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nbd

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Registered since 24/11/05
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concepts of vvvv

It seems that some of the components ( if not all) from v4 are direct derived from directx from microsoft. so if you are somehow familiar with game-programming or directx-programming, v4 will be straight forward.

on the other hand, if you search for help about certain topics from v4 , the development center of microsoft directx and direct3d are very helpful.

Links to microsoft-dev-center:

renderer-modes:http://msdn.microsoft.com/library/default.asp?url=/library/en-us/directx9_c/D3DFORMAT.asphttp://msdn.microsoft.com/library/default.asp?url=/library/en-us/directx9_c/D3DRENDERSTATETYPE.asphttp://msdn.microsoft.com/library/default.asp?url=/library/en-us/directx9_c/Render_States.asphttp://msdn.microsoft.com/library/default.asp?url=/library/en-us/directx9_c/IDirect3DDevice9.asp

experience with video on vvvv

task: playback synchronous video on 5 displays ( resolution 1360*768)

mission accomplished by:

  • using strong hardware
  • being patient
  • patching a lot
  • experiment with video codecs

details:

used hardware were 5 ibm think centre with 3.0 ghz pentium processor 1gb ram ati x700 pci-xpress graphics s-ata drives

main problem:
video playback is smoothest when the video-playback-rate matches the refresh-rate of the display. all flat panel devices today run natively with 60hz. any other input is converted to that framerate.
so the save way for a smooth video playback on flat panel devices is to use 60 hz videos. using a 30 hz videorate is feasible, but 30 hz is a lower frame rate than your eye can recognise. a flicker will occur for this circumstance.

things to know:
at 1360*768 a picture is about 3mbyte. with 60 fps the necessary plain bandwidth is about 180 mbyte/sec.

a word about codecs
The above mentioned bandwidth is quite high. so it is inevitably to use some compression. the usual hard-disk today copes with up to 55 mb/sec ( s-ata seagate barracuda). With some operation system overhead it should be save to stay below 30mb/sec transfer rate for video files.

the unusual ( and high ) resolution of 1360 *768 with 60-fps needs a special codec that can handle such format.

possibilities:

  • some avi-codec
  • windows media 9

mpeg 2 doesn't support 1360*768 /60-fps.

As AVI-codec i tried the pegasus imaging mjpeg-codec. It was praised for it's speed.

Windows Media 9:

With some experimentation ( it always needs that) with the Windows-Media-9-Encoder you can reach very sharp, visually artefact-free pictures. For the best picture quality one should use quality VBR with no constraints. This leads to files up to 25-30 mbit/sec for this constellation. This data-rate is to high to be played even by WindowsMediaPlayer.
But with a constrained CBR with 20mbit you reach nearly equal perfect pictures with smooth playback in WindowsMediaPlayer AND in VVVV. This seems to be a solution for this purpose.

Drawback: Windows Media is not usable for fast scrubbing in video files! This means that for the synchronised playback it does not work. Especially with the VideoSync-patch by Tebjan it does NOT work.

Conclusion:
For a controlled playback Windows Media does NOT work.

mjpeg-codec from pegasus imaging

with this codec ( wich costs money: each decompressor 39 $, the compressor/ decompressor twin is 99$ ) every single frame gets jpeg-coded. this leads to fast decompression times and to fast scrubbing. Again ( with all codecs) you need experience ( get it by experimenting) with the right compression-setting. under the above mentioned circumstances the best picture quality vs. cpu-load was reached with a compression setting of 19 ( the codec has a slider ranging from 1 to 20 with 1 being the most compressed and 20 being the least compressed). notably no use of fields and using a luma/chroma-subsampling of 4:2:2. these are also compression settings.

graphic card & vvvv performance

the ati x700 has windows media support. that means that part of the windows media decompression (and compression as well ?!) is presumably done by the graphic card via DXVA.

The VideoTexture YUV-mode Node is by far more speedier than the VideoTexture (normal mode). With the mjpeg-video and the normal VideoTexture node i got a frame-rate of 53-57 fps and the Perf meter showed quite an efford (about a third of the maximum usage) on processor-side.

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