| Microsoft DirectX 8.1 (C++) |
The AutoTune method scans for a precise signal on the channel's frequency.
Syntax
HRESULT AutoTune(
long lChannel,
long *plFoundSignal
);
Parameters
lChannel
[in] TV channel number.
plFoundSignal
[out] Pointer to a variable indicating whether the channel's frequency was found; nonzero indicates found, zero indicates not found.
Return Values
Returns an HRESULT value that depends on the implementation of the interface.
Remarks
TV channels generally map to a unique frequency depending on regional variances. To avoid interference between multiple transmitters that are assigned the same channel when they are in close geographic proximity, small frequency offsets are introduced at each transmitter. In the United States, this offset ranges up to +/– 26.25 kilohertz (kHz).
This method handles the channel-to-frequency conversion and scans for the most precise frequency. Store these values by calling the IAMTVTuner::StoreAutoTune method. You can find base frequencies for channels in the appendix International Analog TV Tuning.
See Also