6-14
Channel Interface
The read and write pointer registers each contain 20 bits. The most
significant bit is set when the pointer wraps around to the beginning of
the buffer and cleared when the host next reads the register. The next
19 bits are the actual address on 64-bit boundaries since SDRAM
operations are always in bursts of four 16-bit words.
The Audio Decoder and the S/P DIF (IEC958) Formatter both read from
the Audio ES channel buffer so a read pointer is maintained for both; the
Audio ES Channel Buffer Read Address and the S/P DIF Channel Buffer
Read Address.
The number of items (64-bit words) remaining to be read in each of these
buffers is written to the registers listed in Table 6.10 and available to the
host. Again, only the LSB registers are continually updated. The Next
and MSB registers are updated when the host reads the LSB.
6.3.3 PES Packet Structure
Since the Preparser strips headers out of packets in system and
transport stream modes, it is useful to look at a PES packet before
discussing those modes.
Figure 6.7
shows the packet structure. The
Table 6.9
Buffer Write and Read Pointer Registers in ES Mode
Pointer
Registers
Page Ref.
Video ES Channel Buffer Write Address
96–98
4-26
Audio ES Channel Buffer Write Address
99–101
4-26
Video ES Channel Buffer Read Address
108–110
4-27
Audio ES Channel Buffer Read Address
111–113
4-28
S/P DIF Channel Buffer Read Address
120–122
4-30
Table 6.10
Number of Items in Buffers in ES Mode
Buffer No. of Items
Registers
Page Ref.
Video Channel Numitems
134–136
4-32
Audio Channel Numitems
137–139
4-33
S/P DIF Channel Numitems
140–142
4-33