Image decoding device and image decoding method

• US 20070003149A1
• Filed: 04/19/2004
• Published: 01/04/2007
• Est. Priority Date: 04/25/2003
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Suzuki, Teruhiko, Yagasaki, Yoichi, Nagumo, Takefumi
• Granted Patent: US 7,672,522 B2
• Time in Patent Office: Days
• US Class Current: 382/233
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/44 Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/587 involving temporal sub-sampling or interpolation, e.g. decimation or subsequent interpolation of pictures in a video sequence
• CPC Class Codes: H04N 5/783 Adaptations for reproducing at a rate different from the recording rate
• CPC Class Codes: H04N 9/8042 involving data reduction

Abstract

This invention realizes an image decoding apparatus and an image decoding method capable of correctly performing a decoding process in short time with a simple construction. In an image decoding apparatus and an image decoding method for performing a decoding process under a prescribed coding method, simple playback frames comprising an I-picture and following prescribed pieces of P-pictures on the basis of the I-picture existing at a desired position in picture data encoded with the coding method are extracted in a fast playback mode.

Claims

1. An image decoding apparatus for performing a decoding process under a prescribed coding method, comprising:

decoding means for performing the decoding process on picture data encoded with the coding method; and

control means for controlling the decoding means, wherein, in a fast playback mode, said control means controls said decoding means by selectively performing a first process to extract and decode an I-picture and following prescribed pieces of P-pictures on a basis of the I-picture locating at a desired position in the picture data, a second process to decode only spatial prediction based on a prediction method signal obtained through reversible encoding, a third process to decode only direct current components of transformation coefficients with transformation coding, or a fourth process that is a combination of the second and third processes.

2. The image decoding apparatus according to claim 1, wherein

said control unit controls said decoding means so as to decode the I-picture and each of the P-pictures composing the simple playback frames in order, without decoding a part after the simple playback frames, in a case where the fast playback mode is fast forward playback, and controls said decoding means so as to find a part before the simple playback frames, sequentially decode the I-picture and each of the P-pictures composing the simple playback frames, and output the simple playback frames in a reverse order of a decoding order, in a case where the fast playback mode is fast backward playback.

3. (canceled)

4. An image decoding method for performing a decoding process under a prescribed coding method, wherein,

in a fast playback mode, a first process to extract and decode an I-picture and following prescribed pieces of P-pictures on a basis of the I-picture locating at a desired position in picture data encoded with the coding method, a second process to decode only spatial prediction based on a prediction method signal obtained through reversible encoding, a third process to decode only direct current components of transformation coefficients with transformation coding, or a fourth process that is a combination of the second and third processes is selectively performed.

5. The image decoding method according to claim 4, wherein:

in a case where the fast playback mode is fast forward playback, the I-picture and each of the P-pictures composing the simple playback frames are decoded in order, without decoding a part after the simple playback frames; and

in a case where the fast playback mode is fast backward playback, a part before the simple playback frames is found, the I-picture and each of the P-pictures composing the simple playback frames are decoded in order, and the simple playback frames are decoded in a reverse order of a decoding order.

6. (canceled)