Optics: motion pictures – With film carried control signals
Reexamination Certificate
2002-02-25
2004-06-15
Adams, Michael (Department: 2851)
Optics: motion pictures
With film carried control signals
C396S210000
Reexamination Certificate
active
06750942
ABSTRACT:
The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2001-49544 filed on Feb. 26, 2001 and Japanese Patent Application No. 2002-39545 filed on Feb. 18, 2002, which are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motion picture code evaluation apparatus and in particular to a motion picture code communications evaluation technology to evaluate a code and a protocol used for transmission/reception of digital motion picture data.
2. Description of the Related Art
The digital motion picture is a temporal link of instantaneous pictures called motion frames (hereinafter referred to as frames). The digital motion picture generally has enormous data amount. Therefore, generally, compression of information, that is, encoding is made to perform data transmission/reception and the received data is decoded to play back the motion picture.
For example, international standards of the motion picture codes include MPEG (Moving Picture Experts Group)—2 (ISO/IEC13818) and MPEG-4 (ISO/IEC14496) by the ISO/IEC (International Organization for Standardization/International Electrotechnical Commission) and H.261 and H.263 by the ITU (International Telecommunication Union) recommendations.
The aforementioned motion picture code comprises pixels arranged in a shape of a lattice. For example, the CIF format comprising 352 horizontal pixels by 288 vertical pixels and the QCIF format comprising 176 horizontal pixels and 144 vertical pixels are used.
The number of pixels composing a frame is also called the screen size.
In the case of a color picture, for example, in the CIF, the number of pixels includes a luminance screen (Y information) and two chrominance screens (U and V information) There are, for example, 4:2:0 format where one pixel is assigned to the U information of the chrominace screens and one pixel is assigned to the V information of the chrominance screens per the luminance screen having 2 by 2 pixels, 4:2:2 format where one pixel is assigned to the U information the chrominance screens and one pixel is assigned to the V information the chrominance screens per the luminance screen having 2 pixels, and the like.
The 4:2:2 format has twice the number of the pixels in the chrominance screens as many as the 4:2:0 format.
In some case, three primary colors such as RGB (red, green, blue) may be used to represent each of pixels.
In the case of color image, the number of pixels refers to all pixels of the luminance and the chrominance or the three primary colors.
It goes without saying that the more the number of pixels per frame are, the more minute, that is, the higher quality picture is obtained.
The number of frames per unit time is, for example, 30 frames per second or 15 frames per second. The greater this value is, the smoother action is represented, that is, the higher quality picture is obtained.
In digitally representing the brightness, the intermediate gradation levels are quantized from the darkest black to the brightest white.
In such a case, the number of the quantization levels are finite and around 256 levels of gray gradation that can be visually represented in eight bits are used in general applications.
Or, the number of colors represented digitally is finite and around 16 million colors are used.
The number of colors may be referred to as the number of quantization levels.
Unless there is particular reason, the number of quantization levels is the number of colors in the case of color image.
Also, the number of gray quantization levels is greater, the higher quality picture is obtained.
The value obtained by totaling the gray quantization levels in a specific time over all the pixels in the frames is called a motion picture information amount.
Generally, the number of pixels and the number of frames per second are constant but may change the number of pixels or frames.
The number of quantization levels may vary within a frame.
For load applied on a transmission path, a transmitter and a receiver, the smaller amount of motion code provides smaller load.
Thus, an amount of motion picture codes in relation to an amount of an image before information compression, that is, the higher compression ratio or the more coding efficiency is desirable.
For motion codes specified in the international standards or equivalent, the realized encoding efficiency is limited. In order to reduce the load on a transmission path, a transmitter and a receiver, it is practically efficient to reduce the number of pixels, frames and gray quantization levels actually. However, this degrades the picture quality.
An actual operation for compensating the load on a transmission path, a transmitter and a receiver in the transmission of motion pictures requires high cost so that services may be operated by setting the higher charge for the larger amount of motion picture information.
Quality degradation of motion pictures caused by transmission of a motion picture code will be described.
In transmission/reception of a motion picture code, a motion picture received at a receiving party suffers from degradation compared with an original motion picture due to the following causes:
Firstly, a motion picture code is not correctly received due to a transmission error.
Secondly, transmission in packets results in loss of some of the packets halfway and the lost packets are not received.
Thirdly, transmission/reception of a motion picture code takes too much time and displaying after decoding of a motion picture frame is delayed from the timing of regeneration of motion picture, which already have started, so that the display of the motion picture frame is skipped and execution proceeds to processing of the next motion picture frame.
A part of an original motion picture, which is failed to be decoded and be displayed, is referred to a motion picture loss.
Depending on which part of the motion picture code the error occurred in, the transmission error has different influences on the motion picture to be decoded and to be displayed.
A parameter representing specifications of the entire motion picture code such as the screen size, and the chrominance format of a motion picture code or a part of the motion picture code that accommodates codes related to the predictive encoding system for the entire frame and prediction method is referred to a header.
In case that a transmission error has occurred in the header section, decoded display of the entire motion picture is disabled or decoded display of the entire frame is disabled.
In case that a transmission error has occurred in the section related to the gradation of pixels in a frame, decoded display of only corresponding pixels may be disabled.
In this way, there are not a specific relationship between the amount of motion picture code not used for decoded display due to a transmission error or delay and the amount of motion picture loss in a motion picture after decoding. Thus it is necessary to evaluate the motion picture loss in each time.
Assume that a motion picture code is transmitted in the CIF format at present and a service is performed to change to the transmission of a motion picture in QCIF format in accordance with congestion of a transmission path and worsening of transmission error ratio. In this case, the quality of a motion picture is roughly classified into two stages.
The CIF and QCIF formats have 352 horizontal pixels by 288 vertical pixels and 176 horizontal pixels by 144 vertical pixels, respectively. Therefore, difference in the amount of motion picture information between the CIF and QCIF formats is four times.
When several percents of motion picture loss is caused due to the transmission error, the difference in the amount of motion picture information between the CIF and QCIF formats is in a range of 3.8 to 4.2 times.
Even if charging is made in proportion to an amount of correctly transmitted motion picture information, the number of pixels and the number of frames (in other words, which format the motion pictu
Adams Michael
Ando Electric Co. Ltd.
Dalakis Michael
Fish & Richardson P.C.
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