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• How to check if video have visually corrupted frames ?

  1er février, par B Lolo

  I'm using ffmpeg to convert and analyze video, mostly avi to mkv. Sometimes video that I work on have one frame corrupted in random place, , it looks like :

  



  Digital scramble

  



  How to check if frame is visually corrupted in ffmpeg ?

  



  It's not file corruption (not byte corruption), I know that because this video artifact is present in source file, it's just visual corruption.

  



  This command line gives error free result : 
 ffmpeg -i myinput.avi params out.mkv 2> error_log.txt

  



  How to find if similar pattern is on any more frames in video file ? Can something from signalstats could be helpful ?

  


• How can I improve the up-time of my coffee pot live stream ?

  26 avril 2017, par tww0003

  Some Background on the Project :

  Like most software developers I depend on coffee to keep me running, and so do my coworkers. I had an old iPhone sitting around, so I decided to pay homage to the first webcam and live stream my office coffee pot.

  The stream has become popular within my company, so I want to make sure it will stay online with as little effort possible on my part. As of right now, it will occasionally go down, and I have to manually get it up and running again.

  My Setup :

  I have nginx set up on a digital ocean server (my nginx.conf is shown below), and downloaded an rtmp streaming app for my iPhone.

  The phone is set to stream to example.com/live/stream and then I use an ffmpeg command to take that stream, strip the audio (the live stream is public and I don’t want coworkers to feel like they have to be careful about what they say), and then make it accessible at rtmp://example.com/live/coffee and example.com/hls/coffee.m3u8.

  Since I’m not too familiar with ffmpeg, I had to google around and find the appropriate command to strip the coffee stream of the audio and I found this :
  

  ffmpeg -i rtmp://localhost/live/stream -vcodec libx264 -vprofile baseline -acodec aac -strict -2 -f flv -an rtmp://localhost/live/coffee

  Essentially all I know about this command is that the input stream comes from, localhost/live/stream, it strips the audio with -an, and then it outputs to rtmp://localhost/live/coffee.

  I would assume that ffmpeg -i rtmp://localhost/live/stream -an rtmp://localhost/live/coffee would have the same effect, but the page I found the command on was dealing with ffmpeg, and nginx, so I figured the extra parameters were useful.

  What I’ve noticed with this command is that it will error out, taking the live stream down. I wrote a small bash script to rerun the command when it stops, but I don’t think this is the best solution.

  Here is the bash script :

  while true;
  
  do
  
          ffmpeg -i rtmp://localhost/live/stream -vcodec libx264 -vprofile baseline -acodec aac -strict -2 -f flv -an rtmp://localhost/live/coffee
  
          echo 'Something went wrong. Retrying...'
  
          sleep 1
  
  done

  I’m curious about 2 things :

  1. What is the best way to strip audio from an rtmp stream ?
  2. What is the proper configuration for nginx to ensure that my rtmp stream will stay up for as long as possible ?

  Since I have close to 0 experience with nginx, ffmpeg, and rtmp streaming any help, or tips would be appreciated.

  Here is my nginx.conf file :

  worker_processes  1;
  
  
  
  events {
  
      worker_connections  1024;
  
  }
  
  
  
  
  
  http {
  
      include       mime.types;
  
      default_type  application/octet-stream;
  
  
  
      sendfile        on;
  
  
  
      keepalive_timeout  65;
  
  
  
      server {
  
          listen       80;
  
          server_name  localhost;
  
  
  
          location / {
  
              root   html;
  
              index  index.html index.htm;
  
          }
  
  
  
          error_page   500 502 503 504  /50x.html;
  
          location = /50x.html {
  
              root   html;
  
          }
  
  
  
          location /stat {
  
                  rtmp_stat all;
  
                  rtmp_stat_stylesheet stat.xsl;
  
                  allow 127.0.0.1;
  
          }
  
          location /stat.xsl {
  
                  root html;
  
          }
  
          location /hls {
  
                  root /tmp;
  
                  add_header Cache-Control no-cache;
  
          }
  
          location /dash {
  
                  root /tmp;
  
                  add_header Cache-Control no-cache;
  
                  add_header Access-Control-Allow-Origin *;
  
          }
  
      }
  
  }
  
  
  
  rtmp {
  
  
  
      server {
  
  
  
          listen 1935;
  
          chunk_size 4000;
  
  
  
          application live {
  
              live on;
  
  
  
              hls on;
  
              hls_path /tmp/hls;
  
  
  
              dash on;
  
              dash_path /tmp/dash;
  
          }
  
      }
  
  }

  edit :
  I’m also running into this same issue : https://trac.ffmpeg.org/ticket/4401

• The complete guide on tracking your websites and web apps into multiple Piwiks and how to do it easily & efficiently

  23 février 2017, par InnoCraft — Community, Development

  Getting the tracking of your website and apps right is crucial to your success as you need to ensure the measured data is meaningful and correct. That’s why we, at InnoCraft, help our clients setting up their web tracking and digital measurement strategy. Some challenges include tracking your analytics data into multiple Piwik services as well as the tracking of single-page websites and web applications (covered in a previous article). In this blog post, we explain how to track your data into multiple Piwik websites correctly.

  Embedding the tracking code

  First of all you need to embed your JavaScript tracking code into your website or app as usual. If you haven’t done this yet : Log in to your Piwik, click on “Administration” in the top right and go to “Tracking Code”. There you have various options to adjust your tracking code to your needs.

  Tracking the same data into different websites

  Let’s assume you have set up the regular JavaScript tracking code and you want to track the same data into a second Piwik website. This second Piwik website can be either on the same Piwik installation or on a different Piwik. To do this, add the following line to your tracking code :

  _paq.push(['addTracker', 'https://$yourPiwikDomain/piwik.php', idSite]);

  It should look like this :

  var u = '//$yourPiwikDomain';
  
  _paq.push(['addTracker', u + '/piwik.php', var idSite = 2]); // adds an additional tracker
  
  _paq.push(['setSiteId', '1']); // configures your regular Piwik tracker
  
  _paq.push(['setTrackerUrl', u + 'piwik.php']);

  This will track the same data into website 1 and website 2 of your Piwik installation. You can also change the domain in addTracker to point it to a different Piwik installation :

  _paq.push(['addTracker', '//$differentPiwikDomain/piwik.php', var idSite = 2]);

  All Piwik tracker methods that you call afterwards will be applied to all trackers. Say you call _paq.push(['disableCookies']); _paq.push(['trackPageView']);, then both methods will be called on all tracker instances assuring they will behave the same and will track the same data into both Piwik websites.

  Tracking different data into different websites

  If you want to track only certain data into one website, and different data into an additional website, you need to configure the trackers differently. For example, you want to enable link tracking only for one tracker, but not for the other. The problem is that calling _paq.push(['enableLinkTracking']); enables link tracking on all of your trackers. To workaround this limitation, you can configure your trackers differently like this :

  window.piwikAsyncInit = function () {
  
      Piwik.on('TrackerSetup', function (tracker) {
  
        if (tracker.getSiteId() == 2 
  
           || tracker.getTrackerUrl() === '//$yourPiwikDomain/piwik.php') {
  
            tracker.enableLinkTracking();
  
          }
  
      });
  
  };

  Now it enables link tracking only for the tracker that is configured for a certain website ID or Piwik domain.

  Accessing a previously generated tracker instance

  When you configure a tracker via _paq.push, you create a so called “Async tracker” because Piwik will be loaded asynchronously and create the tracker instance as soon as it is loaded. If you need to get the instance of such a tracker, you can use the method Piwik.getAsyncTracker(trackerUrl, idSite). This can be useful if you have a single-page website and want to track different data into different websites :

  window.addEventListener('hashchange', function() {
  
      if ('undefined' === typeof Piwik) {
  
          // Piwik might not be loaded yet
  
          return;
  
      }
  
      var tracker1 = Piwik.getAsyncTracker('//$yourPiwikDomain/piwik.php', var idSite = 1);
  
      var tracker2 = Piwik.getAsyncTracker('//$yourPiwikDomain/piwik.php', var idSite = 2);
  
      tracker1.setCurrentUrl('/' + window.location.hash.substr(1));
  
      tracker2.setCurrentUrl('/mywebsite/' + window.location.hash.substr(1));
  
  });

  Tracking different data into multiple Piwik installations without using “_paq”

  Some users prefer to not use _paq.push and instead directly create tracker instances themselves using the method Piwik.getTracker(trackerUrl, idSite) like this :

  window.piwikAsyncInit = function () {
  
      var tracker1 = Piwik.getTracker('//$yourPiwikdomain/piwik.php', var idSite = 1);
  
      tracker1.disableCookies();
  
      var tracker2 = Piwik.getTracker('//$yourPiwikdomain/piwik.php', var idSite = 2);
  
      tracker2.enableLinkTracking();
  
  
  
      tracker1.trackPageView();
  
      tracker2.trackPageView();
  
  };

  We usually don’t recommend creating trackers manually as it is more complicated and you need to make sure to configure trackers in the right order. For example to prevent the setting of any cookies, it is recommended to call disableCookies before calling any other methods. If you want to create your trackers manually and you use any of the following methods, make sure to call them in this order :

  disableCookies(), setAPIUrl(), enableCrossDomainLinking(), setCookiePath(), setCookieDomain(), setDomains(), setUserId(), enableLinkTracking()

  Roll-Up Reporting – the easy and efficient way

  Often users track data into multiple websites because they need aggregated data over all their websites. They want to see all statistics for a single website, but also which pages were viewed across all their websites, or how much traffic they got from a specific website or search engine across all websites. This means they add a second tracker to all their websites and track data not only into the regular Piwik website, but also into one additional website that gives them statistics over all websites. This has several disadvantages :

  • Complexity in getting the tracking code right and the time needed to integrate and maintain it
  • Slower website performance because everything needs to be tracked into several websites. This can decrease your conversions and sales
  • Slower Piwik performance because it has to handle twice as much traffic. This means tracking becomes slower, generating the report becomes slower, and the database gets twice as big

  Luckily, there is a better solution called Roll-Up Reporting. With Roll-Up Reporting, you can get aggregated data over all websites and / or for a group of websites without any of these disadvantages. It lets you create as many Roll-Ups as you wish and you can choose which websites’ data should be aggregated together into a new website.

  We had customers who were able to remove one Piwik tracker because of this feature which resulted in less server costs, a faster website, and a faster Piwik. On top of all these advantages, it also lets you view the Visitor Log, Real-time Map, and other widgets and reports across several websites.

  Questions ?

  If you got any questions, please let us know and get in touch with us. You can find more information about the Piwik JavaScript tracker on the Piwik Developer Zone. There is a section dedicated to Multiple Piwik Trackers.