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• The use cases for a element in HTML

  27 novembre 2012, 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 <ian@hixie.ch> 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.

• How to reduce size of moov atom of H.264 movies to improve streaming start for smartphones ?

  14 avril 2013, par alebedev

  We run a video service streaming movies to smartphones (iOS&Android).
  We are encoding in H.264+AAC and using the mp4 container.
  We have a problem that long movies (60 minutes+) take a very long time to
  start playing and have tracked this down to the large size of moov
  atom for these movies.
  For 110 minute movies the atom is as large as 4.2Mb which obviously takes a long
  time to download to a smart-phone over 3G !

  Is there anyway to make the moov atom smaller ? We can reduce it bit
  by dropping the audio sampling rate, but obviously anything below 22kHz
  would not really be acceptable.

  We are using ffmpeg as the encoder, and MP4Box to move the metadata
  to the front of the file. Is there any way to get it to make
  a smaller moov ? Any other encoders out there which make a smaller moov ?

  For example...

  Big size (280 Mb, 1h 49min) streamable mp4 (h.264, AAC) file have a big header size (4.2 Mb). File was encoded by two pass ffmpeg and MP4Box for replacing metadata into beginning of the file :

  /usr/bin/ffmpeg -i /var/lib/encoder/incoming/2388 -aspect 320:210 -threads 8 -vcodec libx264 -profile baseline -level 13 -flags +loop+mv4 -cmp 256 -partitions +parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 -me_method hex -subq 7 -trellis 1 -refs 5 -bf 0 -me_range 16 -g 250 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -qmin 10 -qmax 51 -qdiff 4 -b:v 270k -maxrate 270k -bufsize 270k -g 30 -passlogfile /tmp/mediaservice/3100/video-IPH.ffmpeg -an -f rawvideo -pass 1 -y /dev/null
  
  
  
  /usr/bin/ffmpeg -i /var/lib/encoder/incoming/2388 -aspect 320:210 -threads 8 -vcodec libx264 -profile baseline -level 13 -flags +loop+mv4 -cmp 256 -partitions +parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 -me_method hex -subq 7 -trellis 1 -refs 5 -bf 0 -me_range 16 -g 250 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -qmin 10 -qmax 51 -qdiff 4 -b:v 270k -maxrate 270k -bufsize 270k -g 30 -passlogfile /tmp/mediaservice/3100/video-IPH.ffmpeg -acodec libfaac -ac 2 -b:a 32k -ar 44100 -f mp4 -pass 2 -y /var/lib/encoder/encoded/3100/video-IPH.mp4
  
  
  
  /usr/bin/MP4Box -quiet -tmp /tmp/mediaservice/3100/ -inter 500 /var/lib/encoder/encoded/3100/video-IPH.mp4

  Media info (audio sample rate = 44100) :

  General
  
  Count                                    : 278
  
  Count of stream of this kind             : 1
  
  Kind of stream                           : General
  
  Kind of stream                           : General
  
  Stream identifier                        : 0
  
  Count of video streams                   : 1
  
  Count of audio streams                   : 1
  
  Video_Format_List                        : AVC
  
  Video_Format_WithHint_List               : AVC
  
  Codecs Video                             : AVC
  
  Audio_Format_List                        : AAC
  
  Audio_Format_WithHint_List               : AAC
  
  Audio codecs                             : AAC LC
  
  Complete name                            : 1348645218_970458_2465.iph.mp4
  
  File name                                : 1348645218_970458_2465.iph.mp4
  
  File extension                           : mp4
  
  Format                                   : MPEG-4
  
  Format                                   : MPEG-4
  
  Format/Extensions usually used           : mp4 m4v m4a m4b m4p 3gpp 3gp 3gpp2 3g2 k3g jpm jpx mqv ismv isma f4v
  
  Commercial name                          : MPEG-4
  
  Format profile                           : Base Media
  
  Internet media type                      : video/mp4
  
  Codec ID                                 : isom
  
  Codec ID/Url                             : http://www.apple.com/quicktime/download/standalone.html
  
  Codec                                    : MPEG-4
  
  Codec                                    : MPEG-4
  
  Codec/Extensions usually used            : mp4 m4v m4a m4b m4p 3gpp 3gp 3gpp2 3g2 k3g jpm jpx mqv ismv isma f4v
  
  File size                                : 272703970
  
  File size                                : 260 MiB
  
  File size                                : 260 MiB
  
  File size                                : 260 MiB
  
  File size                                : 260 MiB
  
  File size                                : 260.1 MiB
  
  Duration                                 : 6556027
  
  Duration                                 : 1h 49mn
  
  Duration                                 : 1h 49mn 16s 27ms
  
  Duration                                 : 1h 49mn
  
  Duration                                 : 01:49:16.027
  
  Overall bit rate                         : 332767
  
  Overall bit rate                         : 333 Kbps
  
  Stream size                              : 4230761
  
  Stream size                              : 4.03 MiB (2%)
  
  Stream size                              : 4 MiB
  
  Stream size                              : 4.0 MiB
  
  Stream size                              : 4.03 MiB
  
  Stream size                              : 4.035 MiB
  
  Stream size                              : 4.03 MiB (2%)
  
  Proportion of this stream                : 0.01551
  
  HeaderSize                               : 4230683
  
  DataSize                                 : 268473217
  
  FooterSize                               : 70
  
  IsStreamable                             : Yes
  
  File last modification date              : UTC 2012-09-26 12:38:19
  
  File last modification date (local)      : 2012-09-26 21:38:19
  
  Writing application                      : Lavf54.6.100
  
  
  
  Video
  
  Count                                    : 201
  
  Count of stream of this kind             : 1
  
  Kind of stream                           : Video
  
  Kind of stream                           : Video
  
  Stream identifier                        : 0
  
  ID                                       : 1
  
  ID                                       : 1
  
  Format                                   : AVC
  
  Format/Info                              : Advanced Video Codec
  
  Format/Url                               : http://developers.videolan.org/x264.html
  
  Commercial name                          : AVC
  
  Format profile                           : Baseline@L1.3
  
  Format settings                          : 5 Ref Frames
  
  Format settings, CABAC                   : No
  
  Format settings, CABAC                   : No
  
  Format settings, ReFrames                : 5
  
  Format settings, ReFrames                : 5 frames
  
  Format settings, GOP                     : M=1, N=30
  
  Internet media type                      : video/H264
  
  Codec ID                                 : avc1
  
  Codec ID/Info                            : Advanced Video Coding
  
  Codec ID/Url                             : http://www.apple.com/quicktime/download/standalone.html
  
  Codec                                    : AVC
  
  Codec                                    : AVC
  
  Codec/Family                             : AVC
  
  Codec/Info                               : Advanced Video Codec
  
  Codec/Url                                : http://developers.videolan.org/x264.html
  
  Codec/CC                                 : avc1
  
  Codec profile                            : Baseline@L1.3
  
  Codec settings                           : 5 Ref Frames
  
  Codec settings, CABAC                    : No
  
  Codec_Settings_RefFrames                 : 5
  
  Duration                                 : 6556017
  
  Duration                                 : 01:49:16.017
  
  Bit rate                                 : 270000
  
  Bit rate                                 : 270 Kbps
  
  Width                                    : 480
  
  Width                                    : 480 pixels
  
  Height                                   : 270
  
  Height                                   : 270 pixels
  
  Pixel aspect ratio                       : 1.000
  
  Display aspect ratio                     : 1.778
  
  Display aspect ratio                     : 16:9
  
  Rotation                                 : 0.000
  
  Frame rate mode                          : CFR
  
  Frame rate mode                          : Constant
  
  FrameRate_Mode_Original                  : VFR
  
  Frame rate                               : 29.970
  
  Frame rate                               : 29.970 fps
  
  Frame count                              : 196484
  
  Resolution                               : 8
  
  Resolution                               : 8 bits
  
  Colorimetry                              : 4:2:0
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:0
  
  Bit depth                                : 8
  
  Bit depth                                : 8 bits
  
  Scan type                                : Progressive
  
  Scan type                                : Progressive
  
  Interlacement                            : PPF
  
  Interlacement                            : Progressive
  
  Bits/(Pixel*Frame)                       : 0.070
  
  Stream size                              : 220159060
  
  Stream size                              : 210 MiB (81%)
  
  Stream size                              : 210 MiB
  
  Stream size                              : 210 MiB
  
  Stream size                              : 210 MiB
  
  Stream size                              : 210.0 MiB
  
  Stream size                              : 210 MiB (81%)
  
  Proportion of this stream                : 0.80732
  
  Writing library                          : x264 - core 125
  
  Writing library                          : x264 core 125
  
  Writing library/Name                     : x264
  
  Writing library/Version                  : core 125
  
  Encoding settings                        : cabac=0 / ref=5 / deblock=1:0:0 / analyse=0x1:0x131 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=8 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 / weightp=0 / keyint=30 / keyint_min=16 / scenecut=40 / intra_refresh=0 / rc_lookahead=30 / rc=2pass / mbtree=1 / bitrate=270 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / vbv_maxrate=270 / vbv_bufsize=270 / nal_hrd=none / ip_ratio=1.40 / aq=1:1.00
  
  Tagged date                              : UTC 2012-09-25 07:21:37
  
  
  
  Audio
  
  Count                                    : 169
  
  Count of stream of this kind             : 1
  
  Kind of stream                           : Audio
  
  Kind of stream                           : Audio
  
  Stream identifier                        : 0
  
  ID                                       : 2
  
  ID                                       : 2
  
  Format                                   : AAC
  
  Format/Info                              : Advanced Audio Codec
  
  Commercial name                          : AAC
  
  Format profile                           : LC
  
  Codec ID                                 : 40
  
  Codec                                    : AAC LC
  
  Codec                                    : AAC LC
  
  Codec/Family                             : AAC
  
  Codec/CC                                 : 40
  
  Duration                                 : 6556027
  
  Duration                                 : 1h 49mn
  
  Duration                                 : 1h 49mn 16s 27ms
  
  Duration                                 : 1h 49mn
  
  Duration                                 : 01:49:16.027
  
  Bit rate mode                            : VBR
  
  Bit rate mode                            : Variable
  
  Bit rate                                 : 58955
  
  Bit rate                                 : 59.0 Kbps
  
  Maximum bit rate                         : 270000
  
  Maximum bit rate                         : 270 Kbps
  
  Channel(s)                               : 2
  
  Channel(s)                               : 2 channels
  
  Channel positions                        : Front: L R
  
  Channel positions                        : 2/0/0
  
  Sampling rate                            : 44100
  
  Sampling rate                            : 44.1 KHz
  
  Samples count                            : 289120791
  
  Compression mode                         : Lossy
  
  Compression mode                         : Lossy
  
  Stream size                              : 48314149
  
  Stream size                              : 46.1 MiB (18%)
  
  Stream size                              : 46 MiB
  
  Stream size                              : 46 MiB
  
  Stream size                              : 46.1 MiB
  
  Stream size                              : 46.08 MiB
  
  Stream size                              : 46.1 MiB (18%)
  
  Proportion of this stream                : 0.17717
  
  Tagged date                              : UTC 2012-09-25 07:21:37

  Moov atom info (/moov/trak[0] - video, /moov/trak[1] - audio) sample rate 44100 :
  (look stsz and stts nodes in trak)

  Atom ftyp @ 0 of size: 32, ends @ 32
  
  Atom moov @ 32 of size: 4230651, ends @ 4230683
  
       Atom mvhd @ 40 of size: 108, ends @ 148
  
       Atom trak @ 148 of size: 868970, ends @ 869118
  
           Atom tkhd @ 156 of size: 92, ends @ 248
  
           Atom edts @ 248 of size: 36, ends @ 284
  
               Atom elst @ 256 of size: 28, ends @ 284
  
           Atom mdia @ 284 of size: 868834, ends @ 869118
  
               Atom mdhd @ 292 of size: 32, ends @ 324
  
               Atom hdlr @ 324 of size: 45, ends @ 369
  
               Atom minf @ 369 of size: 868749, ends @ 869118
  
                   Atom vmhd @ 377 of size: 20, ends @ 397
  
                   Atom dinf @ 397 of size: 36, ends @ 433
  
                       Atom dref @ 405 of size: 28, ends @ 433
  
                   Atom stbl @ 433 of size: 868685, ends @ 869118
  
                       Atom stsd @ 441 of size: 149, ends @ 590
  
                           Atom avc1 @ 457 of size: 133, ends @ 590
  
                               Atom avcC @ 543 of size: 47, ends @ 590
  
                       Atom stts @ 590 of size: 24, ends @ 614
  
                       Atom stss @ 614 of size: 26340, ends @ 26954
  
                       Atom stsc @ 26954 of size: 52, ends @ 27006
  
                       Atom stsz @ 27006 of size: 785956, ends @ 812962
  
                       Atom stco @ 812962 of size: 56156, ends @ 869118
  
       Atom trak @ 869118 of size: 3361468, ends @ 4230586
  
           Atom tkhd @ 869126 of size: 92, ends @ 869218
  
           Atom edts @ 869218 of size: 36, ends @ 869254
  
               Atom elst @ 869226 of size: 28, ends @ 869254
  
           Atom mdia @ 869254 of size: 3361332, ends @ 4230586
  
               Atom mdhd @ 869262 of size: 32, ends @ 869294
  
               Atom hdlr @ 869294 of size: 45, ends @ 869339
  
               Atom minf @ 869339 of size: 3361247, ends @ 4230586
  
                   Atom smhd @ 869347 of size: 16, ends @ 869363
  
                   Atom dinf @ 869363 of size: 36, ends @ 869399
  
                       Atom dref @ 869371 of size: 28, ends @ 869399
  
                   Atom stbl @ 869399 of size: 3361187, ends @ 4230586
  
                       Atom stsd @ 869407 of size: 91, ends @ 869498
  
                           Atom mp4a @ 869423 of size: 75, ends @ 869498
  
                               Atom esds @ 869459 of size: 39, ends @ 869498
  
                       **Atom stts @ 869498 of size: 2135816, ends @ 3005314**
  
                       Atom stsc @ 3005314 of size: 39712, ends @ 3045026
  
                       **Atom stsz @ 3045026 of size: 1129400, ends @ 4174426**
  
                       Atom stco @ 4174426 of size: 56160, ends @ 4230586
  
       Atom udta @ 4230586 of size: 97, ends @ 4230683
  
           Atom meta @ 4230594 of size: 89, ends @ 4230683
  
               Atom hdlr @ 4230606 of size: 33, ends @ 4230639
  
               Atom ilst @ 4230639 of size: 44, ends @ 4230683
  
                   Atom ©too @ 4230647 of size: 36, ends @ 4230683
  
                       Atom data @ 4230655 of size: 28, ends @ 4230683
  
  Atom mdat @ 4230683 of size: 268473217, ends @ 272703900
  
  Atom free @ 272703900 of size: 8, ends @ 272703908
  
  Atom free @ 272703908 of size: 62, ends @ 272703970
  
  ------------------------------------------------------
  
  Total size: 272703970 bytes; 50 atoms total. AtomicParsley version: 0.9.0 (utf8)
  
  Media data: 268473217 bytes; 4230753 bytes all other atoms (1.551% atom overhead).
  
  Total free atom space: 70 bytes; 0.000% waste. Padding available: 0 bytes.
  
  ------------------------------------------------------

  After reencoding this movie with audio sample rate 11025 header size much less :

  Media info (audio sample rate = 11025) : (crop duplicate info)

  General
  
  ***
  
  HeaderSize                               : 1276359
  
  
  
  Video
  
  ***
  
  
  
  Audio
  
  Count                                    : 169
  
  Count of stream of this kind             : 1
  
  Kind of stream                           : Audio
  
  Kind of stream                           : Audio
  
  Stream identifier                        : 0
  
  ID                                       : 2
  
  ID                                       : 2
  
  Format                                   : AAC
  
  Format/Info                              : Advanced Audio Codec
  
  Commercial name                          : AAC
  
  Format profile                           : LC
  
  Codec ID                                 : 40
  
  Codec                                    : AAC LC
  
  Codec                                    : AAC LC
  
  Codec/Family                             : AAC
  
  Codec/CC                                 : 40
  
  Duration                                 : 6556132
  
  Duration                                 : 1h 49mn
  
  Duration                                 : 1h 49mn 16s 132ms
  
  Duration                                 : 1h 49mn
  
  Duration                                 : 01:49:16.132
  
  Bit rate mode                            : VBR
  
  Bit rate mode                            : Variable
  
  Bit rate                                 : 37991
  
  Bit rate                                 : 38.0 Kbps
  
  Maximum bit rate                         : 128000
  
  Maximum bit rate                         : 128 Kbps
  
  Channel(s)                               : 2
  
  Channel(s)                               : 2 channels
  
  Channel positions                        : Front: L R
  
  Channel positions                        : 2/0/0
  
  Sampling rate                            : 11025
  
  Sampling rate                            : 11.025 KHz
  
  Samples count                            : 72281355
  
  Compression mode                         : Lossy
  
  Compression mode                         : Lossy
  
  Stream size                              : 31134257
  
  Stream size                              : 29.7 MiB (12%)
  
  Stream size                              : 30 MiB
  
  Stream size                              : 30 MiB
  
  Stream size                              : 29.7 MiB
  
  Stream size                              : 29.69 MiB
  
  Stream size                              : 29.7 MiB (12%)
  
  Proportion of this stream                : 0.12327
  
  Tagged date                              : UTC 2012-09-25 13:20:28

  Moov atom info (/moov/trak[0] - video, /moov/trak[1] - audio) sample rate 11025 :

  Atom ftyp @ 0 of size: 32, ends @ 32
  
  Atom moov @ 32 of size: 1276327, ends @ 1276359
  
       Atom mvhd @ 40 of size: 108, ends @ 148
  
       Atom trak @ 148 of size: 821662, ends @ 821810
  
           Atom tkhd @ 156 of size: 92, ends @ 248
  
           Atom edts @ 248 of size: 36, ends @ 284
  
               Atom elst @ 256 of size: 28, ends @ 284
  
           Atom mdia @ 284 of size: 821526, ends @ 821810
  
               Atom mdhd @ 292 of size: 32, ends @ 324
  
               Atom hdlr @ 324 of size: 45, ends @ 369
  
               Atom minf @ 369 of size: 821441, ends @ 821810
  
                   Atom vmhd @ 377 of size: 20, ends @ 397
  
                   Atom dinf @ 397 of size: 36, ends @ 433
  
                       Atom dref @ 405 of size: 28, ends @ 433
  
                   Atom stbl @ 433 of size: 821377, ends @ 821810
  
                       Atom stsd @ 441 of size: 149, ends @ 590
  
                           Atom avc1 @ 457 of size: 133, ends @ 590
  
                               Atom avcC @ 543 of size: 47, ends @ 590
  
                       Atom stts @ 590 of size: 24, ends @ 614
  
                       Atom stss @ 614 of size: 26340, ends @ 26954
  
                       Atom stsc @ 26954 of size: 52, ends @ 27006
  
                       Atom stsz @ 27006 of size: 785956, ends @ 812962
  
                       Atom stco @ 812962 of size: 8848, ends @ 821810
  
       Atom trak @ 821810 of size: 454452, ends @ 1276262
  
           Atom tkhd @ 821818 of size: 92, ends @ 821910
  
           Atom edts @ 821910 of size: 36, ends @ 821946
  
               Atom elst @ 821918 of size: 28, ends @ 821946
  
           Atom mdia @ 821946 of size: 454316, ends @ 1276262
  
               Atom mdhd @ 821954 of size: 32, ends @ 821986
  
               Atom hdlr @ 821986 of size: 45, ends @ 822031
  
               Atom minf @ 822031 of size: 454231, ends @ 1276262
  
                   Atom smhd @ 822039 of size: 16, ends @ 822055
  
                   Atom dinf @ 822055 of size: 36, ends @ 822091
  
                       Atom dref @ 822063 of size: 28, ends @ 822091
  
                   Atom stbl @ 822091 of size: 454171, ends @ 1276262
  
                       Atom stsd @ 822099 of size: 91, ends @ 822190
  
                           Atom mp4a @ 822115 of size: 75, ends @ 822190
  
                               Atom esds @ 822151 of size: 39, ends @ 822190
  
                       Atom stts @ 822190 of size: 161368, ends @ 983558
  
                       Atom stsc @ 983558 of size: 1480, ends @ 985038
  
                       Atom stsz @ 985038 of size: 282372, ends @ 1267410
  
                       Atom stco @ 1267410 of size: 8852, ends @ 1276262
  
       Atom udta @ 1276262 of size: 97, ends @ 1276359
  
           Atom meta @ 1276270 of size: 89, ends @ 1276359
  
               Atom hdlr @ 1276282 of size: 33, ends @ 1276315
  
               Atom ilst @ 1276315 of size: 44, ends @ 1276359
  
                   Atom ©too @ 1276323 of size: 36, ends @ 1276359
  
                       Atom data @ 1276331 of size: 28, ends @ 1276359
  
  Atom mdat @ 1276359 of size: 251293325, ends @ 252569684
  
  Atom free @ 252569684 of size: 8, ends @ 252569692
  
  Atom free @ 252569692 of size: 62, ends @ 252569754
  
  ------------------------------------------------------
  
  Total size: 252569754 bytes; 50 atoms total. AtomicParsley version: 0.9.0 (utf8)
  
  Media data: 251293325 bytes; 1276429 bytes all other atoms (0.505% atom overhead).
  
  Total free atom space: 70 bytes; 0.000% waste. Padding available: 0 bytes.
  
  ------------------------------------------------------

  On slow connection this movie start playing after 30-40 seconds until header info (4.2 Mb) downloading. I need that movie start playing fast as it possible. And i have next questions :

  1. How reduce size of movie header ?

  2. How reduce size of
     /moov[0]/trak[1]/mdia[0]/minf[0]/stbl[0] and why it so big when
     sample rate 44100 ?

• NAB 2010 wrapup

  15 avril 2010

  Another year of NAB has come and gone. Making it out of Vegas with some remaining faith in humanity seems like a successful outcome. So, anything worth talking about at the show ?

  First off, there’s 3d. 3D is The Next Big Thing, and that was obvious to anyone who spent half a second on the show floor. Everything from camera rigs, to post production apps, to display technology was all 3d, all the time. I’m not a huge fan of 3d in most cases, but the industry is at least feigning interest.

  Luckily, at a show as big as NAB, there’s plenty of other cool stuff to see. So, what struck my fancy ?

  First off, Avid and Adobe were showing new versions of Media Composer and Premiere. Both sounded pretty amazing on paper, but I must say I was somewhat underwhelmed by both in reality. Premiere felt a little rough around the edges - the Mercurial Engine wasn’t the sort of next generation tech that I expected. Media Composer 5 has some nice new tweaks, but it’s still rather Avid-y - which is good for Avid people, less interesting for the rest of us.

  In other software news, Blackmagic Design was showing off some of what they’re doing with the DaVinci technology that they acquired. Software-only Da Vinci Resolve for $999 is a pretty amazing deal, and the demos were quite nice. That said, color correction is an art, so just making the technology cheaper isn’t necessarily going to dramatically change the number of folks who do it well - see Color.

  Blackmagic also has a pile of new USB 3.0 hardware devices, including the absolutely gorgeous UltraStudio Pro. Makes me pine for USB 3.0 on the mac.

  On the production side, we saw new cameras from just about everyone. To start at the high end, the Arri Alexa was absolutely stunning. Perhaps the nicest digital cinema footage I’ve seen. Not only that, but they’ve worked out a usable workflow, recording to ProRes plus RAW. At the price point they’re promising, the world is going to get a lot more difficult for RED.

  Sony’s new XDCam EX gear is another good step forward for that format. Nothing groundbreaking, but another nice progression. I was kind of hoping we’d see 4:2:2 EX gear from them, but I suppose they need to justify the disc based formats for a while longer.

  The Panasonic AG-AF100 is another interesting camera, bringing micro 4/3rds into video. The only strange thing is the recording side - AVCHD to SD cards. While I’m thrilled to see them using SD instead of P2, it sure would have been nice to have an AVCIntra option.

  Finally, Canon’s 4:2:2 XF cams are a nice option for the ENG/EFP market. Nothing groundbreaking, aside from the extra color sampling, but it’s a nice step up from what they’ve been doing.

  Speaking of Canon, it’s interesting to see the ways that the 5d and 7d have made their way into mainstream filmmaking. At one point, I thought they’d be relegated to the indie community - folks looking for nice DoF on a budget. Instead, they seem to have been adopted by a huge range of productions, from episodic TV to features. While they’re not right for everyone, the price and quality make them an easy choice in many cases.

  One of the stars of the show for me was the GoPro, a small waterproof HD camera that ships with a variety of mounts, designed to be used in places where you couldn’t or wouldn’t use a more full featured camera. No LCD, just a record button and a wide angle lens. I bought two.

  Those are the things that stand out for me. While there was plenty of interesting stuff to be seen, given the current economic conditions at the University, I wasn’t exactly in a shopping mindset. The show definitely felt more optimistic than it did last year, and companies are again pushing out new products. However, attendances was about 20% lower than 2008, and that was definitely noticeable on the show floor.