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2004 Jan 26 26
Philips Semiconductors Product specification
MPEG-2 video and MPEG-audio/AC-3
audio encoder with multiplexer
SAA6752HS
7.5 Audio compression
7.5.1 GENERAL
The digital audio signal from the I
2
S input port is
compressed according to MPEG-1 layer 2 and DDC
(AC-3) encoding (only for SAA6752HS/V103). The
constant bit rate is programmable via the I
2
C-bus.
An audio stream with 16 to 20 bits and a sampling
frequency of 48 kHz can be processed. A higher accuracy
of more than 20 bits is ignored. A bypass mode can be
selected for LPCM for 16-bit data resolution and
compressed audio signals (MPEG-1 layer 2, MPEG-2, DD
and DTS) according to IEC 61397 or LPCM. The format of
such compressed inputs is identified and made accessible
via the I
2
C-bus.
7.5.2 AUDIO ENCODER CONFIGURATION OPTIONS
The following configuration options can be selected from
the host:
• AUDIO PROCESSING MODES. MPEG-1 L2 or DDC
(AC-3) encoding (only for SAA6752HS/V103) modes
can be selected. Two bypass modes are also available:
LPCM bypass and DVD-compliant bitstream bypass.
• AUDIO MUTE. It is possible to mute the audio data prior
to encoding.
7.5.3 AUDIO ENCODER STATUS INFORMATION
The following configuration options can be selected from
the host:
• DVD-BYPASS HEADER INFORMATION. Header
information is available to allow the host to determine
the content of the bypassed audio data stream. This
includes information from the Preamble Pc, Preamble
Pd and audio frame headers.
7.5.4 MPEG-1 LAYER 2 ENCODING
MPEG-1 layer 2 encoding can be selected. The available
I
2
C-bus settings are:
• No pre-emphasis (default setting)
• 50/15 µs (compliant to ISO 11172-3)
• CCITT J.17 (compliant to ISO 11172-3).
7.5.5 DDC ENCODING (ONLY FOR SAA6752HS/V103)
Dolby Digital Consumer (DDC) encoding mode can be
selected. The encoder performance is suitable for
consumer electronic recordable DVD systems.
7.5.6 LPCM BYPASS
16-bit LPCM audio streams can be bypassed by the audio
encoder module.
7.5.7 DVD-COMPLIANT AUDIO BYPASS
DVD-compliant bypass and pause burst handling is
selectable in accordance to IEC 61937. Preamble Pc,
Preamble Pd and part of the elementary stream header
are captured and made available via the I
2
C-bus. If any
non DVD-compliant formats are detected then these are
flagged via host interrupt.
Table 5 DVD-compliant audio bypass
MODE BIT RATE SAMPLE FREQUENCY CHANNEL CONFIGURATION
MPEG-1/2 layer 2 without
extension
64 to 384 kbit/s 48 kHz only mono, stereo or multi-channel up to 7.1
MPEG-2 layer 2 with
extension
up to 912 kbit/s 48 kHz only mono, stereo or multi-channel up to 7.1
Dolby digital 64 to 448 kbit/s 48 kHz only 1/0, 2/0, 3/0, 2/1, 3/1, 2/2 and 3/2
DTS-1 192 to 1536 kbit/s 48 kHz only stereo or multi-channel up to 5.1
7.6 SDRAM interface
7.6.1 GENERAL
The external SDRAM is used as memory for storing video
and audio information during the compression process.
It is also used as a buffer for the output stream. The
interfacing to and from the functional blocks is done via a
number of internal FIFO memories.
The SAA6752HS will support 16 Mbit@16 bit
(512k × 16 × 2) and 64 Mbit@16 bit (1024k × 16 × 4)
SDRAM devices. The minimum recommended speed of
the SDRAM is 125 MHz. Recommended SDRAMs include
the Samsung K4S641632D-TC/L80 and
K4S161622D-TC/L80 devices.