JP5603840B2 - Video tile size determination method - Google Patents

Description

  The present invention relates to a tile size determination method when a high-resolution video is divided into tiles in a system in which a high-resolution video is cut out according to a gaze area that a user specifies interactively, decoded on a terminal, and displayed on a display.

  As an encoding method for compressing a plurality of camera images together, the international standard encoding method H.264 is used. Multi-view video coding (MVC) is standardized as H.264 Annex H (see Non-Patent Document 1, for example). In MVC, a plurality of encoded video data is compressed and encoded in a multiplexed form. Encoded data of frames having the same time stamp are continuously multiplexed. That is, the encoded data is a stream in which a plurality of video data is multiplexed. Since frames with the same time stamp are continuously multiplexed, the decoder can decode and output MVC encoded data, thereby successively decoding and outputting a plurality of camera images with the same time stamp. it can.

  FIG. 10 is a block diagram showing the configuration of a video transmission system according to the prior art. FIG. 11 is a conceptual diagram illustrating an example of tile division of input video data and assignment of tile IDs. FIG. 12 is a conceptual diagram showing a data ID assigned to video data after video encoding. In the multiplexing device 10, the video dividing unit 100 converts the video data into a plurality of resolutions, and then tiles the video data of each resolution (for example, FIG. 11) to create a tile video composed of video data in a small area. To do. The encoding unit 101 encodes these tile videos at a plurality of encoding rates, and assigns a data ID to the encoded data as shown in FIG. Thereafter, the video data is created by multiplexing with MVC.

  The data storage unit 102 includes tile division information (for example, FIG. 11), tile video data before encoding, encoded and multiplexed video data for each tile video, and tile video created in the course of encoding processing. Accumulate local decoded video data. The evaluation value calculation unit 103 uses the video data stored in the data storage unit 102 to calculate an evaluation value for each frame unit (or a predetermined frame unit), and the evaluation value, each tile image, and the video code The correspondence table of the digitized data is stored in the correspondence table & evaluation value storage unit 104. Note that, after the evaluation value calculation is completed, tile video data before encoding that is no longer necessary is deleted.

  In the video transmission server 20, the data management unit 105 sends N (≦ M) copies to the data storage unit 102 according to the command (stream request using the data ID) received from the command receiving unit 106 from the video playback client 30. By performing the stream request, N streams are extracted from the M streams stored in the data storage unit 102 and transferred to the data transmission unit 107. The data transmission unit 107 transmits N streams to the video reproduction client 30. The command receiving unit 106 receives a command from the video playback client 30. Before transmitting data to the video playback client 30, the data transmission unit 107 sends tile division information (for example, FIG. 11) to the data reception unit 112. Also, the correspondence table & evaluation value transmission unit 108 extracts the correspondence table and the evaluation value information from the evaluation value storage unit 104 and sends them to the evaluation value reception unit 115 of the video reproduction client.

  In the video reproduction client 30, the data reception unit 112 receives tile division information and N streams. The decoding unit 113 decodes N streams. The video display unit 114 reconstructs and displays the decoded partial video based on the tile division information. The correspondence table & evaluation value receiving unit 115 receives the correspondence table and evaluation value information transmitted from the video transmission server 20 and stores them in the correspondence table & evaluation value storage unit 116.

  The tile ID list creation unit 118 determines the tile ID list from the gaze area when the designation of the user's gaze area is changed, determines the data ID corresponding to the corresponding tile ID from the correspondence table, The evaluation value related to the data ID is extracted from the correspondence table & evaluation value storage unit 116, and the correction evaluation value calculation unit 110 corrects the evaluation value (for example, the evaluation value of each frame unit is averaged for each fixed section). Correction process).

  The gaze area designating unit 117 receives a change of the gaze area from the user. The command conversion unit 111 determines a data ID to be requested to the server based on the correction evaluation value and the tile ID when the gaze area designation is changed and the correction evaluation value is changed. The command transmission unit 109 transmits a command based on the data ID determined by the command conversion unit 111.

  The data storage unit 102 and the correspondence table & evaluation value storage unit 104 in the multiplexing apparatus 10 are functionally integrated, and the data transmission unit 107 and the correspondence table & evaluation value transmission unit 108 in the video transmission server 20 are functionally integrated. A configuration in which the data receiving unit 112 and the correspondence table & evaluation value receiving unit 115 in the video reproduction client 30 are functionally integrated is also possible.

  Also, here, a video composed of M streams (whole stream) is “whole video”, a video composed of N (≦ M) streams (partial streams) is “partial video”, A video composed of streams is defined as “unit video”. That is, the entire video is composed of M unit videos, and the partial video is composed of N unit videos (M ≧ N).

  FIGS. 13A and 13B are conceptual diagrams showing examples of tile ID lists created by the tile ID list creating unit 118. FIG. The tile ID list is created as a list of minimum tile IDs including a gaze area that is interactively operated by the user and is translated and scaled. In the example shown in FIGS. 13A and 13B, the tile ID list is (1, 2, 3, 4, 9, 10, 11, 12, 17, 18, 19, 20, 25, 26, 27, 28).

Masayuki Inoue, Hideaki Kizen, Katsuhiko Fukasawa, Nobuhiko Matsuura, "Study of distribution method in interactive panorama video distribution system," IPSJ, Audio-visual complex information processing group, Vol.2010-AVM-69 No.9, 2010.

  In the conventional tile division method in Non-Patent Document 1 described above, a method in which a user experimentally determines several types of tile sizes and coding bit rate patterns in accordance with the terminal and the line bandwidth by trial and error is employed. Therefore, there is a problem that it is very difficult to determine the tile size at the time of tile division.

  The present invention has been made in view of such circumstances, and an object thereof is to determine a video tile size that can automatically calculate a divided tile size based on an upper limit given in advance. Is to provide.

In order to solve the above-described problem, the present invention divides an entire video into a plurality of tile videos, and the tiles that include the gaze area in the whole video according to a gaze area specified by a video playback terminal. a video transmission apparatus for transmitting an image by encoding to the video reproduction terminal, the video reproduction terminal and the video tile of the image transmission system which includes a displaying by decoding a plurality of said tiles image to be transmitted from the video transmission apparatus A method for determining a size, wherein a precondition of a gaze area size of M × N [pixel] and a decoding area upper limit Dmax based on the gaze area size in the video reproduction terminal is input to the video transmission device When the video transmission apparatus calculates an x that satisfies formula (a) based on the precondition, tiles size (M / x) of the tile image × (N / x) [pixel] Image tile size determination method characterized by comprising the steps of calculating, the.
(Ceil (M / (M / x)) + 1) × (ceil (N / (N / x)) + 1)
× (M / x) × (N / x) ≦ Dmax (M × N) (A)
However, ceil () is a function that rounds up the decimal point.

Further, the present invention divides the entire video into a plurality of tile videos, and encodes the tile video including the gaze area in the whole video according to the gaze area specified by the video playback terminal. A video tile size determination method for a video transmission system, comprising: a video transmission device that transmits to a playback terminal; and the video playback terminal that decodes and displays the plurality of tile videos transmitted from the video transmission device, Input to the video transmission apparatus are preconditions of a gaze area size of M × N [pixels], a coding bit rate R of the gaze area size that provides a predetermined quality, and a transmission band upper limit Rmax; A step of calculating x satisfying the formula (B) based on the precondition, and calculating a tile size (M / x) × (N / x) [pixel] of the tile image; Is a method for determining a tile size of a video.
(Ceil (M / (M / x)) + 1) × (ceil (N / (N / x)) + 1)
× (R / x ² ) ≦ Rmax (B)
However, ceil () is a function that rounds up the decimal point.

Further, the present invention divides the entire video into a plurality of tile videos, and encodes the tile video including the gaze area in the whole video according to the gaze area specified by the video playback terminal. A video tile size determination method for a video transmission system, comprising: a video transmission device that transmits to a playback terminal; and the video playback terminal that decodes and displays the plurality of tile videos transmitted from the video transmission device, An encoding bit rate of the gaze area size that provides the video transmission apparatus with a gaze area size of M × N [pixels], a decoding area upper limit Dmax based on the gaze area size in the video playback terminal, and a predetermined quality. R and the transmission bandwidth upper limit Rmax are input as preconditions, and the video transmission apparatus satisfies both the expressions (A) and (B) based on the preconditions. Calculating a to x, and calculating the tile size of the tile image (M / x) × (N / x) [ pixel] is a video tile size determination method, which comprises a.
(Ceil (M / (M / x)) + 1) × (ceil (N / (N / x)) + 1)
× (M / x) × (N / x) ≦ Dmax (M × N) (A)
(Ceil (M / (M / x)) + 1) × (ceil (N / (N / x)) + 1)
× (R / x ² ) ≦ Rmax (B)
However, ceil () is a function that rounds up the decimal point.

  According to the present invention, the tile size can be efficiently determined by using the decoding upper limit value and the video transmission band upper limit instead of determining the tile size by trial and error by trying several patterns. .

4 is a flowchart for explaining a video tile size determination method according to the first embodiment of the present invention; In this 1st Embodiment, it is a conceptual diagram which shows the relationship between a gaze area | region and the tile image | video to deliver. 5 is a flowchart for explaining a video tile size determination method using other parameters in the first embodiment. It is a flowchart for demonstrating the image tile size determination method by this 2nd Embodiment. In this 2nd Embodiment, it is a conceptual diagram which shows the relationship between a gaze area | region and the tile image | video to deliver. It is a flowchart for demonstrating the image tile size determination method by this 3rd Embodiment. In this 3rd Embodiment, it is a conceptual diagram which shows the relationship between a gaze area | region and the tile image | video to deliver. It is a flowchart for demonstrating the image tile size determination method by this 4th Embodiment. In this 4th Embodiment, it is a conceptual diagram which shows the relationship between a gaze area | region and the tile image | video to deliver. It is a block diagram which shows the structure of the video transmission system by a prior art. It is a conceptual diagram which shows the tile division | segmentation of input video data, and the example of provision of tile ID. It is a conceptual diagram which shows data ID provided to the video data after video encoding. It is a conceptual diagram which shows the example of the tile ID list produced in the tile ID list production part 118. FIG.

  The present invention relates to a panoramic video tile dividing method in a panoramic video transmission system. In the present invention, the tile size is determined using the number of tiles when the gaze area reaches the maximum tile ID list, the decoding upper limit value that can be decoded by the video playback client, and the video transmission band upper limit by user operation. It is characterized by that.

  In the present invention, the tile size can be determined more efficiently than the conventional experimental tile size determination method by determining the tile size so as to satisfy the constraints on the decodable area and transmission band. It becomes.

  Here, the position where the gaze area is “maximum tile ID list” is referred to as “worst case position”, and “when the tile ID list is maximum” is referred to as “worst case”. To do.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configuration of the video transmission system of the present invention is basically the same as the configuration according to the prior art shown in FIG. That is, the video transmission system according to the present embodiment divides the entire video into a plurality of tile videos corresponding to a predetermined tile size, and is designated among the whole videos according to the gaze area designated by the video playback client 30. The video transmission server 20 that transmits the video encoded by the multiplexing device 10 to the video reproduction client 30 and the video transmission server 20 transmit the video encoded by the multiplexing device 10. And a video playback terminal 30 for decoding and displaying a plurality of tile videos.

A. First Embodiment FIG. 1 is a flowchart for explaining a video tile size determination method according to a first embodiment of the present invention. FIG. 2 is a conceptual diagram showing the relationship between the gaze area and the tile video to be distributed in the first embodiment.

  Generally, when the tile size is a × b [pixels] and the gaze area size is M × N [pixels], the distribution tile number at the worst case position is expressed as Na × Nb. Here, Na = ceil (M / a) +1 and Nb = ceil (N / b) +1. Note that ceil () is a decimal point round-up function. The decoding area can be expressed by (Na × Nb) × (a × b).

  First, as preconditions, information on the upper limit of the decoding area and the gaze area size is set (step S1). Here, as the precondition, for example, a value corresponding to the environment may be stored in the multiplexing device 10 or the video transmission server 20 in advance, or the precondition is transmitted from the video reproduction client 30 to the user terminal 10. You may make it. Such information is input to the multiplexing apparatus 10 and stored in the storage area of the video dividing unit 100, whereby a precondition is set. For example, the decoding area upper limit: 1.5 HD (HD = HDh × HDv, HDh: HD horizontal width, HDv: HD vertical width), and gaze area size: HD (assuming display display of HD resolution). Next, the tile size is set to a = HDh / x, b = HDv / x (where x is a real number), and x that satisfies the decoding area upper limit is obtained (step S2).

Here, the gaze area size condition is HD, and is expressed as M = HDh and N = HDv.
At this time,
Na = ceil (HDh / (HDh / x)) + 1 = x + 1,
Nb = ceil (HDv / (HDv / x)) + 1 = x + 1
Therefore, from the following formulas (1) to (6), it can be understood that the gaze area can be decoded if x> = 4.5.

  In general, the larger the tile size, the better the video quality. Therefore, the video dividing unit 100 of the multiplexing apparatus 10 determines x = 4.5 (step S3). Therefore, the tile size is set to HD / (4.5 × 4.5), that is, a tile size equivalent to about 1/20 of the HD area that can be played back by the video playback client (step S4). The tile size may be about 1/20 of the HD area, the tile size horizontal width may be HDh / 4, and the tile size vertical width may be HDv / 5. As a result, the relationship between the gaze area and the tile video to be distributed is as shown in FIG. The tile image corresponding to the tile size determined in this way is transmitted from the multiplexing apparatus 10 to the video reproduction client via the video transmission server 20, and is decoded and displayed, thereby efficiently determining the tile size. be able to.

  FIG. 3 is a flowchart for explaining a video tile size determination method using other parameters in the first embodiment. Here, a case where the upper limit of the decoding area is 2HD will be described. First, as a precondition, an upper limit of the decoding area and a gaze area size are set (step S10). For example, the decoding area upper limit: 2HD (HD = HDh × HDv, HDh: HD horizontal width, HDv: HD vertical width), and gaze area size: HD (assuming display display of HD resolution). Next, the tile size is set to a = HDh / x, b = HDv / x (where x is a real number), and x that satisfies the decoding area upper limit is obtained (step S11).

Here, the gaze area size condition is HD, and is expressed as M = HDh and N = HDv.
At this time,
Na = ceil (HDh / (HDh / x)) + 1 = x + 1,
Nb = ceil (HDv / (HDv / x)) + 1 = x + 1
Therefore, it can be understood from the equations (1) to (6) that the gaze area can be decoded if x> = 2.4.

  In general, the larger the tile size, the better the video quality, so x = 2.4 is determined (step S12). Therefore, the tile size is HD / (2.4 × 2.4), that is, the tile size that can be played back by the video playback client and is equivalent to about 1/6 of the HD area (step S13).

B. Second Embodiment Next, a second embodiment of the present invention will be described.
In the third embodiment, the vertical width of the original image, the decoding area upper limit, and the gaze area size are set as preconditions.

  FIG. 4 is a flowchart for explaining a video tile size determination method according to the second embodiment. FIG. 5 is a conceptual diagram showing the relationship between the gaze area and the tile video to be distributed in the second embodiment. First, as preconditions, the vertical width of the original image, the upper limit of the decoding area, and the gaze area size are set (step S20). For example, assuming that the vertical width of the original image is HD high, the upper limit of the decoding area is 1.5 HD (HD = HDh × HDv, HDh: HD horizontal width, HDv: HD vertical width), gaze area size: HD (HD resolution display display is assumed. ). Next, the tile size is set to a = HDh / x, b = HDv (where x is a real number), and x that satisfies the decoding area upper limit is obtained (step S21).

Here, the gaze area size condition is HD, and is expressed as M = HDh and N = HDv.
At this time,
Na = ceil (HDh / (HDh / x)) + 1 = x + 1,
Nb = ceil (HDv / HDv) = 1 = 1 (vertical direction is only one tile)
Therefore, it can be seen from the equations (1) to (6) that the gaze area can be decoded if X> = 2.

  In general, the larger the tile size, the better the video quality, so x = 2 is determined (step S22). Therefore, the tile size is set to HD / 2, that is, the tile size that can be played back by the video playback client and is equivalent to about 1/2 of the HD area (step S23).

  By limiting the size of the original image to HD height as in the second embodiment, even if the upper limit of the decoding area is the same as that in the first embodiment (see FIG. 1), as shown in FIG. Since there are no tiles that are unnecessarily decoded in the height direction when the area is the worst case, the divided tile size can be made larger than that in the first embodiment.

C. Third Embodiment Next, a third embodiment of the present invention will be described.
In the third embodiment, the gaze area size, the transmission band upper limit, and the HD video encoding bit rate that provides sufficient quality are set as preconditions.

  FIG. 6 is a flowchart for explaining a video tile size determination method according to the third embodiment. FIG. 7 is a conceptual diagram showing the relationship between the gaze area and the tile video to be distributed in the third embodiment. First, as preconditions, a gaze area size, an upper limit of a transmission band, and an HD video encoding bit rate capable of obtaining sufficient quality are set (step S30). For example, gaze area size: HD (assuming display display of HD resolution: M × N), upper limit of transmission band is 11 [Mbps], and encoding bit rate of HD video capable of obtaining sufficient quality is 6 [Mbps]. . Next, the tile size is set to a = HDh / x, b = HDv / x (where x is a real number), and x that satisfies the transmission band upper limit is obtained (step S31).

Here, the gaze area size condition is HD, and is expressed as M = HDh and N = HDv.
At this time,
Na = ceil (HDh / (HDh / x)) + 1 = x + 1,
Nb = ceil (HDv / (HDv / x)) + 1 = x + 1
Bit rate per tile = (R / (ceil (M / a) × ceil (N / b)) = (6 / (xx)
Therefore, from the following equations (7) to (12), it can be understood that the gaze area can be decoded if X> = 2.8. Note that R is an HD video encoding bit rate with which sufficient quality can be obtained.

  In general, the larger the tile size, the better the video quality, so x = 2.8 is determined (step S32). Therefore, the tile size is set to HD / (2.8 × 2.8), that is, a tile size equivalent to about 1/8 of the HD area that can be played back by the video playback client (step S33). As a result, the relationship between the gaze area and the tile video to be distributed is as shown in FIG.

  Note that the encoding bit rate of HD video that provides sufficient quality should be set slightly higher than the encoding bit rate of HD video when tile division is not performed, considering that encoding efficiency is reduced by dividing the tile. Good. For example, if the HD video encoding bit rate without tile division is 6 [Mbps], it is necessary to consider setting x to 7 [Mbps].

D. Fourth Embodiment Next, a fourth embodiment of the present invention will be described.
In the fourth embodiment, as preconditions, the vertical width of the original image, the gaze area size, the upper limit of the transmission band, and the HD video encoding bit rate that provides sufficient quality are set.

  FIG. 8 is a flowchart for explaining a video tile size determination method according to the fourth embodiment. FIG. 9 is a conceptual diagram showing the relationship between the gaze area and the tile video to be distributed in the fourth embodiment. First, as preconditions, the vertical width of the original image, the gaze area size, the upper limit of the transmission band, and the HD video encoding bit rate that provides sufficient quality are set (step S40). For example, HD video encoding that can obtain sufficient quality with the height of the original image being HD high, the gaze area size being HD (assuming display of HD resolution display: M × N), the upper limit of the transmission band is 11 [Mbps] The bit rate is 6 [Mbps]. Next, assuming that the tile size is a = HDh / x, b = HDv (where x is a real number), x that satisfies the transmission band upper limit is obtained (step S41).

Here, the gaze area size condition is HD, and is expressed as M = HDh and N = HDv.
At this time,
Na = ceil (HDh / (HDh / x)) + 1 = x + 1,
Nb = ceil (HDv / HDv) = 1 = 1 (vertical direction is only one tile)
Bit rate per tile = (R / (ceil (M / a) × ceil (N / b)) = (6 / (xx)
Therefore, from the equations (7) to (12), it can be understood that the gaze area can be decoded if X> = 1.2. Note that R is an HD video encoding bit rate with which sufficient quality can be obtained.

  Here, since x is a real number, x = 2 is determined (step S42). Therefore, the tile size is set to HD / 2, that is, the tile size that can be played back by the video playback client and is equivalent to about 1/2 of the HD area (step S43). As a result, the relationship between the gaze area and the tile video to be distributed is as shown in FIG.

  In the first to fourth embodiments described above, when there are two upper limits, that is, a decoding area upper limit and a transmission band upper limit, it is only necessary to obtain x that satisfies the constraints imposed by these two upper limits. For example, x satisfying the first embodiment (FIG. 1) and the third embodiment (FIG. 6) satisfies x> = 4.5 satisfying a more restrictive decoding area.

  According to the first to fourth embodiments described above, the number of tiles when the gaze area reaches the position where the tile ID list is maximized by the user operation, the decoding upper limit value that can be decoded by the video playback client, and the video transmission band upper limit. The tile size can be determined more efficiently than the conventional experimental tile size determination method by determining the tile size so as to satisfy the constraints on the area that can be decoded and the transmission band. .

  In the first to fourth embodiments described above, as preconditions, the decoding area upper limit and the gaze area size, or the transmission band upper limit and the gaze area size and the HD video encoding bit rate that provides sufficient quality are set. However, the present invention is not limited to this. The upper limit of the decoding area and the gaze area size, or the upper limit of the transmission band and the gaze area size, or the upper limit of the transmission band, or the upper limit of the decoding area and the gaze area size. In addition to the area size, the number of tiles when the number of divided tiles that overlap the gaze area is the largest, or when the number of divided tiles that overlap the gaze area is the largest in addition to the upper limit of the transmission band and the gaze area size In addition to the number of tiles or the decoding area upper limit and the gaze area size, the transmission band upper limit and the division that overlaps the gaze area The number of tiles when yl speed is most may be set.

DESCRIPTION OF SYMBOLS 10 Multiplexer 20 Video transmission server 30 Video reproduction client 100 Resolution conversion & video division part 101 Coding part 102 Data storage part 103 Evaluation value calculation part 104 Correspondence table & evaluation value storage part 105 Data management part 106 Command reception part 107 Data Transmission unit 108 Correspondence table & evaluation value transmission unit 109 Command transmission unit 110 Correction evaluation value calculation unit 111 Command conversion unit 112 Data reception unit 113 Decoding unit 114 Video display unit 115 Correspondence table & evaluation value reception unit 116 Correspondence table & evaluation value Accumulation unit 117 Gaze area designation unit 118 Tile ID list creation unit

Claims (3)

Video that divides the entire video into a plurality of tile videos, encodes the tile video including the gaze area in the entire video, and transmits the encoded video to the video playback terminal according to the gaze area specified by the video playback terminal A video tile size determination method for a video transmission system, comprising: a transmission device; and the video reproduction terminal that decodes and displays the plurality of tile videos transmitted from the video transmission device,
A step of inputting, to the video transmission device, preconditions of a gaze area size of M × N [pixel] and a decoding area upper limit Dmax based on the gaze area size in the video playback terminal;
The video transmission device calculates x satisfying the formula (A) based on the precondition, and calculates a tile size (M / x) × (N / x) [pixel] of the tile video;
A method for determining a video tile size, comprising:
(Ceil (M / (M / x)) + 1) × (ceil (N / (N / x)) + 1)
× (M / x) × (N / x) ≦ Dmax (M × N) (A)
However, ceil () is a function that rounds up the decimal point. Video that divides the entire video into a plurality of tile videos, encodes the tile video including the gaze area in the entire video, and transmits the encoded video to the video playback terminal according to the gaze area specified by the video playback terminal A video tile size determination method for a video transmission system, comprising: a transmission device; and the video reproduction terminal that decodes and displays the plurality of tile videos transmitted from the video transmission device,
Input to the video transmission apparatus are preconditions of a gaze area size of M × N [pixels] and an encoding bit rate R of the gaze area size for obtaining a predetermined quality and a transmission band upper limit Rmax;
The video transmission device calculates x satisfying the formula (B) based on the precondition, and calculates the tile size (M / x) × (N / x) [pixel] of the tile video;
Film image tile size decision how to comprising a.
(Ceil (M / (M / x)) + 1) × (ceil (N / (N / x)) + 1)
× (R / x ² ) ≦ Rmax (B)
However, ceil () is a function that rounds up the decimal point. Video that divides the entire video into a plurality of tile videos, encodes the tile video including the gaze area in the entire video, and transmits the encoded video to the video playback terminal according to the gaze area specified by the video playback terminal A video tile size determination method for a video transmission system, comprising: a transmission device; and the video reproduction terminal that decodes and displays the plurality of tile videos transmitted from the video transmission device,
An encoding bit rate of the gaze area size that provides the video transmission apparatus with a gaze area size of M × N [pixels], a decoding area upper limit Dmax based on the gaze area size in the video playback terminal, and a predetermined quality. A step of inputting preconditions of R and the transmission band upper limit Rmax;
The video transmission apparatus calculates x satisfying both of the formulas (A) and (B) based on the preconditions, and sets the tile size (M / x) × (N / x) [pixel] of the tile video. A calculating step;
Film image tile size decision how to comprising a.
(Ceil (M / (M / x)) + 1) × (ceil (N / (N / x)) + 1)
× (M / x) × (N / x) ≦ Dmax (M × N) (A)
(Ceil (M / (M / x)) + 1) × (ceil (N / (N / x)) + 1)
× (R / x ² ) ≦ Rmax (B)
However, ceil () is a function that rounds up the decimal point.

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