Python Reference — VapourSynth R72 documentation

# Python Reference

VapourSynth is separated into a core library and a Python module. This section explains how the core library is exposed through Python and some of the special things unique to Python scripting, such as slicing and output.

Note

Any script executed through the vsscript api (that means vspipe, avfs, vsvfw or other API users) will have __name__ set to “__vapoursynth__” unlike normal Python scripts where it usually is “__main__”.

## VapourSynth Structure

Most operations in the VapourSynth library are performed through the singleton core object. This core may load plugins, which all end up in their own unit, or namespace, so to say, to avoid naming conflicts in the contained functions. For this reason you call a plugin function with core.unit.Function().

All arguments to functions have names that are lowercase and all function names are CamelCase. Unit names are also lowercase and usually short. This is good to remember as a general rule.

## Grammar

### Slicing and Other Syntactic Sugar

The VideoNode and AudioNode class (always called “clip” in practice) supports the full range of indexing and slicing operations in Python. If you do perform a slicing operation on a clip, you will get a new clip back with the desired frames. Here are a few examples.

Operation | Description | Equivalent
--- | --- | ---
clip = clip[5] | Make a single frame clip containing frame number 5 | clip = core.std.Trim(clip, first=5, last=5)
clip = clip[5:11] | Make a clip containing frames 5 to 10 [1] | clip = core.std.Trim(clip, first=5, last=10) clip = core.std.AudioTrim(clip, first=5, last=10)
clip = clip[::2] | Select even numbered frames | clip = core.std.SelectEvery(clip, cycle=2, offsets=0)
clip = clip[1::2] | Select odd numbered frames | clip = core.std.SelectEvery(clip, cycle=2, offsets=1)
clip = clip[::-1] | Reverses a clip | clip = core.std.Reverse(clip) clip = core.std.AudioReverse(clip)
clip = clip1 + clip2 | The addition operator can be used to splice clips together | clip = core.std.Splice([clip1, clip2], mismatch=False) clip = core.std.AudioSplice([clip1, clip2])
clip = clip * 10 | The multiplication operator can be used to loop a clip [2] | clip = core.std.Loop(clip, times=10) clip = core.std.AudioLoop(clip, times=10)

[1]

Note that frame numbers, like python arrays, start counting at 0 and the end value of slicing is not inclusive

[2]

Note that multiplication by 0 is a special case that will repeat the clip up to the maximum frame count

Filters can be chained with a dot:

    clip = clip.std.Trim(first=100, last=2000).std.FlipVertical()

Which is equivalent to:

    clip = core.std.FlipVertical(core.std.Trim(clip, first=100, last=2000))

### Function Arguments, Return Types and Property Type Deduction in Python

VapourSynth internally uses a very simple map of key-value pairs to pass values to and from functions. As a result of this every key is actually a one dimensional array of values of a single type. The Python bindings try to hide this as best as possible to make things less annoying. For example a function returning only a single key will have the only the array itself returned and an array with a single value will in turn only have the single value returned.

Similarly function arguments are first converted to the appropriate type specified by the function’s argument string or fails if this isn’t possible. There is however one quirk where the data type’s type hint (utf-8/non-printable raw data) is set based on whether a str or a bytes/bytearray object is passed. Likewise a str object will be returned for all utf-8 hinted data and a bytes object for all other types.

Frame properties and “anything goes” function arguments have much stricter type requirements since the underlying type has to be possible to deduce from them. When using this type of functions, such as SetFrameProps, or property assignment it may be necessary to convert to int, float, str or bytes explicitly to make things works.

### Python Keywords as Filter Arguments

If a filter’s argument happens to be a Python keyword, you may append an underscore to the argument’s name when invoking the filter. The Python module will strip one trailing underscore (if present) from all filter arguments before passing them to the filters.

    clip = core.plugin.Filter(clip, lambda_=1)

Another way to deal with such arguments is to place them in a dictionary:

    kwargs = { "lambda": 1 }
    clip = core.plugin.Filter(clip, **kwargs)

VapourSynth will also support the PEP8 convention of using a single trailing underscore to prevent collisions with python keywords.

### Windows File Paths

If you have a string containing backslashes, you must either prefix the string with “r”, or duplicate every single backslash. The reason is that the backslash is an escape character in Python.

Use os.path.normcase(path) to fix Incorrect path string.

Correct example:

    "B:/VapourSynth/VapourSynth.dll"
    "B:\\VapourSynth\\VapourSynth.dll"
    r"B:\VapourSynth\VapourSynth.dll"

### Output

The normal way of specifying the clip(s) to output is to call clip.set_output(). All standard VapourSynth components only use output index 0, except for vspipe where it’s configurable but defaults to 0. There are also other variables that can be set to control how a format is output. For example, setting alt_output=1 changes the packing of the YUV422P10 format to one that is common in professional software (like Adobe products). Note that currently alt_output modes only has an effect with YUV420P8 (I420, IYUV), YUV422P8 (YUY2, UYVY) and YUV422P10 (v210).

An example on how to get v210 output:

    some_clip = core.resize.Bicubic(clip, format=vs.YUV422P10)
    some_clip.set_output(alt_output=1)

An example on how to get UYVY output:

    some_clip = core.resize.Bicubic(clip, format=vs.YUV422P8)
    some_clip.set_output(alt_output=2)

### Raw Access to Frame Data

The VideoFrame and AudioFrame classes contains one picture/audio chunk and all the metadata associated with it. It is possible to access the raw data using either get_read_ptr(plane) or get_write_ptr(plane) and get_stride(plane) with ctypes.

A more Python friendly wrapping is also available where each plane/channel can be accessed as a Python array using frame[plane/channel].

To get a frame simply call get_frame(n) on a clip. Should you desire to get all frames in a clip, use this code:

    for frame in clip.frames():
        # Do stuff with your frame
        pass

## Classes and Functions

core

  Gets the singleton Core object. If it is the first time the function is called, the Core will be instantiated with the default options. This is the preferred way to reference the core.

get_outputs()

  Return a read-only mapping of all outputs registered on the current node.

  The mapping will automatically update when a new output is registered.

get_output([index = 0])

  Get a previously set output node. Throws an error if the index hasn’t been set. Will return a VideoOutputTuple containing alpha and the alt_output setting for video output and an AudioNode for audio.

clear_output([index = 0])

  Clears a clip previously set for output.

clear_outputs()

  Clears all clips set for output in the current environment.

construct_signature(signature[, injected=None])

  Creates a inspect.Signature object for the given registration signature.

  If injected is not None, the default of the first argument of the signature will be replaced with the value supplied with injected.

register_on_destroy(callback)

  Registers a callback that is called when the script is being finalized. This allows you to release resources at the end of a script.

  A callback must be registered with every script that is run, even if the code is being reused in multiple script runs.

  No new callbacks can be registered when the script is already being finalized.

unregister_on_destroy(callback)

  Unregisters a previously added callback.

class Core

  The Core class uses a singleton pattern. Use the core attribute to obtain an instance. All loaded plugins are exposed as attributes of the core object. These attributes in turn hold the functions contained in the plugin. Use plugins() to obtain a full list of all currently loaded plugins you may call this way.

  num_threads

    The number of concurrent threads used by the core. Can be set to change the number. Setting to a value less than one makes it default to the number of hardware threads.

  max_cache_size

    Set the upper framebuffer cache size after which memory is aggressively freed. The value is in megabytes.

  used_cache_size

    The size of the core’s current cache. The value is in bytes.

  core_version

    Returns the core version as VapourSynthVersion tuple.

    Note

    If you are writing a library, and are not retrieving this from the proxy, you should consider using vapoursynth.__version__ instead not to have to unnecessarily fetch the core and lock inside an environment.

  api_version

    Returns the api version as VapourSynthAPIVersion tuple.

    Note

    If you are writing a library, and are not retrieving this from the proxy, you should consider using vapoursynth.__api_version__ instead not to have to unnecessarily fetch the core and lock inside an environment.

  plugins()

    Containing all loaded plugins.

  get_video_format(id)

    Retrieve a Format object corresponding to the specified id. Returns None if the id is invalid.

  query_video_format(color_family, sample_type, bits_per_sample, subsampling_w, subsampling_h)

    Retrieve a Format object corresponding to the format information, Invalid formats throw an exception.

  create_video_frame(format, width, height)

    Creates a new frame with uninitialized planes with the given dimensions and format. This function is safe to call within a frame callback.

  add_log_handler(handler_func)

    Installs a custom handler for the various error messages VapourSynth emits. The message handler is currently global, i.e. per process, not per VSCore instance. Returns a LogHandle object. handler_func is a callback function of the form func(MessageType, message).

  remove_log_handler(handle)

    Removes a custom handler.

  log_message(message_type, message)

    Send a message through VapourSynth’s logging framework.

  rule6()

    Illegal behavior detection.

class Local

  Internally, there can be more than one core. This is usually the case in previewer-applications. Use this class to store variables that depend on the currently active core.

      l = Local()
      l.test = 1

class VideoNode

  Represents a video clip. The class itself supports indexing and slicing to perform trim, reverse and selectevery operations. Several operators are also defined for the VideoNode class: addition appends clips and multiplication repeats them. Note that slicing and indexing always return a new VideoNode object and not a VideoFrame.

  format

    A Format object describing the frame data. If the format can change between frames, this value is None.

  width

    The width of the video. This value will be 0 if the width and height can change between frames.

  height

    The height of the video. This value will be 0 if the width and height can change between frames.

  num_frames

    The number of frames in the clip.

  fps

    The framerate represented as a Fraction. It is 0/1 when the clip has a variable framerate.

    numerator

      The numerator of the framerate. If the clip has variable framerate, the value will be 0.

    denominator

      The denominator of the framerate. If the clip has variable framerate, the value will be 0.

  fps_num

    Deprecated, use fps.numerator instead

  fps_den

    Deprecated, use fps.denominator instead

  flags

    Special flags set for this clip. This attribute should normally be ignored.

  get_frame(n)

    Returns a VideoFrame from position n.

  get_frame_async(n)

    Returns a concurrent.futures.Future-object which result will be a VideoFrame instance or sets the exception thrown when rendering the frame.

    The future will always be in the running or completed state

  get_frame_async(n, cb: callable)

    Renders a frame in another thread. When the frame is rendered, it will either call cb(Frame, None) on success or cb(None, Exception) if something fails.

    Added: R58

  set_output(index=0, alpha=None, alt_output=0)

    Set the clip to be accessible for output. This is the standard way to specify which clip(s) to output. All VapourSynth tools (vsvfw, vsfs, vspipe) use the clip in index 0. It’s possible to specify an additional containing the alpha to output at the same time. Currently only vspipe takes alpha into consideration when outputting. The alt_output argument is for optional alternate output modes. Currently it controls the FOURCCs used for VFW-style output with certain formats.

  output(fileobj[, y4m = False, prefetch = 0, progress_update = None, backlog=-1])

    Write the whole clip to the specified file handle. It is possible to pipe to stdout by specifying sys.stdout as the file. YUV4MPEG2 headers will be added when y4m is true. The current progress can be reported by passing a callback function of the form func(current_frame, total_frames) to progress_update. The prefetch argument is only for debugging purposes and should never need to be changed. The backlog argument is only for debugging purposes and should never need to be changed.

  frames([prefetch=None, backlog=None, close=False])

    Returns a generator iterator of all VideoFrames in the clip. It will render multiple frames concurrently.

    The prefetch argument defines how many frames are rendered concurrently. Is only there for debugging purposes and should never need to be changed. The backlog argument defines how many unconsumed frames (including those that did not finish rendering yet) vapoursynth buffers at most before it stops rendering additional frames. This argument is there to limit the memory this function uses storing frames. The close argument determines if the frame should be closed after each iteration step. It defaults to false to remain backward compatible.

  is_inspectable(version=None)

    Returns a truthy value if you can use the node inspection API with a given version. The python inspection-api is versioned, as the underlying API is unstable at the time of writing. The version number will be incremented every time the python API changes. There will be no attempt to maintain backwards compatibility as long as the API is marked as unstable.

    This method may never return a truthy value.

    This is the only stable function in the current inspection api-implementation.

    Note

    Be aware that introspection features must be enabled manually by the backing environment. Standalone Python-Scripts, not running inside vspipe or other editors, have introspection enabled automatically.

    Warning

    The graph-inspection-api is unstable. Omitting the version-argument will therefore always return None.

    The current version of the unstable python graph-inspection API is 0.

    Added: R58

    Parameters:

      version – If None, it will use the version number of the last stable API.

class VideoOutputTuple

  This class is returned by get_output if the output is video.

  clip

    A VideoNode-instance containing the color planes.

  alpha

    A VideoNode-instance containing the alpha planes.

  alt_output

    An integer with the alternate output mode to be used. May be ignored if no meaningful mapping exists.

class VideoFrame

  > This class represents a video frame and all metadata attached to it.

  format

    A Format object describing the frame data.

  width

    The width of the frame.

  height

    The height of the frame.

  readonly

    If readonly is True, the frame data and properties cannot be modified.

  props

    This attribute holds all the frame’s properties as a dict. They are also mapped as sub-attributes for compatibility with older scripts. For more information, see: API Reference Note: This includes the data for matrix, transfer and primaries. (_Matrix, _Transfer, _Primaries) See Resize for more information.

  copy()

    Returns a writable copy of the frame.

  close()

    Forcefully releases the frame. Once freed, the you cannot call any function on the frame, nor use the associated FrameProps.

    To make sure you don’t forget to close the frame, the frame is now a context-manager that automatically calls this method for you:

        with core.std.BlankClip().get_frame(0) as f:
            print(f.props)

  closed

    Tells you if the frame has been closed. It will be False if the close()-method has not been called yet.

  get_read_ptr(plane)

    Returns a pointer to the raw frame data. The data may not be modified. Note that this is a thin wrapper for the underlying C-api and as such calls to get_write_ptr, including the ones made internally by other functions in the Python bindings, may invalidate any pointers previously gotten to the frame with get_read_ptr when called.

  get_write_ptr(plane)

    Returns a pointer to the raw frame data. It may be modified using ctypes or some other similar python package. Note that this is a thin wrapper for the underlying C-api and as such calls to get_write_ptr, including the ones made internally by other functions in the Python bindings, may invalidate any pointers previously gotten to the frame with get_read_ptr when called.

  get_stride(plane)

    Returns the stride between lines in a plane.

  readchunks()

    This method is usually used to dump the contents of a VideoFrame to disk. The returned generator yields contiguous chunks of the VideoFrame memory.

        with open('output.raw', 'wb') as file:
           with vs.core.std.BlankClip(color=[25, 50, 60]).get_frame(0) as f:
              for chunk in f.readchunks():
                 file.write(chunk)

    Note

    Usually, the frame contents will be held in a contiguous array, and this method will yield n_planes of data chunks each holding the entire plane. Don’t, however, take this for granted, as it can’t be the case, and you will iterate over lines of plane data instead, which are assured to be contiguous.

    If you want to safely read the whole plane, use frame[plane_idx] to get the plane memoryview.

class VideoFormat

  This class represents all information needed to describe a frame format. It holds the general color type, subsampling, number of planes and so on. The names map directly to the C API so consult it for more detailed information.

  id

    A unique id identifying the format.

  name

    A human readable name of the format.

  color_family

    Which group of colorspaces the format describes.

  sample_type

    If the format is integer or floating point based.

  bits_per_sample

    How many bits are used to store one sample in one plane.

  bytes_per_sample

    The actual storage is padded up to 2^n bytes for efficiency.

  subsampling_w

    The subsampling for the second and third plane in the horizontal direction.

  subsampling_h

    The subsampling for the second and third plane in the vertical direction.

  num_planes

    The number of planes the format has.

  replace(core=None, **kwargs)

    Returns a new format with the given modifications.

    The only supported attributes that can be replaced are color_family, sample_type, bits_per_sample, subsampling_w, subsampling_h.

    The optional core-parameter defines on which core the new format should be registered. This is usually not needed and defaults to the core of the current environment.

class AudioNode

  Represents an audio clip. The class itself supports indexing and slicing to perform trim, reverse and selectevery operations. Several operators are also defined for the AudioNode class: addition appends clips and multiplication repeats them. Note that slicing and indexing always return a new AudioNode object and not a AudioFrame.

  sample_type

    If the format is integer or floating point based.

  bits_per_sample

    How many bits are used to store one sample in one plane.

  bytes_per_sample

    The actual storage is padded up to 2^n bytes for efficiency.

  channel_layout

    A mask of used channels.

  num_channels

    The number of channels the format has.

  sample_rate

    Playback sample rate.

  get_frame(n)

    Returns an AudioFrame from position n.

  get_frame_async(n)

    Returns a concurrent.futures.Future-object which result will be an AudioFrame instance or sets the exception thrown when rendering the frame.

    The future will always be in the running or completed state

  set_output(index=0)

    Set the clip to be accessible for output.

  frames([prefetch=None, backlog=None])

    Returns a generator iterator of all AudioFrames in the clip. It will render multiple frames concurrently.

    The prefetch argument defines how many frames are rendered concurrently. Is only there for debugging purposes and should never need to be changed. The backlog argument defines how many unconsumed frames (including those that did not finish rendering yet) vapoursynth buffers at most before it stops rendering additional frames. This argument is there to limit the memory this function uses storing frames.

  is_inspectable(version=None)

    Returns a truthy value if you can use the node inspection API with a given version. The python inspection-api is versioned, as the underlying API is unstable at the time of writing. The version number will be incremented every time the python API changes. There will be no attempt to maintain backwards compatibility as long as the API is marked as unstable.

    This method may never return a truthy value.

    This is the only stable function in the current inspection api-implementation.

    Note

    Be aware that introspection features must be enabled manually by the backing environment. Standalone Python-Scripts, not running inside vspipe or other editors, have introspection enabled automatically.

    Warning

    The graph-inspection-api is unstable. Omitting the version-argument will therefore always return None.

    The current version of the unstable python graph-inspection API is 0.

    Added: R58

    Parameters:

      version – If None, it will use the version number of the last stable API.

class AudioFrame

  > This class represents an audio frame and all metadata attached to it.

  sample_type

    If the format is integer or floating point based.

  bits_per_sample

    How many bits are used to store one sample in one plane.

  bytes_per_sample

    The actual storage is padded up to 2^n bytes for efficiency.

  channel_layout

    A mask of used channels.

  num_channels

    The number of channels the format has.

  readonly

    If readonly is True, the frame data and properties cannot be modified.

  props

    This attribute holds all the frame’s properties as a dict. Note that audio frame properties are fairly non-sensical as a concept for audio due to an arbitrary number of samples being lumped together and rarely used.

  copy()

    Returns a writable copy of the frame.

  get_read_ptr(plane)

    Returns a pointer to the raw frame data. The data may not be modified.

  get_write_ptr(plane)

    Returns a pointer to the raw frame data. It may be modified using ctypes or some other similar python package.

  get_stride(plane)

    Returns the stride between lines in a plane.

class Plugin

  Plugin is a class that represents a loaded plugin and its namespace.

  namespace

    The namespace of the plugin.

  name

    The name string of the plugin.

  version

    The version of the plugin returned as a PluginVersion tuple.

  plugin_path

    The main library location of the plugin. Note that internal functions don’t have a plugin path and instead return None.

  identifier
  functions()

    Containing all the functions in the plugin, You can access it by calling core.<namespace>.functions().

class Function

  Function is a simple wrapper class for a function provided by a VapourSynth plugin. Its main purpose is to be called and nothing else.

  name

    The function name. Identical to the string used to register the function.

  plugin

    The Plugin object the function belongs to.

  signature

    Raw function signature string. Identical to the string used to register the function.

  return_signature

    Raw function signature string. Identical to the return type string used register the function.

class Environment

  This class represents an environment.

  Some editors allow multiple vapoursynth-scripts to run in the same process, each of them comes with a different Core-instance and their own set of outputs. Each core-instance with their associated outputs represent their own environment.

  At any given time, only one environment can be active (in the same context). This class allows introspection about environments and allows to switch to them at will.

      env = get_current_environment()
      # sometime later
      with env.use():
        # Do stuff inside this env.

  is_single()

    Returns True if the script is _not_ running inside a vsscript-Environment. If it is running inside a vsscript-Environment, it returns False.

  env_id

    Return -1 if the script is not running inside a vsscript-Environment. Otherwise, it will return the current environment-id.

  single

    See is_single()

  alive

    Has the environment been destroyed by the underlying application?

  copy()

    Creates a copy of the environment-object.

    Added: R51

  use()

    Returns a context-manager that enables the given environment in the block enclosed in the with-statement and restores the environment to the one defined before the with-block has been encountered.

        env = get_current_environment()
        with env.use():
            with env.use():
                pass

    Added: R51

get_current_environment()

  Returns an Environment-object representing the environment the script is currently running in. It will raise an error if we are currently not inside any script-environment while vsscript is being used.

  This function is intended for Python-based editors using vsscript.

  Added: R51

class EnvironmentPolicy

  This class is intended for subclassing by custom Script-Runners and Editors. Normal users don’t need this class. Most methods implemented here have corresponding APIs in other parts of this module.

  An instance of this class controls which environment is activated in the current context. The exact meaning of “context” is defined by the concrete EnvironmentPolicy. A environment is represented by a `EnvironmentData`-object.

  To use this class, first create a subclass and then use `register_policy()` to get VapourSynth to use your policy. This must happen before vapoursynth is first used. VapourSynth will automatically register an internal policy if it needs one. The subclass must be weak-referenciable!

  Once the method `on_policy_registered()` has been called, the policy is responsible for creating and managing environments.

  Special considerations have been made to ensure the functions of class cannot be abused. You cannot retrieve the current running policy yourself. The additional API exposed by “on_policy_registered” is only valid if the policy has been registered. Once the policy is unregistered, all calls to the additional API will fail with a RuntimeError.

  Added: R51

  on_policy_registered(special_api)

    This method is called when the policy has successfully been registered. It proivdes additional internal methods that are hidden as they are useless and or harmful unless you implement your own policy.

    Parameters:

      special_api – This is a `EnvironmentPolicyAPI`-object that exposes additional API

  on_policy_cleared()

    This method is called once the python-process exits or when unregister_policy is called by the environment-policy. This allows the policy to free the resources used by the policy.

  get_current_environment()

    This method is called by the module to detect which environment is currently running in the current context. If None is returned, it means that no environment is currently active.

    Returns:

      An `EnvironmentData`-object representing the currently active environment in the current context.

  set_environment(environment)

    This method is called by the module to change the currently active environment. If None is passed to this function the policy may switch to another environment of its choosing.

    Note: The function is responsible to check whether or not the environment is alive. If a dead environment is passed, it should act like None has been passed instead of the dead environment but must never error.

    Parameters:

      environment – The `EnvironmentData` to enable in the current context.

    Returns:

      The environment that was enabled previously.

  is_alive(environment)

    Is the current environment still active and managed by the policy.

    The default implementation checks if EnvironmentPolicyAPI.destroy_environment has been called on the environment.

class EnvironmentPolicyAPI

  This class is intended to be used by custom Script-Runners and Editors. An instance of this class exposes an additional API. The methods are bound to a specific `EnvironmentPolicy`-instance and will only work if the policy is currently registered.

  Added: R51

  wrap_environment(environment)

    Creates a new `Environment`-object bound to the passed environment-id.

    Warning

    This function does not check if the id corresponds to a live environment as the caller is expected to know which environments are active.

  create_environment(flags=0)

    Returns a `Environment` that is used by the wrapper for context sensitive data used by VapourSynth. For example it holds the currently active core object as well as the currently registered outputs.

  set_logger(environment, callback)

    This function sets the logger for the given environment.

    This logger is a callback function that accepts two parameters: Level, which is an instance of vs.MessageType and a string containing the log message.

  destroy_environment(environment)

    Marks an environment as destroyed. Older environment-policy implementations that don’t use this function still work.

    Either EnvironmentPolicy.is_alive must be overridden or this method be used to mark the environment as destroyed.

    Added: R52

  unregister_policy()

    Unregisters the policy it is bound to and allows another policy to be registered.

  get_vapoursynth_api(version)

    Exposes getVapoursynthAPI to python. Returns a ctypes.c_void_p.

    Access to this function is provisional and might be removed if it is abused too much.

    Added: R62

  get_core_ptr(environment)

    Returns a ctypes.c_void_p pointing to the Core*-object that powers the environment.

    Access to this function is provisional and might be removed if it is abused too much.

    Added: R62

register_policy(policy)

  This function is intended for use by custom Script-Runners and Editors. It installs your custom `EnvironmentPolicy`. This function only works if no other policy has been installed.

  If no policy is installed, the first environment-sensitive call will automatically register an internal policy.

  Added: R50

  Note

  This must be done before VapourSynth is used in any way. Here is a non-exhaustive list that automatically register a policy:

  - Using “vsscript_init” in “VSScript.h”

  - Using `get_outputs()`

  - Using `get_output()`

  - Using `clear_output()`

  - Using `clear_outputs()`

  - Using `get_current_environment()`

  - Accessing any attribute of `core`

_try_enable_introspection(version=None)

  Tries to enable introspection. Returns true if it succeeds.

  Parameters:

    version – If not passed it will use the newest stable introspection-api.

  Added: R58

has_policy()

  This function is intended for subclassing by custom Script-Runners and Editors. This function checks if a `EnvironmentPolicy` has been installed.

  Added: R50

class EnvironmentData

  Internal class that stores the context sensitive data that VapourSynth needs. It is an opaque object whose attributes you cannot access directly.

  A normal user has no way of getting an instance of this object. You can only encounter EnvironmentData-objects if you work with EnvironmentPolicies.

  This object is weak-referenciable meaning you can get a callback if the environment-data object is actually being freed (i.e. no other object holds an instance to the environment data.)

  Added: R50

class Func

  Func is a simple wrapper class for VapourSynth VSFunc objects. Its main purpose is to be called and manage reference counting.

exception Error

  The standard exception class. This exception is thrown on most errors encountered in VapourSynth.

## Constants

### Video

#### Color Family

The color family constants describe groups of formats and the basic way their color information is stored. You should be familiar with all of them apart from maybe YCOCG and COMPAT. The latter is a special junk category for non-planar formats. These are the declared constants in the module:

    UNDEFINED
    RGB
    YUV
    GRAY

#### Format

Format constants exactly describe a format. All common and even more uncommon formats have handy constants predefined so in practice no one should really need to register one of their own. These values are mostly used by the resizers to specify which format to convert to. The naming system is quite simple. First the color family, then the subsampling (only YUV has it) and after that how many bits per sample in one plane. The exception to this rule is RGB, which has the bits for all 3 planes added together. The long list of values:

    NONE
    GRAY8
    GRAY9
    GRAY10
    GRAY12
    GRAY14
    GRAY16
    GRAY32
    GRAYH
    GRAYS
    YUV420P8
    YUV422P8
    YUV444P8
    YUV410P8
    YUV411P8
    YUV440P8
    YUV420P9
    YUV422P9
    YUV444P9
    YUV420P10
    YUV422P10
    YUV444P10
    YUV420P12
    YUV422P12
    YUV444P12
    YUV420P14
    YUV422P14
    YUV444P14
    YUV420P16
    YUV422P16
    YUV444P16
    YUV444PH
    YUV444PS
    RGB24
    RGB27
    RGB30
    RGB36
    RGB42
    RGB48
    RGBH
    RGBS

#### Chroma Location

    CHROMA_LEFT
    CHROMA_CENTER
    CHROMA_TOP_LEFT
    CHROMA_TOP
    CHROMA_BOTTOM_LEFT
    CHROMA_BOTTOM

#### Field Based

    FIELD_PROGRESSIVE
    FIELD_TOP
    FIELD_BOTTOM

#### Color Range

    RANGE_FULL
    RANGE_LIMITED

#### Matrix Coefficients

    MATRIX_RGB
    MATRIX_BT709
    MATRIX_UNSPECIFIED
    MATRIX_FCC
    MATRIX_BT470_BG
    MATRIX_ST170_M
    MATRIX_ST240_M
    MATRIX_YCGCO
    MATRIX_BT2020_NCL
    MATRIX_BT2020_CL
    MATRIX_CHROMATICITY_DERIVED_NCL
    MATRIX_CHROMATICITY_DERIVED_CL
    MATRIX_ICTCP

#### TransferCharacteristics

    TRANSFER_BT709
    TRANSFER_UNSPECIFIED
    TRANSFER_BT470_M
    TRANSFER_BT470_BG
    TRANSFER_BT601
    TRANSFER_ST240_M
    TRANSFER_LINEAR
    TRANSFER_LOG_100
    TRANSFER_LOG_316
    TRANSFER_IEC_61966_2_4
    TRANSFER_IEC_61966_2_1
    TRANSFER_BT2020_10
    TRANSFER_BT2020_12
    TRANSFER_ST2084
    TRANSFER_ST428
    TRANSFER_ARIB_B67

#### Color Primaries

    PRIMARIES_BT709
    PRIMARIES_UNSPECIFIED
    PRIMARIES_BT470_M
    PRIMARIES_BT470_BG
    PRIMARIES_ST170_M
    PRIMARIES_ST240_M
    PRIMARIES_FILM
    PRIMARIES_BT2020
    PRIMARIES_ST428
    PRIMARIES_ST431_2
    PRIMARIES_ST432_1
    PRIMARIES_EBU3213_E

### Audio

#### Channels

    FRONT_LEFT
    FRONT_RIGHT
    FRONT_CENTER
    LOW_FREQUENCY
    BACK_LEFT
    BACK_RIGHT
    FRONT_LEFT_OF_CENTER
    FRONT_RIGHT_OF_CENTER
    BACK_CENTER
    SIDE_LEFT
    SIDE_RIGHT
    TOP_CENTER
    TOP_FRONT_LEFT
    TOP_FRONT_CENTER
    TOP_FRONT_RIGHT
    TOP_BACK_LEFT
    TOP_BACK_CENTER
    TOP_BACK_RIGHT
    STEREO_LEFT
    STEREO_RIGHT
    WIDE_LEFT
    WIDE_RIGHT
    SURROUND_DIRECT_LEFT
    SURROUND_DIRECT_RIGHT
    LOW_FREQUENCY2

### Sample Type

    INTEGER
    FLOAT