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• Chrome’s New Audio Notifier

  30 janvier 2014, par Multimedia Mike — General

  Version 32 of Google’s Chrome web browser introduced this nifty feature :

  
  
  

  When a browser tab has an element that is producing audio, the browser’s tab shows the above audio notification icon to inform the user. I have seen that people have a few questions about this, specifically :

  1. How does this feature work ?
  2. Why wasn’t this done sooner ?
  3. Are other browsers going to follow suit ?

  Short answers : 1) Chrome offers a new plugin API that the Flash Player is now using, as are Chrome’s internal media playing facilities ; 2) this feature was contingent on the new plugin infrastructure mentioned in the previous answer ; 3) other browsers would require the same infrastructure support.

  Longer answers follow…

  Plugin History
  Plugins were originally based on the Netscape Plugin API. This was developed in the early 1990s in order to support embedding PDFs into the Netscape web browser. The NPAPI does things like providing graphics contexts for drawing and input processing, and mediate network requests through the browser’s network facilities.

  What NPAPI doesn’t do is handle audio. In the early-mid 1990s, audio support was not a widespread consideration in the consumer PC arena. Due to the lack of audio API support, if a plugin wanted to play audio, it had to go outside of the plugin framework.

  
  
  

  There are a few downsides to this approach :

  • If a plugin wants to play audio, it needs to access unique audio APIs on each supported platform. One of the most famous things I’ve ever written deals concerns this nightmare on Linux. (The picture worth a thousand words.)
  • Plugin necessarily needs free unrestricted access to system facilities, i.e., security measures like sandboxing become more difficult without restricting functionality.
  • Since the browser doesn’t mediate access to the audio APIs, the browser can’t reasonably be expected to know when a plugin is accessing the audio resources.

  So that last item hopefully answers the question of why it has been so difficult for NPAPI-supporting browsers to implement what seems like it would be simple functionality, like implementing a per-tab audio notifier.

  Plugin Future
  Since Google released Chrome in an effort to facilitate advancements on the client side of the internet, they have made numerous efforts to modernize various legacy aspects of web technology. These efforts include the SPDY protocol, Native Client, WebM/WebP, and something call the Pepper Plugin API (PPAPI). This is a more modern take on the classic plugin architecture to supplant the aging NPAPI :

  
  
  

  Right away, we see that the job of the plugin writer is greatly simplified. Where was this API years ago when I was writing my API jungle piece ?

  The Linux version of Chrome was apparently the first version that packaged the Pepper version of the Flash Player (doing so fixed an obnoxious bug in the Linux Flash Player interaction with GTK). Now, it looks like Windows and Mac have followed suit. Digging into the Chrome directory on a Windows 7 installation :

  AppData\Local\Google\Chrome\Application[version]\PepperFlash\pepflashplayer.dll

  This directory exists for version 31 as well, which is still hanging around my system.

  So, to re-iterate : Chrome has a new plugin API that plugins use to access the audio API. Chrome knows when the API is accessed and that allows the browser to display the audio notifier on a tab.

  Other Browsers
  What about other browsers ? “Mozilla is not interested in or working on Pepper at this time. See the Chrome Pepper pages.”

• Revision 52796 : if (!defined("_ECRIRE_INC_VERSION")) return ; sur tout fichier PHP pour ...

  11 juin 2018, par kent1@… — Log

  if (!defined("_ECRIRE_INC_VERSION")) return ; sur tout fichier PHP pour sécurité future principalement

• FFMPEG stops converting

  19 février 2014, par user3328745

  I've got Ubuntu 12.04 LTS, which runs Wowza Media Server, so I use FFmpeg as a transcoder for live streaming and JWplayer on my website. But ffmpeg always stops converting, and I have to input the command again and again. So here is the command :

  nohup ffmpeg -i rtsp://log:pass@<cameraip>:554/live1.sdp -ar 44100 -ab 128k -f flv -b 5000k -s 480x270 -y rtmp://<serverip>:1935/live/camera.stream &amp;
  
  </serverip></cameraip>

  And that's what i get

  ffmpeg version 0.8.10-4:0.8.10-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the Libav developers
  
    built on Feb  6 2014 20:56:59 with gcc 4.6.3
  
  *** THIS PROGRAM IS DEPRECATED ***
  
  This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
  
  [rtsp @ 0x25317a0] Estimating duration from bitrate, this may be inaccurate
  
  
  
  Seems stream 0 codec frame rate differs from container frame rate: 150.00 (150/1) -> 1000.00 (1000/1)
  
  Input #0, rtsp, from &#39;rtsp://log:pass@<cameraip>:554/live1.sdp&#39;:
  
    Metadata:
  
      title           : RTSP/RTP stream 1 from DCS-2132L
  
      comment         : live1.sdp with v2.0
  
    Duration: N/A, start: 0.000000, bitrate: N/A
  
      Stream #0.0: Video: h264 (High), yuvj420p, 640x360 [PAR 1:1 DAR 16:9], 75 fps, 1k tbr, 90k tbn, 150 tbc
  
      Stream #0.1: Audio: pcm_mulaw, 8000 Hz, 1 channels, s16, 64 kb/s
  
  Incompatible pixel format &#39;yuvj420p&#39; for codec &#39;mpeg4&#39;, auto-selecting format &#39;yuv420p&#39;
  
  [buffer @ 0x2539f80] w:640 h:360 pixfmt:yuvj420p
  
  [scale @ 0x253a940] w:640 h:360 fmt:yuvj420p -> w:480 h:270 fmt:yuv420p flags:0x4
  
  Incompatible sample format &#39;s16&#39; for codec &#39;ac3&#39;, auto-selecting format &#39;flt&#39;
  
  [ac3 @ 0x2531120] channel_layout not specified
  
  [ac3 @ 0x2531120] No channel layout specified. The encoder will guess the layout, but it might be incorrect.
  
  [ac3 @ 0x2531120] invalid bit rate
  
  Output #0, avi, to &#39;rtmp://<serverip>:1935/live/camera.stream&#39;:
  
      Stream #0.0: Video: mpeg4, yuv420p, 480x270 [PAR 1:1 DAR 16:9], q=2-31, 1024 kb/s, 90k tbn, 1k tbc
  
      Stream #0.1: Audio: ac3, 22050 Hz, mono, flt, 1024 kb/s
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
    Stream #0.1 -> #0.1
  
  Error while opening encoder for output stream #0.1 - maybe incorrect parameters such as bit_rate, rate, width or height
  
  </serverip></cameraip>

  Plese, help me to correct the errors