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• 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.

• exclude specific streams (e.g. teletext) from ffmpeg conversion

  17 août 2019, par leone1522

  I want to convert several video files (captured from television) to another format, but I want to remove some specific streams. For example, this is one of my input files :

  $ ffprobe -hide_banner -i 'Easy Rider.ts' 2>&1|grep Stream
  
      Stream #0:0[0x4f6]: Unknown: none ([5][0][0][0] / 0x0005)
  
      Stream #0:1[0x4fc]: Unknown: none ([12][0][0][0] / 0x000C)
  
      Stream #0:2[0x13f7]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 50 fps, 50 tbr, 90k tbn, 100 tbc
  
      Stream #0:3[0x13f8](deu): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, fltp, 192 kb/s
  
      Stream #0:4[0x13f9](fra): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, fltp, 192 kb/s
  
      Stream #0:5[0x13fa](deu): Subtitle: dvb_teletext ([6][0][0][0] / 0x0006)
  
      Stream #0:6[0x13fb](deu): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006) (hearing impaired)
  
      Stream #0:7[0x13fc](mul): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, fltp, 192 kb/s
  
      Stream #0:8[0x13fd](mis): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, fltp, 192 kb/s (visual impaired) (descriptions)
  
      Stream #0:9[0x13fe](fra): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006)
  
      Stream #0:10[0x13ff](deu): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006)

  From this file, I want to keep

  • Stream #2 (h264 video)
  • Stream #3 (mp2 audio in german)
  • Stream #10 (dvb_subtitle in german)

  In other words, I want to exclude from conversion

  • all streams of unknown type
  • all audio streams other than german
  • all streams for visual impaired or hearing impaired
  • all dvb_teletext streams

  Of cause, I can do some awk scripting to construct a command like

  $ ffmpeg -hide_banner -ignore_unknown -i 'Easy Rider.ts' -map 0:2 -map 0:3 -map 0:10 -vcodec copy -acodec copy -scodec copy xx.ts

  But I am searching for a solution using ffmpeg’s mapping facilities.
  I already found Mapping streams by language in FFmpeg, which led me to

  $ ffmpeg -hide_banner -ignore_unknown -i 'Easy Rider.ts' -map 0:v -map 0:m:language:deu -vcodec copy -acodec copy -scodec copy xx.ts

  This command creates a file, which still has subtitles for hearing impaired and the dvb_teletext in it

  $ ffprobe -hide_banner -i xx.ts 2>&1|grep Stream
  
      Stream #0:0[0x100]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 50 fps, 50 tbr, 90k tbn, 100 tbc
  
      Stream #0:1[0x101](deu): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, fltp, 192 kb/s
  
      Stream #0:2[0x102](deu): Subtitle: dvb_teletext ([6][0][0][0] / 0x0006), 492x250
  
      Stream #0:3[0x103](deu): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006) (hearing impaired)
  
      Stream #0:4[0x104](deu): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006)

  Up to now, I did not find a way to exclude those streams from the output. Any idea ?

• Revision 6723e34224 : Merge "fix permissions on cpplint.py (0644->0755)" into experimental

  4 mai 2013, par James Zern

  Merge "fix permissions on cpplint.py (0644->0755)" into experimental