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MP3 16kbps Bit Rate Compression

Support for MP3 16 kbps bit rate recording compression began with The GVP 8.5.1 release in December 2014. We tested performance on physical server and Virtual Machine (VM) environments, using Windows 2008 R2 x64.

Physical Server on Single Hex Core

Testing was performed on Hardware Profile 1: a physical server on a single hex core of Dell R410. The three graphs below compare system CPU usage and audio quality related metrics, max jitter and max delta.

Figure 42: Comparison of System CPU Usage, MP3 16kbps vs 32kbps on Physical Server
Figure 43: Comparison of Max Jitter, MP3 16kbps vs 32kbps on Physical Server
Figure 44: Comparison of Max Delta MP3 16kbps vs 32kbps on a Physical Server

MP3 16kbps consumes less CPU memory, which means higher port capacity. The two graphs above that compare Max Jitter with Max Delta also indicate the higher port capacity of MP3 16kbps. Recommended port capacity for MP3 16kbps: 240 ports (20% higher than the 200 recommended port capacity for MP3 32kbps). Peak port capacity: 270 ports (22.7% higher than the 220 peak port capacity for MP3 32kbps).

The table below lists the system disk IOPS:

Figure 45: System Disk IOPS on Physical Server, MP3 only 16 Kbps

Ports Physical Server Disk IOPS (kbps)
Total Reads Writes
60 14.66 0.036 14.62
120 24.00 0.041 23.95
180 33.42 0.029 33.39
210 37.65 0.030 37.62
240 42.21 0.029 42.18
270 47.18 0.036 47.14
300 51.44 0.011 51.43
330 55.81 0.006 55.81
360 60.99 0.002 60.99
390 67.12 0.003 67.11

The graph below compares Table: System Disk IOPS on Physical Server, MP3 only 16 Kbps with Table: Disk IOPS of system level from a physical server with a single hex core, both on a single hex core server:

Figure 46: Comparison of System Disk IOPS on Single Hex Core Physical Server, MP3 16 Kbps vs 32 Kbps

The system disk IOPS for MP3 16kbps and 32kbps are nearly identical to each other; reasonable since the disk IO operations should be the same, and at the same port capacity, no matter which MP3 bit rate is chosen.

MCP IOPS is listed here:

Figure 47: MCP IOPS on physical server of single hex core, MP3 only, 16 Kbps

Ports Physical Server MCP IOPS (kbps)
Total Reads Writes
60 14.56 7.53 7.04
120 28.64 14.92 13.72
180 42.54 22.29 20.25
210 49.42 25.93 23.48
240 56.41 29.64 26.76
270 63.38 33.34 30.04
300 70.36 36.92 33.44
330 77.53 40.79 36.74
360 85.52 44.46 41.06
390 94.68 48.14 46.54

The graph below compares Table: MCP IOPS on physical server of single hex core, MP3 only, 16 Kbps and Table: MCP IOPS on physical server of single hex core, MP3 only:

Figure 48: MCP IOPS on Single Hex Core Physical Server, MP3 16Kbps vs 32Kbps

MP3 16kbps uses less IOPS at the process level, probably be due to fewer network operations for MP3 16kbps.

VMs on Dual Hex Cores Server

The testing for MP3 16kbps was conducted on VM Profile 4 (based on Hardware Profile 4, which is a dual hex cores server). 6 VMs were configured, while only one MCP was installed on each Windows VM. The three graphs below compare overall CPU usage, audio quality related max jitter and max delta for MP3 16kbps vs 32kbps:

Figure 49: Comparison System CPU Usage of MP3 16kbps vs 32kbps on VM env
Figure 50: Comparison of Max Jitter, MP3 16kbps vs 32kbps on VM env
Figure 51: Comparison of Max Delta, MP3 16kbps vs 32kbps on VM environment

MP3 16kbps consumes less CPU memory, which matches test results on a physical server in Figure: Comparison of System CPU Usage, MP3 16kbps vs 32kbps on Physical Server. Both Max Jitter and Max Delta also show a higher port capacity for MP3 16kbps compression, which also matches test results on a physical server from Figure 4: Comparison of Max Jitter, MP3 16kbps vs 32kbps on Physical Server & Figure: Comparison of Max Delta MP3 16kbps vs 32kbps on a Physical Server. Preferred/Recommended port capacity for MP3 16 kbps: 720 ports (20% higher 600 ports for than MP3 32kbps). It’s the same increase as observed from a physical server. Peak port capacity for MP3 16kpbs can be as high as 840 ports (27.3% higher than 660 peak port capacity for MP3 32kbps.

The table below illustrates system disk IOPS:

Figure 52: Overall Disk IOPS on all 6 VMs of dual hex cores, MP3 only, 16 Kbps

Ports Overall 6 VMs Disk IOPS (kbps)
Total Reads Writes
120 26.57 0.13 26.44
360 63.47 0.13 63.34
480 80.66 0.15 80.51
600 93.73 0.04 93.69
660 109.53 0.14 109.39
720 118.76 0.13 118.62
780 126.15 0.07 126.08
840 134.12 0.04 134.09
900 142.21 0.09 142.12

The graph below compares overall disk IOPS of all 6 VMs for MP3 16kpbs against 32kbps in Table: Disk IOPS of sum of all 6 VMs of dual hex cores, MP3 only':

Figure 53: Comparison of Overall 6 VMs Disk IOPS MP3 16 kbps vs 32 kbps

The IOPS from both MP3 16kbps and 32kbps are inline with each other, as in the physical server tests.

Data throughput for MP3 16kbps is listed in following table:

Figure 54: Data Throughputs for MP3 only, 16 kbps

Ports Overall Disk (kbps) SSD Drive Disk (kbps)
Total Reads Writes Total Reads Writes
120 318.17 0.68 317.49 296.313 0.001 296.312
360 892.94 0.52 892.42 856.077 0.001 856.076
480 1175.63 0.79 1174.84 1132.997 0.001 1132.996
600 1537.43 0.19 1537.23 1510.543 0.000 1510.543
660 1729.45 0.58 1728.87 1680.374 0.003 1680.371
720 1890.48 0.58 1889.90 1837.492 0.000 1837.492
780 2045.34 0.35 2045.00 1995.239 0.004 1995.235
840 2191.98 0.15 2191.83 2142.373 0.002 2142.371
900 2349.18 0.75 2348.44 2298.426 0.004 2298.422

Using this formula:
MP3 bitrate * Ports / 8 = kbps
...where MP3 bitrate=16kbps and Ports = 120 and 720 from the table above,

The results...
16 kpbs * 120 / 8 = 240 kbps (compared to 296 in the table -- in SSD)</tt>
and
16 kpbs * 720 / 8 = 14400 kbps (compared to 1837 in the table -- in SSD)

...from real testing for MP3 16kbps are slightly higher than calculations predict, due to other files such as metadata and JSON files being saved in the same cache folder. So the formula still stands.

The following table lists MCP IOPS:

Figure 55: Overall MCP IOPS from 6 VMs of dual hex core, MP3 only, 16kbps

Ports Overall 6 VMs MCP IOPS (kbps)
Total Reads Writes
120 28.931 14.915 14.016
360 86.517 44.456 42.061
480 114.574 59.153 55.421
600 142.112 73.730 68.382
660 156.495 81.359 75.136
720 170.237 88.660 81.577
780 184.173 96.048 88.125
840 197.767 103.263 94.504
900 211.644 110.545 101.099

The graph below compares Overall MCP IOPS with MP3 32k MCP IOPS, and shows the same trend of physical server results that appeared in Figure: MCP IOPS on Single Hex Core Physical Server, MP3 16Kbps vs 32Kbps:

Figure 56: MCP IOPS on 6 VMs of Dual Hex Cores, MP3 16Kbps vs 32Kbps

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This page was last modified on 11 July 2018, at 01:47.