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cybertheque  
#1 Posted : Tuesday, November 29, 2011 5:39:01 PM(UTC)
cybertheque

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Location: mn, usa

Much appreciation for the 'basic version' of vMix; in order for it to be a useful production switcher on a platform that has very good performance as a DVR and settop box (being repurposed for use as a vision mixer), vMix will need to render to TV Out in 3D mode to make use of vsync and GPU acceleration.

A concise summary of the issues:

1. in vMix, selecting EVR to render output and vsync on inputs is ineffective (not implemented)on Nvidia 6150 Nforce4 chipset (GeForce 6); the only way to get vsync and useful GPU acceleration is to run in 3D mode. Currently, both the VMR9 and EVR renderer selections in vMix produce video with lots of noise, tearing and other artifacts that can't be mitigated. The video chipset, like many others, has no 2D vsync capability.

2. Platform is Windows 7 Ultimate 64-bit on AMD Athlon X2 dual core 4400+ with 800MHz DDR2 RAM (2GB at the moment), Nforce4 6150 chipset with HDMI out for main display and Y/C and composite out (NTSC 29.97Hz) for secondary full screen output (used as the 'program' output of the mixer), and dual analog capture cards with y/c and composite input.

3. As a proof-of-concept, MPC-HC X64, build 1.5.2.3456 with MSVC 2010 SP1, FFMPEG with MinGW GCC 4.6.1 (SSE2) using the 'EVR Custom Pres' output renderer driving the NTSC disiplay on Y/C or composite produces video indistinguishable from the capture input (to the calibrated eyeball, although I intend to measure with a vectorscope and waveform monitor later). MPC-HC is used here as a live player, opening the directshow capture device and not playing a file.

The platform is highly integrated, low cost and sufficiently capable that it will make a cost-effective and full-featured vision mixer if this issue can be solved; it shouldn't be necessary to invest in Decklink cards in order to mix and switch analog SD video on a budget and still have good signal quality.

I would like to provide testing and hardware support for this effort and hope that you can implement whatever changes are necessary to the renderer to make it work as it does in MPC-HC.

Regards,

Michael Grigoni

admin  
#2 Posted : Tuesday, November 29, 2011 10:33:31 PM(UTC)
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Hi Michael,

In order to ensure there is no tearing in the video make sure Windows 7 supports the "Aero" transparency mode.
EVR in vMix DOES use 3d mode so if you can't use aero, as a last resort tick the Synchronise option in the vMix settings under performance.

Note that the Geforce 6150 is a very old technology and does not support Windows 7 completely.
I would suggest buying a cheap dedicated graphics card and a converter the secondary output to TV if native support is not available.

Regards,

Martin
vMix

cybertheque  
#3 Posted : Thursday, December 1, 2011 5:34:09 AM(UTC)
cybertheque

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I hope you don't mind extending the discussion on tearing a bit more; I've been beating my head against this issue for live video playout to TV on Windows for more than four years.

Quote:
In order to ensure there is no tearing in the video make sure Windows 7 supports the "Aero" transparency mode. EVR in vMix DOES use 3d mode so if you can't use aero, as a last resort tick the Synchronise option in the vMix settings under performance.


Indeed, with Aero enabled, the EVR renderer produces video without tearing, although I do see some judder (probable field order issues) in some content, although it seems that it is reduced by selecting deinterlace on the input. EVR without Aero in vMix (with or without the Synch option checked) still produces tearing.

Quote:
I would suggest buying a cheap dedicated graphics card and a converter the secondary output to TV if native support is not available.


The intent is to create a stable and glitch-free vision mixer from a highly integrated device without external add-ons; this device works flawlessly under linux with proprietary drivers handling two NTSC live streams, doing various effects and making output to Y/C, component or composite, it just isn't a general purpose production switcher with it's original software. This box has only two PCI-e slots and cannot accomodate any more internal devices of any kind.

MPC-HC has solved the judder and tearing issues with its EVR Custom Presenter, which can use D3D Exclusive mode and doesn't require Aero. Running Aero on my box entails a substantial performance hit. I once approached some devs in that project about forking a vision mixer project to use the technology already proven for the player but got no replies, probably because of the limited 'market'. Perhaps the ideas vfl if not the code itself could be useful for vMix development? Or, please consider an open source fork of vMix Basic which may prove useful in the long run for community contributions that would benefit your full version under a dual licensing scheme (like is done with the Asterisk project).

Some observations on projects that try to combine a vision mixer with a recorder/network streamer; an Italian broadcast media software company tried with a product called Movie Cockpit and failed -- here is an email that I received some time ago:


"I'm sorry to inform you that MovieCockpit is not being developed any further
than what is currently available thru the webstore.

The effects, transition and output modules will not become available
anymore.

An all-in-one software for video recording, switching, live output and
streaming has proved to be almost impossible to build (as reliable as we
wanted it to be) using the current technology.

However we are now working on 2 separate products: one recorder/player and
one switcher.

The recorder/player can be used by itself, but it won't switch.

The switcher/effect with live output can be used by itself, but it won't
record/playback.

With both application, running onto 2 separate machines (networked), you
will be able to obtain everything.

The recorder is almost done and it supports all range of BlackMagic Cards,
all video formats (2K excluded), using the following codecs: MJPEG,
Uncompressed and Cineform HD and RGB. It supports also external LTC
time-code input. Later, MXF files will be generated instead of avi.

The switcher will work with uncompressed I/O only. The switcher will require
one card for output and as many card as you need to match the number of
inputs (the current limit is 8 inputs)."

Indeed, trying to stream or record in vMix on my target platform with two NTSC live inputs is not possible at full frame rate, however I have found that playout of networked mpeg files over GigE to the box, in vMix, works quite well, at very low CPU load, so the above approach seems to have merit.
admin  
#4 Posted : Thursday, December 1, 2011 9:42:10 PM(UTC)
admin

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Hi,

The issue is the graphics card you have chosen unfortunately and vMix is perfectly capable of mixing a large number of HD streams on the right hardware.
We require a modern 3d Graphics card to provide smooth jitter and tearing free video.
While MPC-HC goes to great lengths to solve this on older hardware, you will find running MPC-HC with more than a couple of videos will show the same issues.

All I can suggest is looking for another integrated platform, perhaps the latest Intel Core i5 hardware with built in graphics card as it is not practical for us to support old hardware with limited capabilties.

Regards,

Martin
vMix
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