Introduction
The Synchronous Sample Rate Converter (SSRC) software module converts a mono or stereo audio signal with a certain sampling frequency to an audio signal with a different sampling frequency. The sample rate converter works synchronously, meaning that input and output sampling rates are exactly known for a mutual clock reference.
To accomplish a professional sampling conversion quality and minimal system footprint, the SRC SW module contains highly optimized components.
The SSRC module supports the following features.
Multiple instances of the sample rate converter can run at the same time.
Supported sampling frequencies: 32 kHz, 44.1 kHz, and 48 kHz plus the halves and the quarters of these three sample rates. The input and output sample rates are freely selectable out of the supported sampling rates
Selectable Mono/Stereo Input/Output.
Selectable quality level: high quality/ very high quality.
Acronyms
Table 1 lists the acronyms used in this document.
Acronym |
Description |
|---|---|
Fs |
Sampling Frequency |
FsLOWow |
Lowest sample rate used for the conversion Note: Input sample rate for up sampling and the output sample rate for down sampling |
FsIN |
Input sample rate |
FsOUT |
Output sample rate |
MIPS |
Million Instructions Per Second |
SSRC |
Synchronous sample rate converter |
THD+N |
Total Harmonic Distortion plus Noise Note: The THD+N is defined as the total power of the unwanted signal divided by the power of the wanted signal. The wanted signal is defined as a full scale, 1 kHz sine wave. |
Parent topic:Introduction
Performance figures
The Total Harmonic Distortion Plus Noise (THD+N) of the converted signals is below - 76 (high-quality mode) and - 85 (very high-quality mode) for signal frequencies below 0.45*FsLOW (=90 % of the Nyquist range of the lowest sample clock)
Table 1 and Table 2 give the THD+N performance (FsIN on the vertical axis and FsOUT on the horizontal axis) for the two supported quality levels. The numbers in the tables give the worst-case THD+N measured for signal frequencies below 0.45*FsLOW. For each conversion ratio, 100 THD+N measurements were executed with signal frequencies linearly spread over the complete Nyquist range.
FsIN/ FsOUT |
8000 |
11025 |
12000 |
16000 |
22050 |
24000 |
32000 |
44100 |
48000 |
|---|---|---|---|---|---|---|---|---|---|
8000 |
-92.1 |
-79.7 |
-80.1 |
-80.1 |
-79.6 |
-80.2 |
-79.4 |
-79.1 |
-79.2 |
11025 |
-79 |
-92.9 |
-80 |
-79.9 |
-80.2 |
-79.8 |
-79.9 |
-79.5 |
-78.9 |
12000 |
-79 |
-79.2 |
-92.7 |
-80.1 |
-79.8 |
-80.3 |
-79.8 |
-79.8 |
-79.5 |
16000 |
-81.7 |
-78.8 |
-80.2 |
-93 |
-78.3 |
-77.7 |
-78.3 |
-78.3 |
-77.9 |
22050 |
-77.5 |
-81.8 |
-78.2 |
-79 |
-93 |
-79.9 |
-79.8 |
-80.3 |
-79.9 |
24000 |
-77.4 |
-77.9 |
-81.2 |
-79.1 |
-79.2 |
-92.5 |
-80.1 |
-79.8 |
-79.9 |
32000 |
-81 |
-77.5 |
-78.9 |
-81.2 |
-78.7 |
-80.1 |
-92.9 |
-79.7 |
-79.2 |
44100 |
-79.1 |
-81.2 |
-76.7 |
-77.8 |
-82 |
-78.2 |
-79.1 |
-93 |
-79.7 |
48000 |
-78.7 |
-78.8 |
-81.1 |
-77.6 |
-77.9 |
-81.8 |
-79.1 |
-79.3 |
-93 |
FsIN/ FsOUT |
8000 |
11025 |
12000 |
16000 |
22050 |
24000 |
32000 |
44100 |
48000 |
|---|---|---|---|---|---|---|---|---|---|
8000 |
-92.1 |
-86.6 |
-88.6 |
-91.5 |
-86.4 |
-89 |
-89.7 |
-89.3 |
-89.3 |
11025 |
-89.1 |
-92.9 |
-86.3 |
-86.3 |
-91.6 |
-86.3 |
-86.5 |
-89.7 |
-89.3 |
12000 |
-91.4 |
-88.4 |
-92.7 |
-89.6 |
-86.6 |
-91.5 |
-86.8 |
-86.6 |
-89.7 |
16000 |
-93.1 |
-88.4 |
-90.4 |
-93 |
-86.6 |
-88.8 |
-91.5 |
-86.5 |
-89.4 |
22050 |
-90.7 |
-93.5 |
-89.7 |
-89.3 |
-93 |
-86.5 |
-86.3 |
-91.5 |
-86.6 |
24000 |
-93.8 |
-90.5 |
-93.5 |
-91.7 |
-88.4 |
-92.5 |
-89.7 |
-86.6 |
-91.5 |
32000 |
-93.8 |
-91 |
-91.2 |
-93.3 |
-88.4 |
-90.5 |
-92.9 |
-86.7 |
-89 |
44100 |
-93.7 |
-93.6 |
-91.5 |
-90.6 |
-93.8 |
-89.8 |
-89.3 |
-93 |
-86.5 |
48000 |
-94.1 |
-92.6 |
-94 |
-94 |
-90.1 |
-93.7 |
-91.8 |
-88.4 |
-93 |
Parent topic:Introduction
Resource usage
This section lists the memory and processing requirements for the SSRC module.
Memory requirements
The following are the memory requirements for the SSRC module.
Memory item |
Size in bytes |
|---|---|
Instance memory (persistent) |
548 |
Scratch memory (non-persistent) |
15.536 1 |
Program memory for Arm9E and XScale |
14k |
Program memory for Arm7 |
15k |
Parent topic:Resource usage
1 Worst case number for I/O buffers of 40 ms. If smaller I/O buffers are used, this number is smaller. The required scratch memory is roughly equal to 2 times the buffer size on the highest sample rate.
Processing requirements
The following tables give the MIPS performance of the SSRC module. The cycles are measured with zero wait state memory and for I/O buffers of 40 ms.
Note: The user processing 32-bit processing must refer to the very high-quality MIPS results.
On Arm7 and Arm9
FsIN / FsOUT |
8000 |
11025 |
12000 |
16000 |
22050 |
24000 |
32000 |
44100 |
48000 |
|---|---|---|---|---|---|---|---|---|---|
8000 |
0.13 |
4.77 |
5.17 |
1.84 |
6.75 |
7.33 |
3.55 |
9.1 |
9.89 |
11025 |
5.42 |
0.18 |
5.58 |
6.84 |
2.53 |
7.75 |
9.71 |
4.89 |
10.31 |
12000 |
5.85 |
6.39 |
0.2 |
7.01 |
8.97 |
2.76 |
9.89 |
12.94 |
5.32 |
16000 |
1.69 |
7.74 |
7.99 |
0.26 |
9.54 |
10.33 |
3.68 |
13.5 |
14.65 |
22050 |
7.2 |
2.33 |
10.09 |
10.83 |
0.36 |
11.17 |
13.67 |
5.07 |
15.49 |
24000 |
7.79 |
8.33 |
2.53 |
11.7 |
12.78 |
0.39 |
14.03 |
17.94 |
5.51 |
32000 |
3.12 |
10.32 |
10.58 |
3.38 |
15.48 |
15.98 |
0.52 |
19.08 |
20.66 |
44100 |
9.96 |
4.3 |
13.65 |
14.4 |
4.65 |
20.18 |
21.67 |
0.72 |
22.34 |
48000 |
10.8 |
11.34 |
4.68 |
15.58 |
16.67 |
5.06 |
23.4 |
25.56 |
0.78 |
FsIN / FsOUT |
8000 |
11025 |
12000 |
16000 |
22050 |
24000 |
32000 |
44100 |
48000 |
|---|---|---|---|---|---|---|---|---|---|
8000 |
0.07 |
7.71 |
8.24 |
2.28 |
10.5 |
11.28 |
4.41 |
13.44 |
14.48 |
11025 |
8.19 |
0.1 |
8.96 |
11.04 |
3.14 |
12 |
15.09 |
6.08 |
15.2 |
12000 |
8.76 |
9.52 |
0.1 |
11.3 |
14.48 |
3.41 |
15.36 |
20.07 |
6.61 |
16000 |
2.14 |
11.73 |
12.01 |
0.14 |
15.41 |
16.48 |
4.55 |
21 |
22.56 |
22050 |
10.78 |
2.94 |
15.39 |
16.38 |
0.19 |
17.92 |
22.08 |
6.27 |
24 |
24000 |
11.57 |
12.34 |
3.2 |
17.51 |
19.04 |
0.21 |
22.61 |
28.97 |
6.83 |
32000 |
4.19 |
15.48 |
15.77 |
4.27 |
23.46 |
24.01 |
0.28 |
30.83 |
32.96 |
44100 |
14.78 |
5.77 |
20.56 |
21.56 |
5.89 |
30.77 |
32.75 |
0.38 |
35.83 |
48000 |
15.92 |
16.7 |
6.28 |
23.15 |
24.69 |
6.41 |
35.02 |
38.08 |
0.42 |
FsIN / FsOUT |
8000 |
11025 |
12000 |
16000 |
22050 |
24000 |
32000 |
44100 |
48000 |
|---|---|---|---|---|---|---|---|---|---|
8000 |
0.13 |
13.61 |
14.52 |
4.43 |
19.03 |
20.43 |
8.8 |
25.06 |
26.99 |
11025 |
14.85 |
0.18 |
15.91 |
19.47 |
6.1 |
21.82 |
27.35 |
12.13 |
28.38 |
12000 |
15.84 |
17.36 |
0.2 |
19.97 |
25.4 |
6.64 |
27.85 |
36.26 |
13.21 |
16000 |
4.25 |
21.24 |
21.79 |
0.26 |
27.22 |
29.03 |
8.86 |
38.07 |
40.85 |
22050 |
20.02 |
5.85 |
27.72 |
29.7 |
0.36 |
31.81 |
38.94 |
12.2 |
43.63 |
24000 |
21.45 |
22.98 |
6.37 |
31.68 |
34.71 |
0.39 |
39.94 |
50.8 |
13.28 |
32000 |
8.39 |
28.74 |
29.29 |
8.5 |
42.48 |
43.58 |
0.52 |
54.43 |
58.07 |
44100 |
28.11 |
11.57 |
38.05 |
40.03 |
11.71 |
55.43 |
59.4 |
0.72 |
63.62 |
48000 |
30.19 |
31.71 |
12.59 |
42.9 |
45.96 |
12.74 |
63.36 |
69.42 |
0.78 |
Parent topic:Processing requirements
On Arm9e and XScale
FsIN / FsOUT |
8000 |
11025 |
12000 |
16000 |
22050 |
24000 |
32000 |
44100 |
48000 |
|---|---|---|---|---|---|---|---|---|---|
8000 |
0.03 |
1.14 |
1.25 |
0.54 |
1.95 |
2.14 |
1.04 |
3.85 |
4.23 |
11025 |
1.31 |
0.05 |
1.36 |
1.62 |
0.75 |
2.23 |
2.78 |
1.44 |
4.38 |
12000 |
1.43 |
1.57 |
0.05 |
1.68 |
2.13 |
0.82 |
2.84 |
3.72 |
1.57 |
16000 |
0.5 |
1.86 |
1.93 |
0.07 |
2.27 |
2.5 |
1.09 |
3.9 |
4.29 |
22050 |
2.19 |
0.69 |
2.42 |
2.61 |
0.1 |
2.72 |
3.24 |
1.5 |
4.46 |
24000 |
2.4 |
2.52 |
0.75 |
2.86 |
3.15 |
0.1 |
3.35 |
4.25 |
1.63 |
32000 |
0.92 |
3.12 |
3.18 |
1.01 |
3.72 |
3.86 |
0.14 |
4.55 |
4.99 |
44100 |
4.28 |
1.27 |
4.15 |
4.37 |
1.39 |
4.83 |
5.23 |
0.19 |
5.43 |
48000 |
4.7 |
4.9 |
1.39 |
4.8 |
5.03 |
1.51 |
5.72 |
6.3 |
0.21 |
FsIN / FsOUT |
8000 |
11025 |
12000 |
16000 |
22050 |
24000 |
32000 |
44100 |
48000 |
|---|---|---|---|---|---|---|---|---|---|
8000 |
0.06 |
1.87 |
2.02 |
1.07 |
3.09 |
3.36 |
2.07 |
6.09 |
6.63 |
11025 |
2.27 |
0.09 |
2.25 |
2.66 |
1.47 |
3.56 |
4.4 |
2.85 |
7.01 |
12000 |
2.45 |
2.76 |
0.09 |
2.75 |
3.43 |
1.6 |
4.5 |
5.83 |
3.1 |
16000 |
0.99 |
3.23 |
3.36 |
0.13 |
3.73 |
4.05 |
2.14 |
6.17 |
6.72 |
22050 |
3.69 |
1.36 |
4.14 |
4.55 |
0.17 |
4.51 |
5.31 |
2.95 |
7.13 |
24000 |
4.01 |
4.28 |
1.48 |
4.9 |
5.51 |
0.19 |
5.51 |
6.85 |
3.21 |
32000 |
1.83 |
5.26 |
5.39 |
1.98 |
6.46 |
6.71 |
0.25 |
7.47 |
8.09 |
44100 |
7.22 |
2.52 |
6.94 |
7.38 |
2.72 |
8.27 |
9.1 |
0.35 |
9.02 |
48000 |
7.85 |
8.33 |
2.74 |
8.02 |
8.57 |
2.97 |
9.81 |
11.03 |
0.38 |
FsIN / FsOUT |
8000 |
11025 |
12000 |
16000 |
22050 |
24000 |
32000 |
44100 |
48000 |
|---|---|---|---|---|---|---|---|---|---|
8000 |
0.03 |
1.21 |
1.33 |
0.61 |
2.08 |
2.29 |
1.17 |
4.1 |
4.51 |
11025 |
1.47 |
0.05 |
1.44 |
1.72 |
0.84 |
2.38 |
2.97 |
1.61 |
4.66 |
12000 |
1.62 |
1.76 |
0.05 |
1.78 |
2.26 |
0.91 |
3.03 |
3.98 |
1.75 |
16000 |
0.55 |
2.1 |
2.17 |
0.07 |
2.42 |
2.65 |
1.22 |
4.16 |
4.57 |
22050 |
2.49 |
0.76 |
2.73 |
2.95 |
0.1 |
2.88 |
3.45 |
1.68 |
4.75 |
24000 |
2.75 |
2.86 |
0.83 |
3.23 |
3.52 |
0.1 |
3.56 |
4.53 |
1.83 |
32000 |
1 |
3.56 |
3.63 |
1.11 |
4.2 |
4.34 |
0.14 |
4.84 |
5.3 |
44100 |
4.86 |
1.38 |
4.74 |
4.98 |
1.53 |
5.46 |
5.89 |
0.19 |
5.75 |
48000 |
5.38 |
5.55 |
1.5 |
5.5 |
5.71 |
1.66 |
6.47 |
7.05 |
0.21 |
FsIN / FsOUT |
8000 |
11025 |
12000 |
16000 |
22050 |
24000 |
32000 |
44100 |
48000 |
|---|---|---|---|---|---|---|---|---|---|
8000 |
0.06 |
2.11 |
2.29 |
1.2 |
3.55 |
3.86 |
2.31 |
6.99 |
7.61 |
11025 |
2.62 |
0.09 |
2.52 |
3.01 |
1.66 |
4.07 |
5.07 |
3.19 |
8 |
12000 |
2.85 |
3.15 |
0.09 |
3.11 |
3.9 |
1.81 |
5.17 |
6.75 |
3.47 |
16000 |
1.09 |
3.73 |
3.85 |
0.13 |
4.22 |
4.57 |
2.41 |
7.1 |
7.72 |
22050 |
4.32 |
1.5 |
4.79 |
5.23 |
0.17 |
5.05 |
6.02 |
3.32 |
8.15 |
24000 |
4.74 |
4.99 |
1.64 |
5.69 |
6.3 |
0.19 |
6.22 |
7.8 |
3.61 |
32000 |
1.98 |
6.18 |
6.3 |
2.18 |
7.45 |
7.71 |
0.25 |
8.44 |
9.14 |
44100 |
8.43 |
2.72 |
8.18 |
8.64 |
3.01 |
9.59 |
10.47 |
0.35 |
10.1 |
48000 |
9.26 |
9.66 |
2.97 |
9.49 |
9.97 |
3.27 |
11.39 |
12.59 |
0.38 |
Parent topic:Processing requirements
On Cortex-A8 for worst case of 48000 Hz to 44100 Hz
Mode |
MIPs |
|---|---|
Mono at High Quality |
3.13 |
Stereo at High Quality |
3.61 |
Mono at Very High Quality |
4.13 |
Stereo at Very High Quality |
6.52 |
Parent topic:Processing requirements
Parent topic:Resource usage
Parent topic:Introduction