FlowCombiner#

Added in version 1.4.

class FlowCombiner(**kwargs)#

Utility struct to help handling FlowReturn combination. Useful for Element<!– –>s that have multiple source pads and need to combine the different FlowReturn for those pads.

FlowCombiner works by using the last FlowReturn for all Pad it has in its list and computes the combined return value and provides it to the caller.

To add a new pad to the FlowCombiner use add_pad(). The new Pad is stored with a default value of %GST_FLOW_OK.

In case you want a Pad to be removed, use remove_pad().

Please be aware that this struct isn’t thread safe as its designed to be

used by demuxers, those usually will have a single thread operating it.

These functions will take refs on the passed Pad<!– –>s.

Aside from reducing the user’s code size, the main advantage of using this helper struct is to follow the standard rules for FlowReturn combination. These rules are:

  • %GST_FLOW_EOS: only if all returns are EOS too

  • %GST_FLOW_NOT_LINKED: only if all returns are NOT_LINKED too

  • %GST_FLOW_ERROR or below: if at least one returns an error return

  • %GST_FLOW_NOT_NEGOTIATED: if at least one returns a not-negotiated return

  • %GST_FLOW_FLUSHING: if at least one returns flushing

  • %GST_FLOW_OK: otherwise

%GST_FLOW_ERROR or below, GST_FLOW_NOT_NEGOTIATED and GST_FLOW_FLUSHING are returned immediately from the update_flow() function.

Constructors#

class FlowCombiner
classmethod new() → FlowCombiner#

Creates a new FlowCombiner, use free() to free it.

Added in version 1.4.

Methods#

class FlowCombiner
add_pad(pad: Pad) → None#

Adds a new Pad to the FlowCombiner.

Added in version 1.4.

Parameters:

pad – the Pad that is being added

clear() → None#

Removes all pads from a FlowCombiner and resets it to its initial state.

Added in version 1.6.

free() → None#

Frees a FlowCombiner struct and all its internal data.

Added in version 1.4.

remove_pad(pad: Pad) → None#

Removes a Pad from the FlowCombiner.

Added in version 1.4.

Parameters:

pad – the Pad to remove

reset() → None#

Reset flow combiner and all pads to their initial state without removing pads.

Added in version 1.6.

update_flow(fret: FlowReturn) → FlowReturn#

Computes the combined flow return for the pads in it.

The FlowReturn parameter should be the last flow return update for a pad in this FlowCombiner. It will use this value to be able to shortcut some combinations and avoid looking over all pads again. e.g. The last combined return is the same as the latest obtained FlowReturn.

Added in version 1.4.

Parameters:

fret – the latest FlowReturn received for a pad in this FlowCombiner

update_pad_flow(pad: Pad, fret: FlowReturn) → FlowReturn#

Sets the provided pad’s last flow return to provided value and computes the combined flow return for the pads in it.

The FlowReturn parameter should be the last flow return update for a pad in this FlowCombiner. It will use this value to be able to shortcut some combinations and avoid looking over all pads again. e.g. The last combined return is the same as the latest obtained FlowReturn.

Added in version 1.6.

Parameters: