Image coding method, image decoding method, memory managing method, image coding apparatus, image decoding apparatus, memory managing apparatus, and image coding and decoding apparatus
With an image coding method which allows reduction of processing loads, when pictures included in a video signal are classified into layers so as to belong to their respective layers, a picture that belongs to the second layer that is located in a range restricted according to the first layer to which a current picture to be coded that is one of the pictures belongs, is referred to as a reference picture for the current picture, and the current picture is coded based on the reference picture.
1. An image coding method for coding a video signal using a processor, said image coding method comprising:
classifying a plurality of images included in the video signal into layers, each of the plurality of images belonging to a corresponding one of the layers;
generating a flag to be embedded in the video signal, the flag indicating whether a third image is prohibited to refer to a second image or not, where the third image belongs to a layer equal to or higher layer than a layer to which the second image belongs, the second image precedes a first image in coding order, and the third image follows the first image and the second image in coding order;
coding the first image and the second image; and
coding the third image, where the third image is coded without referring to the second image when the flag indicates that the third image is prohibited to refer to the second image and the third image is able to be coded by referring to the second image when the flag indicates that the third image is not prohibited to refer to the second image.
2. An image coding apparatus which codes a video signal, said image coding apparatus comprising:
a processor; and
a non-transitory memory having stored thereon executable instructions, which when executed, cause the processor to perform:
classifying a plurality of images included in the video signal into layers, each of the plurality of images belonging to a corresponding one of the layers;
generating a flag to be embedded in the video signal, the flag indicating whether a third image is prohibited to refer to a second image or not, where the third image belongs to a layer equal to or higher layer than a layer to which the second image belongs, the second image precedes a first image in coding order, and the third image follows the first image and the second image in coding order;
coding the first image and the second image; and
coding the third image, where the third image is coded without referring to the second image when the flag indicates that the third image is prohibited to refer to the second image and the third image is able to be coded by referring to the second image when the flag indicates that the third image is not prohibited to refer to the second image.
3. An image decoding method for decoding a video signal using a processor, said image decoding method comprising:
classifying a plurality of images included in the video signal into layers, each of the plurality of images belonging to a corresponding one of the layers;
obtaining a flag from the video signal, the flag indicating whether a third image is prohibited to refer to a second image or not, where the third image belongs to a layer equal to or higher layer than a layer to which the second image belongs, the second image precedes a first image in decoding order, and the third image follows the first image and the second image in decoding order;
decoding the first image and the second image; and
decoding the third image, where the third image is decoded without referring to the second image when the flag indicates that the third image is prohibited to refer to the second image and the third image is able to be decoded by referring to the second image when the flag indicates that the third image is not prohibited to refer to the second image.
4. An image decoding apparatus which decodes a video signal, said image decoding apparatus comprising:
a processor; and
a non-transitory memory having stored thereon executable instructions, which when executed, cause the processor to perform:
classifying a plurality of images included in the video signal into layers, each of the plurality of images belonging to a corresponding one of the layers;
obtaining a flag to be embedded in the video signal, the flag indicating whether a third image is prohibited to refer to a second image or not, where the third image belongs to a layer equal to or higher layer than a layer to which the second image belongs, the second image precedes a first image in decoding order, and the third image follows the first image and the second image in decoding order;
decoding the first image and the second image; and
decoding the third image, where the third image is decoded without referring to the second image when the flag indicates that the third image is prohibited to refer to the second image and the third image is able to be decoded by referring to the second image when the flag indicates that the third image is not prohibited to refer to the second image.