Low delay picture coding

An encoder for encoding a picture into a datastream in units of slices into which the picture is partitioned, wherein the encoder is configured to encode the slices into the datastream in accordance with a slice order, the encoder comprising:

• a residual module configured to generate, using a processor, a residual signal related to a current slice of the picture;
• a predictor configured to generate, using the processor, prediction parameters based on a prediction signal, wherein the prediction parameters are encoded into the datastream;
• and
• an entropy encoder configured to determine, using the processor, a syntax element portion for the current slice and entropy encode, into the datastream, the slices based on wavefront parallel processing (WPP) in which the residual signal related to the current slice is entropy encoded according to one of at least two modes indicated by the syntax element portion, wherein the entropy encoder is configured to:
• if the current slice is to be coded in accordance with a first of the at least two modes as indicated by the syntax element portion, encode the residual signal related to the current slice into the datastream using context adaptive entropy encoding comprising a derivation of contexts across slice boundaries, a continuous update of symbol probabilities of the contexts and an initialization of the symbol probabilities depending on saved states of symbol probabilities of a previously encoded slice,
• if the current slice is to be coded in accordance with a second of the at least two modes as indicated by the syntax element portion, encode the residual signal related to the current slice into the datastream using context adaptive entropy encoding with restricting the derivation of the contexts so as to not cross the slice boundaries, a continuous update of symbol probabilities of the contexts and an initialization of the symbol probabilities independent on any previously encoded slice, and
• save symbol probabilities as acquired in context adaptive entropy encoding the previously encoded slice up to a second coding block in a row in accordance with a raster scan order,
• wherein each slice comprises a start syntax portion indicating a position within the picture at which the entropy encoding of the respective slice begins, the entropy encoder being configured to identify entry points of WPP substreams associated with the slices using the slices' start syntax portions.

A method for reconstructing a picture from a datastream into which the picture is coded in units of slices into which the picture is partitioned, the method comprising:

• decoding the slices from the datastream in accordance with a slice order;
• entropy decoding the slices based on wavefront parallel processing (WPP) in which a current slice of the picture is entropy decoded according to one of at least two modes indicated by a syntax element portion within the current slice, wherein the entropy decoding comprises:
• in accordance with a first of the at least two modes indicated by the syntax element portion, decoding data related to the current slice from the datastream using context adaptive entropy decoding to obtain a residual signal, the context adaptive entropy decoding comprising a derivation of contexts across slice boundaries, a continuous update of symbol probabilities of the contexts and an initialization of the symbol probabilities depending on saved states of symbol probabilities of a previously decoded slice,
• in accordance with a second of the at least two modes indicated by the syntax element portion, decoding data related to the current slice from the datastream using context adaptive entropy decoding to obtain a residual signal, the context adaptive entropy decoding comprising restricting the derivation of the contexts so as to not cross the slice boundaries, a continuous update of symbol probabilities of the contexts and an initialization of the symbol probabilities independent on a previously decoded slice,
• saving symbol probabilities as acquired in context adaptive entropy decoding the previously decoded slice up to a second coding block in a row in accordance with a raster scan order, and
• identifying entry points of WPP substreams associated with the slices using slices' start syntax portions, wherein each slice comprises a start syntax portion indicating a position within the picture at which the entropy decoding of the respective slice begins;
• generating a prediction signal based on prediction parameters from the datastream;
• and
• reconstructing a portion of the picture based on the residual signal and the prediction signal.

A method for encoding a picture into a datastream in units of slices into which the picture is partitioned, the method comprising:

• encoding the slices into the datastream in accordance with a slice order;
• generating a residual signal related to a current slice of the picture;
• generating prediction parameters based on a prediction signal, wherein the prediction parameters are encoded into the datastream;
• determining a syntax element portion for, and code same into, the current slice;
• and
• entropy encoding, into the datastream, the slices based on wavefront parallel processing (WPP) in which the residual signal related to the current slice is entropy encoded according to one of at least two modes indicated by the syntax element portion, wherein the entropy encoding comprises:
• if the current slice is to be coded in accordance with a first of the at least two modes as indicated by the syntax element portion, encoding the residual signal related to the current slice into the datastream using context adaptive entropy encoding comprising a derivation of contexts across slice boundaries, a continuous update of symbol probabilities of the contexts and an initialization of the symbol probabilities depending on saved states of symbol probabilities of a previously encoded slice,
• if the current slice is to be coded in accordance with a second of the at least two modes as indicated by the syntax element portion, encoding the residual signal related to the current slice into the datastream using context adaptive entropy encoding with restricting the derivation of the contexts so as to not cross the slice boundaries, a continuous update of symbol probabilities of the contexts and an initialization of the symbol probabilities independent on any previously encoded slice,
• saving symbol probabilities as acquired in context adaptive entropy encoding the previously encoded slice up to a second coding block in a row in accordance with a raster scan order, and
• identifying entry points of WPP substreams associated with the slices using slices' start syntax portions, wherein each slice comprises a start syntax portion indicating a position within the picture at which the entropy encoding of the respective slice begins.

A non-transitory computer-readable medium for storing data associated with a video, comprising:

• a data stream stored in the non-transitory computer-readable medium, the data stream comprising encoded information related to a picture of a video, wherein the picture is encoded into the data stream in units of slices into which the picture is partitioned, wherein the encoded information is coded into the data stream for storing in the non-transitory computer-readable medium by operations including:
• encoding the slices into the data stream in accordance with a slice order;
• generating a residual signal related to a current slice of the picture;
• generating prediction parameters based on a prediction signal, wherein the prediction parameters are encoded into the data stream;
• determining a syntax element portion for, and code same into, the current slice;
• and
• entropy encoding, into the datastream, the slices based on wavefront parallel processing (WPP) in which the residual signal related to the current slice is entropy encoded according to one of at least two modes indicated by the syntax element portion, wherein the entropy encoding comprises:
• if the current slice is to be coded in accordance with a first of the at least two modes as indicated by the syntax element portion, encoding the residual signal related to the current slice into the datastream using context adaptive entropy encoding comprising a derivation of contexts across slice boundaries, a continuous update of symbol probabilities of the contexts and an initialization of the symbol probabilities depending on saved states of symbol probabilities of a previously encoded slice,
• if the current slice is to be coded in accordance with a second of the at least two modes as indicated by the syntax element portion, encoding the residual signal related to the current slice into the datastream using context adaptive entropy encoding with restricting the derivation of the contexts so as to not cross the slice boundaries, a continuous update of symbol probabilities of the contexts and an initialization of the symbol probabilities independent on any previously encoded slice,
• saving symbol probabilities as acquired in context adaptive entropy encoding the previously encoded slice up to a second coding block in a row in accordance with a raster scan order, and
• identifying entry points of WPP substreams associated with the slices using slices' start syntax portions, wherein each slice comprises a start syntax portion indicating a position within the picture at which the entropy encoding of the respective slice begins.