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• ffserver "dimensions not set" when loading stream

  29 mai 2013, par GreenGiant

  I am live streaming a webcam from my raspberry pi using avconv (ffmpeg "replacement")

  avconv -f video4linux2 -v debug -r 5 -s 176x144 -i /dev/video0 -vcodec mjpeg http://192.168.0.3:8090/feed1.ffm

  to my local network OSX machine (for testing) running ffserver

  Port 8090
  
  BindAddress 0.0.0.0
  
  MaxHTTPConnections 2000
  
  MaxClients 1000
  
  MaxBandwidth 10000
  
  CustomLog -
  
  NoDaemon
  
  
  
  <feed>
  
     File feed1.ffm
  
     FileMaxSize 20M
  
     ACL allow 192.168.0.10
  
  </feed>
  
  
  
  <stream>
  
     Feed feed1.ffm
  
     Format mjpeg
  
     NoAudio
  
     VideoQMin 1
  
     VideoQMax 10
  
     VideoSize 176x144
  
     VideoFrameRate 5
  
  </stream>

  When I start avconv it appears to be streaming to ffserver fine :

  Output #0, ffm, to 'http://192.168.0.3:8090/feed1.ffm':
  
    Metadata:
  
      encoder         : Lavf55.0.1
  
      Stream #0.0, 0, 1/1000000: Video: mjpeg, yuvj420p, 320x240, 1/5, q=2-31, 200 kb/s, 1000k tbn, 5 tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (rawvideo -> mjpeg)
  
  Press ctrl-c to stop encoding
  
  frame=  108 fps= 18 q=21.7 size=     688kB time=21.60 bitrate= 260.9kbits/s 

  And the ffserver status page shows the stream

  

  However when I load http://localhost:8090/test.mjpeg in VLC it doesn't play and ffserver spits out :

  Sat May 25 17:25:34 2013 dimensions not set
  
  Sat May 25 17:25:34 2013 Error writing output header
  
  Sat May 25 17:25:34 2013 127.0.0.1 - - [GET] "/test.mjpeg HTTP/1.1" 200 66

  I've tried so many different configurations and settings, I'm at a loss to what is causing that error !

  Thank you

• msvc/icl : Intel Compiler support on Windows

  25 mai 2013, par Alex Smith

  msvc/icl : Intel Compiler support on Windows
  Initial support for the ICL compiler on windows. Requires a new
  
  c99wrap with ICL support (1.0.2+).
  Currently not much different speed wise compared to msvc. In the
  
  future with a few changes it can be made to support the inline asm.
  
  This would be the primary reason for using it.
  Passed all fate tests, versions tested :
  
      13.1.1.171 (2013 Update 3) x86 and x64
  
      12.1.5.344 (2011 Update 11) x86 and x64
  Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
  

  • [DH] configure

• How To Play Hardware Accelerated Video on A Mac

  28 mai 2013, par Multimedia Mike — General

  I have a friend who was considering purchasing a Mac Mini recently. At the time of this writing, there are 3 desktop models (and 2 more “server” models).

  
  
  

  The cheapest one is a Core i5 2.5 GHz. Then there are 2 Core i7 models : 2.3 GHz and 2.6 GHz. The difference between the latter 2 is US$100. The only appreciable technical difference is the extra 0.3 GHz and the choice came down to those 2.

  He asked me which one would be able to play HD video at full frame rate. I found this query puzzling. But then, I have been “in the biz” for a bit too long. Whether or not a computer or device can play a video well depends on a lot of factors.

  Hardware Support
  First of all, looking at the raw speed of the general-purpose CPU inside of a computer as a gauge of video playback performance is generally misguided in this day and age. In general, we have a video standard (H.264, which I’ll focus on for this post) and many bits of hardware are able to accelerate decoding. So, the question is not whether the CPU can decode the data in real time, but can any other hardware in the device (likely the graphics hardware) handle it ? These machines have Intel HD 4000 graphics and, per my reading of the literature, they are capable of accelerating H.264 video decoding.

  Great, so the hardware supports accelerated decoding. So it’s a done deal, right ? Not quite…

  Operating System Support
  An application can’t do anything pertaining to hardware without permission from the operating system. So the next question is : Does Mac OS X allow an application to access accelerated video decoding hardware if it’s available ? This used to be a contentious matter (notably, Adobe Flash Player was unable to accelerate H.264 playback on Mac in the absence of such an API) but then Apple released an official API detailed in Technical Note TN2267.

  So, does this mean that video is magically accelerated ? Nope, we’re still not there yet…

  Application Support
  It’s great that all of these underlying pieces are in place, but if an individual application chooses to decode the video directly on the CPU, it’s all for naught. An application needs to query the facilities and direct data through the API if it wants to leverage the acceleration. Obviously, at this point it becomes a matter of “which application ?”

  My friend eventually opted to get the pricier of the desktop Mac Mini models and we ran some ad-hoc tests since I was curious how widespread the acceleration support is among Mac multimedia players. Here are some programs I wanted to test, playing 1080p H.264 :

  • Apple QuickTime Player
  • VLC
  • YouTube with Flash Player (any browser)
  • YouTube with Safari/HTML5
  • YouTube with Chrome/HTML5
  • YouTube with Firefox/HTML5
  • Netflix

  I didn’t take exhaustive notes but my impromptu tests revealed QuickTime Player was, far and away, the most performant player, occupying only around 5% of the CPU according to the Mac OS X System Profiler graph (which is likely largely spent on audio decoding).

  VLC consistently required 20-30% CPU, so it’s probably leveraging some acceleration facilities. I think that Flash Player and the various HTML5 elements performed similarly (their multi-process architectures can make such a trivial profiling test difficult).

  The outlier was Netflix running in Firefox via Microsoft’s Silverlight plugin. Of course, the inner workings of Netflix’s technology are opaque to outsiders and we don’t even know if it uses H.264. It may very well use Microsoft’s VC-1 which is not a capability provided by the Mac OS X acceleration API (it doesn’t look like the Intel HD 4000 chip can handle it either). I have never seen any data one way or another about how Netflix encodes video. However, I was able to see that Netflix required an enormous amount of CPU muscle on the Mac platform.

  Conclusion
  The foregoing is a slight simplification of the video playback pipeline. There are some other considerations, most notably how the video is displayed afterwards. To circle back around to the original question : Can the Mac Mini handle full HD video playback ? As my friend found, the meager Mac Mini can do an admirable job at playing full HD video without loading down the CPU.