AviSynth was designed to be a very very powerful tool for video post-production. It provides almost unlimited ways of editing and processing videos. AviSynth works as a frameserver, providing instant and very fast editing without the need for temporary files.

AviSynth itself does not provide a graphical user interface (GUI) but instead relies on a script system that allows advanced non-linear editing. While this may at first seem tedious and unintuitive, it is remarkably powerful and is a very good way to manage projects in a precise, consistent, and reproducible manner.

Because text-based scripts are human readable, projects are inherently self-documenting. The scripting language is simple yet powerful, and complex filters can be created from basic operations to develop a sophisticated palette of useful and unique effects.

Changes from previous version

· Additions:
· Added Polish doc translation (by Slim, Krismen & Co).
· Added Japanese translation (by niiyan).
· Installer standalone option for putting avisynth.dll, etc into install directory and NOT updating registry.
· Blankclip added audio channels= and sample_type= arguments.
· ConvertAudio(cii) available to plugins via env->Invoke().
· Added font aspect, rotation and alpha to text routines.
· Added /xxx */ block comments.
· Added [[xxx *] *] nestable block comments.
· SetMemoryMax(0) to just return current Memory Max value.
· Added planar YV12 color format to Compare() [Fizick].
· ColorKeyMask: Allow independant tolerance levels for each channel.
· Added Tweak Hue/Saturation range limiting.
· Added AudioLevels and Color2 modes to Histogram.
· Adding global OPT_UseWaveExtensible=True to your script enables WAVE_FORMAT_EXTENSIBLE audio output.
· Added ShowTime() script verb, like ShowSMPTE() but with milliseconds.
· Added BlackmanResize() and Spline64Resize().
· Modified DeleteFrame()/DuplicateFrame() to process multiple arguments.
· Added Min()/Max() script functions.
· Bugfixes:
· Fixed AviSource() decoding to RGB24 logic regression.
· Added workaround for HuffYUV, Xvid reading past end of input buffer.
· Fixed current_frame value in nested runtime script invocations. (Gavino)
· Fixed Dissolve overlap arg range checking. (gzarkadas)
· Fixed OpenDMLSource() multithreading race problem. (QuaddiMM)
· Fixed unsaved variableName string in ConditionalReader.
· Fixed Parser FunctionTable::TypeMatch() missing compulsory arguments. Dissolve bug (Various).
· Fixed DirectShowSource() QueryId() use CoTaskMemAlloc for returned value (Dean Pavlekovic).
· Fixed DirectShowSource() use GraphBuilder object for media control (Avery Lee).
· Fixed DirectShowSource() remove PulseEvent calls (Avery Lee).
· Fixed DirectShowSource() QueryAccept() modifying VideoInfo in running script (Haali).
· Fixed Blankclip clip= argument parsing.
· Fixed trashed GPF report, i.e reading 0x0 at 0x0 exception reporting.
· Fixed and refactored Overlay RGBYUV conversion routines.
· Fixed ImageReader incompletely inited videoInfo.
· Fixed Layer RGB32 100% alpha implementation, use level=257 (new default).
· Fixed avisynth_c.h avs_is_parity_known().
· Fixed C ConvertAudio::Saturate_int32() rounding.
· Fixed WriteFile(), Now remembers absolute path to file.
· Fixed Info() frame pitch, reports pitch of input frame.
· Fixed Invert() right edge memory overrun/corruption.
· Fixed Histogram() Classic mode pixel values exceeding YUV limits.
· Fixed Histogram() chroma plane initialization to 128.
· Fixed Conditional reader/writer illegally saving IScriptEnvironment pointer.
· Fixed YV12 Blur()/Sharpen() right edge pixel corruption with non-writable input frames.
· Fixed MMX Blur()/Sharpen() code to full 8 bit precision.
· Fixed IsAudioFloat()/IsAudioInt() script functions.
· Fixed Cache memory oversubscription of SetMemoryMax() limit.
· Optimizations:
· DirectShowSource() FPS detection as last attempt tries getting the duration of 1st frame.
· DirectShowSource() convertfps=true rely only on sample start time.
· Refactor horizontal planar resizer, no width restrictions or 2 byte overwrite.
· Provide a simple and fast text writing primatives, see info.h
· Make audio cache actually functional.
· Tweak() speed improvements.
· Subtract() speed improvements.
· Tuneup Overlay() ISSE Convert444ChromaToYV12 and also provide MMX version.
· PokeCache internal interface implemented.
· Cache and Memory management enhancements.
· Changes:
· Test VFB data buffer for NULL mallocs, if so then Throw!
· Initial Memory Max value clamped to 1GB.
· Installer Start menu shortcut names translated.
· Test for UTF-8 and Unicode BOM prefixes and issue a useful warning.
· Removed useless current_sample from runtime script environment.
· Added critical section to CAVIFileSynth class.
· Enable Installer multi language support [Need volunteers to do translations].
· FunctionTable::Lookup() now considers named arguments in making its selection.
· ImageWriter supports negative values as -count for End argument.
· ChanegFPS() use floor instead of round in source frame number calculation.
· Update usage of correct (updated) Rec.709 coefficients.
· Add TCPDeliver.map and DirectShowSource.map to releases.
· Convert to Dynamic Assembled rgb to yuy2 code.
· Avisynth_c.h boolean functions return 1 for true instead of arbitrary non-zero.
· Internal RGB2YUV() now copies Alpha top byte through.
· CoUninitialize() done immediately for S_FALSE CoInitialize() returns, i.e we do not hold a COM use count.
· Pfc, Softwire and SoundTouch updated and added as dependency projects.
· UPX updated to version 2.03 (2006-11-07).
· Default Memory Max value increased to half minus 64Mb when over 256MB free.
· AVISource/WavSource map WAVEFORMATEXTENSIBLE back to equivalent WAVEFORMATEX.
· DirectShowSource() now recognises incorrect AM_MEDIA_TYPE subtype for WAVE_FORMAT_EXTENSIBLE audio and corrects the data and accepts it.
· DirectShowSource() now attempts to use partial graph from failing RenderFile call.
· DirectShowSource() now detects and handles non 32 bit aligned picture lines from dud codecs.
· Crop(align=true) tests actual alignment in each GetFrame call.
· Relax YV12 resizer width restriction, now mod 2 was mod 4.
· .AVSI failures during env->CreateScriptEnvironment() are now available to the GetError() interface.
· SetCacheHints(CACHE_RANGE, n) will now surrender frames to satisfy SetMemoryMax().
· CoInitialize()/CoUninitialize() now done as part of ScriptEnvironment creation/deletion.
· Much code from 2.6 base included. Typically IsYV12() changed to IsPlanar().