Method and device for decoding an image compressed in particular according to the MPEG standards, especially a bidirectional image
AssigneeSTMicroelectronics S.r.l.
InventorsRichard Bramley, Patrice Woodward
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Abstract
A method and device decode a compressed image, and in particular, an image compressed according to the MPEG standards, especially a bidirectional image. To perform two successive decodings of a bidirectional image, the address of the data packet containing the start-of-image identifier of the bidirectional image is tagged, and the temporal reference of this image is stored. After the first decoding, the stored address of the memory is again pointed to and a second decoding is performed after a new detection of the temporal reference of the image.
Claims22
A method for decoding an image including compressed data, the compressed data comprising successive groups of compressed data, which groups relate respectively to successive inbound images, some of which require two successive decodings, each data group associated with an image comprising a start-of-image identifier, followed by a header containing a specific identifier of the image, followed by useful data, the method comprising the steps of:
- storing a stream of compressed data in a memory area of a dynamic memory;
- reading the stream of compressed data in packets of bits located at consecutive addresses of the memory area;
- detecting the presence or the absence of the start-of-image identifier for the packets read from the memory area;
- storing the address of a relevant packet together with the specific identifier of the image when a detected start-of-image identifier corresponds to an image requiring two successive decodings;
- performing a first decoding of the useful data of the image;
- reading the packet data at the stored address from the memory area again;
- and
- performing the second decoding of the image by decoding the packet data following the specific identifier and ignoring the packet data preceding the specific identifier.
A method for decoding an image including compressed data, the compressed data relating to successive images, the compressed data associated with an image comprising a start-of-image identifier, a header containing a specific identifier of the image, and useful data, the method comprising the steps of:
- storing compressed data in a memory;
- reading the compressed data in packets of bits located in the memory;
- detecting the presence of a start-of-image identifier for the packets read from the memory;
- storing the address of a relevant packet when a detected start-of-image identifier corresponds to an image requiring two successive decodings;
- storing the specific identifier of the image requiring two successive decodings;
- decoding the image;
- reading the packet bits at the stored address again;
- and
- decoding the image again by decoding the packet data following the specific identifier and ignoring the packet data preceding the specific identifier.
A method for decoding an image including compressed data, the compressed data relating to successive images, the compressed data associated with an image comprising a start-of-image identifier, a header containing a specific identifier of the image, and useful data, the method comprising the steps of:
- storing the compressed data in a memory;
- reading the compressed data stored in the memory;
- storing an address of a relevant packet when a start-of-image identifier corresponds to a bidirectional image;
- decoding the bidirectional image;
- reading the compressed data at the stored address again;
- and
- decoding the bidirectional image again by decoding data following the specific identifier and ignoring data preceding the specific identifier.
A device for decoding an image including compressed data, the compressed data comprising successive groups of compressed data, which groups relate respectively to successive inbound images, some of which require two successive decodings, each data group associated with an image comprising a start-of-image identifier, followed by a header containing a specific identifier of the image, followed by useful data, the device comprising:
- a dynamic memory including a memory area for storing a stream of compressed data;
- a first address pointer and a second address pointer for making it possible to read the memory area in packets of bits;
- a start-of-image identifier detector for detecting the presence or the absence of the start-of-image identifier in each packet read at an address pointed at by the first address pointer;
- first storage means for storing the address of the packet containing the start-of-image identifier of the current image when a first control signal represents the presence of a current image requiring two successive decodings;
- second storage means for storing the specific identifier of the current image;
- processing means, linked to the start-of-image identifier detector, for providing the first control signal;
- a decoding circuit for decoding the bits of the packet pointed at by the second address pointer;
- pointer management means for, in response to a second control signal transmitted by the decoding circuit and representative of the end of a first decoding of an image, moving the second address pointer to the address stored in the first storage means;
- and
- decoding disabling means for comparing the specific identifier stored in the second storage means with the packet bits at the address stored in the first storage means, and for disabling the decoding circuit until the specific identifier of the image is detected again.
A device for decoding an image including compressed data, the compressed data relating to successive images, the compressed data associated with an image comprising a start-of-image identifier, a header containing a specific identifier of the image, and useful data, the device comprising:
- a memory for storing compressed data;
- a first register for storing an address of compressed data containing the start-of-image identifier of a bidirectional image to be decoded;
- a decoding circuit for decoding the compressed data of the bidirectional image;
- and
- a decoding disabler for reading the compressed data at the address stored in the first register, and for disabling the decoding circuit until the specific identifier of the bidirectional image is detected and for enabling the decoding circuit to decode the compressed data of the bidirectional image again when the specific identifier of the bidirectional image is detected.
Dependencies are inferred from the claim text.