8 Extending Video🔗ℹ

Video offers several extension points. Both for adding new syntactic forms into the language, as well as new video primitives. There is some overlap in what the extensions are capable of, but each are useful in different circumstances.

The documentation in this section needs a lot of work.

8.1 Video Convert🔗ℹ

8.2 Conversion Database🔗ℹ

8.3 Core Forms🔗ℹ

Video also has basic syntax for creating new types of producers, transitions, merges, and filters. This API is still experimental and may change with little notice. Proceed with caution.

These forms are for defining producers, filters, transitions, and merges. Also the forms for building their contracts and writing their documentation.

syntax (define-producer function-header   maybe-subgraph   maybe-properties   maybe-user-properties   body ...)

maybe-subgraph   =       |   #:subgraph subgraph           maybe-properties   =       |   #:properties properties           maybe-user-properties   =       |   #:user-properties user-properties

subgraph   :   (or/c procedure? #f)    properties   :   procedure?

syntax (->producer [extra-args ...] [optional-args ...] maybe-ret)

maybe-ret   =       |   return

syntax (defproducer prototype maybe-return content ...)

prototype   =   (id arg-spec ...)     |   (prototype arg-spec ...)           maybe-ret   =       |   #:return     |   ret

syntax (define-filter function-header   maybe-subgraph   maybe-properties   maybe-source-properties   maybe-user-properties   body ...)

maybe-subgraph   =       |   #:subgraph subgraph           maybe-properties   =       |   #:properties properties           maybe-user-properties   =       |   #:user-properties user-properties           maybe-source-properties   =       |   #:source-props source-properties

subgraph   :   (or/c procedure? #f)    properties   :   procedure?    source-props   :   procedure?

syntax (->filter [extra-args ...] [optional-args ...] maybe-ret)

maybe-ret   =       |   return

syntax (deffilter prototype maybe-return content ...)

prototype   =   (id arg-spec ...)     |   (prototype arg-spec ...)           maybe-ret   =       |   #:return     |   ret

syntax (define-transition function-header   maybe-track1-subgraph   maybe-track2-subgraph   maybe-combined-subgraph   maybe-properties   maybe-source-properties   maybe-user-properties   maybe-producer-1   maybe-producer-2   body ...)

maybe-track1-subgraph   =       |   #:track1-subgraph subgraph           maybe-track2-subgraph   =       |   #:track2-subgraph subgraph           maybe-combined-subgraph   =       |   #:combined-subgraph subgraph           maybe-properties   =       |   #:properties properties           maybe-user-properties   =       |   #:user-properties user-properties           maybe-source-properties   =       |   #:source-props source-properties           maybe-prod1   =       |   #:prod-1 prod1-id           maybe-prod2   =       |   #:prod-2 prod2-id

subgraph   :   (or/c procedure? #f)    properties   :   procedure?    source-props   :   procedure?

syntax (->transition [extra-args ...] [optional-args ...] maybe-ret)

maybe-ret   =       |   return

syntax (deftransition prototype maybe-return content ...)

prototype   =   (id arg-spec ...)     |   (prototype arg-spec ...)           maybe-ret   =       |   #:return     |   ret

syntax (define-merge function-header   maybe-track1-subgraph   maybe-track2-subgraph   maybe-combined-subgraph   maybe-properties   maybe-source-properties   maybe-user-properties   maybe-producer-1   maybe-producer-2   body ...)

maybe-track1-subgraph   =       |   #:track1-subgraph subgraph           maybe-track2-subgraph   =       |   #:track2-subgraph subgraph           maybe-combined-subgraph   =       |   #:combined-subgraph subgraph           maybe-properties   =       |   #:properties properties           maybe-user-properties   =       |   #:user-properties user-properties           maybe-source-properties   =       |   #:source-props source-properties           maybe-prod1   =       |   #:prod-1 prod1-id           maybe-prod2   =       |   #:prod-2 prod2-id

subgraph   :   (or/c procedure? #f)    properties   :   procedure?    source-props   :   procedure?

syntax (->merge [extra-args ...] [optional-args ...] maybe-ret)

maybe-ret   =       |   return

syntax (defmerge prototype maybe-return content ...)

prototype   =   (id arg-spec ...)     |   (prototype arg-spec ...)           maybe-ret   =       |   #:return     |   ret