JP2005167568A - Image encoding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image encoding device that allows a user to subjectively and objectively determine the state of a compressed and encoded moving image.
An encoding parameter setting mechanism for setting an encoding parameter used for compression encoding from the outside, a compression encoder for compressing and encoding a digital moving image with the encoding parameter, and a compression encoder. A decoder 12 that decodes the digital video that has been compression-encoded in the above, a remaining time calculator 15 that calculates the remaining recording time from the above-described encoding parameters and a preset capacity of the recording medium, and a digital video before compression encoding And an image quality evaluator 13 that obtains an image quality evaluation value from the digital video after compression encoding, and a display device 17, and the display device 17 uses the above-described encoding parameter setting value and the digital moving image decoded by the decoder 12. At least one of an image, the remaining recording time, and the image quality evaluation value is displayed.
[Selection] Figure 1

Description

  The present invention relates to an image encoding apparatus for compressing and recording a digital moving image.

  Since the capacity of a digital moving image obtained by digitizing a captured moving image is enormous, a large-capacity recording medium is required if recording is performed as it is. It is also necessary to increase the throughput in the image processing apparatus. Therefore, compression encoding of digital moving images is widely performed. MPEG2 or MPEG4 is widely used as a method for compressing and encoding digital moving images. Both MPEG2 and MPEG4 are standardized moving image compression coding systems. Hereinafter, MPEG2 and MPEG4 are collectively referred to as MPEG unless it is necessary to distinguish between them.

  MPEG divides a digital moving image into blocks and orthogonally transforms each block. The orthogonally transformed data is quantized with a quantization table set for each frequency component. Further, the quantized result is encoded with a Huffman code.

  However, when quantization is performed, image information is discarded because human visual characteristics are used. Therefore, changing the quantization table significantly changes the image quality and the compression rate. Therefore, unless an optimal quantization table is selected, recording with poor image quality or exceeding the capacity of the recording medium makes it impossible to record all moving images. Therefore, a method for selecting an optimal quantization table has been proposed.

  As a known example, there is an example described in Patent Document 1. In this known example, a user inputs a parameter for determining a quantization table, and compression and decompression are performed using the parameter. Further, the original image and the expanded image are compared, and the superiority or inferiority of the image quality is color-coded for each block and displayed on the screen. The user sets parameters based on the objectively displayed image quality evaluation value.

In the above prior art, the degree of image quality deterioration due to compression coding is displayed for each compression coding block, and the optimum coding parameter can be selected without being aware of the numerical value of the coding parameter. Then, after the user selects the encoding parameter, the compressed and encoded image data is written to the recording medium.
Japanese Patent Laid-Open No. 6-334988

  In the above-described conventional example, the image quality table value indicating the degree of image degradation is obtained for each compression-coded block, and displayed in different colors. The user determines the encoding parameter using the color coding on the screen as a criterion.

  However, the total number of pixels of digital still cameras and digital video cameras (hereinafter collectively referred to as digital cameras) exceeds one million pixels, and the total number of compression-coded blocks is also tens of thousands. Count blocks. Therefore, even if the image quality table value is color-coded for each compression coding block and displayed on the liquid crystal screen on the back of the viewfinder or digital camera, it cannot be displayed separately for each compression coding block, There is a problem that it is difficult to see.

  Furthermore, in the case of a moving image, there is a problem that the value of the image quality table changes over time and it is difficult to determine when to determine the encoding parameter. In the conventional example, recording is started after the encoding parameter is determined. For this reason, there is a problem that it is not possible to cope with a change in the shooting situation during recording of a moving image.

  Further, the user does not always determine the encoding parameter only by the image quality table value. Considering the free capacity of the recording medium, it is possible to record with the image quality lowered so as to fit into the recording medium. In this case, an appropriate encoding parameter is determined from the image quality table value and the free space of the recording medium. As described above, there is a problem that the user cannot determine the optimum encoding parameter only by displaying the image quality table value.

  In addition, the user may subjectively determine the image quality by looking at the entire decoded image. If the image quality evaluation values are displayed in different colors as in the conventional example, it can be an objective judgment criterion, but there is a problem that it is not suitable for subjective judgment.

An image encoding apparatus according to the present invention is:
In a moving image recording apparatus for photographing, compressing and encoding a digital moving image,
Encoding parameter setting means for setting an encoding parameter used for the compression encoding from the outside at an arbitrary time;
Compression encoding means for compressing and encoding the digital moving image with the set encoding parameter;
Decoding means for decoding the digital moving image compressed and encoded by the compression encoding means or the digital moving image being compressed and encoded by the compression encoding means;
Means for calculating the remaining recording time from the encoding parameter set by the encoding parameter setting means and the capacity of the preset recording medium;
Means for obtaining an image quality evaluation value from a digital video before compression encoding and a digital video after compression encoding;
Display means,
The display means includes means for displaying at least one of the encoding parameter setting value, the digital moving image decoded by the decoding means, the remaining recording time, and the image quality evaluation value.

Further, in parallel with recording the compression-encoded digital moving image on the recording medium, the compression-encoded digital moving image is read from the recording medium,
A mechanism for inputting to the decoding means is provided.

  As described above, since the decoded digital moving image can be displayed on the display unit with the image quality evaluation value and the remaining recording time, the user can perform both objective judgment and subjective judgment. Therefore, the user can more easily determine the encoding parameter. Furthermore, since the encoding parameter can be changed even during the recording of a moving image, it is possible to follow even if the shooting situation changes.

  In addition, when a compression-encoded digital moving image recorded on a recording medium is used, there is an effect as an operation monitor for confirming whether or not the recording is correctly performed on the recording medium.

  Embodiments of the present invention will be described below with reference to the drawings. Various methods such as MPEG2, MPEG4, and motion JPEG exist as compression encoding methods for moving images. Since the present invention is not an invention specific to a specific encoding / compression method, any moving image compression / encoding method may be used. In the following description of the examples, MPEG is used unless otherwise specified.

  FIG. 1 shows an embodiment relating to the present invention. The compression encoder 11 compresses and encodes the original digital moving image 101 and outputs a compression-encoded digital moving image 102. The decoder 12 decodes the compression-encoded digital moving image 102 or the digital moving image 105 being compressed and encoded, and outputs a decoded digital moving image 103. The image quality evaluator 13 obtains an image quality evaluation value from the original digital moving image 101 and the decoded digital moving image 103. The encoding parameter setting mechanism 14 calculates a necessary bit rate value from the image quality selected by the user, and outputs the bit rate value as the encoding parameter 104. The remaining time calculator 15 calculates and outputs the remaining recording time 107 from the preset capacity of the recording medium 16, the capacity of the compression-encoded digital moving image 102, and the encoding parameter value 104. The recording medium 16 records a compression-encoded digital moving image. The display device 17 displays information selected by the user from the decoded digital moving image 103, the image quality evaluation value 106, and the remaining recording time 107. A working memory is required for compression encoding and decoding of moving images. In FIG. 1, the working memory is omitted.

  The compression encoder 11 obtains a quantization table from the encoding parameter 104. Based on this quantization table, the original digital moving image 101 is compression-encoded. If the encoding parameter 104 changes, that is, if the user changes the image quality, the compression encoder 11 recalculates the quantization table based on the new encoding parameter 104. Then, compression coding is performed using the new quantization table from the next compression coding block.

  The decoder 12 analyzes the header of the compression-coded digital image 102 and decodes the moving image based on the result.

  The image quality evaluator 13 may use any image quality evaluation method. In this embodiment, a mean square error between the original digital moving image 101 and the decoded digital moving image 103 is obtained, and this value is used as an image quality evaluation value.

  The encoding parameter setting mechanism 14 has a mechanism for a user to select an image quality and a function for obtaining an encoding parameter 104 from the selected image quality. FIG. 6 shows an embodiment of the encoding parameter setting mechanism 14. The image quality selection mechanism 201 is a mechanism portion operated by the user. The encoding parameter calculator 202 calculates the encoding parameter value 104 from the state of the image quality selection mechanism 201. When the user presses the switch 203, the encoding parameter value 104 increases. That is, the transition is made to the high image quality side. Conversely, when the user presses switch 204, the encoding parameter value 105 decreases. That is, the transition is made to the low image quality side.

The remaining time calculator 15 obtains the remaining recording time of the recording medium. The remaining time is calculated as follows. However, since the present invention does not depend on the remaining recording time calculation method, the calculation method described here may not be used. In the remaining time calculator 15, the code amount of the compression-encoded digital moving image 102 is accumulated. Then, the remaining recording time 107 is obtained from the following equation.
(Capacity of recording medium 16−accumulated code amount value) / encoding parameter value = remaining recording time If the value of the encoding parameter 104 changes, that is, if the user changes the image quality, the remaining recording time 107 The value changes. For example, if the coding parameter is shifted to the low image quality side during recording of a moving image, the remaining recording time increases.

  The display device 17 displays information selected by the user from the decoded digital moving image 103, the image quality evaluation value 106, and the remaining recording time 107. FIG. 2 shows an embodiment of the display device 17. On the liquid crystal panel 51, a recording image quality display area 52, a remaining recording time display area 53, an image quality selection display area 54, and a moving image display area 55 are provided.

The image quality evaluation value 106 may be displayed on the display device 17 as it is. However, since the image quality evaluation value 106 is a mean square error value, it is difficult to understand even if it is displayed on the display device 17 as it is. Therefore, in this embodiment, the display is divided into four stages as follows. This classification is performed by the display device 17.
Display Image quality evaluation value 106
SUPER FINE 40 or more FINE 30 or more but less than 40
MIDDLE 20 or more and less than 30
Less than LOW 20 The remaining recording time display area 53 is an area for displaying the remaining recording time 107. The accumulated recording time so far may be displayed in the remaining time display area. The image quality selection display area 54 is an area for displaying which switch in the image quality selection mechanism 201 the user has pressed.

  The moving image display area 55 is an area for displaying the decoded digital moving image 103. The user selects the image quality based on the remaining recording time 107 in the remaining recording time display area 53 if necessary while referring to the image quality of the decoded digital moving image 103 displayed in the moving image display area 55.

  FIG. 3 is a diagram illustrating a case where the user does not select the remaining recording time display. FIG. 4 is a diagram showing a case where the entire moving image display area 55 is set.

  FIG. 5 is a diagram showing another embodiment of the present invention. In the embodiment shown in FIG. 5, the compression-encoded digital moving image 108 actually recorded on the recording medium 16 is decoded to obtain the image quality evaluation value 106 and displayed on the display device 17. The embodiment shown in FIG. 5 also has a monitor function for confirming whether or not recording has been correctly performed on the recording medium 16.

  When a moving image is recorded by a digital camera equipped with an image encoding device according to the present invention, the user operates the digital camera as follows.

Before recording: Set encoding parameters and check image quality and recording time
If the image quality and recording time are not satisfactory, the encoding parameters
Even if the image quality is reduced until it can withstand the image quality
Recording time is insufficient, that is, the recording medium capacity is insufficient
If it does, replace the recording medium

Start recording: Press the shooting button to start recording digital video

During recording: Shoot while checking the image quality and remaining recording time.
U
If the image quality and recording time are not satisfactory, the encoding parameters
Even if the image quality is reduced until it can withstand the image quality
Recording time is insufficient, that is, the recording medium capacity is insufficient
If it does, replace the recording medium

It is a figure which shows one Example of this invention. It is a figure which shows one Example of a display apparatus. It is a figure which shows one Example of a display apparatus. It is a figure which shows one Example of a display apparatus. It is a figure which shows one Example of this invention. It is a figure which shows one Example of an encoding parameter setting mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Compression encoder 12 Decoder 13 Image quality evaluator 14 Encoding parameter setting mechanism 15 Remaining time calculator 16 Recording medium 17 Display device 51 Liquid crystal panel 52 Image quality display area 53 Remaining time display area 54 Image quality selection display area 55 Moving image display Area 101 Original digital moving image 102 Compression encoded digital moving image 103 Decoded digital moving image 104 Encoding parameter value 105 Digital moving image in the middle of compression code 106 Image quality evaluation value 107 Remaining recording time 201 Image quality selection mechanism 202 Encoding parameter calculator 203 Switch 204 switch

Claims (3)

In an image encoding device that takes a digital moving image, compresses and encodes it, and records it on a recording medium.
Encoding parameter setting means for setting an encoding parameter used for the compression encoding from the outside at an arbitrary time;
Compression encoding means for compressing and encoding the digital moving image with the set encoding parameter;
Decoding means for decoding the digital moving image compressed and encoded by the compression encoding means or the digital moving image being compressed and encoded by the compression encoding means;
Means for calculating the remaining recording time from the encoding parameter set by the encoding parameter setting means and the capacity of the preset recording medium;
Means for obtaining an image quality evaluation value from a digital video before compression encoding and a digital video after compression encoding;
Display means,
The display means comprises means for displaying at least one of the encoding parameter setting value, the digital moving image decoded by the decoding means, the remaining recording time, and the image quality evaluation value. Device.   As soon as the encoding parameter is changed by the encoding parameter setting means, the compression encoding means compresses and encodes the digital moving image with the new encoding parameter, and the remaining recording time calculation means recalculates the remaining recording time. 2. The image coding apparatus according to claim 1, wherein the means for obtaining the image quality evaluation value recalculates the image quality evaluation value. In parallel with recording the compression-encoded digital moving image on the recording medium, the compression-encoded digital moving image is read from the recording medium,
The image coding apparatus according to claim 1 or 2, further comprising a mechanism for inputting to the decoding means.

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