MPEG-4 Profiles and Levels - A Practical Guide to Video and Audio Compression - page 674

Table G-6 Audio Object Types in MPEG-4 (Continued)

AOT Description ER

HVXC Harmonic Vector XCitation. √

HILN Harmonics, individual lines, and noise. A parametric encoder.

BSAC Bit-Sliced Arithmetic Coding. √

AAC LD Low-Delay coding. √

ULD Ultra-Low Delay. This algorithm introduces only 6 milliseconds

of delay. This makes it ideal for telecoms use or live production
with wireless microphones.

Most of these algorithms can be augmented with error-resilient support, in which
case they would be prefaced with the letters ER and would be identified with a different
ID value. These rows are flagged in the ER column of the table.
Some work on describing the complexity of the encoded data in a numeric way has
been done. Processor Complexity Units have been defined for each of these object types in
order to help plan the computing capacity required. You can find out more about this from
the MPEG Industry Forum.

G.5 H.264 Profiles and Levels

By comparison with MPEG-4 Part 2, the H.264 codec has very few profiles. That does not
mean it has fewer tools, just that there are fewer definitions of how they are made avail-
able in encoding applications. Table G-7 summarizes the profiles.
The support for levels includes 5 main levels and 10 other sub-levels. The 15 levels in
total are available across all of the profiles.

Table G-7 H.264 (JVT) profiles

Profile Description

Baseline Low-latency applications such as videoconferencing.

Main Designed for broadcasting use.

Extended Previously known as Profile-X. This is designed for streaming applications.

G.5.1 Baseline Profile

This profile is designed to encode quickly, and as a consequence, no B-slices are permit-
ted. Therefore, pictures can be transmitted in the same order as they are encoded and no
delay is introduced. The following capabilities are supported: