Video encoder and method of operating the same

A video encoder comprising:

• a frequency converter;
• a quantizer;
• an encoding section;
• an intermediate buffer;
• a code amount estimation section;
• a code amount selector;
• a rate controller;
• a first counter;
• a second counter;
• and
• a selector controller,
• wherein the frequency converter performs a frequency conversion process on an input signal,
• wherein the quantizer performs a quantization process on the result of the frequency conversion process performed by the frequency converter,
• wherein the encoding section generates a compressed video bit stream by performing an encoding process on the result of the quantization process performed by the quantizer,
• wherein the intermediate buffer is coupled between the output terminal of the quantizer and the input terminal of the encoding section,
• wherein the input terminal of the code amount estimation section is coupled to the output terminal of the quantizer,
• wherein an estimated code amount generated from the output terminal of the code amount estimation section is supplied to the first input terminal of the code amount selector,
• wherein an actual code amount of the compressed video bit stream encoded by the encoding section is supplied to the second input terminal of the code amount selector,
• wherein a determination signal indicative of whether the amount of data stored in the intermediate buffer is large or small is supplied to a selection control terminal of the code amount selector,
• wherein the output terminal of the code amount selector is coupled to the input terminal of the rate controller,
• wherein an output signal of the rate controller is used to adjust a quantization scale of the quantizer,
• wherein the first counter retains a first count value by counting the number of an image block, which is a coding process unit and quantized by the quantizer,
• wherein the second counter retains a second count value by counting the number of an image block, which is a coding process unit and encoded by the encoding section,
• wherein the selector controller determines the difference between the first count value of the first counter and the second count value of the second counter,
• wherein, if the difference between the first count value of the first counter and the second count value of the second counter is great, the selector controller determines that a delay of a process performed by the encoding section or the amount of data stored in the intermediate buffer is large, and
• wherein, if the difference between the first count value of the first counter and the second count value of the second counter is small, the selector controller determines that a delay of a process performed by the encoding section or the amount of data stored in the intermediate buffer is small,
• wherein, if the determination signal indicates that the amount of data stored in the intermediate buffer is large, the estimated code amount from the code amount estimation section, which is supplied to the first input terminal of the code amount selector, is output to the output terminal of the code amount selector, and the estimated code amount is used to adjust the quantization scale of the quantizer, and
• wherein, if the determination signal indicates that the amount of data stored in the intermediate buffer is small, the actual code amount from the encoding section, which is supplied to the second input terminal of the code amount selector, is output to the output terminal of the code amount selector, and the actual code amount is used to adjust the quantization scale of the quantizer.

A method of operating a video encoder having a frequency converter, a quantizer, an encoding section, an intermediate buffer, a code amount estimation section, a code amount selector, and a rate controller, the method comprising the steps of:

• causing the frequency converter to perform a frequency conversion process on an input signal;
• causing the quantizer to perform a quantization process on the result of the frequency conversion process performed by the frequency converter;
• causing the encoding section to generate a compressed video bit stream by allowing the encoding section to perform an encoding process on the result of the quantization process performed by the quantizer;
• coupling the intermediate buffer between the output terminal of the quantizer and the input terminal of the encoding section;
• coupling the input terminal of the code amount estimation section to the output terminal of the quantizer;
• causing an estimated code amount, which is generated from the output terminal of the code amount estimation section, to be supplied to a first input terminal of the code amount selector;
• causing an actual code amount of the compressed video bit stream, which is encoded by the encoding section, to be supplied to a second input terminal of the code amount selector;
• causing a determination signal indicative of whether the amount of data stored in the intermediate buffer is large or small to be supplied to a selection control terminal of the code amount selector;
• coupling the output terminal of the code amount selector to the input terminal of the rate controller, an output signal of the rate controller being used to adjust a quantization scale of the quantizer;
• if the determination signal indicates that the amount of data stored in the intermediate buffer is large, causing the estimated code amount from the code amount estimation section, which is supplied to the first input terminal of the code amount selector, to be output to the output terminal of the code amount selector, the estimated code amount then being used to adjust the quantization scale of the quantizer;
• and
• if the determination signal indicates that the amount of data stored in the intermediate buffer is small, causing the actual code amount from the encoding section, which is supplied to the second input terminal of the code amount selector, to be output to the output terminal of the code amount selector, the actual code amount then being used to adjust the quantization scale of the quantizer,
• wherein whether the amount of data stored in the intermediate buffer is large or small is determined by checking whether the amount of stored data is larger than a predetermined threshold or by checking whether the amount of stored data is smaller than the predetermined threshold.