Sur d’autres sites (10791)

• Processing .Raw images using ffmpeg or OpenCV

  23 février 2013, par Ahmed Kato

  After reading Wikipedia page of Raw image format which is the digital negative of any image.

  To be viewed or printed, the output from a camera's image sensor has
  to be processed, that is, converted to a photographic rendering of the
  scene, and then stored in a standard raster graphics format such as
  JPEG. This processing, whether done in-camera or later in a raw-file
  converter, involves a number of operations, typically including

  I have some .raw files grabbed from my Logitech c920 using v4l2 example but when I display the image it looks like this :
  a raw image where in other frames I can see my shadow

  Does anyone knows how to process such files to see the complete frame ?

  Here is a link to the original .raw file

• How to play synchronised multichannel Audio and Video in a C# WPF application ?

  27 mars 2019, par AlexS

  I have video of approximate length 2 mins, and i need to be able to switch between audio streams accompanying the video during playback and even apply varying digital filtering and gain changes to the active audio stream during playback.

  NAudio can cope with the mutlichannel audio, filtering and switching between streams, but there is no support for synchronization with a video.

  How do programmers achieve synchronization, without embedding the audio into the video container directly ?

  Thanks

• How to analyse 404 pages

  1er juillet 2019, par Matomo Core Team — Development, Plugins

  How to analyse “not found” pages (404) in digital analytics

  Have you ever sent out a newsletter and one link wasn’t active yet ? Would you like to know how many users get affected when this happens ? Would you like to know if your visitors are encountering 404 pages ? 

  In this article we’re describing an easy way to analyse “not found” pages on your website with Matomo to increase your visitors’ user experience, user acquisition, and SEO (search engine optimization).

  How to know the number of 404s on my website ?

  There are different ways to get this information. Depending on how your website is built, you may or may not collect this data.

  The easiest way to answer this question is to fire a 404 page on your website, you do this by accessing a wrong url :

  

  As you can see here, in our case, the page title starts with “Page non trouvée” which stands for “Page not found” when translated in English (as the website we are considering here is in French) :

  

  In this example 19 page views have been fired and it generated a bounce rate of 67%. As a result ⅔ of the visits ended here.

  In some cases, the information related to a “not found” page can be found either within the title or within the URL, as some websites redirect you to a specific web page when a page can’t be found.

  If you can’t identify “not found” pages via a page title or a page URL, we strongly advise you to use this specific tracking code method on your 404 page : “How to track error pages in Matomo ?”. 

  You can easily set it with Matomo Tag Manager with a custom HTML tag :

  

  where the trigger is the following :

  

  You will however, have to define this trigger as an exclusion for all the other tags which may conflict with it (here below is the new trigger defined for the generic Matomo tags we are inserting on all pages) :

  

  Once this specific tracking is set, you will be able to track the source of the 404 and will gather all the “not found” pages in a specific group within your Page Title report :

  

  Here, for example, you can identify that the homepage of this website had a link pointing to a 404, in our case it was https://www.webassoc.org/pro-du-web.

  Note that this is just one technique. You could also create a custom dimension report and decide to send the 404 there also.

  How to get notified when a 404 page is visited ?

  Trust us, you’re not going to check everyday whether a 404 page has been visited. In order to avoid checking it manually, you can define custom alerts.

  There are three possible scenarios when “not found” pages can be fired :

  • internal 404 : one link within your website is pointing to a wrong url on the same website.
  • external 404 : someone from an external website made a link to yours and the link is not correct.
  • direct access 404 : someone access directly to a not found page on your website.

  You can define all those three within Matomo, but in your case, you will only have to focus on the first two only. In fact, you can’t really fix the third scenario. That’s the reason why we’re not focusing on it. It would result in irrelevant alerts.

  Custom alert for internal 404

  An internal 404 is defined from a 404 where the source is an internal web page. As a result, it will look like the following in your report :

  

  In this example, we’re using this specific custom implementation, the title of the page will contain “From = https://www.webassoc.org/”. So set our custom alert accordingly :

  

  Now every time a 404 page will be fired from an internal page, you’ll be notified by email.

  Note that you can also decide to not receive any email and track the evolution of alerts with the History of triggered alerts feature.

  Custom alert for external 404

  External 404 is almost the same setup. The only thing you need to keep in mind is that we want to exclude the 404 where the source is not indicated. As a result, your configuration will look like the following :

  

  Here your regular expression pattern is the following one :

  404/URL = .*From = (?!https://www.webassoc.org)[^\s]+

  as you’ll want to have any referrer coming from a website which is not Matomo and not a direct 404.

   

  You can now be notified every time that a 404 is fired from any link.

  Note that this configuration may slightly differ from website to website. So always double check your tracking code and the way the values are sent to your reports. Also try to trigger those alerts first before validating them.

  How to follow the evolution of your 404 over time ?

  It may be interesting to know how good or how bad you are performing in terms of 404.

  In order to check this information, you can click on the evolution icon near the 404 title :

  

  But you may be interested in accessing this information more regularly without having to create this report each time.

  So, one way to analyse the evolution of your 404 is to create a segment such as :

  

  and to click after that on evolution icon :

  

  As you can see below the number of “not found” pages is quite low in general, but we can also notice that a period received an increase in terms of 404 not found pages on May 27. It may be interesting to investigate it :

  

  You can start from the overview of referrers :

  

  As you can notice here the main source of 404 is coming from direct entries which is the most difficult channel to analyse as we don’t really know where the visitors are coming from.

  How to perform your analysis even faster ?

  As you can see analysing reports in Matomo in order to detect 404 pages is a time-consuming activity. In order to make it faster, you can already create a report about it within the Email reports feature with the following settings :

  • Segment : 404
  • Email schedule : never.
  • Visits summary and Page titles as selected report.

  You will then end up with a saved report listing all the URLs concerned :

  

  You can also have a look at the “Custom reports” premium feature.

  It will provide you with more flexibility. You will then be able to focus on the most important thing : the cause of 404.

  Good luck and happy analytics !