CIRCUIT DESCRIPTION
3-3-5. Decode Status
The information below can be accessed from the host
during AC- 3 decoding.
- Error status
- Audio frame information (Sampling rate, bit rate,
mode, etc.)
3-3-6. Decoding Delay in AC-3 Mode
ZR38500 supports all the bit rates (32 kbps to 640 kbps)
and sampling rates (32 kHz, 44.1 kHz, and 48 kHz) pre-
scribed by AC-3 algorithm.
The decoding delay varies depending on how to enter the
compressed data, the bit rate, and the sampling rate.
However, the delay is fixed unless the parameter is
changed.
The decoding delay can be given by the following expres-
sion.
AC-3 frame transfer time x 2/3 (CRC check period) +
period of one audio block (256 samples)
Example 1) For continuous bit stream
In this case, the clock at a serial data input port is the
same as the bit rate and AC-3 data is input at a fixed
rate. The decode delay at that time is fixed by the sam-
pling rate as shown in Table 2.
When data is input using an S/P DIF interface, a burst
transfer is used because the physical bit rate differs from
the bit rate of information. In this case, the decode delay
is determined by the physical interface bit rate, burst size,
AC-3 bit rate, and sampling rate. The decode delay
becomes approximately 11 ms when the sampling fre-
quency is 48 kHz and when the bit rate is 384 kbps.
27 ms
29 ms
40 ms
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