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• Writing Live-Multimedia-Application using OpenGL & Co. saving output to disc [closed]

  21 janvier 2013, par user1997286

  I want to write an application that does the following thing :

  • Getting Commands via ArtNET (DMX over Ethernet, a Control Protocol) for each object (called Layer)
  • each Layer could be one of the following : Live Camera Stream, Movie, Image
  • each layer could be translated, rotated or stretched
  • on each layer I can set filters (Like a Kaleidoscope Effect, Blur, Color Correction, etc.)
  • the rsulting video-stream is in the 3d-space
  • I want to display each part of the image on one Projector (in total up to 3 ones) using a TripleHead2GO (3 Projectors display a different region of my DVI-Output). Each Projecector-Image should have own Soft-Edge and Keystone parameters.
  • the resulting image will also be shown on a Preview-Screen with some Information overlay.

  I think all that should be possible with opengl and openal (for the movie audio)

  I think I'll use C++, OpenGL for Graphics, OpenAL for Audio, if needed ffmpeg for Video conversion, Ubuntu/Debian as OS.

  The software is used to do Multimedia-Shows on Concerts including Cameras & Co.

  All that should happen Live (On a FullHD output), Having i7 3770, GLX 670 and 16GB of Ram for at least 8 Layers. (4 Live-Images at once + Some Overlays like the Actors Name and some Logos)

  But now comes the question.

  Is it also Posible to do the following with that setting :

  • Writing the output Image with all the 3d translations to a Movie File (To Master a DVD later) with Audio
  • Mixing Audio from different Inputs & Files (Ambience Mics, Signal from the Sound Mixer, Playbacks from my own application) to more than one Mix (eg. one Mix for the Recording, one Mix for Live)
  • Stream that Output Complete or in Parts (e.g. the left Part of the Image) over the Network (For example, Projector 1 is near the Server, so I connect it using DVI, Projector 2+3 is connected to a Computer that receives the streams for that two projectors (with soft edge on each stream) and Screen 4 is outside the Concert Hall and shows the complete Live-Stream.
  • What GUI-Framework should I use for that ?
  • is it perhaps event performant enough to use Java for that ?
  • is it posible to use that mechanism for just rendering (eg. I have stored the cut points on Disc and saved every single camera stream to change some errors later or cut out some parts)

• WebRTC Stream Freezes When Picture Complexity Increases

  12 octobre 2021, par user1259576

  I am developing an application that uses WebRTC to display a live video stream being captured from a V4L2 source. The stream originates from a Linux box that has a DVI-USB capture card, is encoded to H264 by ffmpeg and sent to RTP, received by a Janus WebRTC server which is accessed by the web interface.

  


  Here is my current ffmpeg command - pretty simple :
ffmpeg -f v4l2 -i /dev/video0 -vf "transpose=1,scale=768:1024" -vcodec libx264 -profile:v baseline -pix_fmt yuv420p -f rtp rtp ://10.116.80.86:8004

  


  I can't go into details, but the DVI source generates a portrait 768x1024 image that initially is a simple image where the only movement is a small clock near the center that increments every second. At this stage, everything appears to work great. The image is high-quality and continuous/smooth in the browser.

  


  Once I interact with the DVI source, a more complex image is generated, with some text/lines in the upper half. Still not very complex - only 2 colors involved and some basic 1px line shapes, and only the little clock is moving. At this point, the video starts to freeze frequently, and only updates once in a while for a few seconds. Bandwidth should not be an issue here, and the bitrate appears to stay high. However, many fewer frames are decoded.

  


  I have also tried scaling the video down to 480x640 from 768x1024 and with that change the issue does not occur. However, I really need the full resolution and, again, there should not be a bandwidth issue here.

  


  I have also tried capturing the output of ffmpeg to a file rather than streaming to RTP and in the file everything is good.

  


  Here is a screenshot of the WebRTC internals (in Edge) for this stream. You can clearly see when the video image changes from the simple clock to including more shapes & text (nothing is changed here other than the image from the DVI source) :

  


  

  


  In Firefox, the video just freezes whenever frames are not decoded. In Edge, the video goes black after a moment with no frames decoded.

  


  Any ideas as to what might be causing this ?

  


• Revision f6582d6928 : Revert "Simplify mask checking in loop filters" Jingning saw bitstream change w

  4 décembre 2013, par Yunqing Wang

  Changed Paths :
   Modify /vp9/common/vp9_loopfilter.c

  
  
  Revert "Simplify mask checking in loop filters"

  Jingning saw bitstream change with this patch. It could be true
  that (mask_16x16_0 & 1) is 1, but (mask_16x16_1 & 1) is 0 in some
  edge cases.

  This reverts commit 8f05e70340533b9922be5b1c97c37e50607fd862.

  Change-Id : I0a529435ce816a1e14653eb510d5090de276070a