JPH10174058A - Coding quantity control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize encoding of natural image by providing an encoding means for outputting coded data and a coding quantity control means for setting a target per unit segment based on a medium capacity and the number of segments and controlling the coding quantity of the coding data to be outputted by the encoding means. SOLUTION: A free capacity of a recording medium 1 comprising an optical magnetic disk is detected by a medium capacity detecting means 2. The detecting means 2 detects the free capacity by subtracting a recorded data quantity from a total storage capacity. A coding quantity control means 3 finds the number of corresponding segments by entering a recording estimated time, divides the free capacity by the number of segments and finding the target coding quantity per unit segment, and controls the encoding means 4 corresponding to this. Thus obtained coded data is stored in a generated coded quantity detecting means 5. The detecting means 5 feeds back the detected coded quantity to the control means 3 to control so that the coding data quantity per segment approaches to the target coding quantity of the detected coded quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to encoding data such as an image and dynamically changing the encoding bit rate according to the generated code amount, thereby efficiently recording the data on a recording medium having a limited medium capacity. The present invention relates to an encoding device capable of performing the following.

[0002]

2. Description of the Related Art Conventionally, as a method of recording image data encoded by MPEG on a recording medium, a constant bit rate encoding method of recording with a constant code amount for each GOP has been used. On the other hand, Japanese Patent Application Laid-Open No. 5-122655 proposes a real-time variable bit rate encoding method for encoding and recording an image while controlling a target code amount according to the remaining amount of tape and the remaining recording time. I have.

[0003]

According to this prior art, when a complicated image that is difficult to compress occurs at the end of the tape, the image quality may be degraded. Therefore, the present invention realizes a natural image encoding by dispersing the degraded portion of the image quality for each sector in a real-time variable bit rate encoding method.

[0004]

According to the present invention, there is provided an encoding means for encoding data and outputting encoded data, and setting a target or predicted code amount per unit segment based on a medium capacity and the number of segments. Code amount control means for controlling the code amount of the encoded data output from the encoding means,
It is characterized by being arranged respectively.

Further, the present invention is characterized in that the medium capacity is an empty capacity of the medium. Further, the present invention is characterized in that the medium capacity is a capacity of a designated recording area. Further, the present invention is characterized in that the target code amount for each of the segments is common.

Further, the present invention is characterized in that the predicted code amount is set in accordance with a code amount for each of a plurality of past segments stored in a memory. Further, the present invention is characterized in that the memory is reset by a scene change. Further, the present invention is characterized in that the predicted code amount is set by a maximum likelihood estimation method.

Further, the present invention is characterized in that the encoding of the encoding means is restricted by setting an image quality priority mode. Further, the invention is characterized in that the segment is a fixed time.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. (First Embodiment) First, in the first embodiment, the recording medium is a magneto-optical disk, the data is image data, and the encoding method is MP.
The EG is adopted, and the target code amount is set with 5 minutes as one segment. In the present invention, the recording medium, data, coding type, and segment time are particularly described above. It is not limited to things.

As shown in FIG. 1, in the first embodiment, the free capacity, ie, the recordable capacity of the recording medium 1 composed of a magneto-optical disk is detected by the medium capacity detecting means 2. This medium capacity detecting means 2 detects the free capacity by subtracting the recorded data amount from the total storage capacity obtained by reproducing the medium.
The code amount control means 3 inputs the scheduled recording time to determine the number of corresponding segments, divides the free space by the number of segments to obtain a target code amount per unit segment, and calculates the target code amount according to the target code amount. It controls the MPEG encoding means 4 for inputting image data.

The resulting encoded data is recorded on the recording medium 1 and stored in the generated code amount detecting means 5. The generated code amount detection unit 5 feeds back the detected code amount to the code amount control unit 3 and controls the amount of encoded data per segment so that the detected code amount approaches the target code amount.

As a result, the generated code amount converges to a substantially constant value (shown by a circle) for each segment as shown in FIG. As a result, the amount of encoded data is averaged for each segment. In this embodiment, when the setting of the image quality priority mode is performed, the encoding unit 4 performs the code amount control unit 3 during the operation period.
The encoding is restricted prior to the control of (1), and encoding is performed with priority on image quality.

In this embodiment, the empty capacity is defined as the medium capacity. However, in the present invention, when the medium is equally divided into a plurality of recording areas, the capacity recordable in the designated recording area is determined as the medium capacity. May be preset in the code amount control means 3. Further, the target code amount may be set to be constant during the recording period as in this embodiment, but is not necessarily required to be constant in the present invention. For example, if the coding control has some flexibility, the generated code amount may be excessive or deficient with respect to the target code amount, and the target or predicted code amount may be adjusted to absorb the excess or deficiency. It is also meaningful to change successively. (Second Embodiment) Therefore, as a second embodiment, the generated code amount after a scene change is stored in a memory in units of segments, and the estimated code amount is calculated for each segment in accordance with the past history using the maximum likelihood estimation method. An encoding apparatus that performs encoding by changing to (1) will be described with reference to FIG.

In this embodiment, first, the remaining amount detecting means 2A
To detect the empty capacity from the recording medium 1A which enables the magnetic drum. The maximum likelihood estimating means 3A estimates the initial value of the predicted code amount based on the free space and the input recording time to be recorded, that is, the number of segments. This maximum likelihood estimation means 3A
Further, the memory 3B stores a large number of candidate values of a plurality of predicted code amounts, inputs the generated code amount per segment stored after the scene change, estimates the optimal predicted code amount based on the maximum likelihood estimation method, and outputs I do. This maximum likelihood estimation method is a well-known technique disclosed in “Statistical Analysis” published by Baifukan on November 15, 1969, pp. 107-110, and a detailed description thereof will be omitted.

The bit rate control means 3C controls the coding of the coding means 4A based on the estimated code amount. The bit rate control means 3C stores the generated code amount per segment in the memory 3B, and stores all generated code amounts per segment after a scene change. The scene change detecting means 5A detects the scene change by inputting the original image, and resets the memory 3B and the maximum likelihood estimating means 3A.

As a result, the predicted code amount indicated by the broken line shown in FIG. 4 gradually changes more stably than the generated code amount indicated by the solid line after the scene change. Although the recording medium is a magnetic drum in the above-described embodiment, it goes without saying that the recording medium may be an optical disk or a magneto-optical disk.

[0016]

According to the present invention, since the generated code amount of encoded data is controlled for each unit segment, image deterioration is dispersed. Further, according to the present invention, the generated code amount is controlled not only by the free capacity of the medium but also by the capacity of the designated recording area, and free recording is enabled.

Further, the target or predicted code amount can be fixed or variable, and can be freely set. Further, an image in which the predicted code amount is set by the maximum likelihood estimation method becomes more stable. Further, setting of the image quality priority mode enables high image quality recording. Further, the segments are set at a fixed time, and the circuit can be simplified.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a segment and a data amount according to the first embodiment of this invention.

FIG. 3 is a circuit block diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a segment and a data amount according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording medium 3 Code amount control means 4 Encoding means 5A Scene change detection part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideyuki Fujii 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Shuro Ito 2-chome, Keihanhondori, Moriguchi-shi, Osaka No. 5-5 in Sanyo Electric Co., Ltd.

Claims (9)

[Claims] An encoding means for encoding data and outputting encoded data, a target or predicted code amount per unit segment based on a medium capacity and the number of segments, and a code output from the encoding means. And a code amount control means for controlling the generated code amount of the encoded data. 2. The code amount control device according to claim 1, wherein the medium capacity is an empty capacity of the medium. 3. The code amount control device according to claim 1, wherein the medium capacity is a capacity of a designated recording area. 4. The code amount control device according to claim 2, wherein the target code amount for each of the segments is common. 5. The code amount control device according to claim 1, wherein the predicted code amount is set according to a code amount for each of a plurality of past segments stored in a memory. 6. The code amount control device according to claim 5, wherein the memory is reset by a scene change. 7. The code amount control device according to claim 6, wherein the predicted code amount is set by a maximum likelihood estimation method. 8. The encoding control device according to claim 1, wherein the encoding of said encoding means is restricted by setting an image quality priority mode. 9. The encoding apparatus according to claim 1, wherein the segment has a fixed time.