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PQLS with HDMI
1122
922
As shown on right, jitter causes clock timing
error and distorts the D/A conversion timing.
This is one of the biggest factors for sound
degradation during digital transmission, such as
decreased sound localization, and happens even
with HDMI connection.
On the Blu-ray Disc player, the audio clock goes
through algebraic transformation based on the
video pixel clock, then transferred. On the AV
receiver, the audio reference clock is regenerated
using PLL in the algebraic value which came with
the video pixel clock. So the audio reference
clock is influenced by both the HDMI receiving
chip's PLL performance and the video pixel clock,
and can not avoid being regenerated with some
jitter.
Pioneer's Precision Quartz Lock System (PQLS)
was developed as a solution to this problem. PQLS processes
D/A conversion using the high-precision crystal oscillator clock
instead of the audio clock regenerated in the HDMI receiving
chip, and is free from jitter created during HDMI transmission.
The data from the Blu-ray Disc player is temporarily buffered in
the AV receiver's memory, then sequentially reproduced in
sync with the high-precision crystal oscillator clock to prevent
flaw. Additionally, the Blu-ray Disc player's data transmission
clock is controlled by signals from the AV receiver to prevent
overflow or underflow in the buffer.
Three types of PQLS are available depending on the connected
Blu-ray Disc player.
- PQLS 2ch Audio: For CD playback (LPCM).
- PQLS Multi-Surround: For CD/DVD/BD sources, when the
Blu-ray Disc player output is set to LPCM.
- PQLS Bit-stream: For CD/DVD/BD sources, all the time.
For PQLS to be effective, Control with HDMI needs to be on,
and — only for PQLS Multi-Surround — HDMI audio output
needs to be set to PCM.
Sound Degradation from Jitter
Example: Speech Wave
Level
Original
D/A conversion by jitterless clock => same as original
Level
Precise
D/A conversion by clock with jitter => different from original
Level
Imprecise
Jitter effects on D/A conversion prevents accurate signal conversion
Conventional HDMI Transmission
Blu-ray Disc Player
Servo
HDMI
Circuit
Data
IN/OUT
Transfer
AUDIO DATA
AUDIO CLOCK
AV decoder
Audio signal with jitter
Jitterless Transmission (PQLS)
Blu-ray Disc Player
Control Data
Transfer
Servo
HDMI
Circuit
Data
IN/OUT
Transfer
AUDIO DATA
AUDIO CLOCK
AV decoder
CONTROL DATA
Audio signal with jitter
PQLS Backward Compatibility
Blu-ray Disc Players
BDP-LX91
BDP-LX71
BDP-LX52
BDP-LX53/BDP-330
BDP-LX54/BDP-430
BDP-LX55/BDP-440
3
AV RECEIVERS REFERENCE GUIDE
AV Receiver
PLL
HDMI
IN/OUT
DAC
Audio signal with jitter
AV Receiver
Clocking
HDMI
Crystal
IN/OUT
DATA
DAC
MEMORY
Jitterless signal via PQLS
AV Receiver
VSX-1122
VSX-922
2ch
2ch
Multi
Bit-stream