification and make sure it satisfies their basic requirements, which include e.g. applicability to all users (accessibility, internationalization), platforms, and devices (mobile, TV).

  Basically it means that we stop for a “moment”, take a deep breath, polish the feature set that we’ve been working on this far, and make sure we all agree on it, before we get back to changing the world with cool new stuff. In a software project we would call it a release branch with feature freeze.

  Now, as productive as that may sound for software – it’s not actually that exciting for a specification. Firstly, the most exciting things happen when writing new features. Secondly, development of browsers doesn’t just magically stop to get the release (REC) happening. And lastly, if we’ve done our specification work well, there should be only little work to do. Basically, it’s the unthankful work of tidying up that we’re looking at here.

  So, why am I doing it ? I am not doing this for money – I’m currently part-time contracting to Google’s accessibility team working on video accessibility and this editor work is not covered by my contract. It wasn’t possible to reconcile polishing work on a specification with the goals of my contract, which include pushing new accessibility features forward. Therefore, when invited, I decided to offer my spare time to the W3C.

  I’m giving this time under the condition that I’d only be looking at accessibility and video related sections. This is where my interest and expertise lie, and where I’m passionate to get things right. I want to make sure that we create accessibility features that will be implemented and that we polish existing video features. I want to make sure we don’t digress from implementations which continue to get updated and may follow the WHATWG spec or HTML.next or other needs.

  I am not yet completely sure what the editorship will entail. Will we look at tests, too ? Will we get involved in HTML.next ? This far we’ve been preparing for our work by setting up adequate version control repositories, building a spec creation process, discussing how to bridge to the WHATWG commits, and analysing the long list of bugs to see how to cope with them. There’s plenty of actual text editing work ahead and the team is shaping up well ! I look forward to the new experiences.

• Not able to configure FFserver for RTSP

  2 novembre 2015, par Sujith

  I am kind of new to the streaming world... so, please forgive me if I ask kind of dumb question.

  I am trying to stream my pre-recorded file over RTSP through FFserver.

  My config file is :

  RTSPPort 8544
  
  <feed>
  
      File /home/xyz/tmp/feed2.ffm
  
      FileMaxSize 200K
  
      ACL allow 127.0.0.1
  
  </feed>
  
  
  
  <stream>
  
      Feed feed2.ffm
  
      Format rtsp
  
      VideoFrameRate 15
  
      VideoSize 352x240
  
      VideoBitRate 256
  
      VideoBufferSize 40
  
      VideoGopSize 30
  
      AudioBitRate 64
  
      StartSendOnKey
  
  </stream>

  After starting the server, it give the below log :

  $ ./ffserver -f doc/ffserver.conf
  
  ffserver version 0.11.1 Copyright (c) 2000-2012 the FFmpeg developers
  
  built on Sep 17 2012 19:46:38 with gcc 4.1.2 20080704 (Red Hat 4.1.2-52)
  
  configuration: --enable-gpl --enable-libmp3lame --enable-libtheora --enable-libvo-aacenc 
  
  -enable-libvorbis --enable-libvpx --enable-libx264 --enable-version3
  
  libavutil 51. 54.100 / 51. 54.100
  
  libavcodec 54. 23.100 / 54. 23.100
  
  libavformat 54. 6.100 / 54. 6.100
  
  libavdevice 54. 0.100 / 54. 0.100
  
  libavfilter 2. 77.100 / 2. 77.100
  
  libswscale 2. 1.100 / 2. 1.100
  
  libswresample 0. 15.100 / 0. 15.100
  
  libpostproc 52. 0.100 / 52. 0.100
  
  Wed Sep 19 17:03:32 2012 FFserver started.

  And now from my VLC client I am trying to type the URL : rtsp ://xxx.xxx.xxx.xxx:8554/test.sdp

  But, what happens is that, there is no response on the ffserver.

  I have no clue what might be the problem. Thanks in advance.

• OpenCV VideoWriter using ffmpeg with "Could not open codec 'libx264'" Error

  19 avril, par user2262504

  I am new to OpenCV, and I want write Mat images into video using VideoWriter on Ubuntu 12.04. But when constructing VideoWriter, errors came out.

  



  It seems that OpenCV invoke ffmpeg API using default parameters and ffmpeg invoke x264 using its default parameters. Then these setting is broken for libx264. Thus the "Could not open codec 'libx264'" error.

  



  Anyone has ideas to solve this problem ?

  



  More specifically :

  



  

  1. anyone knows where and how OpenCV invoke ffmpeg API ?

  


  2. how to change ffmpeg default settings using code, hopefull, can be easily embeded into OpenCV ?

  


  3. will changes of default in ffmpeg be carried to libx264 ?

  


  



  Errors :

  



  1. Uising CV_FOURCC(&#x27;H&#x27;, &#x27;2&#x27;, &#x27;6&#x27;, &#x27;4&#x27;)&#xA;[libx264 @ 0x255de40] broken ffmpeg default settings detected&#xA;[libx264 @ 0x255de40] use an encoding preset (e.g. -vpre medium)&#xA;[libx264 @ 0x255de40] preset usage: -vpre <speed> -vpre <profile>&#xA;[libx264 @ 0x255de40] speed presets are listed in x264 --help&#xA;[libx264 @ 0x255de40] profile is optional; x264 defaults to high&#xA;Could not open codec &#x27;libx264&#x27;: Unspecified error&#xA;&#xA;2. Using FOURCC = -1 to invoke user customized codec&#xA;OpenCV Error: Unsupported format or combination of formats (Gstreamer Opencv &#xA;backend doesn&#x27;t support this codec acutally.) in CvVideoWriter_GStreamer::open, &#xA;file /home/XXX/Downloads/opencv-2.4.8/modules/highgui/src/cap_gstreamer.cpp, &#xA;line 505 terminate called after throwing an instance of &#x27;cv::Exception&#x27;&#xA;what():  /home/XXX/Downloads/opencv-2.4.8/modules/highgui/src/cap_gstreamer.cpp:&#xA;505: error: (-210) Gstreamer Opencv backend doesn&#x27;t support this codec acutally.&#xA;in function CvVideoWriter_GStreamer::open&#xA;</profile></speed>

  



  Codes :

  



  int main(int argc, char *argv[])
{
    VideoWriter outputVideo;
    bool fourcc_on = true; //switch on / off different error
    if (fourcc_on)
        outputVideo.open("outVideo.avi", CV_FOURCC('H', '2', '6', '4'), 25, Size(100, 100), true);
    else
        outputVideo.open("outVideo.avi", -1, 25, Size(100, 100), true);

    if (!outputVideo.isOpened())
    {
        cout  << "Could not open the output video for write" << endl;
        return -1;
    }
    return 0;
}


  



  OpenCV Configuration :

  



  -- Detected version of GNU GCC: 46 (406)
-- Found OpenEXR: /usr/lib/libIlmImf.so
-- Looking for linux/videodev.h
-- Looking for linux/videodev.h - not found
-- Looking for linux/videodev2.h
-- Looking for linux/videodev2.h - found
-- Looking for sys/videoio.h
-- Looking for sys/videoio.h - not found
-- Looking for libavformat/avformat.h
-- Looking for libavformat/avformat.h - found
-- Looking for ffmpeg/avformat.h
-- Looking for ffmpeg/avformat.h - not found
-- Could NOT find JNI (missing:  JAVA_INCLUDE_PATH JAVA_INCLUDE_PATH2 JAVA_AWT_INCLUDE_PATH) 
-- 
-- General configuration for OpenCV 2.4.8 =====================================
--   Version control:               unknown
-- 
--   Platform:
--     Host:                        Linux 3.8.0-38-generic x86_64
--     CMake:                       2.8.7
--     CMake generator:             Unix Makefiles
--     CMake build tool:            /usr/bin/make
--     Configuration:               RELEASE
-- 
--   C/C++:
--     Built as dynamic libs?:      YES
--     C++ Compiler:                /usr/bin/c++  (ver 4.6)
--     C++ flags (Release):         -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -O3 -DNDEBUG  -DNDEBUG
--     C++ flags (Debug):           -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -g  -O0 -DDEBUG -D_DEBUG
--     C Compiler:                  /usr/bin/gcc
--     C flags (Release):           -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -O3 -DNDEBUG  -DNDEBUG
--     C flags (Debug):             -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -g  -O0 -DDEBUG -D_DEBUG
--     Linker flags (Release):      
--     Linker flags (Debug):        
--     Precompiled headers:         YES
-- 
--   OpenCV modules:
--     To be built:                 core flann imgproc highgui features2d calib3d ml video legacy objdetect photo gpu ocl nonfree contrib python stitching superres ts videostab
--     Disabled:                    world
--     Disabled by dependency:      -
--     Unavailable:                 androidcamera dynamicuda java
-- 
--   GUI: 
--     QT:                          NO
--     GTK+ 2.x:                    YES (ver 2.24.10)
--     GThread :                    YES (ver 2.32.4)
--     GtkGlExt:                    NO
--     OpenGL support:              NO
-- 
--   Media I/O: 
--     ZLib:                        /usr/lib/x86_64-linux-gnu/libz.so (ver 1.2.3.4)
--     JPEG:                        /usr/lib/x86_64-linux-gnu/libjpeg.so (ver )
--     PNG:                         /usr/lib/x86_64-linux-gnu/libpng.so (ver 1.2.46)
--     TIFF:                        /usr/lib/x86_64-linux-gnu/libtiff.so (ver 42 - 3.9.5)
--     JPEG 2000:                   /usr/lib/x86_64-linux-gnu/libjasper.so (ver 1.900.1)
--     OpenEXR:                     /usr/lib/libImath.so /usr/lib/libIlmImf.so /usr/lib/libIex.so /usr/lib/libHalf.so /usr/lib/libIlmThread.so (ver 1.6.1)
-- 
--   Video I/O:
--     DC1394 1.x:                  NO
--     DC1394 2.x:                  YES (ver 2.2.0)
--     FFMPEG:                      YES
--       codec:                     YES (ver 55.58.105)
--       format:                    YES (ver 55.37.101)
--       util:                      YES (ver 52.78.100)
--       swscale:                   YES (ver 2.6.100)
--       gentoo-style:              YES
--     GStreamer:                   
--       base:                      YES (ver 0.10.36)
--       app:                       YES (ver 0.10.36)
--       video:                     YES (ver 0.10.36)
--     OpenNI:                      NO
--     OpenNI PrimeSensor Modules:  NO
--     PvAPI:                       NO
--     GigEVisionSDK:               NO
--     UniCap:                      NO
--     UniCap ucil:                 NO
--     V4L/V4L2:                    Using libv4l (ver 1.0.1)
--     XIMEA:                       NO
--     Xine:                        NO
-- 
--   Other third-party libraries:
--     Use IPP:                     NO
--     Use Eigen:                   NO
--     Use TBB:                     NO
--     Use OpenMP:                  NO
--     Use GCD                      NO
--     Use Concurrency              NO
--     Use C=:                      NO
--     Use Cuda:                    NO
--     Use OpenCL:                  YES
-- 
--   OpenCL:
--     Version:                     dynamic
--     Include path:                /home/shixudongleo/Downloads/opencv-2.4.8/3rdparty/include/opencl/1.2
--     Use AMD FFT:                 NO
--     Use AMD BLAS:                NO
-- 
--   Python:
--     Interpreter:                 /usr/bin/python (ver 2.7.3)
--     Libraries:                   /usr/lib/libpython2.7.so
--     numpy:                       /usr/lib/python2.7/dist-packages/numpy/core/include (ver 1.6.1)
--     packages path:               lib/python2.7/dist-packages
-- 
--   Java:
--     ant:                         NO
--     JNI:                         NO
--     Java tests:                  NO
-- 
--   Documentation:
--     Build Documentation:         NO
--     Sphinx:                      NO
--     PdfLaTeX compiler:           /usr/bin/pdflatex
-- 
--   Tests and samples:
--     Tests:                       YES
--     Performance tests:           YES
--     C/C++ Examples:              NO
-- 
--   Install path:                  /usr/local
-- 
--   cvconfig.h is in:              /home/shixudongleo/Downloads/opencv-2.4.8/build
-- -----------------------------------------------------------------
-- 
-- Configuring done
-- Generating done
-- Build files have been written to: /home/XXX/Downloads/opencv-2.4.8/build


  



  FFMPEG

  



  ffmpeg is enable to support OpenCV and libx264 is enabled when compiling ffmpeg.
By using ffmpeg command line, libx264 is running normally.

  



  $ ffmpeg -i test.avi -vcodec libx264 test.mp4
ffmpeg -i test.avi -vcodec libx264 test.mp4 > ~/Downloads/ffmpeg_log.txt
ffmpeg version 2.2.git Copyright (c) 2000-2014 the FFmpeg developers
  built on Apr 24 2014 16:39:51 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-nonfree --enable-postproc --enable-version3 --enable-x11grab --enable-shared --enable-pic
  libavutil      52. 78.100 / 52. 78.100
  libavcodec     55. 58.105 / 55. 58.105
  libavformat    55. 37.101 / 55. 37.101
  libavdevice    55. 13.100 / 55. 13.100
  libavfilter     4.  4.100 /  4.  4.100
  libswscale      2.  6.100 /  2.  6.100
  libswresample   0. 18.100 /  0. 18.100
  libpostproc    52.  3.100 / 52.  3.100
Input #0, avi, from 'test.avi':
  Duration: 00:00:03.73, start: 0.000000, bitrate: 1757 kb/s
    Stream #0:0: Video: msvideo1 (CRAM / 0x4D415243), rgb555le, 320x240, 1781 kb/s, 15 tbr, 15 tbn, 15 tbc
    Metadata:
      title           : julius.avi Video #1
File 'test.mp4' already exists. Overwrite ? [y/N] y
No pixel format specified, yuv444p for H.264 encoding chosen.
Use -pix_fmt yuv420p for compatibility with outdated media players.
[libx264 @ 0x25d08e0] using cpu capabilities: none!
[libx264 @ 0x25d08e0] profile High 4:4:4 Predictive, level 1.2, 4:4:4 8-bit
[libx264 @ 0x25d08e0] 264 - core 142 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=15 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'test.mp4':
  Metadata:
    encoder         : Lavf55.37.101
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv444p, 320x240, q=-1--1, 15360 tbn, 15 tbc
    Metadata:
      title           : julius.avi Video #1
Stream mapping:
  Stream #0:0 -> #0:0 (msvideo1 -> libx264)
Press [q] to stop, [?] for help
frame=   56 fps=0.0 q=-1.0 Lsize=     321kB time=00:00:03.60 bitrate= 731.0kbits/s    
video:320kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.409949%
[libx264 @ 0x25d08e0] frame I:3     Avg QP:15.36  size:  7975
[libx264 @ 0x25d08e0] frame P:38    Avg QP:26.05  size:  6230
[libx264 @ 0x25d08e0] frame B:15    Avg QP:28.25  size:  4418
[libx264 @ 0x25d08e0] consecutive B-frames: 46.4% 53.6%  0.0%  0.0%
[libx264 @ 0x25d08e0] mb I  I16..4:  1.4% 72.8% 25.8%
[libx264 @ 0x25d08e0] mb P  I16..4:  1.6%  5.7% 15.1%  P16..4:  7.6%  6.3%  7.4%  0.0%  0.0%    skip:56.3%
[libx264 @ 0x25d08e0] mb B  I16..4:  0.2%  1.0%  2.0%  B16..8: 13.3%  7.8%  8.7%  direct: 8.3%  skip:58.8%  L0:34.9% L1:36.6% BI:28.5%
[libx264 @ 0x25d08e0] 8x8 transform intra:37.7% inter:2.3%
[libx264 @ 0x25d08e0] coded y,u,v intra: 52.1% 42.1% 30.1% inter: 19.6% 9.2% 5.2%
[libx264 @ 0x25d08e0] i16 v,h,dc,p: 56% 17% 24%  2%
[libx264 @ 0x25d08e0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 10% 16% 68%  1%  1%  1%  1%  1%  1%
[libx264 @ 0x25d08e0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 18% 28%  5%  6%  5%  7%  5%  6%
[libx264 @ 0x25d08e0] Weighted P-Frames: Y:31.6% UV:21.1%
[libx264 @ 0x25d08e0] ref P L0: 70.5%  9.0% 12.1%  6.5%  2.0%
[libx264 @ 0x25d08e0] ref B L0: 91.3%  8.7%
[libx264 @ 0x25d08e0] kb/s:700.56