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2.2.5 About audio settings
Encoding & Frequency
The unit supports the following audio formats:
• MPEG1 / MPEG2 (solo half-duplex)
•
uLaw/aLaw
• PCM MSB/LSB first
The passive receiver of a half-duplex system
automatically recognizes the audio format but only
for audio formats with fixed content.

AES3 / S-PDIF input uses MPEG1 and the sample rate
detects automatically (32, 44.1 o 48 KHz).
Remember: The playback buffer size is a very
important question. This value expresses the buffer
size in miliseconds. Smaller values minimize the delay,
but increase the chance of audio drops. The optimal
value depends on audio format and sample rate.
MP3 baja tasa de bits 400 mS
MP3 alta tasa de bits 200 mS
PCM 44.1/48 KHz 40 mS
2.2.6 Calculating the bit rate
The final bit rate is the sum of the audio bit rate and
encapsulation of audio packets make the network
protocol used. For RTP the calculation is:
The Ethernet total overhead per packet is 300 bit.
The IP total overhead per packet is 160 bit.
The UDP total overhead per packet is 64 bit.
The RTP total overhead per packet is 128 bit (considering the enclousure
MP3 MPA into the usable RTP overhead, that have a extra header of 32
bit).
Total overhead of bits per packet =
Ethernet Overhead + IP Overhead + UDP Overhead + RTP
Overhead = 652 bit
The audio bit rate expressed in bits/s, but the
overhead is expressed in bits/packet. So we have to
translate the overhead (bit/packet) in overhead rate
(bits/sec). For this we need to know the number of
packets per second, depending on the audio format.
It can be measured with a software network protocol
analyzer such as the "Wireshark".
Overhead/s = Overhead/Packet x Packet/s
Total Bit Rate (Kbit/s) = Audio Data Rate (Kbit/s) + Overhead/sec (Kbit/s)
(1Kbit = 1000 bits)
Audio Format
Audio
Data Rate
(Kbit/s)
Packet/sec
(Wireshark)
Overhea
d
(bit)
Total Bit
Rate
(Kbit/s)
MPEG1 48KHz quality 0, stereo 88 41.7 652 115.2
MPEG1 48KHz quality 4, stereo 144 41.7 652 171.2
MPEG1 48KHz quality 7, stereo 192 41.7 652 219.2
MPEG1 48KHz quality 4, mono 96 41.7 652 123.2
MPEG1 44.1KHz quality 0,
mono
65 38.3 652 90
MPEG1 44.1KHz quality 4,
mono
90 38.3 652 114.97
MPEG1 44.1KHz quality 7,
mono
140 38.3 652 164.97
MPEG2 16KHz quality 0, mono 28 27.8 652 46.12
MPEG2 16KHz quality 4, mono
44 27.8 652 62.12
MPEG2 16KHz quality 7, mono 64 27.8 652 82.12
Audio Format (STL)
Audio
Data
Rate
(Kbit/s)
Packet/
sec
(Wireshark
)
Overhea
d (bit)1
Total
Bit
Rate
(Mbit/s)
2
ALaw 8 Khz, mono 64 50 620 0.09
PCM MSB 16 bit 8 KHz mono 128 50 620 0.16
PCM MSB 16 bit 11.025 KHz mono
176.4 50 620 0.2
PCM MSB 16 bit 12 KHz mono 192 50 620 0.22
PCM MSB 16 bit 16 KHz mono 256 50 620 0.29
PCM MSB 16 bit 22.050 KHz mono 352.8 50 620 0.38
PCM MSB 16 bit 24 KHz mono
384 50 620 0.41
PCM MSB 16 bit 32 KHz mono
512 50 620 0.54
PCM MSB 16 bit 44.1 KHz mono 705.6 70 620 0.75
PCM MSB 16 bit 48 KHz mono 768 75 620 0.81
PCM MSB 16 bit 8 KHz stereo 256 50 620 0.29
PCM MSB 16 bit 11.025 KHz
stereo
352.8 50 620 0.38
PCM MSB 16 bit 12 KHz stereo 384 50 620 0.41
PCM MSB 16 bit 16 KHz stereo 512 50 620 0.54
PCM MSB 16 bit 22.050 KHz
stereo
705.6 70 620 0.75
PCM MSB 16 bit 24 KHz stereo 768 75 620 0.81
PCM MSB 16 bit 32 KHz stereo 1024 100 620 1.08
PCM MSB 16 bit 44.1 KHz stereo 1411.2 137 620 1.5
PCM MSB 16 bit 48 KHz stereo 1536 150 620 1.63
2.2.7 Emergency pendrive
If the incoming streaming drops, ADA102 can play
audio files from a pendrive plugged on USB port.
When the audio stream is reestablished the system
will fold back to incoming streaming.
SOLIDYNE ADA102 CODER/DECODER Page 15