Synchronization method of image decoder

An image decoding apparatus for decoding an image from a digital transport stream obtained by multiplexing a digital video bit stream being frame-coded or field-coded, and a time stamp signal comprising:

• de-multiplexing means for extracting the digital video bit stream and the time stamp signal from the digital transport stream;
• first clock reproducing means for reproducing a first clock signal from the time stamp signal;
• second clock reproducing means for reproducing a second clock signal from the first clock signal;
• decoding means for decoding the digital video bit stream and outputting a first digital video signal having a first frame frequency synchronized with the timing of first clock signal;
• graphic generating means for generating a graphic signal;
• overlaying means for overlaying the first digital video signal and the graphic signal and the graphic signal and outputting a second overlaid digital signal synchronized with the timing of first clock signal and having a second frame frequency;
• memory means for storing at least the first digital video signal;
• digital-to-analog converting means for converting the second overlaid digital signal into a second analog signal synchronized with the timing of first clock signal timing generating means for generating a third clock signal independent of the second clock signal;
• and
• switching means for choosing one clock signal between the second clock signal and the third clock signal and outputting the chosen clock signal,
• wherein the digital-to-analog converting means is synchronized with the clock signal output from the switching means.

An image decoding apparatus for decoding an image from a digital transport stream obtained by multiplexing a digital video bit stream being frame-coded or field-coded, and a time stamp signal, comprising:

• de-multiplexing means for extracting the digital video bit stream and the time stamp signal from the digital transport stream;
• first clock reproducing means for reproducing a first clock signal from the time stamp signal;
• second clock reproducing means for reproducing a second clock signal from the first clock signal;
• decoding means for decoding the digital video bit stream arid outputting a first digital video signal having a first frame frequency synchronized with the timing of first clock signal;
• graphic generating means for generating a graphic signal;
• interpolating means for outputting a second digital video signal obtained by increasing a spatial resolution of the first digital video signal;
• overlaying means for overlaying the second digital video signal and the graphic signal and outputting a third overlaid digital signal synchronized with the timing of first clock signal;
• memory means for storing at least the second digital video signal;
• digital-to-analog converting means for converting the third overlaid digital signal into a third analog signal synchronized with the timing of first clock signal timing generating means for generating a third clock signal independent to the second clock signal;
• and
• switching means for choosing one clock signal between the second clock signal and the third clock signal and outputting the chosen clock signal,
• wherein the digital-to-analog converting means is synchronized with the clock signal output from the switching means.

An image decoding apparatus for decoding an image from a digital transport stream obtained by multiplexing a digital video bit stream being frame-coded or field-coded, and a time stamp signal, comprising:

• de-multiplexing means for extracting the digital video bit stream and the time stamp signal from the digital transport stream;
• first clock reproducing means for reproducing a first clock signal from the time stamp signal;
• second clock reproducing means for reproducing a second clock signal from the first clock signal;
• decoding means for decoding the digital video bit stream and outputting a first digital video signal having a first frame frequency synchronized with the timing of the first clock signal;
• graphic generating means for generating a graphic signal;
• decimating means for outputting a third digital video signal obtained by decreasing a spatial resolution of the first digital video signal;
• overlaying means for overlaying the third digital video signal and the graphic signal and outputting a fourth overlaid digital signal synchronized with the timing of second clock signal;
• memory means for storing at least the third digital video signal;
• digital-to-analog converting means for converting the fourth overlaid digital signal into a fourth analog signal synchronized with the timing of second clock signal timing generating means for generating a third clock signal independent of the second clock signal;
• and
• switching means for choosing one clock signal between the second clock signal and the third clock signal and outputting the chosen signal,
• wherein the digital-to-analog converting means is synchronized with the clock signal output from the switching means.