Graphics Reference
In-Depth Information
Tabl e 2. 6
(continued)
SEI message
Type
Description
Decoding unit info
Prefix
Provides HRD parameters for sub-AU
decoding units
Temporal sub layer zero index
Prefix
Provides information to assist decoder to
detect missing coded pictures
Scalable nesting
Prefix
Associates other SEI messages with
bitstream subsets
Region refresh info
Prefix
Indicates if slice segments belong to a
refreshed region of the picture
Reserved
Prefix/suffix
For future extensions
to the temporal level zero dependency representation index SEI message in AVC's
SVC extension. Some of the newly introduced SEI messages in HEVC are described
below.
The decoded picture hash SEI provides a calculated hash for each colour
component of the decoded picture. Three different hash calculation methods are
supported: MD5, CRC, and checksum. This SEI message is intended for debugging
and interoperability testing, and allows a decoder to determine if the decoded picture
exactly matches that of the encoder.
The display orientation SEI message informs the decoder of a recommended
transformation to be applied to the cropped decoded picture prior to display. The
message includes indications to flip the picture horizontally or vertically, and an
anticlockwise rotation amount.
The structure of pictures SEI message provides information about patterns of
coded pictures within the coded video sequence. Patterns of pictures in terms of
their values of NAL unit type, temporal ID values, short-term reference picture set
index, and POC delta.
The active parameter sets SEI message provides easily accessible information to
a middle box or decoder of the active video parameter set ID value, and optionally
sequence parameter set ID values. Without using this SEI message, it is required to
parse the slice header to find the PPS ID, access the contents of the picture parameter
set to find the SPS ID, and access the contents of the sequence parameter set to
determine the VPS ID.
2.6
Hypothetical Reference Decoder (HRD)
The operation of the HRD in HEVC [
1
] behaves similarly to the HRD of
H.264/AVC, but provides additional functionalities. The HRD allows an encoder
to specify the constraints of a bitstream to identify the capabilities needed to
ensure that the bitstream can be correctly buffered, decoded, and output. Signaling
of HRD parameters is optional for an encoder. HRD parameters do not directly
