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.
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:
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:
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:
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':
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)
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:
