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• FFmpeg pan filter error when routing stereo audio to rear channels of 5.1 output

  13 avril, par MilkyTech

  I'm trying to mix a stereo commentary track into the rear surround channels of a 5.1 audio stream using FFmpeg on Windows 10. My goal is to lower the volume of the original 5.1 movie audio, then add the stereo commentary so it plays from the rear left and right speakers (SL and SR).

  


  I've already converted the commentary to EAC3 to match the main track's codec :

  


  ffmpeg -i "CastCommentary.m4a" -c:a eac3 -b:a 640k CastCommentary.eac3

  


  Then I tried mixing them like this (from within Command Prompt, not PowerShell or a batch file) :

  


  ffmpeg -i "Tropic.Thunder.2008.UNRATED.mkv" -i "CastCommentary.eac3" -filter_complex "[0:a:0]volume=0.4[aud1]; [1:a:0]pan=5.1:FL=0:FR=0:FC=0:LFE=0:SL=c0:SR=c1[cm_rear]; [aud1][cm_rear]amix=inputs=2[aout]" -map 0:v -map "[aout]" -map 0:s? -t 600 -c:v copy -c:s copy -c:a eac3 -b:a 640k "Tropic.Thunder.5.1.commentary.test.mkv"


  


  But I keep getting errors like :

  


  [fc#0 @ ...] Error applying option 'SL' to filter 'pan': Option not found
Error : Option not found


  


  Or :

  


  [Parsed_pan_1 @ ...] Expected in channel name, got ""


  


  Or even :

  


  Output channel layout 5.1 does not match the number of channels mapped 2.


  


  I’ve tried variations of the pan syntax :

  


  

  • pan=5.1:FL=0:FR=0:FC=0:LFE=0:SL=c0:SR=c1

  


  • pan=5.1|FL=0|FR=0|FC=0|LFE=0|SL=c0|SR=c1

  


  • Wrapping in single/double

  


  • quotes Escaping for CMD (no caret issues in current runs)

  


  


  Nothing seems to work.

  


  🎯 Goal :

  


  

  • Keep 5.1 audio from the original movie (volume lowered)

  


  • Add stereo commentary to SL and SR

  


  • Output a proper 5.1 EAC3 mix

  


  


  🔧 System :

  


  

  • Windows 10

  


  • FFmpeg version : [latest static build from ffmpeg.org]

  


  • Running in true Command Prompt (not PowerShell)

  


  • Source audio : 5.1 EAC3 from a .mkv, stereo .eac3 from .m4a

  


  


  What’s the correct filter_complex syntax to route a stereo track to the rear channels of a 5.1 layout using FFmpeg on Windows ? Am I missing something about pan, amix, or Windows quirks ?

  


• How (and Why) to Run a Web Accessibility Audit in 2024

  7 mai 2024, par Erin

  When most businesses design their websites, they primarily think about aesthetics, not accessibility. However, not everyone who visits your website has the same abilities or access needs. Eight percent of the US population has visual impairments.

  The last thing you want is to alienate website visitors with a bad experience because your site isn’t up to accessibility standards. (And with growing international regulation, risk fines or lawsuits as a result.)

  A web accessibility audit can help you identify and fix any issues for users with impaired vision, hearing or other physical disabilities. In this article, we’ll cover how to conduct such an audit efficiently for your website in 2024.

  What is a web accessibility audit ?

  A web accessibility audit is a way to evaluate the usability of your website for users with visual, auditory or physical impairments, as well as cognitive disabilities or neurological issues. The goal is to figure out how accessible your website is to each of these affected groups and solve any issues that come up.

  To complete an audit, you use digital tools and various manual accessibility testing processes to ensure your site meets modern web accessibility standards.

  Why is a web accessibility audit a must in 2024 ?

  For far too long, many businesses have not considered the experiences of those with disabilities. The growing frustrations of affected internet users have led to a new focus on web accessibility laws and enforcement.

  Lawsuits related to the ADA (Americans with Disabilities Act) reached all-time highs in 2023 — over 4,500 digital-related lawsuits were filed. The EU has also drawn up the European Accessibility Act (EAC), which goes into effect in June 2025.

  But at the end of the day, it’s not about accessibility legislation. It’s about doing right by people.

  

  This video by voice actor, YouTuber, and surfer Pete Gustin demonstrates why accessibility measures are so important. If buttons, navigation and content sections aren’t properly labelled, sight-impaired people who rely on speech-to-text to browse the web can’t comfortably interact with your site.

  And you’re worse off for it. You can lose some of your best customers and advocates this way. 

  With stronger enforcement of accessibility regulations in the US and new regulations coming into effect in the EU in 2025, the time to act is now. It’s not enough to “keep accessibility in mind” — you must take concrete steps to improve it.

  Who should lead a web accessibility audit ?

  Ideally, you want to hire a third-party web accessibility expert to lead the audit. They can guide you through multiple stages of manual accessibility testing to ensure your site meets regulations and user needs. 

  Experienced accessibility auditors are familiar with common pitfalls and can help you avoid them. They ensure you meet the legal requirements with proper solutions, not quick fixes.

  If this isn’t an option, find someone with relevant experience within your company. And involve someone with “skin in the game” in the process. Hire someone with visual impairments to usability test your site. Don’t just do automated tests or “put yourself in their shoes.” Make sure the affected users can use your site without issues.

  Automated vs. manual audits and the danger of shortcuts

  While there are automated audits, they only check for the bare minimum :

  • Do your images have alt tags ? (They don’t check if the alt tag is descriptive or just SEO junk text.)
  • Are clickable buttons identified with text for visually impaired users ?
  • Is your text size adjustable ?
  • Are your background and foreground colours accessible for colour-blind users ? Is there a sufficient contrast ratio ?

  

  They don’t dive into the user journey (and typically can’t access login-locked parts of your site). They can be a good starting point, but it’s a bad idea to rely completely on automated audits.

  They’ll miss more complex issues like :

  • Dynamic content and animated elements or videos that could put people with epilepsy at risk of seizures
  • A navigational flow that is unnecessarily challenging for users with impairments
  • Video elements without proper captions

  So, don’t rely too much on automated tests and audits. Many lawsuits for ADA infractions are against companies that think they’ve already solved the problem. For example, 30% of 2023 lawsuits were against sites that used accessibility overlays.

  Key elements of the Web Content Accessibility Guidelines (WCAG)

  The international standard for web accessibility is the Web Content Accessibility Guidelines (WCAG). In the most recent version, WCAG 2.2, there are new requirements for visual elements and focus and other updates.

  Here’s a quick overview of the key priorities of WCAG :

  

  Perceivable : Any user can read or listen to your site’s content

  The first priority is for any user to be able to perceive the actual content on your site. To be compliant, you need to make these adjustments and more :

  • Use text that scales with browser settings.
  • Avoid relying on colour contrasts to communicate something.
  • Ensure visual elements are explained in text.
  • Offer audio alternatives for things like CAPTCHA.
  • Form fields and interactive elements are properly named.

  Operable : Any user can navigate the site and complete tasks without issue

  The second priority is for users to navigate your website and complete tasks. Here are some of the main considerations for this section :

  • Navigation is possible through keyboard and text-to-speech interfaces.
  • You offer navigation tools to bypass repeated blocks of content.
  • Buttons are properly titled and named.
  • You give impaired users enough time to finish processes without timing out.
  • You allow users to turn off unnecessary animations (and ensure none include three flashes or more within one second).
  • Links have a clear purpose from their alt text (and context).

  Understandable : Any user can read and understand the content

  The third priority is making the content understandable. You need to communicate as simply and as clearly as possible. Here are a few key points :

  • Software can determine the default language of each page.
  • You use a consistent method to explain jargon or difficult terms.
  • You introduce the meaning of unfamiliar abbreviations and acronyms.
  • You offer tools to help users double-check and correct input.
  • The reading grade is not higher than grade 9. If it is, you must offer an alternative text with a lower grade.
  • Use consistent and predictable formatting and navigation.

  This intro to accessibility guidelines should help you see the wide range of potential accessibility issues. Accessibility is not just about screen readers — it’s about ensuring a good user experience for users with a wide range of disabilities.

  Note : If you’re not hiring a third-party expert for the manual accessibility audit, this introduction isn’t enough. You need to familiarise yourself with all 50 success criteria in WCAG 2.2.

  How to do your first web accessibility audit

  Ready to find and fix the accessibility issues across your website ? Follow the steps outlined below to do a successful accessibility audit.

  Start with an automated accessibility test

  To point you in the right direction, start with a digital accessibility checker. There are many free alternatives, including :

  • Accessibility Checker
  • Silktide accessibility checker
  • AAArdvark

  When choosing a tool, check it’s up-to-date with the newest accessibility guidelines. Many accessibility evaluation tools are still based on the WCAG 2.1 version rather than WCAG 2.2.

  The tool will give you a basic evaluation of the accessibility level of your site. A free report can quickly identify common issues with navigation, labelling, colour choices and more. 

  But this is only good as a starting point. Remember that even paid versions of these testing tools are limited and cannot replace a manual audit.

  Look for common issues

  The next step is to manually look for common issues that impact your site’s level of accessibility :

  • Undescriptive alt text
  • Colour combinations (and lack of ability to change background and foreground colours)
  • Unscalable text
  • Different site content sections that are not properly labelled

  The software you use to create your site can lead to many of these issues. Is your content management system (CMS) compliant with ADA or WCAG ? If not, you may want to move to a CMS before continuing the audit.

  Pinpoint customer journeys and test them for accessibility 

  After you’ve fixed common issues, it’s essential to put the actual customer journey to the test. Explore your most important journeys with behavioural analytics tools like session recordings and funnel analysis.

  Analysing funnel reports lets you quickly identify each page that usually contributes to a sale. You will also have an overview of the most popular funnels to evaluate for accessibility.

  If your current web analytics platform doesn’t offer behavioural reports like these, Matomo can help. Our privacy-friendly web analytics solution includes funnel reports, session recordings, A/B testing, form analytics, heatmaps and more.

  Try Matomo for Free

  Get the web insights you need, without compromising data accuracy.

  Start for free

  No credit card required

  If you don’t have the budget to test every page individually, this is the perfect place to start. You want to ensure that users with disabilities have no issues completing the main tasks on your site. 

  Don’t focus solely on your web pages 

  Accessibility barriers can also exist outside of your standard web pages. So ensure that other file formats like PDFs and videos are also accessible. 

  Remember that downloadable materials are also part of your digital experience. Always consider the needs of individuals with disabilities when accessing things like case studies or video tutorials. 

  Highlight high-priority issues in a detailed report

  To complete the audit, you need to summarise and highlight high-priority issues. In a larger company, this will be in the form of a report. W3’s Web Accessibility Initiative offers a free accessibility report template and an online tool to generate a report.

  For smaller teams, it may make sense to input issues directly into the product backlog or a task list. Then, you can tackle the issues, starting with high-priority pages identified earlier in this process.

  Avoid quick fixes and focus on sustainable improvement

  As mentioned, AI-powered overlay solutions aren’t compliant and put you at risk for lawsuits. It’s not enough to install a quick accessibility tool and pat yourself on the back.

  And it’s not just about accessibility compliance. These solutions provide a disjointed experience that alienates potential users. 

  The point of a digital accessibility audit is to identify issues and provide a better experience to all your users. So don’t try to cut corners. Do the work required to implement solutions that work seamlessly for everyone. Invest in a long-term accessibility remediation process.

  Deliver a frictionless experience while gaining insight into your users

  An accessibility audit is crucial to ensure an inclusive experience — that a wide variety of users can read and interact with your site.

  But what about the basic usability of your website ? Are you sure the experience is without friction ? Matomo’s behavioural analytics tools can show how users interact with your website.

  For example, heatmaps can show you where users are clicking — which can help you identify a pattern, like many users mistaking a visual element for a button.

  Plus, our privacy-friendly web analytics are compliant with GDPR, CCPA and other data privacy regulations. That helps protect you against privacy-related lawsuits, just as an accessibility audit protects you against ADA lawsuits.

  And it never hurts that your users know you respect their privacy. Try Matomo free for 21-days. No credit card required.

  Try Matomo for Free

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• 10 Key Google Analytics Limitations You Should Be Aware Of

  9 mai 2022, par Erin

  Google Analytics (GA) is the biggest player in the web analytics space. But is it as “universal” as its brand name suggests ?
  

  Over the years users have pointed out a number of major Google Analytics limitations. Many of these are even more visible in Google Analytics 4. 

  Introduced in 2020, Google Analytics 4 (GA4) has been sceptically received. As the sunset date of 1st, July 2023 for the current version, Google Universal Analytics (UA), approaches, the dismay grows stronger.

  To the point where people are pleading with others to intervene : 

  

  Main limitations of Google Analytics

  Google Analytics 4 is advertised as a more privacy-centred, comprehensive and “intelligent” web analytics platform. 

  According to Google, the newest version touts : 

  • Machine learning at its core provides better segmentation and fast-track access to granular insights 
  • Privacy-by-design controls, addressing restrictions on cookies and new regulatory demands 
  • More complete understanding of customer journeys across channels and devices 

  Some of these claims hold true. Others crumble upon a deeper investigation. Newly advertised Google Analytics capabilities such as ‘custom events’, ‘predictive insights’ and ‘privacy consent mode’ only have marginal improvements. 

  Complex setup, poor UI and lack of support with migration also leave many other users frustrated with GA4. 

  

  Let’s unpack all the current (and legacy) limitations of Google Analytics you should account for. 

  1. No Historical Data Imports 

  Google rushed users to migrate from Universal Analytics to Google Analytics 4. But they overlooked one important precondition — backwards compatibility. 

  You have no way to import data from Google Universal Analytics to Google Analytics 4. 

  Historical records are essential for analysing growth trends and creating benchmarks for new marketing campaigns. Effectively, you are cut short from past insights — and forced to start strategising from scratch. 

  At present, Google offers two feeble solutions : 

  • Run data collection in parallel and have separate reporting for GA4 and UA until the latter is shut down. Then your UA records are gone. 
  • For Ecommerce data, manually duplicate events from UA at a new GA4 property while trying to figure out the new event names and parameters. 

  Google’s new data collection model is the reason for migration difficulties. 

  In Google Analytics 4, all analytics hits types — page hits, social hits, app/screen view, etc. — are recorded as events. Respectively, the “‘event’ parameter in GA4 is different from one in Google Universal Analytics as the company explains : 

  

  This change makes migration tedious — and Google offers little assistance with proper events and custom dimensions set up. 

  2. Data Collection Limits 

  If you’ve wrapped your head around new GA4 events, congrats ! You did a great job, but the hassle isn’t over. 

  You still need to pay attention to new Google Analytics limits on data collection for event parameters and user properties. 

  

  These apply to :

  • Automatically collected events
  • Enhanced measurement events
  • Recommended events 
  • Custom events 

  When it comes to custom events, GA4 also has a limit of 25 custom parameters per event. Even though it seems a lot, it may not be enough for bigger websites. 

  You can get higher limits by upgrading to Google Analytics 360, but the costs are steep. 

  3. Limited GDPR Compliance 

  Google Analytics has a complex history with European GDPR compliance. 

  A 2020 ruling by the Court of Justice of the European Union (CJEU) invalidated the Privacy Shield framework Google leaned upon. This framework allowed the company to regulate EU-US data transfers of sensitive user data. 

  But after this loophole was closed, Google faced a heavy series of privacy-related fines :

  • French data protection authority, CNIL, ruled that  “the transfers to the US of personal data collected through Google Analytics are illegal” — and proceeded to fine Google for a record-setting €150 million at the beginning of 2022. 
  • Austrian regulators also deemed Google in breach of GDPR requirements and also branded the analytics as illegal. 

  Other EU-member states might soon proceed with similar rulings. These, in turn, can directly affect Google Analytics users, whose businesses could face brand damage and regulatory fines for non-compliance. In fact, companies cannot select where the collected analytics data will be stored — on European servers or abroad — nor can they obtain this information from Google.

  Getting a web analytics platform that allows you to keep data on your own servers or select specific Cloud locations is a great alternative. 

  Google also has been lax with its cookie consent policy and doesn’t properly inform consumers about data collection, storage or subsequent usage. Google Analytics 4 addresses this issue to an extent. 

  By default, GA4 relies on first-party cookies, instead of third-party ones — which is a step forward. But the user privacy controls are hard to configure without losing most of the GA4 functionality. Implementing user consent mode to different types of data collection also requires a heavy setup. 

  4. Strong Reliance on Sampled Data 

  To compensate for ditching third-party cookies, GA4 more heavily leans on sampled data and machine learning to fill the gaps in reporting. 

  In GA4 sampling automatically applies when you :

  • Perform advanced analysis such as cohort analysis, exploration, segment overlap or funnel analysis with not enough data 
  • Have over 10,000,000 data rows and generate any type of non-default report 

  Google also notes that data sampling can occur at lower thresholds when you are trying to get granular insights. If there’s not enough data or because Google thinks it’s too complex to retrieve. 

  In their words :

  

  Data sampling adds “guesswork” to your reports, meaning you can’t be 100% sure of data accuracy. The divergence from actual data depends on the size and quality of sampled data. Again, this isn’t something you can control. 

  Unlike Google Analytics 4, Matomo applies no data sampling. Your reports are always accurate and fully representative of actual user behaviours. 

  5. No Proper Data Anonymization 

  Data anonymization allows you to collect basic analytics about users — visits, clicks, page views — but without personally identifiable information (or PII) such as geo-location, assigns tracking ID or other cookie-based data. 

  This reduced your ability to :

  • Remarket 
  • Identify repeating visitors
  • Do advanced conversion attribution 

  But you still get basic data from users who ignored or declined consent to data collection. 

  By default, Google Analytics 4 anonymizes all user IP addresses — an upgrade from UA. However, it still assigned a unique user ID to each user. These count as personal data under GDPR. 

  For comparison, Matomo provides more advanced privacy controls. You can anonymize :

  • Previously tracked raw data 
  • Visitor IP addresses
  • Geo-location information
  • User IDs 

  This can ensure compliance, especially if you operate in a sensitive industry — and delight privacy-mindful users ! 

  6. No Roll-Up Reporting

  Getting a bird’s-eye view of all your data is helpful when you need hotkey access to main sites — global traffic volume, user count or percentage of returning visitors.

  With Roll-Up Reporting, you can see global-performance metrics for multiple localised properties (.co.nz, .co.uk, .com, etc,) in one screen. Then zoom in on specific localised sites when you need to. 

  

  7. Report Processing Latency 

  The average data processing latency is 24-48 hours with Google Analytics. 

  Accounts with over 200,000 daily sessions get data refreshes only once a day. So you won’t be seeing the latest data on core metrics. This can be a bummer during one-day promo events like Black Friday or Cyber Monday when real-time information can prove to be game-changing ! 

  Matomo processes data with lower latency even for high-traffic websites. Currently, we have 6-24 hour latency for cloud deployments. On-premises web analytics can be refreshed even faster — within an hour or instantly, depending on the traffic volumes. 

  8. No Native Conversion Optimisation Features

  Google Analytics users have to use third-party tools to get deeper insights like how people are interacting with your webpage or call-to-action.

  You can use the free Google Optimize tool, but it comes with limits : 

  • No segmentation is available 
  • Only 10 simultaneous running experiments allowed 

  There isn’t a native integration between Google Optimize and Google Analytics 4. Instead, you have to manually link an Optimize Container to an analytics account. Also, you can’t select experiment dimensions in Google Analytics reports.

  What’s more, Google Optimize is a basic CRO tool, best suited for split testing (A/B testing) of copy, visuals, URLs and page layouts. If you want to get more advanced data, you need to pay for extra tools. 

  Matomo comes with a native set of built-in conversion optimization features : 

  • Heatmaps 
  • User session recording 
  • Sales funnel analysis 
  • A/B testing 
  • Form submission analytics 

  

  9. Deprecated Annotations

  Annotations come in handy when you need to provide extra context to other team members. For example, point out unusual traffic spikes or highlight a leak in the sales funnel. 

  This feature was available in Universal Analytics but is now gone in Google Analytics 4. But you can still quickly capture, comment and share knowledge with your team in Matomo. 

  You can add annotations to any graph that shows statistics over time including visitor reports, funnel analysis charts or running A/B tests. 

  10. No White Label Option 

  This might be a minor limitation of Google Analytics, but a tangible one for agency owners. 

  Offering an on-brand, embedded web analytics platform can elevate your customer experience. But white label analytics were never a thing with Google Analytics, unlike Matomo. 

  Wrap Up 

  Google set a high bar for web analytics. But Google Analytics inherent limitations around privacy, reporting and deployment options prompt more users to consider Google Analytics alternatives, like Matomo. 

  With Matomo, you can easily migrate your historical data records and store customer data locally or in a designated cloud location. We operate by a 100% unsampled data principle and provide an array of privacy controls for advanced compliance. 

  Start your 21-day free trial (no credit card required) to see how Matomo compares to Google Analytics ! 

  21 day free trial. No credit card required.

  Your email address
  

  Your website address
  

  Your Analytics subdomain will be .matomo.cloud (change)

  Choose your analytics subdomain
  

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  I hereby accept the terms and conditions and the data processing agreeement (DPA).

  
  Your information will be used to create an account on our cloud service. For more information please consult our privacy policy.
  
  

  » Start improving your websites now