Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
19-28
Freescale Semiconductor
Asynchronous Sample Rate Converter
19.5
Functional Description
19.5.1
Algorithm Description
19.5.1.1
Signal Processing Flow
Figure 19-19. Signal Processing Configurations for ASRC
shows the possible signal processing configurations for the ASRC. Each configuration
consists of 2 to 4 stages:
•
×
2 up-sampling rate expander (zero insertion only) (Input path I0),
or direct connection (Input path I1),
or low-pass pre-decimation filter (consisting of a low-pass half-band FIR filter with x0.5
downsampling rate decimator) (Input path I2)
•
Low-pass pre-filter, the low-pass bandwidth is at most
, where Fs is the sampling rate of
the input signal to this low-pass pre-filter,
•
Polyphase filter
•
×
2 post-upsampling filter (consisting of a
×
2 up-sampling rate expander (zero insertion only) with
low-pass half-band FIR filter) (
Output path O0
),
or direct connection (
Output path O1
),
or low-pass post-decimation filter (consisting of a low-pass half-band FIR filter with x0.5
downsampling rate decimator) (
Output path O2
).
Polyphase
Filter
11 taps
Low-Pass
Pre-Filter
FIR
×
2
UpSampling
Rate Expander
Low-pass
Half-band FIR
I0
I1
I2
×
0.5
Down-Sampling
Rate
×
2
UpSampling
Rate Expander
O0
O1
Low-Pass
Half-band
FIR
Low-pass
Half-band
FIR
O2
×
0.5
Down-Sampling
Rate
Fs
in
Fs
out
Post-Upsampling Filter
Post-Decimation Filter
Pre-Decimation Filter
Fs
p po ut
Pre-Processing
Input
Paths
Output
Paths
Post-Processing
0.25
Fs
×