L64105 LSI Logic Corporation, L64105 Datasheet - Page 349

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

If the data in the Linear PCM bitstream does not agree with the options
available, the decoder sets the Context Error Interrupt bit in Register 4
(page
4-8), asserts INTRn to the host if the interrupt is not masked,
mutes the audio output, and searches for the next sync word.
Dynamic Range Control is a compressed gain value that should be
applied to all the samples in an audio frame. One audio frame has 80 or
160 samples when the sampling frequency is 48 or 96 kHz, respectively.
One audio frame can extend across an audio pack boundary. The first
byte location of an audio frame is defined by the first access pointer. All
Linear PCM samples in one audio frame have a unique dynamic range
control gain value, even if the audio frame is separated by an audio pack
boundary. The host can turn Dynamic Range Control on or off by setting
or clearing the Dynamic Range On bit in Register 364
(page
4-87). When
the Dynamic Range Control is off, the default gain value is one. When
Dynamic Range Control is on, the decoder uses the dynamic range
control value (dynrange_value) included in the bitstream for each audio
frame. The host can also specify dynscale values in Registers 360 and
361
(page
4-83) to scale the bitstream dynrange_value. The dynscale
factors are in increments of 1/256.
The host can also program a direct scale factor into the PCM Scale [7:0]
bits in Register 362
(page
4-84). Settings here are also in 1/256
increments. The final sample value is computed using the following
equation:
final sample value = [|dynrange_value - 1| * dynscale(high/low) + 1]
* PCM Scale * decoded sample
The Linear PCM Decoder produces stereo PCM and S/P DIF outputs.
Up to two channels of Linear PCM samples can be decoded; additional
channel samples are dropped. When the Linear PCM bitstream contains
only one channel, PCM and S/P DIF output samples in the first channel
are duplicated in the second channel.
Linear PCM Audio Decoder
10-17