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SERVICE MANUAL
audio is downmixed before emerging as stereo or Dolby Pro Logic compatible encoded audio.
Simultaneous MPEG audio decoding and output of Dolby streams on the S/PDIF is also supported. SRS
Labs' TruSurroundXT is also provided for two speaker virtual surround sound. The integrated DACs
provide analog stereo output directly from the device using a single-ended interface.Multichannel streams
can be passed through to the IEC958 output for external decoding. Audio sample rates of 32 kHz, 44.1
kHz and 48 kHz are supported.The audio digital-to-analog converter is a high performance stereo audio
converter operating at 256 Fs system clock using single-ended voltage. This DAC accepts a 24-bit input
data in I 2 S format from the audio decoder macro block and converts them into up to 2 Vrms output
voltage. Digitized analog audio can also be input to the STi5100 using the PCM input interface and
buffered in memory via DMA. 26/830 STMicroelectronics Confidential 7603604B The audio subsystem
consists of the following units.
Audio datastream controller
The audio datastream controller receives, buffers and reformats audio data. It handles up to three audio
data flows concurrently.
It receives a raw PCM stream from an external source via the PCM input interface or receives a
compressed data stream from an internal source such as the PTI and stores this in a memory buffer via
DMA. This is used to buffer and play the main audio for the digital or analog program.
It receives a PCM file or stream from a memory buffer via DMA and delivers this to the audio decoder's
second input for sample rate conversion and mixing with the main audio.
The router is able route either source to either input of the audio decoder.
Audio decoder 24-bit audio digital signal processor
The digital signal processor processes audio streams sent to it by the CD player and PCM file player.
S/PDIF player
The independent S/PDIF player can output a compressed Dolby Digital audio stream independently of the
stream being decoded.
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