A worldwide television tuning system is configurable to the television
standards and channel frequencies of multiple different countries based on
a country's ITU long-distance country code. The television tuning system
is architected in parallel hardware and software components. The hardware
components include tuner circuitry to tune to various television
frequencies carrying television video signals and video decoder circuitry
coupled to receive a television video signal from the tuner circuitry and
to convert the television video signal to digital video data. The software
components include a tuner module coupled to adjust the tuner circuitry to
a particular television frequency and a video decoder module to decode the
digital video data according to a particular video standard. A driver
interface layer interfaces the software layer and the hardware circuitry.
When a new channel is requested, the tuner module generates and sends a
beginning tuning packet to inform the video decoder module of an impending
change to the new channel. In addition to the video decoder module, this
tuning packet also propagates to all downstream modules (e.g., audio
decoder module, VBI decoders, etc.). The tuner module then controls the
tuner circuitry to tune to a new television frequency that corresponds to
the new channel. Afterward, the tuner module generates and sends an ending
tuning packet to inform the video decoder module that the channel change
is complete. The tuning packet includes a designation of country within
which the tuning system is configured to receive television signals, a
channel to be tuned, the particular video standard, and flags indicating
whether the tuning packet represents a beginning of a tuning operation or
an ending of the tuning operation.