Difference between revisions of "Bit Rate Calculation"

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{| class="wikitable" border="1" cellspacing="0"
{| class="wikitable" border="1" cellspacing="0"


! Audio Format   !!   Audio Data Rate (Kbit/sec)   !! Total Bit Rate (Kbit/sec)
! Audio Format !! Audio Data Rate (Kbit/sec) !! Total Bit Rate (Kbit/sec)
|-
|-
| Riga 1 cella 1 || Riga 1 cella 2
| Riga 1 cella 1 || Riga 1 cella 2
|-
|-
| Riga 2 cella 1 || Riga 2 cella 2
| Riga 2 cella 1 || Riga 2 cella 2
|}
<center>'''BIT RATE CALCULATION WITH BARIX DEVICES'''</center>
With this document we want to explain how to calculate the total bit rate flowing on an Ethernet cable connected to a Barix device.
The total bit rate is equal at the audio bit rate plus the overhead due to the encapsulation of audio packet inside the layers of OSI stack ([http://en.wikipedia.org/wiki/Osi_model http://en.wikipedia.org/wiki/Osi_model]).
We have used for the test an Instreamer 100 configured first in RAW UDP and then in RTP.
<center>RAW UDP STREAMING MODE</center>
For the structure of the Ethernet packet see here: [http://en.wikipedia.org/wiki/Ethernet http://en.wikipedia.org/wiki/Ethernet]
The Total Ethernet Overhead per packet is 300 bit.
For the structure of the IP packet see here: [http://en.wikipedia.org/wiki/Ethernet http://en.wikipedia.org/wiki/Ipv4]
The Total IP Overhead per packet is 160 bit.
For the structure of the UDP packet see here: [http://en.wikipedia.org/wiki/Ethernet http://en.wikipedia.org/wiki/UDP_packet]
The Total UDP Overhead per packet is 64 bit.
'''Total Bit of Overhead per Packet ='''
'''Ethernet Overhead + IP Overhead + UDP Overhead = 524 bit'''
The Audio Bit rate is expressed in bit/sec but the Overhead is expressed in bit/packet.
So we have to translate the Overhead (bit/packet) in Overhead rate (bit/sec).
For this we need to know the amount of packet/sec, that depends by Audio Format and is measurable with Network Protocol Analyzer software like Wireshark.
The values of Audio Data for audio format, sampling frequency and quality, come from Instreamer Manual (firmware V3.0 – page 20 - [http://www.barix.com/downloads/file/Instreamer_Manual_V300_PDF/7231/81 www.barix.com/downloads/file/Instreamer_Manual_V300_PDF/7231/81])
'''Overhead/sec = Overhead/Packet x Packet/sec'''
'''Total Bit Rate (Kbit/sec) = Audio Data Rate (Kbit/sec) + Overhead/sec (Kbit/sec)'''
{| class="prettytable"
| <center>'''Audio Format'''</center>
| <center>'''Audio Data Rate (Kbit/sec)'''</center>
| <center>'''Total Bit Rate (Kbit/sec)'''</center>
|-
| <center>PCM 16 bit 8 KHz</center>
| <center>128</center>
| <center>135.1</center>
|-
| <center>PCM 16 bit 24 KHz</center>
| <center>384</center>
| <center>406.12</center>
|-
| <center>uLaw 8 KHz</center>
| <center>64</center>
| <center>67.5</center>
|-
| <center>ALaw 8 KHz</center>
| <center>64</center>
| <center>67.5</center>
|-
| <center>ALaw 24KHz</center>
| <center>192</center>
| <center>202.62</center>
|-
| <center>uLaw 24 KHz</center>
| <center>192</center>
| <center>202.62</center>
|-
| <center>MPEG1 48KHz, quality 0, stereo</center>
| <center>88</center>
| <center>96.62</center>
|-
| <center>MPEG1 48KHz, quality 4, stereo</center>
| <center>144</center>
| <center>155.82</center>
|-
| <center>MPEG1 48KHz, quality 7, stereo</center>
| <center>192</center>
| <center>206.57</center>
|-
| <center>MPEG1 48KHz, quality 4, mono</center>
| <center>96</center>
| <center>104.42</center>
|-
| <center>MPEG1 44.1KHz, quality 0, mono</center>
| <center>65</center>
| <center>71.43</center>
|-
| <center>MPEG1 44.1KHz, quality 4, mono</center>
| <center>90</center>
| <center>98.25</center>
|-
| <center>MPEG1 44.1KHz, quality 7, mono</center>
| <center>140</center>
| <center>153.1</center>
|-
| <center>MPEG2 16KHz, quality 0, mono</center>
| <center>28</center>
| <center>31.03</center>
|-
| <center>MPEG2 16KHz, quality 4, mono</center>
| <center>44</center>
| <center>47.97</center>
|-
| <center>MPEG2 16KHz, quality 7, mono</center>
| <center>64</center>
| <center>70</center>
|}
<center>RTP STREAMING MODE</center>
For the structure of the RTP packet see here: [http://en.wikipedia.org/wiki/Ethernet http://en.wikipedia.org/wiki/Real-time_Transport_Protocol]
The Total RTP Overhead per packet is 96 bit.
'''Total Bit of Overhead per Packet ='''
'''Ethernet Overhead + IP Overhead + UDP Overhead + RTP Overhead = 620 bit'''
The values of Audio Data for audio format, are the same of above, since the transmission protocol doesn't affect audio bit rate.
'''Overhead/sec = Overhead/Packet x Packet/sec'''
'''Total Bit Rate (Kbit/sec) = Audio Data Rate (Kbit/sec) + Overhead/sec (Kbit/sec)'''
{| class="prettytable"
| <center>'''Audio Format'''</center>
| <center>'''Audio Data Rate'''</center>
<center>'''(Kbit/sec)'''</center>
| <center>'''Total Bit Rate (Kbit/sec)'''</center>
|-
| <center>ALaw 8 KHz</center>
| <center>64</center>
| <center>95</center>
|-
| <center>MPEG1 48KHz, quality 0, stereo</center>
| <center>88</center>
| <center>113.8</center>
|-
| <center>MPEG1 48KHz, quality 4, stereo</center>
| <center>144</center>
| <center>169.85</center>
|-
| <center>MPEG1 48KHz, quality 7, stereo</center>
| <center>192</center>
| <center>217.85</center>
|-
| <center>MPEG1 48KHz, quality 4, mono</center>
| <center>96</center>
| <center>121.85</center>
|-
| <center>MPEG1 44.1KHz, quality 0, mono</center>
| <center>65</center>
| <center>88.7</center>
|-
| <center>MPEG1 44.1KHz, quality 4, mono</center>
| <center>90</center>
| <center>113.7</center>
|-
| <center>MPEG1 44.1KHz, quality 7, mono</center>
| <center>140</center>
| <center>163.7</center>
|-
| <center>MPEG2 16KHz, quality 0, mono</center>
| <center>28</center>
| <center>45.2</center>
|-
| <center>MPEG2 16KHz, quality 4, mono</center>
| <center>44</center>
| <center>61.2</center>
|-
| <center>MPEG2 16KHz, quality 7, mono</center>
| <center>64</center>
| <center>81.2</center>
|}
|}

Revision as of 14:47, 27 February 2009

Audio Format Audio Data Rate (Kbit/sec) Total Bit Rate (Kbit/sec)
Riga 1 cella 1 Riga 1 cella 2
Riga 2 cella 1 Riga 2 cella 2


BIT RATE CALCULATION WITH BARIX DEVICES


With this document we want to explain how to calculate the total bit rate flowing on an Ethernet cable connected to a Barix device.

The total bit rate is equal at the audio bit rate plus the overhead due to the encapsulation of audio packet inside the layers of OSI stack (http://en.wikipedia.org/wiki/Osi_model).



We have used for the test an Instreamer 100 configured first in RAW UDP and then in RTP.


RAW UDP STREAMING MODE


For the structure of the Ethernet packet see here: http://en.wikipedia.org/wiki/Ethernet


The Total Ethernet Overhead per packet is 300 bit.


For the structure of the IP packet see here: http://en.wikipedia.org/wiki/Ipv4


The Total IP Overhead per packet is 160 bit.


For the structure of the UDP packet see here: http://en.wikipedia.org/wiki/UDP_packet


The Total UDP Overhead per packet is 64 bit.


Total Bit of Overhead per Packet =


Ethernet Overhead + IP Overhead + UDP Overhead = 524 bit


The Audio Bit rate is expressed in bit/sec but the Overhead is expressed in bit/packet.


So we have to translate the Overhead (bit/packet) in Overhead rate (bit/sec).

For this we need to know the amount of packet/sec, that depends by Audio Format and is measurable with Network Protocol Analyzer software like Wireshark.


The values of Audio Data for audio format, sampling frequency and quality, come from Instreamer Manual (firmware V3.0 – page 20 - www.barix.com/downloads/file/Instreamer_Manual_V300_PDF/7231/81)


Overhead/sec = Overhead/Packet x Packet/sec


Total Bit Rate (Kbit/sec) = Audio Data Rate (Kbit/sec) + Overhead/sec (Kbit/sec)


Audio Format
Audio Data Rate (Kbit/sec)
Total Bit Rate (Kbit/sec)
PCM 16 bit 8 KHz
128
135.1
PCM 16 bit 24 KHz
384
406.12
uLaw 8 KHz
64
67.5
ALaw 8 KHz
64
67.5
ALaw 24KHz
192
202.62
uLaw 24 KHz
192
202.62
MPEG1 48KHz, quality 0, stereo
88
96.62
MPEG1 48KHz, quality 4, stereo
144
155.82
MPEG1 48KHz, quality 7, stereo
192
206.57
MPEG1 48KHz, quality 4, mono
96
104.42
MPEG1 44.1KHz, quality 0, mono
65
71.43
MPEG1 44.1KHz, quality 4, mono
90
98.25
MPEG1 44.1KHz, quality 7, mono
140
153.1
MPEG2 16KHz, quality 0, mono
28
31.03
MPEG2 16KHz, quality 4, mono
44
47.97
MPEG2 16KHz, quality 7, mono
64
70
RTP STREAMING MODE


For the structure of the RTP packet see here: http://en.wikipedia.org/wiki/Real-time_Transport_Protocol


The Total RTP Overhead per packet is 96 bit.


Total Bit of Overhead per Packet =


Ethernet Overhead + IP Overhead + UDP Overhead + RTP Overhead = 620 bit


The values of Audio Data for audio format, are the same of above, since the transmission protocol doesn't affect audio bit rate.


Overhead/sec = Overhead/Packet x Packet/sec


Total Bit Rate (Kbit/sec) = Audio Data Rate (Kbit/sec) + Overhead/sec (Kbit/sec)


Audio Format
Audio Data Rate
(Kbit/sec)
Total Bit Rate (Kbit/sec)
ALaw 8 KHz
64
95
MPEG1 48KHz, quality 0, stereo
88
113.8
MPEG1 48KHz, quality 4, stereo
144
169.85
MPEG1 48KHz, quality 7, stereo
192
217.85
MPEG1 48KHz, quality 4, mono
96
121.85
MPEG1 44.1KHz, quality 0, mono
65
88.7
MPEG1 44.1KHz, quality 4, mono
90
113.7
MPEG1 44.1KHz, quality 7, mono
140
163.7
MPEG2 16KHz, quality 0, mono
28
45.2
MPEG2 16KHz, quality 4, mono
44
61.2
MPEG2 16KHz, quality 7, mono
64
81.2
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