L64105 LSI Logic Corporation, L64105 Datasheet - Page 225

• Manufacturer Part Number: L64105
• Description: Mpeg-2 Audio/video Decoder
• Manufacturer: LSI Logic Corporation

6.4.2 Detecting Potential Underflow Conditions in the Video Channel
In the case of audio, the host can select the read pointer for the Audio
Decoder or the S/P DIF Formatter by setting the Enable Audio Read
Compare bits in Register 69 so that synchronization can be maintained
against either one. When the compare produces a match, INTRn is
asserted if not masked and the DTS Audio Event Interrupt bit
is set.
The Picture Start Code Read Address (Registers 128–130,
and the Audio Sync Code Read Address (Registers 131–133,
can be used in conjunction with the Picture Start Code Detect Interrupt
bit and the Audio Sync Code Detect Interrupt bit (both in Register 1,
page
As previously mentioned, the Channel Buffer Controller keeps track of
the number of items (64-bit words) and pictures in the Video ES Channel
Buffer and reports these to the host through a set of registers. The
Channel Buffer Controller can also be configured by the host to alert the
internal microcontroller when the Video ES Channel Buffer does not
contain enough unread data to construct an entire picture.
To enable this feature, the host writes a numitems/pics threshold value
in Registers 134–136 (see
Panic Mode Select bits to alert the microcontroller when either the
number of items or pictures falls below the threshold. The microcontroller
then takes suitable action, which may include suspending reconstruction
in order for the video channel to build up. The display is frozen (field
freeze) on the previously reconstructed picture during the period that
reconstruction is suspended.
Table 6.14
The host can read the video numitems at any given time from Registers
134–136 and the number of pics in the channel at any time from
Registers 150 and 151
Channel Buffer Controller
Function
Video Numitems/Pics Panic Mode Select
Video Numitems/Pics in Channel Compare Panic
4-3).
Video Channel Underflow Control Registers
(page
Table
4-38).
6.14) and sets the Video Numitems/Pics
Registers
134–136
69
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Page Ref.
4-22
4-32
4-31)
4-31)
4-6)
6-29