MPEG video decoder having a high bandwidth memory

Apparatus for decoding a data stream including a plurality of variable length encoded data values representing an image where the data stream represents video signals having luminance components and chrominance components, the apparatus comprising:

• a memory for storing image data where the memory has a single memory port which includes first and second channels, arranged in parallel, wherein each memory operation to the single memory port concurrently transfers data via the first and second channels and the image data is arranged in the memory to allow components of the image data to be accessed concurrently using the first and second channels;
• means for receiving the data stream and for storing the data stream into a buffer area of the memory via the single memory port;
• decoding means including:
• (a) means for fetching the variable length encoded data stream from the memory via the single memory port;
• (b) means for (1) processing the fetched variable length encoded data stream to produce first decoded values and (2) generating luminance values and corresponding chrominance values as the first decoded values;
• (c) means for fetching reference image data from the memory via the single memory port;
• (d) means for combining the fetched reference image data with the first decoded values to produce second decoded values;
• and
• (e) means (1) for storing the second decoded values in the memory via the single memory port and (2) for storing luminance components of the second decoded values using one of the first and second channels and storing corresponding chrominance components of the second decoded values using the other one of the first and second channels;
• and
• means (1) for fetching image data from the memory, via the single memory port, for display and (2) for fetching luminance components of the image data using one of the first and second channels and for fetching the corresponding chrominance components of the image data using the other one of the first and second channels.

A circuit for decoding video signals encoded according to the MPEG-2 standard, consisting essentially of:

• an image memory for storing image data where the image memory has a single memory port which includes first and second channels, arranged in parallel, wherein each memory operation which uses the single memory port concurrently transfers data via the first and second channels and the image data is arranged in the memory to allow respectively different components of the image data to be accessed concurrently using the first and second channels;
• a decoding processor including:
• a variable length decoder coupled to the image memory via the single memory port;
• an inverse quantization processor;
• an inverse discrete cosine transform processor;
• and
• a motion compensation processor, coupled to the image memory via the single memory port;
• and
• a block to raster converter, coupled to the image memory via the single memory port.

A system which synchronizes an internally generated oscillatory signal to an externally supplied multi-bit phase reference signal comprising:

• an oscillator, responsive to a control signal for generating the oscillatory signal;
• a counter, coupled to the oscillator for counting pulses of the oscillatory signal to produce a count value;
• a digital comparator for comparing the count value to the multi-bit phase reference signal to generate a phase difference signal;
• means for filtering the phase difference signal to generate a phase change signal;
• a source of phase reference signal, said phase reference signal, when applied to the oscillator as the control signal, causing the oscillator to generate the oscillatory signal at a predetermined frequency;
• means for combining the multi-bit phase reference signal with the phase change signal to generate the control signal;
• and
• synchronizing means for substituting at least a first portion of the multi-bit phase reference signal for the count value to synchronize the count value to the phase reference signal.