Optics: motion pictures – Picture carriers – Strip type
Reexamination Certificate
2003-02-20
2004-06-29
Adams, Russell (Department: 2851)
Optics: motion pictures
Picture carriers
Strip type
C375S240260, C375S240290
Reexamination Certificate
active
06755531
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motion picture code evaluator and in particular to a motion picture code communications evaluation technology to simultaneously evaluate and test the motion picture quality of digital motion picture data transmitted in parallel to a large number of users by using a scalability code.
2. Description of Related Art
A related art technology concerning a motion picture code communications evaluator for evaluating the motion picture quality of transmitted digital motion picture data is disclosed in the Japanese Patent Application No. 2001-049544 “A motion picture communications evaluator and related systems” by the same inventor.
The related art technology will be summarized insofar as it is related to the invention.
A digital motion picture is a continuous sequence of instantaneous pictures in time called motion picture frames.
Data of a digital motion picture is generally huge. Thus, motion picture code transmission is generally performed where compression or encoding of information is made for data communications, followed by a decoding process to regenerate a motion picture. A sequence of motion codes is also called a stream.
A scalability code refers to a method for transmitting codes in hierarchical form to input only codes fit for the processing scale of the receiver or only those fit for the transmission path when there are a variety of receivers and transmission path scales.
Specific examples will be given later.
For example, international standards for motion picture codes includes, for example, MPEG (Moving Picture Experts Group)-2 (ISO/IEC13818) and MPEG-4 (ISO/IEC14496) specified by ISO/IEC (International organization for Standardization/International Electrotechnical Commission), and H.263 specified by ITU (International Telecommunication Union) recommendations.
The invention is applicable to similar motion picture codes as well as the international standards.
In the aforementioned motion picture code, frames comprise pixels arranged in a shape of a grating. A format comprising 352 pixels in the horizontal direction and 288 pixels in the vertical direction are often used.
The number of pixels which constitute a frame is also called resolution or a screen size.
In the case of a color image, the number of pixels is often referred to as the structure of a luminance screen (Y).
Colors and gray-scale levels in a color image are often represented as a luminance and two types of color difference values to represent colors.
A format which assigns two color difference pixels per luminance of two by two pixels or one which assigns four difference pixels are available.
The number of frames per unit time may be 30 frames per second or 15 frames per second. The greater this figure is, the smoother motion is represented, that is, the higher-quality picture is obtained.
The greater the number of pixels per frame is, the higher-resolution motion picture is obtained. The greater the number of pixels per unit time is, the smoother motion picture, or higher-resolution motion picture is obtained. However, this results in a greater load on a transmission path, transmitter or receiver.
This problem is solved by a motion picture communications method whereby the resolution is increased or decreased by twice or four times in the midst of transmission in order to keep up with a change in the substantial throughput caused by network congestion or radio wave propagation.
In terms of representation of colors and gray-scale levels in digital values, intermediate halftones from the darkest black to the lightest white are quantized. In general applications, levels in the neighborhood of 256-level gray scale which can be visually represented in eight bits are often used.
An image with a smaller change in gray-scale levels can be represented by a smaller number of gray-scale levels. For a color image, the number of quantization levels is the number of colors unless otherwise specified.
The greater the number of gray-scale levels or colors is, the higher-quality picture is obtained although this places a greater load on a transmission path, transmitter or receiver. This problem is solved by extending the width of quantization thus reducing the number of gray-scale levels.
A change in the number of gray-scale levels is often made even within a single frame.
Talking of a certain pixel, the narrower the quantization width is, that is, the greater the number of gray-scale levels or colors is, the more information is included.
The total sum value of the number of gray-scale quantization levels within a specified period across the pixels in all the frames is called the motion picture information amount here.
Roughly speaking, the larger the motion picture information amount is, the higher-quality picture is obtained.
As far as the compression ratio of motion picture encoding does not noticeably vary, the wider the band of a motion code is, the larger the motion picture information amount is, thus the higher-quality picture is obtained. This results in a greater load on a transmission path, transmitter or receiver. A method for operating a service with a high charge may be used to offset this drawback.
Charging on the basis of the occupied bandwidth and occupied time focuses on the cost of transmission path and transmission equipment while charging on the basis of the motion picture information amount focuses on the quality of an application. The latter method is importance because it likely to gain the consensus of users.
Quality degradation of a motion picture in the course of transmission of a motion picture code will be described.
In communications of a motion picture code, the receiving party obtains a lower quality picture than the original for the following reasons:
A transmission error may prevent a motion picture code from being properly received.
Some packets may be lost halfway as a result of data transmission in packets.
Communications of motion picture codes may take excessive time. An encoded motion picture frame may not be ready for display at the timing of the display in the ongoing motion picture playback. In this case, display of the motion picture frame is skipped to shift to the processing of the next motion picture frame.
In this way, a section which failed to display an encoded picture of the original motion picture is called a loss of motion picture.
A transmission error has different effects on the decoded motion picture to be displayed, depending on the section where the error has taken place.
A section which accommodates parameters to represent the specifications for the entire motion picture codes such as the screen size of a motion picture code and a color difference format as well as codes used in the predictive encoding system and prediction method for the entire frame is called a header.
In case a transmission error has occurred in the header section, the entire motion picture may be seriously affected or display of the entire decoded frame may be disabled.
In case a transmission error has occurred in a section concerning the gray-scale level of pixels in a frame, display of the decoded pixel may be disabled.
In this way, the amount of motion picture codes not used for display of decoded pictures due to a transmission error and a delay and the amount of loss of a decoded motion picture are not in a fixed relationship. Thus, a loss of the motion picture must be evaluated on demand.
However, calculating the motion picture information amount and motion picture loss amount each time motion codes are received on all the receivers will require a huge processing scale.
In particular, processing to decode a motion picture and reproduce a picture involves a huge workload. Thus, in practice, only limited sections are read such as the header of a motion picture code for further processing.
Actually, an effective motion picture quality check is conducted before starting a service. This check includes a server load test which verifies whether a motion picture server or cache server can transmit quality
Adams Russell
Ando Electric Co. Ltd.
Fish & Richardson P.C.
Smith Arthur A
LandOfFree
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