gstreamer/docs/random/wtay/scheduling_ideas

Element types
-------------

SOURCES
-------

* never chain-based
* have no sinkpads

1) get based src

   (----------)
   ! fakesrc  !
   !         src-   (get based)
   (----------)

  * no sinkpads
  * srcpad(s) that are get-based

2) loop based src

   (----------)
   ! fakesrc  !
   !         src-   (loop based)
   (----------)

  * no sinkpads
  * element is loop-based
  * data is pushed on the srcpad(s)

FILTERS
-------

3) chain based filter

   (----------)
   ! identity !
 -sink       src- 
   (----------)

  * sinkpad(s) have a chain function
  * srcpad(s) push data

4) loop-based filter

   (----------)
   ! identity !
 -sink       src- 
   (----------)

  * element is loop-based
  * data is pushed on the srcpads
  * data is pulled from sinkpad(s)


SINKS
-----

5) chain based sink

   (----------)
   ! fakesink !
 -sink        !
   (----------)

  * sinkpad(s) have a chain function
  * no srcpads

6) loop-based sink

   (----------)
   ! fakesink !
 -sink        !
   (----------)

  * element is loop-based
  * data is pulled from sinkpad(s)


DECOUPLED
---------

7) decoupled element


   (----------)
   ! queue    !
 -sink       src- 
   (----------)

  * sinkpad(s) have chain function
  * srcpad(s) have get function
  * never loop-based
  * always acts like a chain-based sink for upstream elements
  * always acts like a get-based src for downstream elements


Connection types
----------------

1) get based src
2) loop based src
3) chain based filter
4) loop-based filter
5) chain based sink
6) loop-based sink
7) decoupled element


   !  1  !  2  !  3  !  4  !  5  !  6  !  7  !
---+-----+-----+-----+-----+-----+-----+-----+
 1 !  X  !  X  !  A  !  C  !  A  !  C  !  A  !
   !     !     !     !     !     !     !     !
 2 !  X  !  X  !  B  !  F  !  B  !  F  !  B  !
   !     !     !     !     !     !     !     !
 3 !  X  !  X  !  D  !  E  !  D  !  E  !  D  !
   !     !     !     !     !     !     !     !
 4 !  X  !  X  !  B  !  F  !  B  !  F  !  B  !
   !     !     !     !     !     !     !     !
 5 !  X  !  X  !  X  !  X  !  X  !  X  !  X  !
   !     !     !     !     !     !     !     !
 6 !  X  !  X  !  X  !  X  !  X  !  X  !  X  !
   !     !     !     !     !     !     !     !
 7 !  X  !  X  !  A  !  C  !  A  !  C  !  X  !
   !     !     !     !     !     !     !     !


A)

  src       -> sink
  src       -> filter
  src       -> decoupled
  decoupled -> sink
  decoupled -> filter

 - get based source
 - chain based sink

  * src at start of chain and entry point
  * _get from src, push to sink

B)

  src    -> sink
  src    -> filter
  src    -> decoupled
  filter -> sink
  filter -> filter
  filter -> decoupled

 - loop based source/filter
 - chain based sink/filter/decoupled

 * src/filter at start of chain and entry point
 * loop on src, pushhandler set to chain function


C) 

  src       -> sink
  src       -> filter
  decoupled -> sink
  decoupled -> filter

 - get based source/decoupled
 - loop based sink/filter

 * loop based element is entry point
 * loop on sink/filter, pullhandler set to _getfunction
 

D)

  filter -> filter
  filter -> sink
  filter -> decoupled

  - chain based filter
  - chain based filter/sink/decoupled

  * no entry point
  * pushhandler set to peer chainfunction
  
E)

  filter  -> filter
  filter  -> sink

  - chain based filter
  - loop based filter/sink

  * entry point in chain of filter
  * pushhandler set to loop wrapper

F)

  src     -> filter
  src     -> sink
  filter  -> filter
  filter  -> sink

  - loop based filter/src
  - loop based filter/sink

  * entry point in chain of filter/src
  * pushhandler set to loop wrapper
  

Grouping
--------

 * a group has at most one loop based element
 * elements in a group are sorted, src elements first
 * a group has one cothread
 * get-based plugins are put in the same group as a peer loop based element
 * chain based elements are put in the same group
 * entry point in the group is:
   - leftmost loopbased element 
   - first src element if no loopbased elements exist in the group


examples:
---------

 % = loop based
 * = entry point of group
   
.
  (-group1---------------)
  !                      !
  ! *fakesrc -> fakesink !
  (----------------------)

.
  (-group1---------------------------------------)
  !                                              !
  ! *fakesrc -> identity -> identity -> fakesink !
  (----------------------------------------------)

.
  (-group1-----------------------------------------)
  !                                                !
  ! fakesrc -> %*identity -> identity -> fakesink  !
  (------------------------------------------------)

.
  (-group1---------------) (-group2-----------------)
  !                      ! !                        !
  ! *fakesrc -> identity --> *%identity -> fakesink !
  (----------------------) (------------------------)

.
  (-group1------------------------------------)
  !                                           ! 
  ! *fakesrc -> tee  --> identity -> fakesink !
  !                  --> identity -> fakesink !  
  (-------------------------------------------)

.
  (-group1------------------------------------)
  !                                           ! 
  ! *fakesrc -> tee  --> identity -> fakesink !
  (--------------!----------------------------)
                 v
              (-group2-----------------)
              !                        !
              ! *%identity -> fakesink !
              (------------------------)

.
  (-group1----------) (-group2-----------------)
  !                 ! !                        !
  ! *fakesrc -> tee --> *%identity -> fakesink !
  (--------------!--) (------------------------)
                 v
              (-group3-----------------)
              !                        !
              ! *%identity -> fakesink !
              (------------------------)

.
  (-group1-----------------------) (-group2----------------------)
  !                              ! !                             !
  ! filesrc -> *%mpegdemux  --> queue* -> mpeg2dec -> xvideosink !
  !                              ! (-----------------------------)
  !                              ! (-group3----------------------)
  !                              ! !                             !
  !                         --> queue* -> mad -> osssink         !  
  (------------------------------) (-----------------------------)