
L64005 MPEG-2 Audio/Video Decoder Technical Manual
7-7
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
Table 7.2
Location of Maskable
Interrupts
The L64005 handles the various types of audio errors encountered dur-
ing decoding as follows:
SYNC ERROR – The L64005 only synchronizes to syntactically cor-
rect MPEG audio data. If synchronization is achieved and then lost
because of corrupted data, the ASE bit is set. The audio output
pauses until sync is reacquired.
CRC ERROR – A CRC error indicates that bits have been corrupted
in either the header, allocation, or scale-factor portions of the audio
frame. If the MUTE bit (Group 6, Register 48, Bit 1) is set, only the
bad frame is soft-muted. If MUTE is not set, the frame is played.
ILLEGAL BITS – Illegal bits include all other syntactically incorrect
bitstreams besides the CRC errors. If Mute on Audio Error is set, the
bad frame is soft-muted. But if MUTE is not set, the frame is played
exactly as it is decoded.
RECONSTRUCTION ERRORS – Similar to video reconstruction
errors, reconstruction errors occur when either a whole or portion of
an audio frame is not decoded in time for presentation. It is typically
caused by either channel underow or an inability to sync to the
available audio data. If a reconstruction error occurs, the output
pauses until the condition is no longer present.
The most common problem in a decoder is that it underruns because of
channel errors. This is because data that does not reach the decoder or
Interrupt
Location
Description
Audio Channel Buffer Overow (ACBO) Group 4, Register 1, Bit 0
Channel buffer overow; data is
lost.
Audio Channel Buffer Underow (ACU) Group 4, Register 1, Bit 2
Channel buffer underow; if not cor-
rected, reconstruction error results.
Audio CRC or Illegal Bit Error (ACE)
Group 6, Register 1, Bit 3
Corrupted audio data. If not cor-
rected, sync error results.
Audio Sync Error (ASE)
Group 6, Register 1, Bit 4
Sync lost because of corrected or
unexpected audio data
Audio Reconstruction Error (ARE)
Group 6, Register 1, Bit 5
Audio decoding not complete by
presentation time because of either
channel underow and/or corrupted
data