class UsbVideoStream

UsbVideoStream State Machine:

[DISCONNECTED] ------

<GetChannel

()>---------> [STOPPED]

/|

\

/ |

| --------

<stream

.OnClose()> |

<control

.OnClose>--/-------------- / |

| /

\

|

\

|/

[STREAMING]

<

--Start()--- [READY]

<

---

<CreateStream

()>

All states ------> Unbind() ----> [UNBOUND]

State transition table:

Cells marked with Error will return an error if attempted, but

will not result in a state transition.

Cells marked with N/A are not possible due to lack of channel to

make the call.

Initial State

| DISCONNECTED | STOPPED | READY | STREAMING

GetChannel | STOPPED | Error! | Error! | Error!

CreateStream | N/A | READY | Error! | Error!

Start | N/A | N/A | STREAMING | Error!

Stop | N/A | N/A | Error! | READY

stream close | N/A | N/A | STOPPED | STOPPED

control close | N/A | DISCONNECTED| DISCONNECTED | DISCONNECTED

Unbind | UNBOUND | UNBOUND | UNBOUND | UNBOUND

The Unbind action closes all channels, and disallows any further state transitions.

The state can be determined as follows:

if (unbind callback set) -> UNBOUND

if (!control channel) -> DISCONNECTED

elif (!stream channel) -> STOPPED

elif (!is_streaming_) -> READY

else -> STREAMING

This device does not allow multiple simultaneous control connections via GetChannel,

nor does it allow multiple streaming connections via CreateStream.

Any failure in communication over the control or stream channel will result in that channel

being closed, along with the state transitions that closure implies.

Calling Stop() may not stop the usb device from streaming video frames, but

It will cause this device to stop notifying the client of new frames via OnFrameAvailable.

When Start() is called after calling Stop(), OnFrameAvailable will be called when the next

available frame is filled, so the capture time may have occurred before Start() was called.

The stream_token eventpair passed with CreateStream will be ignored by this device,

although it will retain ownership of the token until the stream is shut down following

closure of the stream channel.

Unless specified otherwise, all methods of this class are assumed to be called

on the single threaded dispatcher owned by this class.