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• The use cases for a element in HTML

  1er janvier 2014, par silvia

  The W3C HTML WG and the WHATWG are currently discussing the introduction of a <main> element into HTML.

  The <main> element has been proposed by Steve Faulkner and is specified in a draft extension spec which is about to be accepted as a FPWD (first public working draft) by the W3C HTML WG. This implies that the W3C HTML WG will be looking for implementations and for feedback by implementers on this spec.

  I am supportive of the introduction of a <main> element into HTML. However, I believe that the current spec and use case list don’t make a good enough case for its introduction. Here are my thoughts.

  Main use case : accessibility

  In my opinion, the main use case for the introduction of <main> is accessibility.

  Like any other users, when blind users want to perceive a Web page/application, they need to have a quick means of grasping the content of a page. Since they cannot visually scan the layout and thus determine where the main content is, they use accessibility technology (AT) to find what is known as “landmarks”.

  “Landmarks” tell the user what semantic content is on a page : a header (such as a banner), a search box, a navigation menu, some asides (also called complementary content), a footer, …. and the most important part : the main content of the page. It is this main content that a blind user most often wants to skip to directly.

  In the days of HTML4, a hidden “skip to content” link at the beginning of the Web page was used as a means to help blind users access the main content.

  In the days of ARIA, the aria @role=main enables authors to avoid a hidden link and instead mark the element where the main content begins to allow direct access to the main content. This attribute is supported by AT – in particular screen readers – by making it part of the landmarks that AT can directly skip to.

  Both the hidden link and the ARIA @role=main approaches are, however, band aids : they are being used by those of us that make “finished” Web pages accessible by adding specific extra markup.

  A world where ARIA is not necessary and where accessibility developers would be out of a job because the normal markup that everyone writes already creates accessible Web sites/applications would be much preferable over the current world of band-aids.

  Therefore, to me, the primary use case for a <main> element is to achieve exactly this better world and not require specialized markup to tell a user (or a tool) where the main content on a page starts.

  An immediate effect would be that pages that have a <main> element will expose a “main” landmark to blind and vision-impaired users that will enable them to directly access that main content on the page without having to wade through other text on the page. Without a <main> element, this functionality can currently only be provided using heuristics to skip other semantic and structural elements and is for this reason not typically implemented in AT.

  Other use cases

  The <main> element is a semantic element not unlike other new semantic elements such as <header>, <footer>, <aside>, <article>, <nav>, or <section>. Thus, it can also serve other uses where the main content on a Web page/Web application needs to be identified.

  Data mining

  For data mining of Web content, the identification of the main content is one of the key challenges. Many scholarly articles have been published on this topic. This stackoverflow article references and suggests a multitude of approaches, but the accepted answer says “there’s no way to do this that’s guaranteed to work”. This is because Web pages are inherently complex and many <div>, <p>, <iframe> and other elements are used to provide markup for styling, notifications, ads, analytics and other use cases that are necessary to make a Web page complete, but don’t contribute to what a user consumes as semantically rich content. A <main> element will allow authors to pro-actively direct data mining tools to the main content.

  Search engines

  One particularly important “data mining” tool are search engines. They, too, have a hard time to identify which sections of a Web page are more important than others and employ many heuristics to do so, see e.g. this ACM article. Yet, they still disappoint with poor results pointing to findings of keywords in little relevant sections of a page rather than ranking Web pages higher where the keywords turn up in the main content area. A <main> element would be able to help search engines give text in main content areas a higher weight and prefer them over other areas of the Web page. It would be able to rank different Web pages depending on where on the page the search words are found. The <main> element will be an additional hint that search engines will digest.

  Visual focus

  On small devices, the display of Web pages designed for Desktop often causes confusion as to where the main content can be found and read, in particular when the text ends up being too small to be readable. It would be nice if browsers on small devices had a functionality (maybe a default setting) where Web pages would start being displayed as zoomed in on the main content. This could alleviate some of the headaches of responsive Web design, where the recommendation is to show high priority content as the first content. Right now this problem is addressed through stylesheets that re-layout the page differently depending on device, but again this is a band-aid solution. Explicit semantic markup of the main content can solve this problem more elegantly.

  Styling

  Finally, naturally, <main> would also be used to style the main content differently from others. You can e.g. replace a semantically meaningless <div id=”main”> with a semantically meaningful <main> where their position is identical. My analysis below shows, that this is not always the case, since oftentimes <div id=”main”> is used to group everything together that is not the header – in particular where there are multiple columns. Thus, the ease of styling a <main> element is only a positive side effect and not actually a real use case. It does make it easier, however, to adapt the style of the main content e.g. with media queries.

  Proposed alternative solutions

  It has been proposed that existing markup serves to satisfy the use cases that <main> has been proposed for. Let’s analyse these on some of the most popular Web sites. First let’s list the propsed algorithms.

  Proposed solution No 1 : Scooby-Doo

  On Sat, Nov 17, 2012 at 11:01 AM, Ian Hickson <ian@hixie.ch> wrote :
  | The main content is whatever content isn’t
  | marked up as not being main content (anything not marked up with <header>,
  | <aside>, <nav>, etc).
  

  This implies that the first element that is not a <header>, <aside>, <nav>, or <footer> will be the element that we want to give to a blind user as the location where they should start reading. The algorithm is implemented in https://gist.github.com/4032962.

  Proposed solution No 2 : First article element

  On Sat, Nov 17, 2012 at 8:01 AM, Ian Hickson  wrote :
  | On Thu, 15 Nov 2012, Ian Yang wrote :
  | >
  | > That’s a good idea. We really need an element to wrap all the <p>s,
  | > <ul>s, <ol>s, <figure>s, <table>s ... etc of a blog post.
  |
  | That’s called <article>.
  

  This approach identifies the first <article> element on the page as containing the main content. Here’s the algorithm for this approach.

  Proposed solution No 3 : An example heuristic approach

  The readability plugin has been developed to make Web pages readable by essentially removing all the non-main content from a page. An early source of readability is available. This demonstrates what a heuristic approach can perform.

  Analysing alternative solutions

  Comparison

  I’ve picked 4 typical Websites (top on Alexa) to analyse how these three different approaches fare. Ideally, I’d like to simply apply the above three scripts and compare pictures. However, since the semantic HTML5 elements <header>, <aside>, <nav>, and <footer> are not actually used by any of these Web sites, I don’t actually have this choice.

  So, instead, I decided to make some assumptions of where these semantic elements would be used and what the outcome of applying the first two algorithms would be. I can then compare it to the third, which is a product so we can take screenshots.

  Google.com

  http://google.com – search for “Scooby Doo”.

  The search results page would likely be built with :

  • a <nav> menu for the Google bar
  • a <header> for the search bar
  • another <header> for the login section
  • another <nav> menu for the search types
  • a <div> to contain the rest of the page
  • a <div> for the app bar with the search number
  • a few <aside>s for the left and right column
  • a set of <article>s for the search results

  “Scooby Doo” would find the first element after the headers as the “main content”. This is the element before the app bar in this case. Interestingly, there is a <div @id=main> already in the current Google results page, which “Scooby Doo” would likely also pick. However, there are a nav bar and two asides in this div, which clearly should not be part of the “main content”. Google actually placed a @role=main on a different element, namely the one that encapsulates all the search results.

  “First Article” would find the first search result as the “main content”. While not quite the same as what Google intended – namely all search results – it is close enough to be useful.

  The “readability” result is interesting, since it is not able to identify the main text on the page. It is actually aware of this problem and brings a warning before displaying this page :

  

  Facebook.com

  https://facebook.com

  A user page would likely be built with :

  • a <header> bar for the search and login bar
  • a <div> to contain the rest of the page
  • an <aside> for the left column
  • a <div> to contain the center and right column
  • an <aside> for the right column
  • a <header> to contain the center column “megaphone”
  • a <div> for the status posting
  • a set of <article>s for the home stream

  “Scooby Doo” would find the first element after the headers as the “main content”. This is the element that contains all three columns. It’s actually a <div @id=content> already in the current Facebook user page, which “Scooby Doo” would likely also pick. However, Facebook selected a different element to place the @role=main : the center column.

  “First Article” would find the first news item in the home stream. This is clearly not what Facebook intended, since they placed the @role=main on the center column, above the first blog post’s title. “First Article” would miss that title and the status posting.

  The “readability” result again disappoints but warns that it failed :

  

  YouTube.com

  http://youtube.com

  A video page would likely be built with :

  • a <header> bar for the search and login bar
  • a <nav> for the menu
  • a <div> to contain the rest of the page
  • a <header> for the video title and channel links
  • a <div> to contain the video with controls
  • a <div> to contain the center and right column
  • an <aside> for the right column with an <article> per related video
  • an <aside> for the information below the video
  • a <article> per comment below the video

  “Scooby Doo” would find the first element after the headers as the “main content”. This is the element that contains the rest of the page. It’s actually a <div @id=content> already in the current YouTube video page, which “Scooby Doo” would likely also pick. However, YouTube’s related videos and comments are unlikely to be what the user would regard as “main content” – it’s the video they are after, which generously has a <div id=watch-player>.

  “First Article” would find the first related video or comment in the home stream. This is clearly not what YouTube intends.

  The “readability” result is not quite as unusable, but still very bare :

  

  Wikipedia.com

  http://wikipedia.com (“Overscan” page)

  A Wikipedia page would likely be built with :

  • a <header> bar for the search, login and menu items
  • a <div> to contain the rest of the page
  • an &ls ; article> with title and lots of text
  • <article> an <aside> with the table of contents
  • several <aside>s for the left column

  Good news : “Scooby Doo” would find the first element after the headers as the “main content”. This is the element that contains the rest of the page. It’s actually a <div id=”content” role=”main”> element on Wikipedia, which “Scooby Doo” would likely also pick.

  “First Article” would find the title and text of the main element on the page, but it would also include an <aside>.

  The “readability” result is also in agreement.

  

  Results

  In the following table we have summarised the results for the experiments :

  Site	Scooby-Doo	First article	Readability
  Google.com	FAIL	SUCCESS	FAIL
  Facebook.com	FAIL	FAIL	FAIL
  YouTube.com	FAIL	FAIL	FAIL
  Wikipedia.com	SUCCESS	SUCCESS	SUCCESS

  Clearly, Wikipedia is the prime example of a site where even the simple approaches find it easy to determine the main content on the page. WordPress blogs are similarly successful. Almost any other site, including news sites, social networks and search engine sites are petty hopeless with the proposed approaches, because there are too many elements that are used for layout or other purposes (notifications, hidden areas) such that the pre-determined list of semantic elements that are available simply don’t suffice to mark up a Web page/application completely.

  Conclusion

  It seems that in general it is impossible to determine which element(s) on a Web page should be the “main” piece of content that accessibility tools jump to when requested, that a search engine should put their focus on, or that should be highlighted to a general user to read. It would be very useful if the author of the Web page would provide a hint through a <main> element where that main content is to be found.

  I think that the <main> element becomes particularly useful when combined with a default keyboard shortcut in browsers as proposed by Steve : we may actually find that non-accessibility users will also start making use of this shortcut, e.g. to get to videos on YouTube pages directly without having to tab over search boxes and other interactive elements, etc. Worthwhile markup indeed.

• The use cases for a element in HTML

  1er janvier 2014, par silvia

  The W3C HTML WG and the WHATWG are currently discussing the introduction of a <main> element into HTML.

  The <main> element has been proposed by Steve Faulkner and is specified in a draft extension spec which is about to be accepted as a FPWD (first public working draft) by the W3C HTML WG. This implies that the W3C HTML WG will be looking for implementations and for feedback by implementers on this spec.

  I am supportive of the introduction of a <main> element into HTML. However, I believe that the current spec and use case list don’t make a good enough case for its introduction. Here are my thoughts.

  Main use case : accessibility

  In my opinion, the main use case for the introduction of <main> is accessibility.

  Like any other users, when blind users want to perceive a Web page/application, they need to have a quick means of grasping the content of a page. Since they cannot visually scan the layout and thus determine where the main content is, they use accessibility technology (AT) to find what is known as “landmarks”.

  “Landmarks” tell the user what semantic content is on a page : a header (such as a banner), a search box, a navigation menu, some asides (also called complementary content), a footer, …. and the most important part : the main content of the page. It is this main content that a blind user most often wants to skip to directly.

  In the days of HTML4, a hidden “skip to content” link at the beginning of the Web page was used as a means to help blind users access the main content.

  In the days of ARIA, the aria @role=main enables authors to avoid a hidden link and instead mark the element where the main content begins to allow direct access to the main content. This attribute is supported by AT – in particular screen readers – by making it part of the landmarks that AT can directly skip to.

  Both the hidden link and the ARIA @role=main approaches are, however, band aids : they are being used by those of us that make “finished” Web pages accessible by adding specific extra markup.

  A world where ARIA is not necessary and where accessibility developers would be out of a job because the normal markup that everyone writes already creates accessible Web sites/applications would be much preferable over the current world of band-aids.

  Therefore, to me, the primary use case for a <main> element is to achieve exactly this better world and not require specialized markup to tell a user (or a tool) where the main content on a page starts.

  An immediate effect would be that pages that have a <main> element will expose a “main” landmark to blind and vision-impaired users that will enable them to directly access that main content on the page without having to wade through other text on the page. Without a <main> element, this functionality can currently only be provided using heuristics to skip other semantic and structural elements and is for this reason not typically implemented in AT.

  Other use cases

  The <main> element is a semantic element not unlike other new semantic elements such as <header>, <footer>, <aside>, <article>, <nav>, or <section>. Thus, it can also serve other uses where the main content on a Web page/Web application needs to be identified.

  Data mining

  For data mining of Web content, the identification of the main content is one of the key challenges. Many scholarly articles have been published on this topic. This stackoverflow article references and suggests a multitude of approaches, but the accepted answer says “there’s no way to do this that’s guaranteed to work”. This is because Web pages are inherently complex and many <div>, <p>, <iframe> and other elements are used to provide markup for styling, notifications, ads, analytics and other use cases that are necessary to make a Web page complete, but don’t contribute to what a user consumes as semantically rich content. A <main> element will allow authors to pro-actively direct data mining tools to the main content.

  Search engines

  One particularly important “data mining” tool are search engines. They, too, have a hard time to identify which sections of a Web page are more important than others and employ many heuristics to do so, see e.g. this ACM article. Yet, they still disappoint with poor results pointing to findings of keywords in little relevant sections of a page rather than ranking Web pages higher where the keywords turn up in the main content area. A <main> element would be able to help search engines give text in main content areas a higher weight and prefer them over other areas of the Web page. It would be able to rank different Web pages depending on where on the page the search words are found. The <main> element will be an additional hint that search engines will digest.

  Visual focus

  On small devices, the display of Web pages designed for Desktop often causes confusion as to where the main content can be found and read, in particular when the text ends up being too small to be readable. It would be nice if browsers on small devices had a functionality (maybe a default setting) where Web pages would start being displayed as zoomed in on the main content. This could alleviate some of the headaches of responsive Web design, where the recommendation is to show high priority content as the first content. Right now this problem is addressed through stylesheets that re-layout the page differently depending on device, but again this is a band-aid solution. Explicit semantic markup of the main content can solve this problem more elegantly.

  Styling

  Finally, naturally, <main> would also be used to style the main content differently from others. You can e.g. replace a semantically meaningless <div id=”main”> with a semantically meaningful <main> where their position is identical. My analysis below shows, that this is not always the case, since oftentimes <div id=”main”> is used to group everything together that is not the header – in particular where there are multiple columns. Thus, the ease of styling a <main> element is only a positive side effect and not actually a real use case. It does make it easier, however, to adapt the style of the main content e.g. with media queries.

  Proposed alternative solutions

  It has been proposed that existing markup serves to satisfy the use cases that <main> has been proposed for. Let’s analyse these on some of the most popular Web sites. First let’s list the propsed algorithms.

  Proposed solution No 1 : Scooby-Doo

  On Sat, Nov 17, 2012 at 11:01 AM, Ian Hickson <ian@hixie.ch> wrote :
  | The main content is whatever content isn’t
  | marked up as not being main content (anything not marked up with <header>,
  | <aside>, <nav>, etc).
  

  This implies that the first element that is not a <header>, <aside>, <nav>, or <footer> will be the element that we want to give to a blind user as the location where they should start reading. The algorithm is implemented in https://gist.github.com/4032962.

  Proposed solution No 2 : First article element

  On Sat, Nov 17, 2012 at 8:01 AM, Ian Hickson  wrote :
  | On Thu, 15 Nov 2012, Ian Yang wrote :
  | >
  | > That’s a good idea. We really need an element to wrap all the <p>s,
  | > <ul>s, <ol>s, <figure>s, <table>s ... etc of a blog post.
  |
  | That’s called <article>.
  

  This approach identifies the first <article> element on the page as containing the main content. Here’s the algorithm for this approach.

  Proposed solution No 3 : An example heuristic approach

  The readability plugin has been developed to make Web pages readable by essentially removing all the non-main content from a page. An early source of readability is available. This demonstrates what a heuristic approach can perform.

  Analysing alternative solutions

  Comparison

  I’ve picked 4 typical Websites (top on Alexa) to analyse how these three different approaches fare. Ideally, I’d like to simply apply the above three scripts and compare pictures. However, since the semantic HTML5 elements <header>, <aside>, <nav>, and <footer> are not actually used by any of these Web sites, I don’t actually have this choice.

  So, instead, I decided to make some assumptions of where these semantic elements would be used and what the outcome of applying the first two algorithms would be. I can then compare it to the third, which is a product so we can take screenshots.

  Google.com

  http://google.com – search for “Scooby Doo”.

  The search results page would likely be built with :

  • a <nav> menu for the Google bar
  • a <header> for the search bar
  • another <header> for the login section
  • another <nav> menu for the search types
  • a <div> to contain the rest of the page
  • a <div> for the app bar with the search number
  • a few <aside>s for the left and right column
  • a set of <article>s for the search results

  “Scooby Doo” would find the first element after the headers as the “main content”. This is the element before the app bar in this case. Interestingly, there is a <div @id=main> already in the current Google results page, which “Scooby Doo” would likely also pick. However, there are a nav bar and two asides in this div, which clearly should not be part of the “main content”. Google actually placed a @role=main on a different element, namely the one that encapsulates all the search results.

  “First Article” would find the first search result as the “main content”. While not quite the same as what Google intended – namely all search results – it is close enough to be useful.

  The “readability” result is interesting, since it is not able to identify the main text on the page. It is actually aware of this problem and brings a warning before displaying this page :

  

  Facebook.com

  https://facebook.com

  A user page would likely be built with :

  • a <header> bar for the search and login bar
  • a <div> to contain the rest of the page
  • an <aside> for the left column
  • a <div> to contain the center and right column
  • an <aside> for the right column
  • a <header> to contain the center column “megaphone”
  • a <div> for the status posting
  • a set of <article>s for the home stream

  “Scooby Doo” would find the first element after the headers as the “main content”. This is the element that contains all three columns. It’s actually a <div @id=content> already in the current Facebook user page, which “Scooby Doo” would likely also pick. However, Facebook selected a different element to place the @role=main : the center column.

  “First Article” would find the first news item in the home stream. This is clearly not what Facebook intended, since they placed the @role=main on the center column, above the first blog post’s title. “First Article” would miss that title and the status posting.

  The “readability” result again disappoints but warns that it failed :

  

  YouTube.com

  http://youtube.com

  A video page would likely be built with :

  • a <header> bar for the search and login bar
  • a <nav> for the menu
  • a <div> to contain the rest of the page
  • a <header> for the video title and channel links
  • a <div> to contain the video with controls
  • a <div> to contain the center and right column
  • an <aside> for the right column with an <article> per related video
  • an <aside> for the information below the video
  • a <article> per comment below the video

  “Scooby Doo” would find the first element after the headers as the “main content”. This is the element that contains the rest of the page. It’s actually a <div @id=content> already in the current YouTube video page, which “Scooby Doo” would likely also pick. However, YouTube’s related videos and comments are unlikely to be what the user would regard as “main content” – it’s the video they are after, which generously has a <div id=watch-player>.

  “First Article” would find the first related video or comment in the home stream. This is clearly not what YouTube intends.

  The “readability” result is not quite as unusable, but still very bare :

  

  Wikipedia.com

  http://wikipedia.com (“Overscan” page)

  A Wikipedia page would likely be built with :

  • a <header> bar for the search, login and menu items
  • a <div> to contain the rest of the page
  • an &ls ; article> with title and lots of text
  • <article> an <aside> with the table of contents
  • several <aside>s for the left column

  Good news : “Scooby Doo” would find the first element after the headers as the “main content”. This is the element that contains the rest of the page. It’s actually a <div id=”content” role=”main”> element on Wikipedia, which “Scooby Doo” would likely also pick.

  “First Article” would find the title and text of the main element on the page, but it would also include an <aside>.

  The “readability” result is also in agreement.

  

  Results

  In the following table we have summarised the results for the experiments :

  Site	Scooby-Doo	First article	Readability
  Google.com	FAIL	SUCCESS	FAIL
  Facebook.com	FAIL	FAIL	FAIL
  YouTube.com	FAIL	FAIL	FAIL
  Wikipedia.com	SUCCESS	SUCCESS	SUCCESS

  Clearly, Wikipedia is the prime example of a site where even the simple approaches find it easy to determine the main content on the page. WordPress blogs are similarly successful. Almost any other site, including news sites, social networks and search engine sites are petty hopeless with the proposed approaches, because there are too many elements that are used for layout or other purposes (notifications, hidden areas) such that the pre-determined list of semantic elements that are available simply don’t suffice to mark up a Web page/application completely.

  Conclusion

  It seems that in general it is impossible to determine which element(s) on a Web page should be the “main” piece of content that accessibility tools jump to when requested, that a search engine should put their focus on, or that should be highlighted to a general user to read. It would be very useful if the author of the Web page would provide a hint through a <main> element where that main content is to be found.

  I think that the <main> element becomes particularly useful when combined with a default keyboard shortcut in browsers as proposed by Steve : we may actually find that non-accessibility users will also start making use of this shortcut, e.g. to get to videos on YouTube pages directly without having to tab over search boxes and other interactive elements, etc. Worthwhile markup indeed.

• No sounds on Apple devices after encoding videos [migrated]

  15 décembre 2013, par Ricardo

  I'm having a problem setting up a media server.
  Everything works just great except the sound of Apple devices, I'm not sure if that's something with "mute" on iOS or our codecs are just not compatible with iOS.

  OS :

  Ubuntu 12.04

  FFMPEG Config :

  ffmpeg version 0.10.8-7:0.10.8-1~lucid1 Copyright 2000-2013 the FFmpeg developers
  
    built on Sep  5 2013 19:50:14 with gcc 4.4.3
  
    configuration: --arch=amd64 --disable-stripping --enable-pthreads --enable-runtime-cpudetect --extra-version='7:0.10.8-1~lucid1' --libdir=/usr/lib --prefix=/usr --enable-bzlib --enable-libdc1394 --enable-libfreetype --enable-frei0r --enable-gnutls --enable-libgsm --enable-libmp3lame --enable-libopenjpeg --enable-libpulse --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-vdpau --enable-libvorbis --enable-libvpx --enable-zlib --enable-gpl --enable-postproc --enable-libcdio --enable-x11grab --enable-libx264 --shlibdir=/usr/lib --enable-shared --disable-static
  
    avcodec     configuration: --arch=amd64 --disable-stripping --enable-pthreads --enable-runtime-cpudetect --extra-version='7:0.10.8-1~lucid1' --libdir=/usr/lib --prefix=/usr --enable-bzlib --enable-libdc1394 --enable-libfreetype --enable-frei0r --enable-gnutls --enable-libgsm --enable-libmp3lame --enable-libopenjpeg --enable-libpulse --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-vdpau --enable-libvorbis --enable-libvpx --enable-zlib --enable-gpl --enable-postproc --enable-libcdio --enable-x11grab --enable-libx264 --shlibdir=/usr/lib --enable-shared --disable-static --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb
  
    libavutil      51. 35.100 / 51. 35.100
  
    libavcodec     53. 61.100 / 53. 61.100
  
    libavformat    53. 32.100 / 53. 32.100
  
    libavdevice    53.  4.100 / 53.  4.100
  
    libavfilter     2. 61.100 /  2. 61.100
  
    libswscale      2.  1.100 /  2.  1.100
  
    libswresample   0.  6.100 /  0.  6.100
  
    libpostproc    52.  0.100 / 52.  0.100
  
  Hyper fast Audio and Video encoder

  Codecs :

   D..... = Decoding supported
  
   .E.... = Encoding supported
  
   ..V... = Video codec
  
   ..A... = Audio codec
  
   ..S... = Subtitle codec
  
   ...S.. = Supports draw_horiz_band
  
   ....D. = Supports direct rendering method 1
  
   .....T = Supports weird frame truncation
  
   ------
  
   D V D  4xm             4X Movie
  
   D V D  8bps            QuickTime 8BPS video
  
   D A D  8svx_exp        8SVX exponential
  
   D A D  8svx_fib        8SVX fibonacci
  
    EV    a64multi        Multicolor charset for Commodore 64
  
    EV    a64multi5       Multicolor charset for Commodore 64, extended with 5th color (colram)
  
   DEA D  aac             Advanced Audio Coding
  
   D A D  aac_latm        AAC LATM (Advanced Audio Codec LATM syntax)
  
   D V D  aasc            Autodesk RLE
  
   DEA D  ac3             ATSC A/52A (AC-3)
  
    EA    ac3_fixed       ATSC A/52A (AC-3)
  
   D A D  adpcm_4xm       ADPCM 4X Movie
  
   DEA D  adpcm_adx       SEGA CRI ADX ADPCM
  
   D A D  adpcm_ct        ADPCM Creative Technology
  
   D A D  adpcm_ea        ADPCM Electronic Arts
  
   D A D  adpcm_ea_maxis_xa ADPCM Electronic Arts Maxis CDROM XA
  
   D A D  adpcm_ea_r1     ADPCM Electronic Arts R1
  
   D A D  adpcm_ea_r2     ADPCM Electronic Arts R2
  
   D A D  adpcm_ea_r3     ADPCM Electronic Arts R3
  
   D A D  adpcm_ea_xas    ADPCM Electronic Arts XAS
  
   D A D  adpcm_ima_amv   ADPCM IMA AMV
  
   D A D  adpcm_ima_apc   ADPCM IMA CRYO APC
  
   D A D  adpcm_ima_dk3   ADPCM IMA Duck DK3
  
   D A D  adpcm_ima_dk4   ADPCM IMA Duck DK4
  
   D A D  adpcm_ima_ea_eacs ADPCM IMA Electronic Arts EACS
  
   D A D  adpcm_ima_ea_sead ADPCM IMA Electronic Arts SEAD
  
   D A D  adpcm_ima_iss   ADPCM IMA Funcom ISS
  
   DEA D  adpcm_ima_qt    ADPCM IMA QuickTime
  
   D A D  adpcm_ima_smjpeg ADPCM IMA Loki SDL MJPEG
  
   DEA D  adpcm_ima_wav   ADPCM IMA WAV
  
   D A D  adpcm_ima_ws    ADPCM IMA Westwood
  
   DEA D  adpcm_ms        ADPCM Microsoft
  
   D A D  adpcm_sbpro_2   ADPCM Sound Blaster Pro 2-bit
  
   D A D  adpcm_sbpro_3   ADPCM Sound Blaster Pro 2.6-bit
  
   D A D  adpcm_sbpro_4   ADPCM Sound Blaster Pro 4-bit
  
   DEA D  adpcm_swf       ADPCM Shockwave Flash
  
   D A D  adpcm_thp       ADPCM Nintendo Gamecube THP
  
   D A D  adpcm_xa        ADPCM CDROM XA
  
   DEA D  adpcm_yamaha    ADPCM Yamaha
  
   DEA D  alac            ALAC (Apple Lossless Audio Codec)
  
   D A D  als             MPEG-4 Audio Lossless Coding (ALS)
  
   D A D  amrnb           Adaptive Multi-Rate NarrowBand
  
   D A D  amrwb           Adaptive Multi-Rate WideBand
  
   DEV    amv             AMV Video
  
   D V D  anm             Deluxe Paint Animation
  
   D V D  ansi            ASCII/ANSI art
  
   D A D  ape             Monkey's Audio
  
   DES    ass             Advanced SubStation Alpha subtitle
  
   DEV D  asv1            ASUS V1
  
   DEV D  asv2            ASUS V2
  
   D A D  atrac1          Atrac 1 (Adaptive TRansform Acoustic Coding)
  
   D A D  atrac3          Atrac 3 (Adaptive TRansform Acoustic Coding 3)
  
   D V D  aura            Auravision AURA
  
   D V D  aura2           Auravision Aura 2
  
   DEV D  avrp            Avid 1:1 10-bit RGB Packer
  
   D V D  avs             AVS (Audio Video Standard) video
  
   D V D  bethsoftvid     Bethesda VID video
  
   D V D  bfi             Brute Force & Ignorance
  
   D A D  binkaudio_dct   Bink Audio (DCT)
  
   D A D  binkaudio_rdft  Bink Audio (RDFT)
  
   D V    binkvideo       Bink video
  
   D V D  bintext         Binary text
  
   DEV D  bmp             BMP image
  
   D A D  bmv_audio       Discworld II BMV audio
  
   D V    bmv_video       Discworld II BMV video
  
   D V D  c93             Interplay C93
  
   D V D  camstudio       CamStudio
  
   D V D  camtasia        TechSmith Screen Capture Codec
  
   D V D  cavs            Chinese AVS video (AVS1-P2, JiZhun profile)
  
   D V D  cdgraphics      CD Graphics video
  
   D V D  cinepak         Cinepak
  
   DEV D  cljr            Cirrus Logic AccuPak
  
   D A D  cook            COOK
  
   D V D  cyuv            Creative YUV (CYUV)
  
   DEA D  dca             DCA (DTS Coherent Acoustics)
  
   D V D  dfa             Chronomaster DFA
  
   D V    dirac           BBC Dirac VC-2
  
   DEV D  dnxhd           VC3/DNxHD
  
   DEV    dpx             DPX image
  
   D A D  dsicinaudio     Delphine Software International CIN audio
  
   D V D  dsicinvideo     Delphine Software International CIN video
  
   DES    dvbsub          DVB subtitles
  
   DES    dvdsub          DVD subtitles
  
   DEV D  dvvideo         DV (Digital Video)
  
   D V D  dxa             Feeble Files/ScummVM DXA
  
   D V D  dxtory          Dxtory
  
   DEA D  eac3            ATSC A/52 E-AC-3
  
   D V D  eacmv           Electronic Arts CMV video
  
   D V D  eamad           Electronic Arts Madcow Video
  
   D V D  eatgq           Electronic Arts TGQ video
  
   D V    eatgv           Electronic Arts TGV video
  
   D V D  eatqi           Electronic Arts TQI Video
  
   D V D  escape124       Escape 124
  
   D V D  escape130       Escape 130
  
   DEV D  ffv1            FFmpeg video codec #1
  
   DEVSD  ffvhuff         Huffyuv FFmpeg variant
  
   DEA D  flac            FLAC (Free Lossless Audio Codec)
  
   DEV D  flashsv         Flash Screen Video
  
   DEV D  flashsv2        Flash Screen Video Version 2
  
   D V D  flic            Autodesk Animator Flic video
  
   DEVSD  flv             Flash Video (FLV) / Sorenson Spark / Sorenson H.263
  
   D V D  fraps           Fraps
  
   D V D  frwu            Forward Uncompressed
  
   DEA D  g722            G.722 ADPCM
  
   DEA    g723_1          G.723.1
  
   DEA D  g726            G.726 ADPCM
  
   D A D  g729            G.729
  
   DEV D  gif             GIF (Graphics Interchange Format)
  
   D A D  gsm             GSM
  
   D A D  gsm_ms          GSM Microsoft variant
  
   DEV D  h261            H.261
  
   DEVSDT h263            H.263 / H.263-1996
  
   D VSD  h263i           Intel H.263
  
    EV    h263p           H.263+ / H.263-1998 / H.263 version 2
  
   D V D  h264            H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
  
   D V D  h264_vdpau      H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (VDPAU acceleration)
  
   DEVSD  huffyuv         Huffyuv / HuffYUV
  
   D V D  idcinvideo      id Quake II CIN video
  
   D V D  idf             iCEDraw text
  
   D V D  iff_byterun1    IFF ByteRun1
  
   D V D  iff_ilbm        IFF ILBM
  
   D A D  imc             IMC (Intel Music Coder)
  
   D V D  indeo2          Intel Indeo 2
  
   D V    indeo3          Intel Indeo 3
  
   D V    indeo4          Intel Indeo Video Interactive 4
  
   D V    indeo5          Intel Indeo Video Interactive 5
  
   D A D  interplay_dpcm  DPCM Interplay
  
   D V D  interplayvideo  Interplay MVE video
  
   DEV    j2k             JPEG 2000
  
   DEV D  jpegls          JPEG-LS
  
   D V D  jv              Bitmap Brothers JV video
  
   D V    kgv1            Kega Game Video
  
   D V D  kmvc            Karl Morton's video codec
  
   D V D  lagarith        Lagarith lossless
  
   DEA D  libgsm          libgsm GSM
  
   DEA D  libgsm_ms       libgsm GSM Microsoft variant
  
    EA    libmp3lame      libmp3lame MP3 (MPEG audio layer 3)
  
   DEA D  libopencore_amrnb OpenCORE Adaptive Multi-Rate (AMR) Narrow-Band
  
   D A D  libopencore_amrwb OpenCORE Adaptive Multi-Rate (AMR) Wide-Band
  
   DEV D  libopenjpeg     OpenJPEG based JPEG 2000 encoder
  
   DEV    libschroedinger libschroedinger Dirac 2.2
  
   DEA D  libspeex        libspeex Speex
  
    EV    libtheora       libtheora Theora
  
    EA    libvorbis       libvorbis Vorbis
  
   DEV    libvpx          libvpx VP8
  
    EV    libx264         libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
  
    EV    libx264rgb      libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 RGB
  
    EV    ljpeg           Lossless JPEG
  
   D V D  loco            LOCO
  
   D A D  mace3           MACE (Macintosh Audio Compression/Expansion) 3:1
  
   D A D  mace6           MACE (Macintosh Audio Compression/Expansion) 6:1
  
   D V D  mdec            Sony PlayStation MDEC (Motion DECoder)
  
   D V D  mimic           Mimic
  
   DEV D  mjpeg           MJPEG (Motion JPEG)
  
   D V D  mjpegb          Apple MJPEG-B
  
   D A D  mlp             MLP (Meridian Lossless Packing)
  
   D V D  mmvideo         American Laser Games MM Video
  
   D V D  motionpixels    Motion Pixels video
  
   D A D  mp1             MP1 (MPEG audio layer 1)
  
   D A D  mp1float        MP1 (MPEG audio layer 1)
  
   DEA D  mp2             MP2 (MPEG audio layer 2)
  
   D A D  mp2float        MP2 (MPEG audio layer 2)
  
   D A D  mp3             MP3 (MPEG audio layer 3)
  
   D A D  mp3adu          ADU (Application Data Unit) MP3 (MPEG audio layer 3)
  
   D A D  mp3adufloat     ADU (Application Data Unit) MP3 (MPEG audio layer 3)
  
   D A D  mp3float        MP3 (MPEG audio layer 3)
  
   D A D  mp3on4          MP3onMP4
  
   D A D  mp3on4float     MP3onMP4
  
   D A D  mpc7            Musepack SV7
  
   D A D  mpc8            Musepack SV8
  
   DEVSDT mpeg1video      MPEG-1 video
  
   D V DT mpeg1video_vdpau MPEG-1 video (VDPAU acceleration)
  
   DEVSDT mpeg2video      MPEG-2 video
  
   DEVSDT mpeg4           MPEG-4 part 2
  
   D V DT mpeg4_vdpau     MPEG-4 part 2 (VDPAU)
  
   D VSDT mpegvideo       MPEG-1 video
  
   D V DT mpegvideo_vdpau MPEG-1/2 video (VDPAU acceleration)
  
   D VSDT mpegvideo_xvmc  MPEG-1/2 video XvMC (X-Video Motion Compensation)
  
   DEVSD  msmpeg4         MPEG-4 part 2 Microsoft variant version 3
  
   D VSD  msmpeg4v1       MPEG-4 part 2 Microsoft variant version 1
  
   DEVSD  msmpeg4v2       MPEG-4 part 2 Microsoft variant version 2
  
   D V D  msrle           Microsoft RLE
  
   DEV D  msvideo1        Microsoft Video-1
  
   D V D  mszh            LCL (LossLess Codec Library) MSZH
  
   D V D  mxpeg           Mobotix MxPEG video
  
   DEA D  nellymoser      Nellymoser Asao
  
   D V D  nuv             NuppelVideo/RTJPEG
  
   DEV D  pam             PAM (Portable AnyMap) image
  
   DEV D  pbm             PBM (Portable BitMap) image
  
   DEA D  pcm_alaw        PCM A-law
  
   D A D  pcm_bluray      PCM signed 16|20|24-bit big-endian for Blu-ray media
  
   D A D  pcm_dvd         PCM signed 20|24-bit big-endian
  
   DEA D  pcm_f32be       PCM 32-bit floating point big-endian
  
   DEA D  pcm_f32le       PCM 32-bit floating point little-endian
  
   DEA D  pcm_f64be       PCM 64-bit floating point big-endian
  
   DEA D  pcm_f64le       PCM 64-bit floating point little-endian
  
   D A D  pcm_lxf         PCM signed 20-bit little-endian planar
  
   DEA D  pcm_mulaw       PCM mu-law
  
   DEA D  pcm_s16be       PCM signed 16-bit big-endian
  
   DEA D  pcm_s16le       PCM signed 16-bit little-endian
  
   D A D  pcm_s16le_planar PCM 16-bit little-endian planar
  
   DEA D  pcm_s24be       PCM signed 24-bit big-endian
  
   DEA D  pcm_s24daud     PCM D-Cinema audio signed 24-bit
  
   DEA D  pcm_s24le       PCM signed 24-bit little-endian
  
   DEA D  pcm_s32be       PCM signed 32-bit big-endian
  
   DEA D  pcm_s32le       PCM signed 32-bit little-endian
  
   DEA D  pcm_s8          PCM signed 8-bit
  
   D A D  pcm_s8_planar   PCM signed 8-bit planar
  
   DEA D  pcm_u16be       PCM unsigned 16-bit big-endian
  
   DEA D  pcm_u16le       PCM unsigned 16-bit little-endian
  
   DEA D  pcm_u24be       PCM unsigned 24-bit big-endian
  
   DEA D  pcm_u24le       PCM unsigned 24-bit little-endian
  
   DEA D  pcm_u32be       PCM unsigned 32-bit big-endian
  
   DEA D  pcm_u32le       PCM unsigned 32-bit little-endian
  
   DEA D  pcm_u8          PCM unsigned 8-bit
  
   D A D  pcm_zork        PCM Zork
  
   DEV D  pcx             PC Paintbrush PCX image
  
   DEV D  pgm             PGM (Portable GrayMap) image
  
   DEV D  pgmyuv          PGMYUV (Portable GrayMap YUV) image
  
   D S    pgssub          HDMV Presentation Graphic Stream subtitles
  
   D V D  pictor          Pictor/PC Paint
  
   DEV D  png             PNG image
  
   DEV D  ppm             PPM (Portable PixelMap) image
  
   DEV D  prores          Apple ProRes
  
   D V D  prores_lgpl     Apple ProRes (iCodec Pro)
  
   D V D  ptx             V.Flash PTX image
  
   D A D  qcelp           QCELP / PureVoice
  
   D A D  qdm2            QDesign Music Codec 2
  
   D V D  qdraw           Apple QuickDraw
  
   D V D  qpeg            Q-team QPEG
  
   DEV D  qtrle           QuickTime Animation (RLE) video
  
   DEV D  r10k            AJA Kona 10-bit RGB Codec
  
   DEV D  r210            Uncompressed RGB 10-bit
  
   DEV    rawvideo        raw video
  
   DEA D  real_144        RealAudio 1.0 (14.4K) encoder
  
   D A D  real_288        RealAudio 2.0 (28.8K)
  
   D V D  rl2             RL2 video
  
   DEA D  roq_dpcm        id RoQ DPCM
  
   DEV D  roqvideo        id RoQ video
  
   D V D  rpza            QuickTime video (RPZA)
  
   DEV D  rv10            RealVideo 1.0
  
   DEV D  rv20            RealVideo 2.0
  
   D V D  rv30            RealVideo 3.0
  
   D V D  rv40            RealVideo 4.0
  
   D A D  s302m           SMPTE 302M
  
   DEV    sgi             SGI image
  
   D A D  shorten         Shorten
  
   D A D  sipr            RealAudio SIPR / ACELP.NET
  
   D A D  smackaud        Smacker audio
  
   D V D  smackvid        Smacker video
  
   D V D  smc             QuickTime Graphics (SMC)
  
   DEV D  snow            Snow
  
   D A D  sol_dpcm        DPCM Sol
  
   DEA D  sonic           Sonic
  
    EA    sonicls         Sonic lossless
  
   D V D  sp5x            Sunplus JPEG (SP5X)
  
   DES    srt             SubRip subtitle
  
   D V D  sunrast         Sun Rasterfile image
  
   DEV D  svq1            Sorenson Vector Quantizer 1 / Sorenson Video 1 / SVQ1
  
   D VSD  svq3            Sorenson Vector Quantizer 3 / Sorenson Video 3 / SVQ3
  
   DEV D  targa           Truevision Targa image
  
   D VSD  theora          Theora
  
   D V D  thp             Nintendo Gamecube THP video
  
   D V D  tiertexseqvideo Tiertex Limited SEQ video
  
   DEV D  tiff            TIFF image
  
   D V D  tmv             8088flex TMV
  
   D A D  truehd          TrueHD
  
   D V D  truemotion1     Duck TrueMotion 1.0
  
   D V D  truemotion2     Duck TrueMotion 2.0
  
   D A D  truespeech      DSP Group TrueSpeech
  
   D A D  tta             True Audio (TTA)
  
   D A D  twinvq          VQF TwinVQ
  
   D V D  txd             Renderware TXD (TeXture Dictionary) image
  
   D V D  ultimotion      IBM UltiMotion
  
   D V D  utvideo         Ut Video
  
   DEV D  v210            Uncompressed 4:2:2 10-bit
  
   D V D  v210x           Uncompressed 4:2:2 10-bit
  
   DEV D  v308            Uncompressed packed 4:4:4
  
   DEV D  v410            Uncompressed 4:4:4 10-bit
  
   D V    vb              Beam Software VB
  
   D V D  vble            VBLE Lossless Codec
  
   D V D  vc1             SMPTE VC-1
  
   D V D  vc1_vdpau       SMPTE VC-1 VDPAU
  
   D V D  vc1image        Windows Media Video 9 Image v2
  
   D V D  vcr1            ATI VCR1
  
   D A D  vmdaudio        Sierra VMD audio
  
   D V D  vmdvideo        Sierra VMD video
  
   D V D  vmnc            VMware Screen Codec / VMware Video
  
   DEA D  vorbis          Vorbis
  
   D VSD  vp3             On2 VP3
  
   D V D  vp5             On2 VP5
  
   D V D  vp6             On2 VP6
  
   D V D  vp6a            On2 VP6 (Flash version, with alpha channel)
  
   D V D  vp6f            On2 VP6 (Flash version)
  
   D V D  vp8             On2 VP8
  
   D V D  vqavideo        Westwood Studios VQA (Vector Quantized Animation) video
  
   D A D  wavesynth       Wave synthesis pseudo-codec
  
   D A D  wavpack         WavPack
  
   D A    wmalossless     Windows Media Audio 9 Lossless
  
   D A D  wmapro          Windows Media Audio 9 Professional
  
   DEA D  wmav1           Windows Media Audio 1
  
   DEA D  wmav2           Windows Media Audio 2
  
   D A D  wmavoice        Windows Media Audio Voice
  
   DEVSD  wmv1            Windows Media Video 7
  
   DEVSD  wmv2            Windows Media Video 8
  
   D V D  wmv3            Windows Media Video 9
  
   D V D  wmv3_vdpau      Windows Media Video 9 VDPAU
  
   D V D  wmv3image       Windows Media Video 9 Image
  
   D V D  wnv1            Winnov WNV1
  
   D A D  ws_snd1         Westwood Audio (SND1)
  
   D A D  xan_dpcm        DPCM Xan
  
   D V D  xan_wc3         Wing Commander III / Xan
  
   D V D  xan_wc4         Wing Commander IV / Xxan
  
   D V D  xbin            eXtended BINary text
  
   D V D  xl              Miro VideoXL
  
   DES    xsub            DivX subtitles (XSUB)
  
   DEV D  xwd             XWD (X Window Dump) image
  
   DEV D  y41p            Uncompressed YUV 4:1:1 12-bit
  
   D V    yop             Psygnosis YOP Video
  
   DEV D  yuv4            Uncompressed packed 4:2:0
  
   DEV D  zlib            LCL (LossLess Codec Library) ZLIB
  
   DEV D  zmbv            Zip Motion Blocks Video

  Library we use to convert :

  public function getAvailableAudioCodecs()
  
      {
  
          return array('libvo_aacenc', 'libfaac', 'libmp3lame');
  
      }

  By default I use 'libmp3lame' now because 'libfaac' is not supported by ffmpeg
  and when Im trying to encode sound by libfaac I'm getting that codec not found

  Thanks in advance !