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• Different ways of embedding the Piwik tracking code for faster website performance

  18 avril 2017, par InnoCraft — Community, Development

  Many studies have shown that performance matters a lot. For each 100ms a websites takes longer to load, a business may lose about 0.1% to 1% in revenue. It also matters because Google judges page speed as a ranking factor for search results page. At InnoCraft, we help our clients optimizing their Piwik integration and recommend different ways of embedding the tracking code tailored to their needs. The best way to embed the tracking code depends on your website, what you want to achieve, and how important tracking is to you.

  This technical blog post mainly focuses on improving the time to load your website. This is an important metric as for example Google usually measures the time it took to load a page. Many businesses therefore want to get to the page load event as quickly as possible.

  The regular way of embedding the tracking code

  By default, Piwik is embedded in the header or footer of your website. This is a sensible default. While it is loaded asynchronously and deferred, it still does delay the onload event. Depending on the performance of your Piwik, how fast your website loads, how your website’s resources are embedded, and other factors you may want to consider alternatives. Three of them I will introduce below.

  Embedding the tracker after the load event

  To ensure that your website will always load even if the Piwik server is un-available, you may want to load the tracking code only after the website is loaded like this :

  var _paq = _paq || [];
  
  _paq.push(["trackPageView"]);
  
  _paq.push(["enableLinkTracking"]);
  
  
  
  function embedTrackingCode() {
  
     var u="https://your.piwik.domain/";
  
     _paq.push(["setTrackerUrl", u+"piwik.php"]);
  
     _paq.push(["setSiteId", "1"]);
  
  
  
     var d=document, g=d.createElement("script"), s=d.getElementsByTagName("script")[0]; g.type="text/javascript";
  
     g.defer=true; g.async=true; g.src=u+"piwik.js"; s.parentNode.insertBefore(g,s);    
  
  }
  
  
  
  if (window.addEventListener) { 
  
      window.addEventListener("load", embedTrackingCode, false); 
  
  } else if (window.attachEvent) { 
  
      window.attachEvent("onload",embedTrackingCode); 
  
  } else {
  
      embedTrackingCode();
  
  }

  The downside is you won’t track all of your visitors because some will have already left your website by the time your website is fully loaded. Especially when you have a JavaScript-heavy website or when your website takes longer to load in general. To detect the load event correctly cross browser, you may want to use a library like jQuery.

  Delaying the tracking

  Another technique is to load the tracking with a little delay at the end of your website like this :

  setTimeout(function () {
  
      embedTrackingCode();
  
  }, 5);

  This time the tracking script will still track most of your visitors but does not slow down loading the rest of your website as much as it would do by default (at least perceived). In some cases, you will notice a performance improvement when looking at the “time to load” but it depends on your website.

  Not loading the JavaScript Tracker at all

  With Piwik you also have the option to not embed the tracking code into your websites at all and instead generate reports from the webserver logs using Piwik Log Analytics. This works very well but some data might not be available like the device resolution which can be only captured using JavaScript. On the bright side this solution also captures users with ad blockers or tracking blockers.

  Questions ?

  We invite you to test different ways to see what makes sense for you and how it affects your website performance as well as the perceived performance. If you have any questions, feel free to get in touch with us.

  Read on

  The last post in this series is Performance optimizations you can apply today to load the Piwik JavaScript tracker faster.

• Announcing the World’s Worst VP8 Encoder

  5 octobre 2010, par Multimedia Mike — Outlandish Brainstorms, VP8

  I wanted to see if I could write an extremely basic VP8 encoder. It turned out to be one of the hardest endeavors I have ever attempted (and arguably one of the least successful).

  Results
  I started with the Big Buck Bunny title image :

  
  
  

  And this is the best encoding that this experiment could yield :

  
  
  

  Squint hard enough and you can totally make out the logo. Pretty silly effort, I know. It should also be noted that the resultant .webm file holding that single 400×225 image was 191324 bytes. When FFmpeg decoded it to a PNG, it was only 187200 bytes.

  The Story
  Remember my post about a naive SVQ1 encoder ? Long story short, I set out to do the same thing with VP8. (I wanted to the same thing with VP3/Theora for years. But take a good look at what it would entail to create even the most basic bitstream. As involved as VP8 may be, its bitstream is absolutely trivial compared to VP3/Theora.)
  

  With the naive SVQ1 encoder, the goal was to create a minimally compliant SVQ1 encoded bitstream. For this exercise, I similarly hypothesized what it would take to create the most basic, syntactically correct VP8 bitstream with the least amount of effort. These are the overall steps I came up with :

  • Intra-only
  • Create a basic bitstream header that disables any extra features (no modification of default tables)
  • Use a static quantizer
  • Use intra 16×16 coding for each macroblock
  • Use vertical prediction for the 16×16 intra coding

  For coding each macroblock :

  • Subtract vertical predictor from each row
  • Perform forward transform on each 4×4 sub block
  • Perform forward WHT on luma plane DCT coefficients
  • Pack the coefficients into the bitstream via the Boolean encoder

  It all sounds so simple. But, like I said in the SVQ1 post, it’s all very much like carefully bootstrapping a program to run on a particular CPU, and the VP8 decoder serves as the CPU. I’m confident that I have the bitstream encoding correct because, at the very least, the decoder agrees precisely with the encoder about the numbers represented by those 0s and 1s.

  What’s Wrong ?
  Compromises were made for the sake of getting some vaguely recognizable image encoded in a minimally valid manner. One big stumbling block is that I couldn’t seem to encode an end of block (EOB) condition correctly. I then realized that it’s perfectly valid to just encode a lot of zero coefficients rather than signaling EOB. An encoding travesty, I know, and likely one reason that the resulting filesize is so huge.

  More drama occurred when I hit my first block that had all zeros. There were complications in that situation that I couldn’t seem to avoid. So I forced the first AC coefficient to be 1 in that case. Hey, the decoder liked it.

  As for the generally weird look of the decoded image, I’m thinking that could either be : A) an artifact of forcing 16×16 vertical prediction or ; or B) a mistake in the way that I transformed and predicted stuff before sending it to the decoder. The smart money is on a combination of both A and B.

  Then again, as the SVQ1 experiment demonstrated, I shouldn’t expect extraordinary visual quality when setting the bar this low (i.e., just getting some bag of bits that doesn’t make the decoder barf).

• avcodec/codec2utils : move the remaining avpriv functions to lavf

  26 octobre 2020, par James Almer

  avcodec/codec2utils : move the remaining avpriv functions to lavf
  They are only used by the codec2 demuxers.
  The symbols are kept around until the next major bump.
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavcodec/codec2utils.c
  • [DH] libavcodec/codec2utils.h
  • [DH] libavformat/codec2.c