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• How would I assign multiple MMAP's from single file descriptor ?

  9 juin 2011, par Alex Stevens

  So, for my final year project, I'm using Video4Linux2 to pull YUV420 images from a camera, parse them through to x264 (which uses these images natively), and then send the encoded stream via Live555 to an RTP/RTCP compliant video player on a client over a wireless network. All of this I'm trying to do in real-time, so there'll be a control algorithm, but that's not the scope of this question. All of this - except Live555 - is being written in C. Currently, I'm near the end of encoding the video, but want to improve performance.

  To say the least, I've hit a snag... I'm trying to avoid User Space Pointers for V4L2 and use mmap(). I'm encoding video, but since it's YUV420, I've been malloc'ing new memory to hold the Y', U and V planes in three different variables for x264 to read upon. I would like to keep these variables as pointers to an mmap'ed piece of memory.

  However, the V4L2 device has one single file descriptor for the buffered stream, and I need to split the stream into three mmap'ed variables adhering to the YUV420 standard, like so...

  buffers[n_buffers].y_plane = mmap(NULL, (2 * width * height) / 3,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset);
  
  buffers[n_buffers].u_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 1) /
  
                                      sysconf(_SC_PAGE_SIZE));
  
  buffers[n_buffers].v_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 
  
                                      width * height / 6 + 1) / 
  
                                      sysconf(_SC_PAGE_SIZE));

  Where "width" and "height" is the resolution of the video (eg. 640x480).

  From what I understand... MMAP seeks through a file, kind of like this (pseudoish-code) :

  fd = v4l2_open(...);
  
  lseek(fd, buf.m.offset + (2 * width * height) / 3);
  
  read(fd, buffers[n_buffers].u_plane, width * height / 6);

  My code is located in a Launchpad Repo here (for more background) :
  http://bazaar.launchpad.net/ alex-stevens/+junk/spyPanda/files (Revision 11)

  And the YUV420 format can be seen clearly from this Wiki illustration : http://en.wikipedia.org/wiki/File:Yuv420.svg (I essentially want to split up the Y, U, and V bytes into each mmap'ed memory)

  Anyone care to explain a way to mmap three variables to memory from the one file descriptor, or why I went wrong ? Or even hint at a better idea to parse the YUV420 buffer to x264 ? :P

  Cheers ! ^^

• Piwik 2.10.0 – Release Candidate

  22 décembre 2014, par Piwik Core Team — Community

  We are proud to announce that the release candidate for Piwik 2.10.0 is now available !

  How do I upgrade to the release candidate ?

  You can upgrade to the release candidate in one click, by following instructions in this FAQ.

  Think you’ve found a bug ?

  Please create a bug report in our issue tracker.

  What’s new in Piwik 2.10.0 ?

  Since our last release Piwik 2.9.1 one month ago, over 100 issues have been closed. We’ve focused on fixing bugs, improving performance, and we created a new plugin that will let you better scale Piwik to very high traffic websites using Redis.

  Much improved Log Analytics

  Log Analytics is the powerful little-known feature of Piwik that lets you import dozens of different server logs into Piwik. In Piwik 2.10.0 you can now import Netscaler logs, IIS Advanced Logging Module logs, W3C extended logs and AWS CloudFront logs. Piwik will also automatically track the username as the User ID and/or the Page Generation Time when it is found in the server logs.

  Better scalability using Redis (advanced users)

  At Piwik PRO we are working on making Piwik scale when tracking millions of requests per month. In this release we have revamped the Tracking API. By using the new QueuedTracking plugin you can now queue tracking requests in a Redis database, which lets you scale the Piwik tracking service. The plugin is included as Free/libre software in the core Piwik platform. More information in the QueuedTracking user guide.

  Better performance

  A few performance challenges have been fixed in this release.

  The Visitor Log and the Live API will render much faster on very high traffic websites. Any custom date ranges that you have selected as default in your User Settings (eg. ‘Last 7 days’ or ‘Previous 30 days’) will now be pre-processed so that your analytics dashboard will always load quickly.

  For users on shared hosting, the real time widgets could be use a lot of server resource as they are refreshed every ten seconds. We’ve improved this by only requesting data when the Browser Tab containing the Real time widgets is active.

  Other changes

  We packed in many other changes in this release such as compatibility with Mysql 5.6 and Geo location support for IPv6 addresses. A community member made Piwik compatible with Internet Explorer 9 when running in compatibility mode (which is still used in several companies).

  The Tracker algorithm has been updated : when an existing visit uses a new Campaign then it will force creating a new visit (same behavior as Google Analytics).

  If you need professional support or guidance, get in touch with Piwik PRO.

  Changelog for Piwik 2.10.0 – we plan to release Piwik 2.10.0 around 2015 Jan 5th.

  Happy Analytics, and we wish you a nice holiday season !

• Piwik 2.10.0 – Release Candidate

  22 décembre 2014, par Piwik Core Team — Community

  We are proud to announce that the release candidate for Piwik 2.10.0 is now available !

  How do I upgrade to the release candidate ?

  You can upgrade to the release candidate in one click, by following instructions in this FAQ.

  Think you’ve found a bug ?

  Please create a bug report in our issue tracker.

  What’s new in Piwik 2.10.0 ?

  Since our last release Piwik 2.9.1 one month ago, over 100 issues have been closed. We’ve focused on fixing bugs, improving performance, and we created a new plugin that will let you better scale Piwik to very high traffic websites using Redis.

  Much improved Log Analytics

  Log Analytics is the powerful little-known feature of Piwik that lets you import dozens of different server logs into Piwik. In Piwik 2.10.0 you can now import Netscaler logs, IIS Advanced Logging Module logs, W3C extended logs and AWS CloudFront logs. Piwik will also automatically track the username as the User ID and/or the Page Generation Time when it is found in the server logs.

  Better scalability using Redis (advanced users)

  At Piwik PRO we are working on making Piwik scale when tracking millions of requests per month. In this release we have revamped the Tracking API. By using the new QueuedTracking plugin you can now queue tracking requests in a Redis database, which lets you scale the Piwik tracking service. The plugin is included as Free/libre software in the core Piwik platform. More information in the QueuedTracking user guide.

  Better performance

  A few performance challenges have been fixed in this release.

  The Visitor Log and the Live API will render much faster on very high traffic websites. Any custom date ranges that you have selected as default in your User Settings (eg. ‘Last 7 days’ or ‘Previous 30 days’) will now be pre-processed so that your analytics dashboard will always load quickly.

  For users on shared hosting, the real time widgets could be use a lot of server resource as they are refreshed every ten seconds. We’ve improved this by only requesting data when the Browser Tab containing the Real time widgets is active.

  Other changes

  We packed in many other changes in this release such as compatibility with Mysql 5.6 and Geo location support for IPv6 addresses. A community member made Piwik compatible with Internet Explorer 9 when running in compatibility mode (which is still used in several companies).

  The Tracker algorithm has been updated : when an existing visit uses a new Campaign then it will force creating a new visit (same behavior as Google Analytics).

  If you need professional support or guidance, get in touch with Piwik PRO.

  Changelog for Piwik 2.10.0 – we plan to release Piwik 2.10.0 around 2015 Jan 5th.

  Happy Analytics, and we wish you a nice holiday season !