VSScript4.h

VSScript provides a convenient wrapper for VapourSynth’s scripting interface(s), allowing the evaluation of VapourSynth scripts and retrieval of output clips.

At this time, VapourSynth scripts can be written only in Python (version 3).

Here are a few users of the VSScript library:

vspipe

vsvfw

an example program

the video player mpv

Note

If libvsscript is loaded with dlopen(), the RTLD_GLOBAL flag must be used. If not, Python won’t be able to import binary modules. This is due to Python’s design.

Structs

VSScript

A script environment. All evaluation and communication with evaluated scripts happens through a VSScript object.

VSScriptAPI

This struct is the way to access VSScript’s public API.

Functions

getVSScriptAPI

const VSSCRIPTAPI *getVSScriptAPI(int version)

Returns a struct containing function pointer for the api. Will return NULL is the specified version isn’t supported.

It is recommended to always pass VSSCRIPT_API_VERSION.

getAPIVersion

int getAPIVersion(): Returns the api version provided by vsscript.

getVSAPI

const VSAPI *getVSAPI(int version)

Retrieves the VSAPI struct. Exists mostly as a convenience so the vapoursynth module doesn’t have to be explicitly loaded.

This could return NULL if the VapourSynth library doesn’t provide the requested version.

createScript

VSScript *createScript(VSCore *core)

Creates an empty script environment that can be used to evaluate scripts. Passing a pre-created core can be usful to have custom core creation flags, log callbacks or plugins pre-loaded. Passing NULL will automatically create a new core with default settings.

Takes over ownership of the core regardless of success or failure. Returns NULL on error.

getCore

VSCore *getCore(VSScript *handle)

Retrieves the VapourSynth core that was created in the script environment. If a VapourSynth core has not been created yet, it will be created now, with the default options (see the Python Reference).

VSScript retains ownership of the returned core object.

Returns NULL on error.

evaluateBuffer

int evaluateBuffer(VSScript *handle, const char *buffer, const char *scriptFilename)

Evaluates a script contained in a C string. Can be called multiple times on the same script environment to successively add more processing.

handle

Pointer to a script environment.

buffer

The entire script to evaluate, as a C string.

scriptFilename

A name for the script, which will be displayed in error messages. If this is NULL, the name “<string>” will be used.

The special __file__ variable will be set to scriptFilename’s absolute path if this is not NULL.

Returns non-zero in case of errors. The error message can be retrieved with getError(). If the script calls sys.exit(code) the exit code can be retrieved with getExitCode(). The working directory behavior can be changed by calling evalSetWorkingDir() before this function.

evaluateFile

int evaluateFile(VSScript *handle, const char *scriptFilename)

Evaluates a script contained in a file. This is a convenience function which reads the script from a file for you. It will only read the first 16 MiB which should be enough for everyone.

Behaves the same as evaluateBuffer().

getError

const char *getError(VSScript *handle)

Returns the error message from a script environment, or NULL, if there is no error.

It is okay to pass NULL.

VSScript retains ownership of the pointer and it is only guaranteed to be valid until the next vsscript operation on the handle.

getExitCode

int getExitCode(VSScript *handle)

Returns the exit code if the script calls sys.exit(code), or 0, if the script fails for other reasons or calls sys.exit(0).

It is okay to pass NULL.

getVariable

int getVariable(VSScript *handle, const char *name, VSMap *dst)

Retrieves a variable from the script environment.

If a VapourSynth core has not been created yet in the script environment, one will be created now, with the default options (see the Python Reference).

name: Name of the variable to retrieve.
dst: Map where the variable’s value will be placed, with the key name.

Behaves like getVariableEx with flags 0: a GPU resident node comes back with a GPUDownload automatically inserted, and fetching a variable that holds a GPU resident frame fails, since a lone frame cannot be wrapped.

Returns non-zero on error.

setVariables

int setVariables(VSScript *handle, const VSMap *vars)

Sets variables in the script environment.

The variables are now available to the script.

If a VapourSynth core has not been created yet in the script environment, one will be created now, with the default options (see the Python Reference).

vars: Map containing the variables to set.

Returns non-zero on error.

getOutputNode

VSNode *getOutputNode(VSScript *handle, int index)

Retrieves a node from the script environment. A node in the script must have been marked for output with the requested index.

The returned node has its reference count incremented by one.

Behaves like getOutputNodeEx with flags 0: a GPU resident output comes back with a GPUDownload automatically inserted, so the frames it produces are always CPU readable.

Returns NULL if there is no node at the requested index.

getOutputAlphaNode

VSNode *getOutputAlphaNode(VSScript *handle, int index)

Retrieves an alpha node from the script environment. A node with associated alpha in the script must have been marked for output with the requested index.

The returned node has its reference count incremented by one.

Behaves like getOutputAlphaNodeEx with flags 0, see getOutputNode.

Returns NULL if there is no alpha node at the requested index.

getAltOutputMode

int getAltOutputMode(VSScript *handle, int index)

Retrieves the alternative output mode settings from the script. This value has no fixed meaning but in vspipe and vsvfw it indicates that alternate output formats should be used when multiple ones are available. It is up to the client application to define the exact meaning or simply disregard it completely.

Returns 0 if there is no alt output mode set.

freeScript

void freeScript(VSScript *handle)

Frees a script environment. handle is no longer usable.

Cancels any clips set for output in the script environment.
Clears any variables set in the script environment.
Clears the error message from the script environment, if there is one.
Frees the VapourSynth core used in the script environment, if there is one.

Since this function frees the VapourSynth core, it must be called only after all frame requests are finished and all objects obtained from the script have been freed (frames, nodes, etc).

It is safe to pass NULL.

evalSetWorkingDir

void evalSetWorkingDir(VSScript *handle, int setCWD): Set whether or not the working directory is temporarily changed to the same location as the script file when evaluateFile is called. Off by default.

getAvailableOutputNodes

int getAvailableOutputNodes(VSScript *handle, int size, int *dst)

Writes the list of output index values set in the script to dst, at most size of them. Always returns the total number of available output index values.

Added in VSSCRIPT_API_MINOR 2.

GPU resident outputs and the Ex functions

Scripts may legally leave their outputs and variables GPU resident. The Ex variants below take a flags bitmask of VSScriptGetFlags; a consumer that passes sgfAllowGPUResident declares it can handle GPU residency and receives nodes and frames exactly as the script set them. Without the flag — and through every non-Ex function, which behaves exactly like flags 0 — GPU resident nodes come back with a GPUDownload automatically inserted so their frames are CPU readable, and a variable fetch that would hand out a GPU resident frame fails instead. All four were added in VSSCRIPT_API_MINOR 4.

getOutputNodeEx

VSNode *getOutputNodeEx(VSScript *handle, int index, int flags): getOutputNode with residency control, see above.

getOutputAlphaNodeEx

VSNode *getOutputAlphaNodeEx(VSScript *handle, int index, int flags): getOutputAlphaNode with residency control, see above.

getAvailableOutputNodesEx

int getAvailableOutputNodesEx(VSScript *handle, int size, int *dst, int flags): getAvailableOutputNodes with the same signature scheme as the other Ex functions. Every output is listed whichever way it will be retrieved, so flags currently changes nothing; it exists so the Ex family stays uniform.

getVariableEx

int getVariableEx(VSScript *handle, const char *name, VSMap *dst, int flags): getVariable with residency control, see above. Without sgfAllowGPUResident a GPU resident node value is replaced by a GPUDownload wrapped one, and a GPU resident frame value fails the whole fetch with nothing stored.