MVTools

Revision as of 14:07, 11 June 2014

Official documentation: http://avisynth.org.ru/mvtools/mvtools2.html

About MVTools

MVTools plugin for AviSynth 2.5 is a collection of functions for estimation and compensation of objects motion in video clips. Motion compensation may be used for strong temporal denoising, advanced framerate conversions, image restoration and other tasks.

The plugin contains the motion estimation server-function MAnalyse to find the motion vectors and several motion compensation client-functions (MCompensate, MMask and others) which use these vectors.

Plugin uses block-matching method of motion estimation (similar methods are used in MPEG2, MPEG4, etc). At analysis stage plugin divides frames by small blocks and try to find for every block in current frame the most similar (matching) block in second frame (previous or next). The relative shift of these blocks is motion vector. The main measure of block similarity is sum of absolute differences (SAD) of all pixels of these two blocks compared. SAD is a value which says how good the motion estimation was.

The output of MAnalyse (server) is special clip with motion vector information in some format.

At compensation stage the plugin client functions read the motion vectors and use them to move blocks and form motion compensated frame (or realize some other full or partial motion compensation or interpolation function). Every object (block) in this (fully) compensated frame is placed in the same position as this object in current frame. So, we may (for example) use strong temporal denoising even for quite fast moving objects without producing annoying artifacts and ghosting (object's features and edges are coincide if compensation is perfect). Plugin can create compensated neighbor frames for every current frame, and denoise it by internal function. Alternatively, you can use compensated and original frames to create interleaved clip, denoise it by any external temporal filter, and select central cleaned original frames for output (see examples).

Of course, the motion estimation and compensation is not ideal and precise. In some complex cases (video with fading, ultra-fast motion, or periodic structures) the motion estimation may be completely wrong, and compensated frame will be blocky and (or) ugly. Severe difficulty is also due to objects mutual screening (occlusion) or reverse opening. Complex Avisynth scripts with many motion compensation functions may eat huge amount of memory and result in very slow processing. It is not simple but quite advanced plugin. Use it for appropriate cases only, and try to tune its parameters. There are many discussions about motion compensation using at doom9 Avisynth forum. In particular see old MVTools thread, true motion thread, new MVTools thread and some other. Try to read the postings in addition to this documentation and ask for support there. If you really interested in motion estimation and compensation topics, you can easy find numerous scientific publications (use WWW search).

Notes: The plugin is still under development. Current version has some limitations. Only progressive YV12, YUY2 video is supported. Use color format conversion and try use (smart) bob-deinterlace for interlaced video (SeparateFields may works too with or without SelectEven/SelectOdd). Some complex scripts (MVBOB, MCBOB, TempGaussMC) use MVTools for motion compensated deinterlace. Alternatively you can try to use Motion plugin by mg262.

Common parameters

Filters that use motion vectors have common parameters. Those are the scene-change detection thresholds, and the isse mmx flag. They also use one or several vectors stream, which are produced by MAnalyse.

thSCD1 (int): threshold which decides whether a block has changed between the previous frame and the current one. When a block has changed, it means that motion estimation for it isn't relevant. It occurs for example at scene changes. So it is one of the thresholds used to tweak the scene changes detection engine. Raising it will lower the number of blocks detected as changed. It may be useful for noisy or flickered video. The threshold is compared to the SAD (Sum of Absolute Differences, a value which says how bad the motion estimation was ) value. For exactly identical blocks we have SAD=0. But real blocks are always different because of objects complex movement (zoom, rotation, deformation), discrete pixels sampling, and noise. Suppose we have two compared 8x8 blocks with every pixel different by 5. It this case SAD will be 8x8x5 = 320 (block will not detected as changed for thSCD1=400). If you use 4x4 blocks, SAD will be 320/4. If you use 16x16 blocks, SAD will be 320*4. Really this parameter is scaled internally in MVTools, and you must always use reduced to block size 8x8 value. Default is 400 (since v.1.4.1).

thSCD2 (int): threshold which sets how many blocks have to change for the frame to be considered as a scene change. It is ranged from 0 to 255, 0 meaning 0 %, 255 meaning 100 %. Default is 130 ( which means 51 % ).

isse (int): flag which allows to enable (if set to True) or disable (if set to False) ISSE, MMX and other CPU optimizations (for debugging). Default is True. If your processor doesn't support CPU optimizations, it will be disabled anyway ( and you won't be able to activate them ).

planar (bool): flag to use special planar color format for YUY2 clips both for input and output of function. It uses special trick for storing of frames with planar color data organization (separate Y, U, V planes in memory) in normal interleaved YUY2 frames format as a container. This way we can avoid numerous internal interleaved to planar conversions and increase speed. You can convert normal interleaved YUY2 source clip to planar format with Interleaved2planar function from RemoveGrain plugin by kassandro, and convert final result by Planar2interleaved function. This special planar YUY2 format is also supported by Removegrain plugin by Kassandro, MaskTools2 plugin by Manao and some others. This trick will not be needed in Avisynth v2.6 with native support of planar YV16 format. This parameter is ignored for YV12 clips. Note: super clip is always planar. Default is planar=false.

Filters

Changelog

http://avisynth.org.ru/mvtools/mvtools2.html#revisions

Links

• http://forum.doom9.org/showthread.php?t=84770