Chapter 6 Audio Modules
AHC-RAC Module
© 2015 Harmonic Inc. All rights reserved.
58
Electra 9200, Rev O
Note the following limitations:
n
ATSC Standard A/53 specifies that only 48 kHz sampling may be used, and that ES bit
rates must be less than or equal to 384 Kbps for a complete service. It also specifies that
a two-channel dialog-only service must be less than or equal to 192 Kbps. Total ES rates
for all services must be less than or equal to 512 Kbps.
n
Embedded audio must be 48 kHz sampling and synchronous with the video. See SMPTE
272M for definitions.
MPEG AAC and HE AAC can be placed into the output Transport Stream encapsulated in
either of two methods
n
ADTS
ADTS is an acronym for “Audio Data Transport Stream.” This is the default used if the user
selects MPEG-2 AAC/HE AAC. ADTS is assigned a stream type of 0x0F.
n
LATM/LOAS
LATM is an acronym for ”Low Overhead Audio Transport Multiplex.” LOAS is an acronym
for ”Low Overhead Audio Stream,” and furnishes an outer wrapper for LATM's inner
wrapper of the raw audio Elementary Stream syntax. MPEG-4 AAC and HE AAC
bitstreams are encapsulated as LATM/LOAS and assigned a stream type value of
0x11.Encapsulation mode is controlled by selecting ”MPEG-2” or ”MPEG-4” as required.
MPEG AAC
compression
n
Single channel (1.0)
32 kHz
44.1 kHz
48 kHz
32, 48, 56, 64, 96, 112,
128, 182, 192
n
Dual channel (1+1)
n
Stereo channel (2.0)
n
Joint stereo channel
32 kHz
44.1 kHz
48 kHz
64, 96, 112, 128, 144, 182,
192, 224, 256, 320, 384
Multi-channel (5.1)
32 kHz
44.1 kHz
48 kHz
224, 256, 288, 320, 352,
384, 448, 512, 576, 640
a.
These rates are not compliant with A/53.
b.
These rates are valid for 1.0 coding only.
c.
AHC-561 supports 48 kHz sampling rate only.
d.
Above 56 kbps (1.0), 112 kbps )2.0) or 192 kbps (5.1), the system automatically configures
compressions for AAC-LC even if HE AAC is selected.
Table 6–5: AHC-RAC Audio Bit Rates continued
AHC-RAC Feature
Coding Mode
Sampling
Frequency
ES Bit Rates
Supported (Kbps)
