Difference between revisions of "Bit Rate Calculation"

Latest revision as of 11:55, 7 June 2013

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 [1].

We have used for the test an Instreamer 100 (with standard firmware) configured first in RAW UDP and then in RTP, and an Exstreamer 1000 (with STL firmware).

RAW UDP STREAMING MODE

For the structure of the Ethernet packet see here: [2]

The Total Ethernet Overhead per packet is 300 bit.

For the structure of the IP packet see here: [3]

The Total IP Overhead per packet is 160 bit.

For the structure of the UDP packet see here: [4]

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 (MP3 bitrate average), come from Instreamer Manual (firmware V3.10 – page 18 - [5])

For MPEG1/2 Layer3 (MP3) bit rate

the following Encoding range is supported as Constant & Variable Bit Rate in IPAM102 based devices (e.g. new Instreamer):

28kbps (MPEG2@16KHz mono) - 320kbps (MPEG1@48KHz stereo)

the following Encoding range is supported as Variable Bit Rate in IPAM100 based devices (e.g. old Instreamer100):

28kbps (MPEG2@16KHz mono) - 192kbps (MPEG1@48KHz stereo)

Decoding range on both IPAM100 and IPAM300 as Constant or Variable Bit Rate is:

8kbps (MPEG2) - 320kbps (MPEG1)

Overhead/sec = Overhead/Packet x Packet/sec

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

^{(1 Kbit = 1000 bit)}

Audio Format (MP3 in VBR)	Audio Data Rate (Kbit/sec)	Packet/sec (Wireshark)	Overhead (bit)	Total Bit Rate (Kbit/sec)
PCM 16 bit 8 KHz, mono	128	13.551	524	135.1
PCM 16 bit 24 KHz, mono	384	42.213	524	406.12
uLaw 8 KHz, mono	64	6.7	524	67.5
ALaw 8 KHz, mono	64	6.7	524	67.5
ALaw 24KHz, mono	192	20.28	524	202.62
uLaw 24 KHz, mono	192	20.28	524	202.62
MPEG1 48KHz quality 0, stereo	88	16.46	524	96.62
MPEG1 48KHz quality 4, stereo	144	22.56	524	155.82
MPEG1 48KHz quality 7	192	27.81	524	206.57
MPEG1 48KHz quality 4, mono	96	16.08	524	104.42
MPEG1 44.1KHz, quality 0, mono	65	12.27	524	71.43
MPEG1 44.1KHz, quality 4, mono	90	15.76	524	98.25
MPEG1 44.1KHz, quality 7, mono	140	25	524	153.1
MPEG2 16KHz quality 0, mono	28	5.8	524	31.03
MPEG2 16KHz quality 4, mono	44	7.58	524	47.97
MPEG2 16KHz quality 7	64	11.5	524	70

Without Ethernet Overhead

Audio Format (MP3 in VBR)	Audio Data Rate (Kbit/sec)	Packet/sec (Wireshark)	Overhead (bit)	Total Bit Rate (Kbit/sec)
PCM 16 bit 8 Khz, mono	128	13.551	224	131.4
PCM 16 bit 24 Khz, mono	384	42.213	224	393.46
uLaw 8 Khz, mono	64	6.7	224	65.5
ALaw 8 Khz, mono	64	6.7	224	65.5
ALaw 24KHz, mono	192	20.28	224	196.54
uLaw 24 Khz, mono	192	20.28	224	196.54
MPEG1 48KHz quality 0, stereo	88	16.46	224	91.69
MPEG1 48KHz quality 4, stereo	144	22.56	224	149.05
MPEG1 48KHz quality 7, stereo	192	27.81	224	198.23
MPEG1 48KHz quality 4, mono	96	16.08	224	99.6
MPEG1 44.1KHz quality 0, mono	65	12.27	224	67.75
MPEG1 44.1KHz quality 4, mono	90	15.76	224	93.53
MPEG1 44.1KHz quality 7, mono	140	25	224	145.6
MPEG2 16KHz quality 0, mono	28	5.8	224	29.3
MPEG2 16KHz quality 4, mono	44	7.58	224	45.7
MPEG2 16KHz quality 7, mono	64	11.5	224	66.58

RTP STREAMING MODE

For the structure of the RTP packet see here: [6]

The Total RTP Overhead per packet is 128 bit (counting also the MP3 MPA wrapper inside the RTP payload, which has an extra 32 bit header).

Total Bit of Overhead per Packet =

Ethernet Overhead + IP Overhead + UDP Overhead + RTP Overhead = 652 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)

^{(1 Kbit = 1000 bit)}

Audio Format (VBR)	Audio Data Rate (Kbit/sec)	Packet/sec (Wireshark)	Overhead (bit)	Total Bit Rate (Kbit/sec)
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/sec)	Packet/sec (Wireshark)	Overhead (bit)¹	Total Bit Rate (Mbit/sec)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

^{1 - in PCM and A/uLaw streaming mode, there is not MPA wrapper.}

^{2 - 1 Mbit = 1000 Kbit.}

Without Ethernet Overhead

Audio Format (VBR)	Audio Data Rate (Kbit/sec)	Packet/sec (Wireshark)	Overhead (bit)	Total Bit Rate (Kbit/sec)
MPEG1 48KHz quality 0, stereo	88	41.7	352	102.67
MPEG1 48KHz quality 4, stereo	144	41.7	352	158.67
MPEG1 48KHz quality 7, stereo	192	41.7	352	206.67
MPEG1 48KHz quality 4, mono	96	41.7	352	110.67
MPEG1 44.1KHz quality 0, mono	65	38.3	352	78.48
MPEG1 44.1KHz quality 4, mono	90	38.3	352	103.48
MPEG1 44.1KHz quality 7, mono	140	38.3	352	153.48
MPEG2 16KHz quality 0, mono	28	27.8	352	37.78
MPEG2 16KHz quality 4, mono	44	27.8	352	53.78
MPEG2 16KHz quality 7, mono	64	27.8	352	73.78

Audio Format (STL)	Audio Data Rate (Kbit/sec)	Packet/sec (Wireshark)	Overhead (bit)¹	Total Bit Rate (Mbit/sec)²
ALaw 8 Khz, mono	64	50	320	0.08
PCM MSB 16 bit 8 KHz mono	128	50	320	0.14
PCM MSB 16 bit 11.025 KHz mono	176.4	50	320	0.2
PCM MSB 16 bit 12 KHz mono	192	50	320	0.2
PCM MSB 16 bit 16 KHz mono	256	50	320	0.27
PCM MSB 16 bit 22.050 KHz mono	352.8	50	320	0.36
PCM MSB 16 bit 24 KHz mono	384	50	320	0.4
PCM MSB 16 bit 32 KHz mono	512	50	320	0.52
PCM MSB 16 bit 44.1 KHz mono	705.6	70	320	0.72
PCM MSB 16 bit 48 KHz mono	768	75	320	0.8
PCM MSB 16 bit 8 KHz stereo	256	50	320	0.27
PCM MSB 16 bit 11.025 KHz stereo	352.8	50	320	0.36
PCM MSB 16 bit 12 KHz stereo	384	50	320	0.4
PCM MSB 16 bit 16 KHz stereo	512	50	320	0.52
PCM MSB 16 bit 22.050 KHz stereo	705.6	70	320	0.72
PCM MSB 16 bit 24 KHz stereo	768	75	320	0.8
PCM MSB 16 bit 32 KHz stereo	1024	100	320	1.05
PCM MSB 16 bit 44.1 KHz stereo	1411.2	137	320	1.45
PCM MSB 16 bit 48 KHz stereo	1536	150	320	1.58

^{1 - in PCM and A/uLaw streaming mode, there is not MPA wrapper.}

^{2 - 1 Mbit = 1000 Kbit.}

The PDF version of the original document is downloadable here [[media:bit_rate_calculation_3_0.pdf]].

Back to FAQ

@@ Line 33: / Line 33: @@
-The values of Audio Data for audio format, sampling frequency and quality (MP3 bitrate average), come from Instreamer Manual (firmware V3.10 – page 18 - [http://www.barix.com/downloads/file/Instreamer_Firmware_User_Manual_V310_PDF/7471/81])
+The values of Audio Data for audio format, sampling frequency and quality (MP3 bitrate average), come from Instreamer Manual (firmware V3.10 – page 18 - [http://www.barix.com/downloads/Instreamer_Standard_Firmware/1981/])
+For MPEG1/2 Layer3 (MP3) bit rate
+the following Encoding range is supported as Constant & Variable Bit Rate in IPAM102  based devices (e.g. new Instreamer):
+kbps (MPEG2@16KHz mono) - 320kbps (MPEG1@48KHz stereo)<br>
+the following Encoding range is supported as Variable Bit Rate in IPAM100 based devices (e.g. old Instreamer100):
+kbps (MPEG2@16KHz mono) - 192kbps (MPEG1@48KHz stereo)<br>
+Decoding range on both IPAM100 and IPAM300 as Constant or Variable Bit Rate is:
+kbps (MPEG2) - 320kbps (MPEG1)
@@ Line 40: / Line 57: @@
 '''Total Bit Rate (Kbit/sec) = Audio Data Rate (Kbit/sec) + Overhead/sec (Kbit/sec)'''
-(1 Kbit = 1000 bit)
+<sup>''(1 Kbit = 1000 bit)''</sup>
 {| class="wikitable" border="1" cellspacing="0"
-| <center>'''Audio Format'''</center>
+| <center>'''Audio Format (MP3 in VBR)'''</center>
 | <center>'''Audio Data Rate (Kbit/sec)'''</center>
 | <center>'''Packet/sec (Wireshark)'''</center>
@@ Line 167: / Line 185: @@
 {| class="wikitable" border="1" cellspacing="0"
-| <center>'''Audio Format'''</center>
+| <center>'''Audio Format (MP3 in VBR)'''</center>
 | <center>'''Audio Data Rate (Kbit/sec)'''</center>
 | <center>'''Packet/sec (Wireshark)'''</center>
@@ Line 307: / Line 325: @@
 '''Total Bit Rate (Kbit/sec) = Audio Data Rate (Kbit/sec) + Overhead/sec (Kbit/sec)'''
-(1 Kbit = 1000 bit)
+<sup>''(1 Kbit = 1000 bit)''</sup>
 {| class="wikitable" border="1" cellspacing="0"
-| <center>'''Audio Format'''</center>
+| <center>'''Audio Format (VBR)'''</center>
 | <center>'''Audio Data Rate (Kbit/sec)'''</center>
 | <center>'''Packet/sec (Wireshark)'''</center>
@@ Line 391: / Line 410: @@
 {| class="wikitable" border="1" cellspacing="0"
-| <center>'''Audio Format'''</center>
+| <center>'''Audio Format (STL)'''</center>
 | <center>'''Audio Data Rate (Kbit/sec)'''</center>
 | <center>'''Packet/sec (Wireshark)'''</center>
-| <center>'''Overhead (bit)*'''</center>
+| <center>'''Overhead (bit)<sup>1'''</sup>'''</center>
-| <center style="background-color:#FFB6C1">'''Total Bit Rate (Mbit/sec)**'''</center>
+| <center style="background-color:#FFB6C1">'''Total Bit Rate (Mbit/sec)<sup>2'''</sup>'''</center>
 |-
@@ Line 531: / Line 550: @@
 |}
+<sup>''1 - in PCM and A/uLaw streaming mode, there is not MPA wrapper.''</sup>
-*in PCM and A/ULaw streaming mode, there is not MPA wrapper.
+<sup>''2 - 1 Mbit = 1000 Kbit.''</sup>
-**1 Mbit = 1000 Kbit
@@ Line 539: / Line 558: @@
 {| class="wikitable" border="1" cellspacing="0"
-| <center>'''Audio Format'''</center>
+| <center>'''Audio Format (VBR)'''</center>
 | <center>'''Audio Data Rate (Kbit/sec)'''</center>
 | <center>'''Packet/sec (Wireshark)'''</center>
-| <center>'''Overhead (bit)*'''</center>
+| <center>'''Overhead (bit)'''</center>
 | <center style="background-color:#FFB6C1">'''Total Bit Rate (Kbit/sec)'''</center>
@@ Line 619: / Line 638: @@
 {| class="wikitable" border="1" cellspacing="0"
-| <center>'''Audio Format'''</center>
+| <center>'''Audio Format (STL)'''</center>
 | <center>'''Audio Data Rate (Kbit/sec)'''</center>
 | <center>'''Packet/sec (Wireshark)'''</center>
-| <center>'''Overhead (bit)*'''</center>
+| <center>'''Overhead (bit)<sup>1'''</sup>'''</center>
-| <center style="background-color:#FFB6C1">'''Total Bit Rate (Mbit/sec)**'''</center>
+| <center style="background-color:#FFB6C1">'''Total Bit Rate (Mbit/sec)<sup>2'''</sup></center>
 |-
@@ Line 759: / Line 778: @@
 |}
-*in PCM and A/ULaw streaming mode, there is not MPA wrapper.
+<sup>''1 - in PCM and A/uLaw streaming mode, there is not MPA wrapper.''</sup>
-**1 Mbit = 1000 Kbit
+<sup>''2 - 1 Mbit = 1000 Kbit.''</sup>
+The PDF version of the original document is downloadable here [[[[media:bit_rate_calculation_3_0.pdf]]]].
-The PDF version of the original document is downloadable here [[[[bit_rate_calculation_3_0.pdf]]]]
 Back to [[FAQ]]