JP2000050208A - Image reproduction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain search by a time code at a high speed. SOLUTION: This method selects a jump block address of image data, assumingly that they are fixed bit rate data according to a designated time code (steps 11, 12), a GOP header in the vicinity of the jump block address is read sequentially (steps 13, 14) to generate a cross reference table between time codes and addresses (step 18-21). Then an address closest to an object time code is figured out, based on the cross reference table and the address is selected to be a jump address (step 22). Thus, reproduction is started from an object time code position in a short time (step 23).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image which enables reproduction from a designated time code position when reproducing variable length coded moving image data including a time code compressed based on the MPEG standard or the like. It relates to a reproduction method.

[0002]

2. Description of the Related Art Encoded video data compressed in accordance with the MPEG-2 standard has a different bit amount between a portion having a small amount of motion and a portion having a large amount of motion. It has a variable length bit rate. Therefore, there is basically no correlation between the time information from the start of reproduction and the offset position from the head of the encoded data, and it has been difficult to jump to an arbitrary time code position and start reproduction.

Conventionally, when performing a search using a time code, a method of sequentially decoding and obtaining / collating time code information included in a GOP header from the beginning until a desired time code is obtained is known. Had been taken.

[0004]

When performing a search by a time code on the variable-length compressed image data of the MPEG-2 standard by the above-described conventional method, the jump destination (desired time code) is set at the beginning of the data. The further away you are,
It took a lot of time. Then, even if reading is performed in sequence header units, in this case, decoding processing is required in the same manner as in actual reproduction, and the processing requires a lot of time, which is extremely inefficient. was there.

Accordingly, an object of the present invention is to provide an image reproducing method capable of performing a time code search at a high speed.

[0006]

As a means for achieving the above object, according to the present invention, a jump is performed on a designated time code assuming fixed-length bit rate data, and a GOP in the vicinity of the jump destination is executed. The header is sequentially read to create a correlation table between the time code and the offset address. Then, by determining the offset address closest to the target time code from the correlation table and jumping, the reproduction can be started from the target time code position in a short time.

The present invention relates to an image reproducing method for reproducing variable-length coded moving image data including a time code from a designated time code position, wherein the variable-length coded moving image data is fixed-length data. Calculates the logical block data corresponding to the specified time code position, jumps to the address position indicated by the calculated logical block data, detects a time code at a nearby position, and detects the detected time code. When the specified time code position matches the specified time code position, the reproduction is started from that position, and when the detected time code does not match the specified time code position, the reproduction is started closest to the specified time code position. An image reproducing method characterized in that a time code is detected and reproduced from a position indicated by the time code. It is.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an image reproducing method according to the present invention will be described with reference to the drawings. In the present embodiment, a case will be described in which image data recorded on a recording medium such as a disk is reproduced from a designated time code position.

FIG. 1 is an explanatory diagram showing a schematic configuration of a data format of image data encoded according to the MPEG-2 standard.
As shown in the drawing, the schematic configuration of image data (Video Sequence) encoded according to the MPEG-2 standard is a sequence header (Sequence Header) 1 and a sequence extension unit (S
sequence extension) 2 and a plurality of GOPs (Group of Pics)
tures) and sequence end code (Sequence End)
GOP), and each GOP has a GOP header including a group start code (Group Start Code) 6 and a time code (Time Code) 7.
3 and a plurality of sets of picture headers 4 and subsequent picture data. As can be seen from this configuration, the time code 7 is included in the GOP header 3, and the time for displaying the first image (picture) included in the GOP is recorded. Also, since the amount of picture data varies depending on the content of the image, the time code position does not match the block address.

When reproducing the image data in such a data format from the designated time code position, the processing is performed according to the processing procedure shown in the flowchart of FIG.

First, assuming that image data is fixed-length bit rate data, a time code specified as a reproduction start position is converted into an LBA (logical block address) (step 11). Specifically, one frame of MPEG2 image data is 1/75 second, and in the case of fixed length, one frame is 2048 bytes. Therefore, the time code converted into seconds is multiplied by 75 and 2048 to obtain the LBA. Get. That is, assuming that the time code hour: minute: second: frame is X: Y: Z: F, respectively, LBA = ｛(X × 3
600 + Y × 60 + Z) × 75 + F｝ × 2048.

Next, the seek operation is performed while counting the data amount from the start position of the image data, and the offset address, which is the data address from the start position of the image data, is the same as the LBA obtained in step 11. Jump to (step 12). At this time, the seek is performed while counting the offset address, but since the data is not decoded, the jump takes almost no time.

Then, the sequence header 1 is searched for and decoded in the vicinity of the jumped offset address, and the GOP header 3 is detected (step 13). If the GOP header 3 cannot be detected (step 14 → N
o), an error message is displayed and the process is terminated (step 1)
5). Normally, since the GOP header 3 is detected (Step 14 → Yes), the time code 7 of the detected GOP header 3 is read and compared with the designated time code (Step 16). Here, the detected GOP header 3
If the time code 7 and the designated time code match (step 16 → Yes), the search is terminated and reproduction is started from this GOP (step 17).

The time code 7 of the detected GOP header 3
Does not match the specified time code (step 16 → No), the magnitudes are compared (step 18), and if the detected time code 7 of the GOP header 3 is smaller than the specified time code, (Step 18 → Yes), the time code 7 of the succeeding GOP header 3 is sequentially detected until a value larger than the designated time code is detected, and recorded in the memory (not shown) (Step 19). . If the detected time code 7 of the GOP header 3 is larger than the specified time code (Step 18 → No), the previous GOP header 3 is sequentially read until a value smaller than the specified time code is detected. The time code 7 of No. 3 is detected retroactively and recorded (step 20).

The search is performed in such a manner that the time codes 7 are sequentially recorded, and the offset addresses (addresses obtained from the amount of data from the head of the image data) corresponding to the time codes 7 are detected. A correlation table as shown in FIG. 3 is created (step 21). Here, the time code is converted into an LBA and recorded.
Is calculated in the same manner as the method calculated in step 11 described above, and the time code 7 (hour: minute:
Second: frame = X: Y: Z: F), LBA =
{(X × 3600 + Y × 60 + Z) × 75 + F} × 20
48 can be obtained.

The correlation table shown in FIG. 3 is a file of text data in which a set of an offset address from the head and an LBA obtained from a time code is listed in a space-separated manner. The value after the space is the LBA.

Since the designated time code has been converted to an LBA in step 11, the LBA is compared with the LBA in the correlation table to detect a matching or closest LBA, and the LBA corresponding to the LBA is detected. An offset address value is obtained (Step 22). Further, the reproduction is started by jumping to the offset address position (step 23).

As a specific example, for example, consider a case where reproduction is performed from a time point 20 minutes after the start point of image data. Since the time code at this time is (00: 20: 00: 00: 00), LBA = 20 × 60 × 75 × 2048 = 184
320000 (step 11). And this L
A seek is performed to a position having the same offset address as BA (step 12), and a nearby GOP header 3 is detected (step 13). Further, the time code 7 of the detected GOP header 3 is read and compared with the designated time code (step 16). Here, the detected GOP
If the time code 7 of the header 3 is a value smaller than 20 minutes (step 18 → Yes), the designated 20
Successive GOPs until a value greater than
The time code 7 in the header 3 is detected, converted to LBA and recorded (step 19).

In this way, the LBA obtained by sequentially converting the time code 7 and the offset address corresponding thereto are detected to create a correlation table as shown in FIG. 3 (step 2).
1). In FIG. 3, the preceding value is the offset address, and the value after the space is the LBA. Step 13
When the LBA obtained by converting the time code 7 of the GOP header 3 detected first in step is “183980000”, 2
Since the value is smaller than 0 minute (1844320000) (step 18 → Yes), the GOP header 3
Time code 7 is detected, and LBA is set to 20 minutes (1843).
When "1844450000" larger than 20,000) is detected, decoding is temporarily terminated (step 19). Then, the LBA "1844450000" and the L
Comparing with BA “184300000”, the previous LB
A: "184300000" takes 20 minutes (184320
000), so the previous LBA "1843000
00 "corresponding to the offset address value" 184580
000 "is obtained from the correlation table (step 22). Finally, the offset address position “18458000
The reproduction is started by jumping to "0" (step 23).

According to the present invention, reproduction is performed in this way, and the range in which decoding and reading of the time code are actually performed is limited only to the vicinity of the reproduction start position, so that the time until reproduction can be greatly reduced. it can.

[0021]

According to the image reproducing method of the present invention, the method of searching while decoding the time code from the beginning of the conventional method requires several minutes or more before starting reproduction from the designated time code. Thus, reproduction can be performed in only a few seconds. As a result, when applied to a multimedia authoring system or the like using MPEG encoded data that requires a time search, there is an effect that the processing efficiency is greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of an MPEG2 image compression data format.

FIG. 2 is a flowchart illustrating an embodiment of an image reproducing method according to the present invention.

FIG. 3 is a flowchart illustrating an embodiment of a correlation table.

[Explanation of symbols]

 Reference Signs List 1 Sequence Header 2 Sequence Extension 3 GOP Header 4 Picture Header 5 Sequence End Code 6 Sequence Start Code 6 Group Start Code 7 Time Code (Time Code)

Claims (1)

[Claims] 1. An image reproducing method for reproducing variable-length encoded moving image data including a time code from a designated time code position, assuming that the variable-length encoded moving image data is fixed-length data. Calculate logical block data corresponding to the specified time code position, jump to an address position indicated by the calculated logical block data, detect a time code at a nearby position, and determine the detected time code and the specified time code. When the time code position matches, the reproduction is started from that position. When the detected time code does not match the specified time code position, the time code closest to the specified time code position is detected. And reproducing the image from the position indicated by the time code.