
8-16
System Stream Decoding and Synchronization
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
Two registers, DECFS (Decode Frame Store) and DISFS (Display Frame
Store) may be used to indicate which frame is currently being used. They
have patterns for ‘Forward’, ‘Backward’, and currently being ‘Displayed’.
Refer to Section 2.9.29 for details on these registers. They are in Group
7, Register 55 bits [4:3] and [6:5] respectively.
8.4.3
Audio Decoder
Rate Control
Like the video decoder, the audio decoder can be programmed to adjust
its output rate. The L64005 allows a section of audio frame to be
repeated or skipped on request. This slows down or speeds up the effec-
tive play rate and allows the decoder to resynchronize with the video. The
ASRS[1:0] bits in Group 6, Register 54 control the play mode of the
When the decoder is paused, the output PCM value holds the same data
as the last sample before the decoder is paused. When normal play
resumes, no samples are lost. This is different from stopping the
decoder. If the decoder is stopped, and restarted, it re-synchronizes to
the input stream when restored and samples are lost.
You can also control of the audio output rate with the L64005 Numeric
Control Oscillator (NCO) feature. Registers 49, 50 and 51 in Group 6
in these registers are used to determine the output sample rate.
L64005 receives external audio clock in rates of 256
fs and 384 fs.