67
audio streams
LiveShot by default encodes audio using the
AAC-ELD
algorithm, which is a highly regarded codec
designed to balance low delay and high quality audio. It is a variant of the
AAC-LC
algorithm,
popularized by Portable media players.
AAC-ELD
adds to
AAC-LC
in two ways:
1
Low Delay (LD) Operation
- Using a shorter framesize, overall processing delay is
reduced to a fraction of
AAC-LC
. This is important because of LiveShot’s extremely
low delay video codec. Use of
AAC-ELD
removes the need to delay video in order
to maintain A/V sync.
2
Spectral Band Replication (SBR)
- This is a technique used to reduce network
bitrate by applying synthesis algorithms to high frequencies. The
AAC
variant that
utilizes
SBR
(without the low delay aspect) is known as
HE-AAC
.
Each of these options of
AAC
(LD and SBR) can be enabled and disabled in your audio stream. This may
be important for compatibility with other decoding devices or players. In order to create a stream using
an
AAC
variant, use this guide:
•
AAC-LC
(or just plain AAC) --- LD and SBR disabled.
•
HE-AAC
--- LD mode disabled, SBR enabled.
•
AAC-LD
--- LD mode enabled, SBR disabled.
•
AAC-ELD
--- LD and SBR modes enabled.
