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• truehd_core : Correct output size

  6 juillet 2019, par Andreas Rheinhardt

  truehd_core : Correct output size
  If truehd_core strips Atmos data away, three parts of the output differ
  
  in size compared to the input access unit : a) The major_sync_info block
  
  if the extra_channel_meaning_data is present, as the newly written
  
  output never contains said block ; b) the substream_directory (because
  
  entries relating to discarded substreams are discarded, too) ; and c)
  
  the actual substream data. b) and c) have already been taken into account
  
  when choosing the size of the output packet, but a) has been forgotten.
  This is also the reason behind the end of the output buffer having been
  
  uninitialized until 801d78f0. The workaround added in said commit has
  
  been removed, too.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/truehd_core_bsf.c

• avformat/avformat.h : Correct some comments

  9 août 2019, par Andreas Rheinhardt

  avformat/avformat.h : Correct some comments
  1. When set_parameters was removed from AVOutputFormat in 2fb75019, it
  
  was forgotten to remove the comment pertaining to it. Said comment now
  
  appeared to apply to interleave_packet() ; it is of course nonsense and
  
  has been replaced by an accurate description.
  
  2. The description of av_write_uncoded_frame() suggested
  
  av_interleaved_write_frame() as a replacement if the input is not
  
  already correctly interleaved ; it also referred to said function for
  
  details. Given that said function can't write AVFrames and that the
  
  specifics of writing uncoded frames are explained in the description
  
  of av_interleaved_write_uncoded_frame(), both references have been fixed.
  
  3. Removed an outdated comment about avformat_seek_file().
  Reviewed-by : Marton Balint <cus@passwd.hu>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/avformat.h

• The First Problem

  19 janvier 2011, par Multimedia Mike — HTML5

  A few years ago, The Linux Hater made the following poignant observation regarding Linux driver support :

  Drivers are only just the beginning... But for some reason y’all like to focus on the drivers. You know why lusers do that ? Because it just happens to be the problem that people notice first.

  And so it is with the HTML5 video codec debate, re-invigorated in the past week by Google’s announcement of dropping native H.264 support in their own HTML5 video tag implementation. As I read up on the fiery debate, I kept wondering why people are so obsessed with this issue. Then I remembered the Linux Hater’s post and realized that the video codec issue is simply the first problem that most people notice regarding HTML5 video.

  I appreciate that the video codec debate has prompted Niedermayer to post on his blog once more. Otherwise, I’m just munching popcorn on the sidelines, amused and mildly relieved that the various factions are vociferously attacking each other rather than that little project I help with at work.

  Getting back to the "first problem" aspect— there’s so much emphasis on the video codec ; I wonder why no one ever, ever mentions word one about an audio codec. AAC is typically the codec that pairs with H.264 in the MPEG stack. Dark Shikari once mentioned that "AAC’s licensing terms are exponentially more onerous than H.264′s. If Google didn’t want to use H.264, they would sure as hell not want to use AAC." Most people are probably using "H.264" to refer to the entire MPEG/H.264/AAC stack, even if they probably don’t understand what all of those pieces mean.

  Anyway, The Linux Hater’s driver piece continues :

  Once y’all have drivers, the fight will move to the next layer up. And like I said, it’s a lot harder at that layer.

  A few months ago, when I wanted to post the WebM output of my new VP8 encoder and thought it would be a nice touch to deliver it via a video tag, I ignored the video codec problem (just encoded a VP8/WebM file) only to immediately discover a problem at a different layer— specifically, embedding a file using a video tag triggers a full file download when the page is loaded, which is unacceptable from end user and web hosting perspectives. This is a known issue but doesn’t get as much attention, I guess because there are bigger problems to solve first (c.f. video codec issue).

  For other issues, check out the YouTube blog’s HTML5 post or Hulu’s post that also commented on HTML5. Issues such as video streaming flexibility, content protection, fullscreen video, webcam/microphone input, and numerous others are rarely mentioned in the debates. Only "video codec" is of paramount importance.

  But I’m lending too much weight to the cacophony of a largely uninformed internet debate. Realistically, I know there are many talented engineers down in the trenches working to solve at least some of these problems. To tie this in with the Linux driver example, I’m consistently stunned these days regarding how simple it is to get Linux working on a new computer— most commodity consumer hardware really does just work right out of the box. Maybe one day, we’ll wake up and find that HTML5 video has advanced to the point that it solves all of the relevant problems to make it the simple and obvious choice for delivering web video in nearly all situations.

  It won’t be this year.