Querying The H.263 Encoder For Status; Figure 3. Task Partitioning In The Modified Application - Texas Instruments DSP/BIOS Real-Time Analysis (RTA User Manual

Dsp/bios real-time analysis (rta) and debugging applied to a video application

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if(controlVideoProc.frameRateChanged) {

txMsg.cmd

txMsg.arg1 = chanNum;

txMsg.arg2 = controlVideoProc.frameRateTarget;

controlVideoProc.frameRateChanged = FALSE;

MBX_post( &mbxProcess, &txMsg, 0 );

}

While implementing control via the host PC did not specifically require a separate task in the

modified application, adding a discrete control task makes the application more scalable. For

example, a user interface or communications link from another processor could send control

commands to a DSP-based video system. The control task could then service that user interface

or communications link. In the modified example, the control task simply monitors a global

structure for commands, and sends appropriate commands to the processing task if necessary.

The priority of the control TSK is set to a lower level than that of the tskVideoProcess, tskInput,

and tskOutput TSKs. This prevents the control task from adding latency or CPU overhead when

responding to control commands. The control commands are only serviced at times when the

three TSKs in the data stream are all in the blocked state and the processor would normally be

running its background loop.

Figure 3 shows the task partitioning added to the application flow in Figure 2.

YA fter420

Device

414 KB

Driver

B uffer

Y u v

422to

3 fram es

420

CbAfter420

CrAfter420

scratch1

14 KB = 20 lines

tskInp ut

Figure 3.

3.3