L64105 LSI Logic Corporation, L64105 Datasheet - Page 184

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

5-8
In the Capture Mode, the host can select an event in the bitstream to use
for capturing the value of the SCR counter. When the preparser in the
chip detects the selected event, the SCR counter value is loaded into the
SCR Compare/Capture registers. The host can read these registers at
some later time to determine exactly when the event occurred. The
following events can be selected for SCR capture:
The Compare Mode can be used to generate an interrupt, start the video
decoder, or start the audio decoder. To generate an interrupt, the host
writes the desired compare value into the SCR Compare/Capture
registers. When the SCR counter reaches the compare value, the INTRn
output signal to the host is asserted. To start video decoding on compare,
the host writes the compare value as just described and sets the Video
Start on Compare bit in Register 19. When the SCR counter reaches the
compare value, an autostart signal is sent to the video decoder.
To start audio on compare, the host writes the compare value in the SCR
Compare Audio registers (Registers 20 through 23) and sets the Audio
Start on Compare bit in Register 19. This generates an autostart to the
audio Decoder when the SCR counter reaches the compare value.
Note that the video decoder must be stopped prior to the autostart video
signal and the audio decoder must be PAUSED prior to the autostart
audio signal. The autostart functions commonly are used at the start-up
time of the system and after a channel change.
Host Interface
Picture Start Code
Audio Sync Code
Beginning of Active Video (BAV)
Pack Data Ready
Audio PES Ready
Video PES Ready
DTS Video
DTS Audio
Note:
The compare/capture circuits can only be used in one
mode at a time. Usually, they are initially set to the No
Compare or Capture mode so the PCR value in the first
System header can be loaded into the SCR counter. Then
they are placed in the autostart on Compare mode while
the channel buffers are filling up. Once the decoding has
started, the SCR circuits can be placed in the Capture
mode to monitor the progress of decoding based on
incoming events.