MFPreview object properties – Medialooks Help Center

The properties are stored in the system registry:

[HKEY_CURRENT_USER\SOFTWARE\Medialooks\MFormats\MFPreview]

and can be set with the PropsSet method.

Name	Default value	Description
rate_control	true	Makes the MFPreview object to control the playback rate
preview.downscale	dword:00000001	Downscales preview video to optimize performance. Possible values: 0 - don't use downscaling. In this mode, preview receives a full-sized frame (so if your preview panel is, for example, 640x480, it receives a full HD frame of 1920x1080 and then the image is scaled according to the control size). It leads to higher performance of preview, but it is recommended for a full-screen preview where quality matters. 1 - downscale vertically only. In this mode, preview receives an image with cut each other horizontal line (so instead of 1920x1080 frame, it receives 1920x540 surface that is scaled to the control size). It reduces CPU usage of a preview and keeps preview quality acceptable for controls that aren't big (not full screen). 2 - downscale both vertically and horizontally. In this mode, preview receives an image that is 2 times reduced vertically and horizontally. It leads to lower CPU usage of the preview process, but preview quality is poor in this case. Recommended for really small preview controls where quality is not important.
preview.drop_frames	false	Once enabled, an MPreview object can drop frames in case frame processing takes a long time.
preview.crop	0.0%,0.0%,0.0%,0.0%	Default preview crop configuration.
preview.buffers	dword:00000001	Sets a buffer size of frames.
preview.type	dx9	Type of preview. Possible values: "dshow" - uses DirectShow-based preview "dx11" - uses DirectX11-based preview. Requires DirectX11 to be installed on a system. "dx9" - uses DirectX9-based preview. Requires DirectX9 to be installed on a system.
wpf_preview	false	Enables WPF preview.
wpf_preview.sync_texture	false	Synchronizes D3DTexture objects in case of multiple preview instances are used.
wpf_preview.update	dword:0000001e	Sets update period for WPF preview.
wpf_preview.downscale	dword:00000000	Sets downscale parameter for WPF preview.
wpf_preview.cpu_dx11	false	Forces DX11 preview in CPU mode.
deinterlace	true	Enables deinterlacing mode.
maintain_ar	true	Makes MPreview object to maintain the source aspect ratio. If disabled, the preview video stretches to the control size.
direct3d.pixel_format	auto	Sets pixel format for Direct3D-based preview.
direct3d.scale_filter	dword:00000002	Sets scale filter for Direct3D-based preview.
direct3d.scale_backbuffer	true	Enables scaling for a back buffer for Direct3D-based preview.
preview.background	checker	Sets default background for preview. Possible values: "checker" - checkerboard as a background is used a path to a local file a hex-code of a color
preview.alpha_channel	gpu	Add a possibility to use the alpha channel. Content with transparency is displayed with a checkerboard background on a preview. Possible values: "gpu" - the alpha channel is processed only if gpu_pipeline = true; "true" - alpha channel processed with CPU and GPU; "false" - alpha channel won't process.
preview.skip_fields	dword:00000000	Sets a mode for skipping fields (for interlaced video only). Possible values: 0 - don't skip frames 1 - skip top fields 2 - skip bottom fields
audio.buffer_size_msec	dword:00000064	Sets a buffer size for audio data in msec.
audio.correct_rate	true
audio.enabled	true	Enables audio preview by default.
video.enabled	true	Enabled video preview by default.
on_frame.sync	false	Makes OnFrame and OnFrameSafe events synchronous, so frame grabbing process won't continue until OnFrame event isn't over.
on_frame.data	false	Enables objects of OnFrame and OnFrameSafe events to contain MFrame data.
on_event.sync	false	Makes OnEvent and OnEventSafe events synchronous, so frame grabbing process won't continue until OnFrame event isn't over.
events.use_window	true	Use events (OnFrame, OnEvent, OnEventSafe and OnFrameSafe) in the thread of your application. If you use a service or an application without windows, then disable this mode.
audio_renderer		Sets audio renderer that is used for preview. The empty string means default audio device.
debug.test_tone		Sets a test tone in Hz. Debug-only property.
audio.direct_sound	false	Enables direct sound mode.
overlay_rms	false	Enables RMS overlay.
overlay_rms.pos	0.05	Specifies RMS overlay position relative to the left side.
overlay_rms.color	green	Specifies RMS overlay color. Possible values: color - blue - text color(255) - blue(128) - text + (alpha) [#]RGB - #0000FF - hex ("#" - optional) [#]ARGB - #ff0000ff - hex ("#" - optional)
overlay_waveform	false	Enables waveform overlay.
overlay_waveform.pos	0.3	Specifies the waveform overlay position relative to the center.
overlay_waveform.color		Specifies the waveform overlay color.
preview.external_process	false	Once "true", MFPreview is processed in a separated MServer.exe process to increase the overall stability (if preview fails the whole app stays alive - the only thing that fails is the MServer.exe process that is related to the MFPreview object).
object_name	MFPreview	The default name of the object.
dx11.swap_chain_latency_wait	true	Sets DX11 preview to wait until the swap operation is complete.
dx11.swap_chain_scale	1.5	Sets DX11 preview scaling quality.
dx11.windowless	false	For DX11 mode only. Use preview in a windowless mode.
dx11.use_vsync	false	Enables VSync use for DX11 preview.
dx11.swap_chain_resize	true	For DX11 mode only. Swap DirectX chain on preview resize.
dx11.field_only		For DX11 mode only. Preview a single field only.

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