Picture coding method, picture decoding method, picture coding apparatus, picture decoding apparatus, and program thereof

Abstract

A picture coding method of the present invention codes a picture signal and a ratio of a number of luminance pixels and a number of chrominance pixels for the picture signal, and then one coding method out of at least two coding methods is selected depending on the ratio. Next, data related to a picture size is coded in accordance with the selected coding method. The data related to the picture size indicates a size of the picture corresponding to the picture signal or an output area, which is a pixel area to be outputted in decoding in a whole pixel area coded in the picture signal coding.

Description

picuture picture data DataV in the demultiplexing unit DeMuxU. The coding picture data DataV is decoded using anti-orthogonal transformation, anti-quantization, variable length decoding, motion compensation and so on by pixel decoding unit DecU. The pixels values obtained by the decoding is outputted as decoded picture data DecV. The color format decoding unit ChromaFormatDecU decodes the color format coding information ChromaFormatData by such as the variable length code table in FIG. 4A. And then the decoded color format coding information ChromaFormatData is outputted as color format ChromaFormat. Similarly the output area information decoding unit CropDec U decodes the output area coding information CropData by such as the variable length code table in FIG. 4B. And then the decoded output area coding information CropData is outputted as output area information Crop. The output area specifying unit AreaDecU converts the output area information Crop into the output area Area depending on color format ChromaFormat.

For example, in the case where color format ChromaFormat indicates that the ratio of the number of pixels of luminance to chrominance is M:1 in horizontal direction and N:1 in vertical direction, since the output area information Crop represents LCrop/M, RCrop/M, TCrop/N and BCrop/N, LCrop, RCrop, TCrop and BCrop representing the output area Area can be obtained by multiplying by M or N respectively. The output area extracting unit CropU extracts the area indicated by output area Area out of decoding picture data DecV, and outputs as output picture Vout.

It should be noted that the output area information Crop are indicated by LCrop, RCrop, TCrop and BCrop, and Width and Height may be used as a part of data substitutively. Additionally, in the case where LCrop and Tcrop of the output area are zero, only TCrop and BCrop may be decoded out of output information CropData.

Furthermore, the picture size of the whole pixel area to be coded, that is the number of horizontal pixels MBWidth and the number of vertical pixels MBHeight shown in FIG. 1 may be decoded similarly together with output area information or substitutively as a data related to the picture size.

FIG. 7A is a flowchart to show a picture coding method of the present invention and to show a procedure of a picture coding method as shown in a block diagram of the picture coding apparatus of the present invention in FIG. 5.

First the output area Area and the color format ChromatFormat are obtained from outside (Step 10). The derivation process for output area information Crop is changed depending on the color format ChromaFormat, which is either 4:2:0, 4:2:2 or 4:4:4 (Step 11). In the case where color format ChormaFormat is 4:2:0, width (value in horizontal direction) and height (value in vertical direction), which are contained in the output area information, are multiplied by ½ respectively, and the result of the multiplication by ½ is used as output area information Crop (Step 12). In the case where color format ChromaFormat is 4:2:2, only width (value in horizontal direction), which is contained in the output area information, is multiplied by ½, and the result of the multiplication by ½ is used as output area information Crop (Step 13). After an input picture Vin is coded (Step 14), the color format ChromaFormat and output area information Crop are coded (Step 15).

It should be noted that Step 14 may be performed before Steps 10 and 11, and the case that Step 14 is performed before Step 11 is shown in FIG. 7B.

Additionally, the codings of the color format ChromaFormat and the output area information Crop (Step 15) may be executed before the coding of the input picture Vin (Step 14). In that case, Step 14 is executed immediately after Step 15 in the flowcharts of FIG. 7A and FIG. 7B.

Besides, in the embodiment, it is exemplified that the color formats ChromaFormat are 4:2:0, 4:2:2 and 4:4:4 only. However, in the case where the ratio of the number of pixels of luminance to chrominance is M:1 in horizontal direction and N:1 in vertical direction, the width can be multiplied by 1/M instead of ½ and the height can be multiplied by 1/N instead of ½ for functioning practically.

Furthermore, the picture size of the whole pixel area to be coded, that is the number of horizontal pixels MBWidth and the number of vertical pixels MBHeight shown in FIG. 1, may be coded similarly together with output area information or substitutively as a data related to the picture size.

FIG. 8A is a flowchart to show a picture decoding method of the present invention and is showing the procedure of the picture decoding method as shown in the block diagram of the picture decoding method in FIG. 6.

First the output area information Crop and the color format ChromaFormat are decoded (Step 20). The decoding process of the output area information Crop is changed depending on the color format ChromaFormat, which is either 4:2:0, 4:2:2 or 4:4:4 (Step 21). In the case where color format ChromaFormat is 4:2:0, width (value in horizontal direction) and height (value in vertical direction), which are contained in the output area information indicated in output area information Crop, are multiplied by 2 respectively, and the result of the multiplication by 2 is used as output area Area (Step 22). In the case where the color format

ChromaFormat is 4:2:2, only width (value in horizontal direction), which is contained in output area information indicated in output area information Crop, is multiplied by 2, and the result of the multiplication by 2 is used as output area Area (Step 23). After the picture signal is decoded out of the bitstream Str (Step 24), a part of the decoded picture is extracted depending on the output area Area, and outputted as an output picture Vout (Step 25).

It should be noted that Step 24 may be performed before Steps 20 and 21, and the case that Step 24 is performed before Step 21 is shown in FIG. 8B.

Besides, in the embodiment, it is exemplified that the color formats ChromaFormat are 4:2:0, 4:2:2 and 4:4:4 only. However, in the case where the ratio of the number of pixels of luminance to chrominance is M:1 in horizontal direction and N:1 in vertical direction, the width can be multiplied by M instead of 2 and the height can be multiplied by N instead of 2 for functioning practically.

Furthermore, the picture size of the whole pixel area to be coded, that is the number of horizontal pixels MBWidth and the number of vertical pixels MBHeight shown in FIG. 1 may be decoded similarly together with output area information or substitutively as a data related to the picture size.

Moreover, if a program for realizing the picture coding method and the picture decoding method mentioned above are recorded on a recording medium such as a flexible disk, it is possible to easily perform the processing presented above in an independent computer system.

FIG. 9A, FIG. 9B and FIG. 9C are diagrams illustrating a recording medium that stores a program for realizing the picture coding method and the picture decoding method according to the above-mentioned embodiment.

FIG. 9B shows a front view of an appearance, a section structure for a flexible disc and a flexible disc, FIG. 9A shows an example of a physical format of flexible disc as a recording medium. The flexible disk FD is contained in a case F, and plural of tracks Tr are formed concentrically on the surface of the flexible disk FD from periphery toward inner periphery, each track being divided into 16 sectors Se in the angular direction. Therefore, in the flexible disk storing the abovementioned program, the picture coding method and the picture decoding method as such programs are recorded in an area allocated for it on the flexible disk FD.

Further, FIG. 9C shows a structure for recording and replaying of above said programs into a flexible disc FD. When the above programs to realize the picture coding method and the picture decoding method are to be recorded on the flexible disk FD, such programs shall be written using computer system Cs via a flexible disk drive FDD. Meanwhile, when the picture coding method and the picture decoding method, which realize the picture coding method and the picture decoding method by the programs in flexible disc FD, are to be constructed in the computer system, the program shall be read out from flexible disk FD via the flexible disk drive FDD and then transferred to computer system Cs.

It should be noted that a flexible disc is exemplified as a recoding medium in the above-mentioned description, but an optical disc also can be used likewise. Further recording media are not limited to above examples, but any program recordable media such as an IC card, a ROM cassette and so on can be practical.

The following describes application examples of the picture coding method and the picture decoding method as shown above as well as a system employing them.

FIG. 10 shows a whole structure of a content providing system ex100 that realizes a content providing service. The area for providing a communication service is divided into cells of desired size, and base stations ex107 to ex110, which are fixed wireless stations, are placed in the respective cells.

In this content providing system ex100, devices such as a computer ex111, a PDA (Personal Digital Assistant) ex112, a camera ex113, a cellular phone ex114, and a camera-equipped cellular phone ex115 are respectively connected to Internet ex101 via an Internet service provider ex102, a telephone network ex104, and base stations ex107˜ex110.

However, content providing system ex100 is not limited to the combination as shown in FIG. 10, and may be connected to a combination of any of them. Also, each of the devices may be connected directly to telephone network ex104, not via base stations ex107 to ex110, which are fixed wireless stations. Camera ex113 is a device such as a digital video camera capable of taking moving pictures. The cellular phone may be a cellular phone of a PDC (Personal Digital Communication) system, a CDMA (Code Division Multiple Access) system, a W-CDMA (Wideband-Code Division Multiple Access) system or a GSM (Global System for Mobile Communications) system, a PHS (Personal Handyphone system) or the like, and may be any one of these.

Furthermore, a streaming server ex103 is connected to camera ex113 via base station ex109 and telephone network ex104, which enables live distribution or the like based on coded data transmitted by a user using camera ex113. Either camera ex113 or a server and the like capable of data transmission processing may code the data taken. Also, moving picture data taken by a camera ex116 may be transmitted to streaming server ex103 via computer ex111. Camera ex116 is a device such as a digital camera capable of taking still pictures and moving pictures. In this case, either camera ex116 or computer ex111 may code the moving picture data. In this case, an LSI ex117 included in computer ex111 or camera ex116 performs coding processing. Note that software for coding and decoding may be integrated into a certain type of storage medium (such as a CD-ROM, a flexible disk and a hard disk) that is a recording medium readable by computer ex111 and the like. Furthermore, camera-equipped cellular phone ex115 may transmit a moving picture data. This moving picture data is data coded by an LSI included in cellular phone ex115.

In this content providing system ex100, content (e.g. a music live video) which has been taken by a user using camera ex113, camera ex116 or the like is coded in the same manner as the above embodiment and transmitted to streaming server ex103, while streaming server ex103 distributes the content data to subscribers upon request. The subscribers here include computer ex111, PDA ex112, camera ex113, cellular phone ex114 and so on capable of decoding the above coded data. Content providing system ex100 with the above configuration is a system that enables the subscribers to receive and reproduce the coded data and realizes personal broadcasting by allowing them to receive, decode and reproduce the data in real time.

The picture coding apparatus and the picture decoding apparatus presented in the above embodiment can be used for coding and decoding to be performed in each of the device constructing the above system.

An example for a cellular phone is described hereinafter.

FIG. 11 is a diagram showing cellular phone ex115 that employs the picture coding method and the picture decoding method described in the above embodiment. Cellular phone ex115 has an antenna ex201 for transmitting/receiving radio waves to and from base station ex110, a camera unit ex203 such as a CCD camera capable of taking video and still pictures, a display unit ex202 such as a liquid crystal display for displaying the decoded data, that are a video taken by camera unit ex203 and a video received through antenna ex201 and the like, a main unit equipped with a group of operation keys ex204, a voice output unit ex208 such as a speaker for outputting voices, a voice input unit ex205 such as a microphone for inputting voices, a recording medium ex207 for storing coded data or decoded data such as data of moving pictures or still pictures taken by the camera, data of received e-mails and moving picture data or still picture data, and a slot unit ex206 for enabling recording medium ex207 to be attached to cellular phone ex115. Recording medium ex207 is embodied as a flash memory element, a kind of EEPROM (Electrically Erasable and Programmable Read Only Memory) that is an electrically erasable and rewritable non-volatile memory, stored in a plastic case such as an SD card.

Next, referring to FIG. 12, a description of cellular phone ex115 is given. In cellular phone ex115, a main control unit ex311 for centrally controlling display unit ex202 and each unit of the main unit having the operation keys ex204 is configured in a manner in which a power supply circuit unit ex310, an operation input control unit ex304, a picture coding unit ex312, a camera interface unit ex303, an LCD (Liquid Crystal Display) control unit ex302, a picture decoding unit ex309, a multiplexing/demultiplexing unit ex308, a recording/reproducing unit ex307, a modem circuit unit ex306 and a voice processing unit ex305 are interconnected via a synchronous bus ex313.

When a call-end key or a power key is turned on by a user operation, power supply circuit unit ex310 supplies each unit with power from a battery pack, and activates camera-equipped digital cellular phone ex115 to make it into a ready state.

In the cellular phone ex115, voice processing unit ex305 converts a voice signal received by the voice input unit ex205 in conversation mode into digital voice data under the control of main control unit ex311 comprised of a CPU, a ROM, a RAM and others, the modem circuit unit ex306 performs spread spectrum processing on it, and a transmit/receive circuit unit ex301 performs digital-to-analog conversion processing and frequency transformation processing on the data, so as to transmit the resultant via antenna ex201. Also, in cellular phone ex115, data received by antenna ex201 in conversation mode is amplified and performed of frequency transformation processing and analog-to-digital conversion processing, modem circuit unit ex306 performs inverse spread spectrum processing on the resultant, and voice processing unit ex305 converts it into analog voice data, so as to output it via voice output unit ex208.

Furthermore, when sending an e-mail in data communication mode, text data of the e-mail inputted by operating operation keys ex204 on the main unit is sent out to main control unit ex311 via operation input control unit ex304. In main control unit ex311, after modem circuit unit ex306 performs spread spectrum processing on the text data and transmit/receive circuit unit ex301 performs digital-to-analog conversion processing and frequency transformation processing on it, the resultant is transmitted to base station ex110 via antenna ex201.

When picture data is transmitted in data communication mode, the picture data taken by camera unit ex203 is supplied to picture coding unit ex312 via camera interface unit ex303. When picture data is not to be transmitted, it is also possible to display such picture data taken by camera unit ex203 directly on display unit ex202 via camera interface unit ex303 and LCD control unit ex302.

Picture coding unit ex312, which includes the picture coding apparatus according to the present invention, performs compression coding on the picture data supplied from camera unit ex203 using the coding method employed by the picture coding apparatus presented in the above embodiment, so as to convert it into coded picture data, and sends it out to multiplexing/demultiplexing unit ex308. At this time, cellular phone ex115 sends voices received by voice input unit ex205 during the shooting by camera unit ex203, to multiplexing/demultiplexing unit ex308 as digital voice data via voice processing unit ex305.

Multiplexing/demultiplexing unit ex308 multiplexes the coded picture data supplied from picture coding unit ex312 and the voice data supplied from voice processing unit ex305 using a predetermined method, modem circuit unit ex306 performs spread spectrum processing on the resulting multiplexed data, and the transmit/receive circuit unit ex301 performs digital-to-analog conversion processing and frequency transformation processing on the resultant, so as to transmit the processed data via the antenna ex201.

When receiving, in data communication mode, moving picture file data which is linked to a Web page or the like, modem circuit unit ex306 performs inverse spread spectrum processing on the received signal received from base station ex110 via antenna ex201, and sends out the resulting multiplexed data to multiplexing/demultiplexing unit ex308.

In order to decode the multiplexed data received via antenna ex201, multiplexing/demultiplexing unit ex308 separates the multiplexed data into a coded bitstream of picture data and a coded bitstream of voice data, and supplies such coded picture data to picture decoding unit ex309 and such voice data to voice processing unit ex305 via synchronous bus ex313.

Next, picture decoding unit ex309, which includes the picture decoding apparatus according to the present invention, decodes the coded bitstream of the picture data using the decoding method paired with the coding method shown in the above-mentioned embodiment so as to generate moving picture data for reproduction, and supplies such data to display unit ex202 via LCD control unit ex302. Accordingly, moving picture data included in the moving picture file linked to a Web page, for instance, is displayed. At the same time, voice processing unit ex305 converts the voice data into an analog voice signal, and then supplies this to voice output unit ex208. Accordingly, voice data included in the moving picture file linked to a Web page, for instance, is reproduced.

Note that the abovementioned system is not an exclusive example and therefore that at least either the picture coding apparatus or the picture decoding apparatus of the above embodiment can be incorporated into a digital broadcasting system as shown in FIG. 13, in a circumstance that satellite/terrestrial digital broadcasting has been a recent topic of conversation. To be more specific, at a broadcasting station ex409, a coded bitstream of video information is transmitted, by radio waves, to a satellite ex410 for communications or broadcasting. Upon receipt of it, broadcast satellite ex410 transmits radio waves for broadcasting, an antenna ex406 of a house equipped with satellite broadcasting reception facilities receives such radio waves, and an apparatus such as a television (receiver) ex401 and a set top box (STP) ex407 decodes the coded bitstream and reproduces the decoded data. The picture decoding apparatus as shown in the abovementioned embodiment can be performed in reproduction apparatus ex403 for reading and decoding the coded bit-stream recorded on a storage medium ex402 that is a recording medium such as a CD and a DVD. In this case, a reproduced video signal is displayed on a monitor ex404. It is also conceivable that the picture decoding apparatus is performed in the set top box ex407 connected to a cable ex405 for cable television or the antenna ex406 for satellite/terrestrial broadcasting so as to reproduce it on a television monitor ex408. In this case, the picture decoding apparatus may be incorporated into the television, not in the set top box. Or, a car ex412 with an antenna ex411 can receive a signal from satellite ex410, base station ex107 or the like, so as to reproduce a moving picture on a display device such as a car navigation system ex413 mounted on car ex412.

Furthermore, it is also possible to code a picture signal by the picture coding apparatus presented in the above embodiment and to record the resultant on a recording medium. Examples include a DVD recorder for recording a picture signal on a DVD disc ex421 and a recorder ex420 such as a disc recorder for recording a picture signal on a hard disk. Moreover, a picture signal can also be recorded in an SD card ex422. If the recorder ex420 is equipped with the picture decoding apparatus presented in the above embodiment, it is possible to reproduce a picture signal recorded on DVD disc ex421 or in SD card ex422, and display it on monitor ex408.

As the configuration of the car navigation system ex413, the configuration without camera unit ex203 and the camera interface unit ex303, out of the configuration shown in FIG. 12, is conceivable. The same is applicable to computer ex111, television (receiver) ex401 and the like.

Concerning the terminals such as cellular phone ex114, a transmitting/receiving terminal having both a coder and a decoder, as well as a transmitting terminal only with a coder, and a receiving terminal only with a decoder are the three possible forms substantially.

As stated above, it is possible to employ the picture coding method and the picture decoding method presented in the above embodiment into any one of the above-mentioned devices and systems. Accordingly, it becomes possible to achieve an effect described in the abovementioned embodiment.

As mentioned hereinbefore, it is possible to code the output area coding information CropData with less number of bits without deteriorating accuracy of output pixel to be presented, and the practical value is high.

Note that each function block in the block diagram shown in FIG. 5 and FIG. 6 can be realized as an LSI that is an integrated circuit apparatus typically. Such LSI may be incorporated in one or plural chips e.g., function blocks other than a memory may be incorporated into a single chip. Here, LSI is exemplified, however, it may be called as “IC”, “system LSI”, “super LSI” and “ultra LSI” depending on the integration degree.

The method for incorporation into an integrated circuit is not limited to the LSI, and it may be realized with an exclusive line or a general processor. After manufacturing of LSI, a Field Programmable Gate Array (FPGA) that is programmable, or a reconfigurable processor that can reconfigure the connection and settings for the circuit cell in the LSI, may be utilized.

Furthermore, along with the arrival of technique for incorporation into an integrated circuit, which replaces the LSI owing to a progress in semiconductor technology or another extended technique, integration of the function blocks may be carried out using the newly-arrived technology. Application of bio-technology may be cited as one of the examples.

And also in each function block, a unit to store data may be structured individually as an record medium in the embodiment and not necessary to be a chip.

In each function block of block diagrams shown in FIG. 5 and FIG. 6, and the flowcharts shown in FIG. 7A, FIG. 7B, FIG. 8A and FIG. 8B, the essential part is realized by a micro processor and a program, the present invention, therefore, may be constructed as a program.

Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.

Claims

1. A picture coding method comprising:

coding, using a processor, a picture signal;

coding a ratio of a number of luminance pixels to a number of chrominance pixels for the picture signal;

selecting one coding method out of at least two coding methods, the one coding method being selected based on the ratio; and

coding data related to a picture size in accordance with the selected coding method,

wherein the data related to the picture size indicates a size of a picture corresponding to the picture signal,

wherein, when a ratio of a number of horizontal luminance pixels to a number of horizontal chrominance pixels is M:1, said selecting selects a coding method coding 1/M of a number of horizontal pixels, the horizontal luminance pixels and the horizontal chrominance pixels being included in the picture signal, and

wherein the data related to the picture size indicates an output area in a whole pixel area coded in said coding of the picture signal, the output area being a pixel area to be outputted in decoding.

2. A picture coding apparatus comprising:

a picture coding unit including a processor operable to code a picture signal;

a ratio coding unit operable to code a ratio of a number of luminance pixels to a number of chrominance pixels for the picture signal;

a selecting unit operable to select one coding method out of at least two coding methods, the one coding method being selected based on the ratio; and

a data coding unit operable to code data related to a picture size in accordance with the selected coding method,

wherein the data related to the picture size indicates a size of a picture corresponding to the picture signal,

wherein, when a ratio of a number of horizontal luminance pixels to a number of horizontal chrominance pixels is M:1, said selecting unit selects a coding method coding 1/M of a number of horizontal pixels, the horizontal luminance pixels and the horizontal chrominance pixels being included in the picture signal, and

wherein the data related to the picture size indicates an output area in a whole pixel area coded by said picture coding unit, the output area being a pixel area to be outputted in decoding.

3. A non-transitory computer-readable recording medium having a picture coding program recorded thereon, the picture coding program causing a computer to execute a method comprising:

coding, using a processor, a picture signal;

coding a ratio of a number of luminance pixels to a number of chrominance pixels for the picture signal;

selecting one coding method out of at least two coding methods, the one coding method being selected based on the ratio; and

coding data related to a picture size in accordance with the selected coding method,

wherein the data related to the picture size indicates a size of a picture corresponding to the picture signal,

wherein, when a ratio of a number of horizontal luminance pixels to a number of horizontal chrominance pixels is M:1, said selecting selects a coding method coding 1/M of a number of horizontal pixels, the horizontal luminance pixels and the horizontal chrominance pixels being included in the picture signal, and

wherein the data related to the picture size indicates an output area in a whole pixel area coded in said coding of the picture signal, the output area being a pixel area to be outputted in decoding.

4. A picture coding method comprising:

coding, using a processor, a picture signal;

coding a ratio of a number of luminance pixels to a number of chrominance pixels for the picture signal;

selecting one coding method out of at least two coding methods, the one coding method being selected based on the ratio; and

coding data related to a picture size in accordance with the selected coding method,

wherein the data related to the picture size indicates a size of a picture corresponding to the picture signal,

wherein, when a ratio of a number of horizontal luminance pixels to a number of horizontal chrominance pixels is M:1, said selecting selects a coding method coding 1/M of a number of horizontal pixels, the horizontal luminance pixels and the horizontal chrominance pixels being included in the picture signal, the coding method corresponding to one of: a 4:2:0 chroma format, a 4:2:2 chroma format, or a 4:4:4 chroma format, and

wherein the data related to the picture size indicates an output area in a whole pixel area coded in said coding of the picture signal, the output area being a pixel area to be outputted in decoding.

5. The method of claim 4, wherein the coding method corresponds to a 4:2:0 chroma format.

6. The method of claim 4, wherein the coding method corresponds to a 4:2:2 chroma format.

7. The method of claim 4, wherein the coding method corresponds to a 4:4:4 chroma format.