JPH0628446B2 - Compressed recorded image playback method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressed recording image reproduction method suitable for high-speed reproduction of an image compressed and recorded by predictive coding.

[Prior Art] A high-efficiency coding method used for compression recording of a color moving image is effective in reducing the average number of bits per pixel of an image, and in particular, DPCM (differential pulse code modulation) between frames that are image units. It is said that the predictive coding method using is suitable for processing a television signal having a small frame difference signal because of high inter-frame correlation. The predictive coding method compresses by subtracting a predicted value predicted using data of one frame before from image data regarding pixels in an XY two-dimensional image plane and coding the difference as prediction error data. It is a method.

Since the prediction error data can be approximated by the Laplace distribution, the conventional compressed image data recording / reproducing system 1 shown in FIG. 2 uses the logarithmic compression as the quantizing circuit 3 in the encoder 2 used in the recording system. A non-linear quantization circuit is used. The encoder 2 supplies the input image data to the quantization circuit 3 via a subtracter 4 that takes the difference from its predicted value. One of the prediction error data converted from the level value to the level number in the quantization circuit 3 is converted into an unequal length code in the code conversion circuit 5 and recorded in the CD-ROM 6, while
It is fed back to the subtracter 4 via the local decoder 7. The local decoder 7 supplies the output of the inverse quantization circuit 8 for inversely converting the quantization, ie, the level number to the level value, to the subtractor 4 via the predictor 9, while the input side of the predictor 9 is supplied. Positive feedback is provided to the adder 10 provided in the.

In the case of this example, the predictor 9 connects the inter-frame predicting circuit 9a and the intra-frame predicting circuit 9b in parallel, and selectively switches one of them by the selector switch 9c.
It is configured to connect to. This is because, when there is a scene change (scene change), the first image after the scene change has no correlation with the image signal of the previous frame,
This is because the intraframe predictive coding using the intraframe correlation of the image has higher coding efficiency than the interframe predictive coding. In the case of this example, at the scene change, the prediction mode control circuit 11 operates based on the scene change information from the scene change information generation circuit 11a, and the changeover switch 9c is switched to the intra-frame prediction circuit 9b.
Switch to the side. Therefore, C is the first time after a scene change.
The prediction error data E (1) ′ recorded in the D-ROM 6 is
By setting the intra-frame prediction mode for the predictor 9, E (1) '= F [V (1)]. However, the dash code indicates that it is based on intra-frame prediction, and F is a coding function for intra-frame predictive coding. Since the inter-frame prediction mode is set for the predictor 9 from the second frame following the first frame, E (i) = V (i) -V (i) = V for the image of the first frame. The prediction error data E (i) obtained by the calculation (i) -V (i-1) is the CD
-Recorded in ROM6. However, V (i) is the predicted value of V (i), that is, the image data V (i-1) of the previous frame.

On the other hand, the decoder 12 for decoding the prediction error data E (i) or E (i) 'read from the CD-ROM 6 inversely transforms the prediction error data code-converted by the unequal length coding, A code inverse conversion circuit 13 for returning to the equal-length code and a code inverse conversion circuit 1
The dequantization circuit 14 dequantizes the output of No. 3 and the adder 15 and the predictor 16 that form the image data V (i) from the output prediction error data of the dequantization circuit 14. The output of the inverse quantization circuit 14 is output through the adder 15 while
The image data V (i) is reproduced by the positive feedback to the adder 15 via the predictor 16 and the cyclic addition of the prediction error data and its decoded output. The predictor 16 is connected to a prediction mode control circuit 17 that switches the prediction mode according to the prediction mode used in the process of generating prediction error data.

The image data V (i) decoded by the decoder 12
Is generated as V (i) = G [E (i) ′] when i = 1, and when i ≧ 2, the prediction error data E (i) is added to the prediction value V (i). By adding, V = (i) = V (i) + E (i) is generated. However, G represents an intraframe decoding function.

[Problems to be Solved by the Invention] The conventional compressed image data recording / reproducing system 1 described above is C
Since the image data recorded in the D-ROM 6 is recorded as prediction error data, it is intended for high-speed reproduction,
-Even if the pickup head for scanning the recording track of the ROM 6 is skipped and the intermittent reproduction is repeated, the image data compressed by the intraframe predictive coding must be reproduced before the subsequent interframe prediction error data can be reproduced. Therefore, there is a problem that the images that can be actually reproduced are limited.

[Means for Solving the Problems] The present invention solves the above problems, and reproduces a moving image compressed and recorded by inter-image unit predictive coding while interlacing intra-image unit predictive coding. A method of reproducing a recorded image, characterized in that, of the compressed and recorded moving images, only a moving image portion compressed and recorded by intra-image predictive coding is selectively reproduced.

[Operation] The present invention reproduces the moving image compressed and recorded by the inter-image unit predictive coding while interweaving the intra-image unit predictive coding, and predicts the intra-image unit predictive coding among the compressed and recorded moving images. By selectively reproducing the moving image portion compressed and recorded by, the high speed reproduction is performed, and the redundancy accompanying the reproduction of the moving image portion compressed and recorded by the inter-image predictive coding is eliminated.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a system configuration diagram showing an embodiment of a compressed image data recording / reproducing system to which the compressed recording image reproducing system of the present invention is applied.

In FIG. 1, the compressed image data recording / reproducing system 21 is
Among the moving images compressed and recorded on the CD-ROM 6 which is a recording medium of the compressed image data, only the moving image portion compressed and recorded by the intra-image predictive coding is selectively reproduced. Reference numeral 22 is a prediction mode determination circuit provided in the preceding stage of the decoder 12, and is connected to the read track control circuit 23 of the CD-ROM 6. The prediction mode determination circuit 22 is configured to make a required determination in accordance with the frame prediction mode added for each prediction error data without referring to, for example, an address recorded in the directory area of the CD-ROM 6. Read track control circuit 2
Reference numeral 3 denotes a circuit for performing tracking control of the pickup head 24 that scans the tracks of the CD-ROM 6, and drives the pickup head 24 only when the prediction mode determination circuit 22 determines that it is in the intra-frame prediction mode. Play the recorded track.

That is, the pickup head 24, the prediction mode determination circuit 22 and the read track control circuit 2 shown in the embodiment.
3 constitutes a closed loop, and after reading the intra-frame prediction error data, the following inter-frame prediction error data can be skipped and the next intra-frame prediction error data can be reproduced. Therefore, during high-speed playback, by selectively playing back only the moving image parts that have been compressed and recorded by intraframe predictive coding, you can skip over only important scenes and, at the same time, record video that is compressed and recorded by interframe predictive coding. Redundancy associated with the reproduction of the image portion can be eliminated.

In this way, the compressed image data recording / reproducing system 21
Is for reproducing a moving image compressed and recorded by the inter-frame predictive coding while interweaving the intra-frame predictive coding, and the moving image part compressed and recorded by the intra-frame predictive coding among the compressed and recorded moving images. Since only Nimi is selectively played back, efficient and high-speed playback is possible by eliminating the redundancy associated with the playback of moving image parts that have been compressed and recorded by inter-frame predictive coding, and compressed by intra-frame prediction. The recorded moving image portion is often a portion having important information such as a scene change portion in many cases, and therefore, even if only that portion is selectively reproduced, important information is less likely to be lost, The entire image of the video recorded for a long time can be grasped in a short time by the skip reproduction.

In the above embodiment, the CD-ROM 6 is used as the compressed image data recording medium, but the recording medium is not limited to this, and may be another type such as a video tape.

Further, in the above description, inter-frame differential encoding is taken as an example of the predictive encoding method using the correlation between image units, but other methods such as motion-compensated inter-frame prediction can also be used. . Further, it is also possible to perform orthogonal transform coding or vector quantization on the prediction error data generated in these coding processes.

[Effects of the Invention] As described above, according to the present invention, when a moving image compressed and recorded by inter-image unit predictive encoding is reproduced while interlacing intra-image unit predictive encoding, the compressed and recorded moving image is reproduced. Of these, only the moving image part compressed and recorded by intra-image predictive coding is selected and reproduced, so that redundancy associated with the reproduction of the compressed and recorded moving image by inter-image predictive coding is eliminated to improve efficiency. It is possible to perform high-speed playback with good accuracy, and the moving image part that is compressed and recorded by intra-image prediction is often a part that has important information such as a scene change part, so only that part can be selectively selected. Even when reproduced, important information is less likely to be lost, and an excellent effect such that the entire image of a video recorded for a long time can be grasped in a short time by skip reproduction is achieved.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of a compressed image data recording / reproducing system to which a compressed recording image reproducing system of the present invention is applied, and FIG. 2 is an example of a conventional compressed image data recording / reproducing system. It is a system configuration diagram showing. 9a ... Inter-frame prediction circuit, 9b ... In-frame prediction circuit, 11 ... Prediction mode control circuit, 21 ... Compressed image data recording / reproducing circuit, 22 ... Prediction mode determination circuit,
23 ... Read-out track control circuit, 24 ... Pickup head.

Front page continuation (72) Inventor Muta Ota 5-33-1 Shiba, Minato-ku, Tokyo Inside NEC Corporation (72) Hideto Kunihiro 3-5-24 Miyahara, Yodogawa-ku, Osaka, Japan Electric Home Electronics Co., Ltd.

Claims (1)

[Claims] 1. A reproduction method of a compressed and recorded image for reproducing a moving image compressed and recorded by inter-image unit predictive coding while interlacing intra-image unit predictive coding, wherein: A reproduction method of a compressed recording image, which selectively reproduces only a moving image portion compressed and recorded by intra-image predictive coding.