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• lavc/ccaption_dec : check for bprint completeness outside the loop

  9 janvier 2016, par Clément Bœsch

  lavc/ccaption_dec : check for bprint completeness outside the loop
  

  • [DH] libavcodec/ccaption_dec.c

• 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

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  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.

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• Trying to create mp4 proxy from Sony RAW file using FFMPEG

  16 avril 2021, par Daniel Akerman

  I'm trying to create a viewable mp4 proxy file (MPEG-4 AVC with AAC LC audio) from a Sony RAW SQ mxf file.

  


  I was able to create an mp4 with a single track of audio but no video by using this :

  


  ffmpeg -i Raw.mxf -c:v libx264 -c:a aac -strict experimental Raw-test.mp4


  


  I have a Mac, using ffmpeg version 4.3.2

  


  This is the file I'm trying to convert:
File spec:
General
Complete name                            : Raw.mxf
Format                                   : MXF
Format version                           : 1.3
Format profile                           : OP-1a
Format settings                          : Closed / Complete
File size                                : 2.33 GiB
Duration                                 : 20 s 200 ms
Overall bit rate                         : 990 Mb/s
Encoded date                             : 2019-06-23 19:48:44.000
Writing application                      : Sony AXS 2.0.0.0.1
Writing library                          : Sony SC Platform 8.2.0.0.1

Video
ID                                       : 2
Format                                   : Sony RAW SQ
Format settings, wrapping mode           : Frame (D-10)
Codec ID                                 : 0E060D0302010100-0E06040102040201
Duration                                 : 20 s 200 ms
Bit rate                                 : 986 Mb/s
Width                                    : 4 096 pixels
Original width                           : 4 128 pixels
Height                                   : 2 160 pixels
Original height                          : 2 192 pixels
Display aspect ratio                     : 1.896
Frame rate                               : 25.000 FPS
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 4.457
Stream size                              : 2.32 GiB (100%)

Audio #1
ID                                       : 3
Format                                   : PCM
Format settings                          : Little
Format settings, wrapping mode           : Frame (AES)
Codec ID                                 : 0D01030102060300
Duration                                 : 20 s 200 ms
Bit rate mode                            : Constant
Bit rate                                 : 1 152 kb/s
Channel(s)                               : 1 channel
Sampling rate                            : 48.0 kHz
Frame rate                               : 25.000 FPS (1920 SPF)
Bit depth                                : 24 bits
Stream size                              : 2.77 MiB (0%)
Locked                                   : Yes

Audio #2
ID                                       : 4
Format                                   : PCM
Format settings                          : Little
Format settings, wrapping mode           : Frame (AES)
Codec ID                                 : 0D01030102060300
Duration                                 : 20 s 200 ms
Bit rate mode                            : Constant
Bit rate                                 : 1 152 kb/s
Channel(s)                               : 1 channel
Sampling rate                            : 48.0 kHz
Frame rate                               : 25.000 FPS (1920 SPF)
Bit depth                                : 24 bits
Stream size                              : 2.77 MiB (0%)
Locked                                   : Yes

Audio #3
ID                                       : 5
Format                                   : PCM
Format settings                          : Little
Format settings, wrapping mode           : Frame (AES)
Codec ID                                 : 0D01030102060300
Duration                                 : 20 s 200 ms
Bit rate mode                            : Constant
Bit rate                                 : 1 152 kb/s
Channel(s)                               : 1 channel
Sampling rate                            : 48.0 kHz
Frame rate                               : 25.000 FPS (1920 SPF)
Bit depth                                : 24 bits
Stream size                              : 2.77 MiB (0%)
Locked                                   : Yes

Audio #4
ID                                       : 6
Format                                   : PCM
Format settings                          : Little
Format settings, wrapping mode           : Frame (AES)
Codec ID                                 : 0D01030102060300
Duration                                 : 20 s 200 ms
Bit rate mode                            : Constant
Bit rate                                 : 1 152 kb/s
Channel(s)                               : 1 channel
Sampling rate                            : 48.0 kHz
Frame rate                               : 25.000 FPS (1920 SPF)
Bit depth                                : 24 bits
Stream size                              : 2.77 MiB (0%)
Locked                                   : Yes

Other #1
ID                                       : 1-Material
Type                                     : Time code
Format                                   : MXF TC
Frame rate                               : 25.000 FPS
Time code of first frame                 : 20:50:05:08
Time code settings                       : Material Package
Time code, striped                       : Yes

Other #2
ID                                       : 1-Source
Type                                     : Time code
Format                                   : MXF TC
Frame rate                               : 25.000 FPS
Time code of first frame                 : 20:50:05:08
Time code settings                       : Source Package
Time code, striped                       : Yes

Other #3
ID                                       : 7
Format                                   : Acquisition Metadata
Muxing mode                              : Ancillary data / RDD 18
Duration                                 : 20 s 200 ms
Frame rate                               : 25.000 FPS
CaptureGammaEquation_FirstFrame          : SceneLinear
MacroSetting_FirstFrame                  : Off
OpticalExtenderMagnification_FirstFrame  : 100%
LensAttributes_FirstFrame                : Unknown
AutoExposureMode_FirstFrame              : Manual
NeutralDensityFilterWheelSetting_FirstFr : Clear
ImageSensorDimensionEffectiveWidth_First : 24.003 mm
ImageSensorDimensionEffectiveHeight_Firs : 12.658 mm
CaptureFrameRate_FirstFrame              : 25.000 fps
ImageSensorReadoutMode_FirstFrame        : Progressive frame
ShutterSpeed_Angle_FirstFrame            : 180.0°
ShutterSpeed_Time_FirstFrame             : 1/50 s
CameraMasterGainAdjustment_FirstFrame    : 0.00 dB
ISOSensitivity_FirstFrame                : 1250
ElectricalExtenderMagnification_FirstFra : 100%
AutoWhiteBalanceMode_FirstFrame          : Preset
WhiteBalance_FirstFrame                  : 3200 K
CameraMasterBlackLevel_FirstFrame        : 3.0%
CameraAttributes_FirstFrame              : F55 101044
ExposureIndexofPhotoMeter_FirstFrame     : 1250
GammaForCDL_FirstFrame                   : Undefined
ASC_CDL_V12_FirstFrame                   : sR=1.0 sG=1.0 sB=1.0 oR=0.0 oG=0.0 oB=0.0 pR=1.0 pG=1.0 pB=1.0 sat=1.0
EffectiveMarkerCoverage_FirstFrame       : 4096x4096
EffectiveMarkerAspectRatio_FirstFrame    : 4096x2160
CameraProcessDiscriminationCode_FirstFra : 201
RawBlackCodeValue_FirstFrame             : 512
RawGrayCodeValue_FirstFrame              : 1504
RawWhiteCodeValue_FirstFrame             : 5472
MonitoringDescriptions_FirstFrame        : SonyProf2:LC-709typA
MonitoringBaseCurve_FirstFrame           : 0E06040101010408

Other #4
Type                                     : Time code
Format                                   : SMPTE TC
Muxing mode                              : SDTI
Frame rate                               : 25.000 FPS
Time code of first frame                 : 20:50:05:08


  


  I'm not sure which camera it is from, I only have the information extracted by MediaInfo that I included.

  


  The FFMEG log is:
$ ffmpeg -i /Users/Aker84150/Downloads/Raw.mxf -c:v libx264 -c:a aac -strict experimental /Users/Aker84150/Downloads/Raw-test.mp4ffmpeg version 4.3.2 Copyright (c) 2000-2021 the FFmpeg developers  built with Apple clang version 11.0.0 (clang-1100.0.33.17)  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.2_4 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox  libavutil      56. 51.100 / 56. 51.100  libavcodec     58. 91.100 / 58. 91.100  libavformat    58. 45.100 / 58. 45.100  libavdevice    58. 10.100 / 58. 10.100  libavfilter     7. 85.100 /  7. 85.100  libavresample   4.  0.  0 /  4.  0.  0  libswscale      5.  7.100 /  5.  7.100  libswresample   3.  7.100 /  3.  7.100  libpostproc    55.  7.100 / 55.  7.100[mxf @ 0x7f808f008800] could not resolve sub descriptor strong ref[mxf @ 0x7f808f008800] source track 2: stream 0, no descriptor found[mxf @ 0x7f808f008800] could not resolve sub descriptor strong ref    Last message repeated 4 times[mxf @ 0x7f808f008800] Could not find codec parameters for stream 0 (Video: none, none): unknown codecConsider increasing the value for the 'analyzeduration' and 'probesize' optionsGuessed Channel Layout for Input Stream #0.1 : monoGuessed Channel Layout for Input Stream #0.2 : monoGuessed Channel Layout for Input Stream #0.3 : monoGuessed Channel Layout for Input Stream #0.4 : monoInput #0, mxf, from '/Users/Aker84150/Downloads/Raw.mxf':  Metadata:    operational_pattern_ul: 060e2b34.04010101.0d010201.01010900    product_uid     : cede1604-8280-11de-8a39-08004678031c    uid             : e8f36160-95ef-11e9-83ab-08004632275a    generation_uid  : e8f3616a-95ef-11e9-b502-08004632275a    company_name    : Sony    product_name    : AXS     product_version : 2.0    application_platform: Sony SC Platform    modification_date: 2019-06-23T19:48:44.000000Z    material_package_umid: 0x060A2B340101010501010D43130000009CDA54D3578605DC080046020132275A    timecode        : 20:50:05:08  Duration: 00:00:20.20, start: 0.000000, bitrate: 990426 kb/s    Stream #0:0: Video: none, none, 25 tbr, 25 tbn, 25 tbc    Stream #0:1: Audio: pcm_s24le, 48000 Hz, mono, s32 (24 bit), 1152 kb/s    Metadata:      file_package_umid: 0x060A2B340101010501010D43130000009DDA54D3578605DC080046020132275A    Stream #0:2: Audio: pcm_s24le, 48000 Hz, mono, s32 (24 bit), 1152 kb/s    Metadata:      file_package_umid: 0x060A2B340101010501010D43130000009DDA54D3578605DC080046020132275A    Stream #0:3: Audio: pcm_s24le, 48000 Hz, mono, s32 (24 bit), 1152 kb/s    Metadata:      file_package_umid: 0x060A2B340101010501010D43130000009DDA54D3578605DC080046020132275A    Stream #0:4: Audio: pcm_s24le, 48000 Hz, mono, s32 (24 bit), 1152 kb/s    Metadata:      file_package_umid: 0x060A2B340101010501010D43130000009DDA54D3578605DC080046020132275A    Stream #0:5: Data: none    Metadata:      file_package_umid: 0x060A2B340101010501010D43130000009DDA54D3578605DC080046020132275A      data_type       : vbi_vanc_smpte_436MStream mapping:  Stream #0:1 -> #0:0 (pcm_s24le (native) -> aac (native))Press [q] to stop, [?] for helpOutput #0, mp4, to '/Users/Aker84150/Downloads/Raw-test.mp4':  Metadata:    operational_pattern_ul: 060e2b34.04010101.0d010201.01010900    product_uid     : cede1604-8280-11de-8a39-08004678031c    uid             : e8f36160-95ef-11e9-83ab-08004632275a    generation_uid  : e8f3616a-95ef-11e9-b502-08004632275a    company_name    : Sony    product_name    : AXS     product_version : 2.0    application_platform: Sony SC Platform    modification_date: 2019-06-23T19:48:44.000000Z    material_package_umid: 0x060A2B340101010501010D43130000009CDA54D3578605DC080046020132275A    timecode        : 20:50:05:08    encoder         : Lavf58.45.100    Stream #0:0: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp (24 bit), 69 kb/s    Metadata:      file_package_umid: 0x060A2B340101010501010D43130000009DDA54D3578605DC080046020132275A      encoder         : Lavc58.91.100 aacsize=     176kB time=00:00:20.20 bitrate=  71.3kbits/s speed=66.6x    video:0kB audio:171kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.619946%[aac @ 0x7f808f89a800] Qavg: 121.639


  


  Thanks