1. High-end A/V processors
A hifi-plaza.com session by
Frederic Vanden Poel
Presented at the Home Theatherdag 2002
1/06/2002 Nieuwegein, Utrecht

2. Todays topics Surround formats : the basics
A/V processors : building blocks
Hot formats
Case study
installing a 7.1-ready room
Demo
setup the Tag Mc Laren av32r

3. The basics : surround formats
Decoding of established formats
Dolby Digital
DTS
PCM
Additional processing
Pro logic (Pro logic II) for PCM or DD sources
THX post-processing
Additional surround modes

4. Established formats The established format for DVD, HDTV, games
Lossy psycho-acoustic coding
Typical bitrate : 384kbps, 448kbps
5 main channels, one sub = 5.1
48 Khz, 20 bit word gives usable 120dB dynamic range
Extensible to 6.1 : SURROUND-EX
Multimedia : Nvidia N-Force, X-Box

5. Established formats Alternative format on DVD, also lossy
Higher bitrate than DD !
Typical bitrate
754 Kbits (half)
1.5 Mbps (full)
5 main channels, one sub = 5.1
44.1 Khz (e.g. DTS CD/LD) & 48 Khz (DVD)
Up to 24/192
Extensible to 6.1 : DTS-ES & discrete

6. Established formats : less is more
When watching the HT discussion groups, one may notice the never-ending thread …

7. Established formats : less is more
Common arguments
DTS uses less compression, must be better
More bass depth, layering

8. Less is more … but Bitrate is not everything
Compression efficiency matters
a 128 kbps MP3 sounds similar to a 192 kpbs MP2
Mpeg 4 is 5 to 10 times more efficient than Mpeg2 at same rate
DTS adds 10dB to the LFE track (see also HDCD)
On the tag av32r this can also be switched on/off
a DD movie soundtrack will typically play 4 dB softer than an otherwise identical DTS soundtrack
After normalization of levels & A/B encoding/decoding tests with identical masters: difference that was once claimed to be night and day disappears.

9. Established formats : PCM
Just as DD & DTS are carried digitally, we must not forget PCM
a multibit technology, e.g. 16 bits in one word at a rate of 44.1 khz, also denoted 16/44.1
Used to transport CD-Audio (redbook)
But also any stereo track that has been processed for Dolby Pro-Logic (2)
Current A/V processors will typically sample the analog inputs for further decoding/processing to more channels (e.g. 2:4 pro-logic decoding, 2:5.1 pl2)
Also the internal format inside the processor after DD or DTS has been decoded

10. Additional processing : pro-logic
4:2:4 encoding/decoding chain
4 channels are matrix encoded onto a 2 ch transport (e.g. Nicam)
full bandwidth L/C/R
limited (8Khz) mono surround

11. Additional processing : THX
Not a coding standard
Cinema : quality standard
Home : quality and post-processing
De-correlation of S
Re-EQ : subtle roll off filter
Variants :
THX (past), now THX-Ultra
THX-Select
THX2

12. Additional processing : music
Adds reverb/ambience/ to a stereo source
Early days : Yamaha DSP (but a bit fake)
Some contemporary examples :
Proprietary
Oem
Yamaha Cinema DSP
Tag Mc Laren TM Surround
Lexicon Logic 7
DTS Neo 6 Music Mode
Pro Logic II Music Mode

13. Additional processing : surround
Create more channels than physically coded in format
Early days : Yamaha Cinema DSP : 2 height channels
Now :
Proprietary
Oem
Yamaha Cinema DSP (Trifield)
Lexicon Logic 7
DTS Neo 6
Pro Logic II

14. A/V processor building blocks
Digital I/O
Analog I/O
Video I/O
DSP
Domotica I/O
Software AD DA
Vol
Pre-amp

15. Building blocks : digital I/O

16. Building blocks : digital I/O
SP/DIF = Sony/Philips Digital Interface
Formats transported : PCM/DD/DTS
A real standard
Problems :
Clock recovery & jitter
Typical usage upto 24/96

17. SP/DIF : jitter
Subtle delay variations : bits or frames do not arrive exactly in time
Sound becomes harsh
Solutions :
Clock recovery
Buffering (but introduces lipsync problem)
Proprietary techniques using the above
When buffering is NOT an option : clock sync e.g. Tag Sync Link : sync clocks between av32r & dvd32r (but costly player)

18. SP/DIF : 2 common types Optical Coaxial
One extra conversion : jitter++
Error resilient
Electrical connection
Best sound quality in multiple tests (on Parasound/Tag)
But : interference from other equipment (spikes) : lost sync

19. How about DVD-A/SACD DVD-A Players will output AC3/DTS/PCM digitally
PCM from DVD-A is always downmixed !
No full resolution digital output from decoded MLP data !
Technics DVD-A10

20. Why did it come this far ? DeCSS
How about DVD-A/SACD
SACD
Players will output PCM digitally, namely the CD layer on the hybrid SACD disk
No digital link yet for DSD, only proprietary, e.g. Sharp with 1bit amp
In the best case we get a downmix or CD layer digitally
Sony SCD1
Why did it come this far ? DeCSS

21. Possible solutions Now Future Proprietary digital solutions
Denon : Denon Digital Link (gigabit ethernet alike)
Tag Mc Laren : dvi panellink A/V
Meridian : 3 SP/DIF cables
Integra/Onkyo : firewire
No established standard for content protection : IP/DRM
Analog 5.1 bypass as a lesser alternative
Future
Secure content exchange between devices : what about consumer rights ? DMCA v.s. Fair Use
One digital interface for everything
Buy transport/dvd player from A, buy processor from B …

22. Building blocks : analog IO + A/D

23. Building blocks : analog I/O
Required for analog equipment such as VCR’s, Tuners, ...
or those sources which are kept analog like SACD and DVD-A

24. Analog sources : 2 options
A/D + processing + D/A + volume control
Useful for surround decoding, bass management, time alignment and relative SPL level
Some offer even processing of 5.1 analog input (new Pioneer THX2 integrated amp)
Relay signal directly towards the volume control 5.1 (or 7.1) analog bypass
Some processors already have a 5.1 input
Others were designed to A/D everything (e.g. Tag/Sony 9000)

25. Add-on solution from Tag

26. Add-on solution from Tag

27. Building blocks : DSP

28. DSP : the heart of the processor
Most important functions of the DSP
Digital format decoding
DD/DTS/DTS-ES/DD-EX/...
Post processing
Pro-logic,THX, HDCD, …
Bass management
Time alignment : delays
Level adjustment (also possible analog)

29. DSP : software
Software support is important : being able to keep your A/V processor up to date (website updates) -> demo
Serious price difference between vendors
Some pre/pro’s which support SW upgrades
Onkyo Integra RDC-7
Rotel RSP-1066
Tag Mc Laren av32r
Sony TAE-9000ES
BUT : vendor commitment is also required, e.g.Tag : every month SW update, Integra : when major format arrives (e.g. DPL2, THX2…)

30. DSP : software limitations
The current algorithms are designed for PCM
Except for some simple operations (time alignment = delay bitstream, level management), processing on DSD is not yet common.
Solution : digitise 5.1 analog bypass
Now we have full PCM based processing on a decoded DSD stream which was made analog
Multi-bit artefacts reappear

31. DSP : Hardware limitations
DSP is always limiting factor and like your PC on which you received the invitation for this workshop, your pre/pro will once run out of steam. Spare DSP sockets delay this process (Lexicon MC12)
DSP’s can easily run out of steam when serializing
TM5 on 24/96 but not PL
PL or HDCD but not PL+HDCD
AC3+THX/PL+THX OK but not DD PL + THX
When a processor was not designed with sample rate conversion in mind, DTS 24/96 will never work as it still uses a 48 Khz input stream.

32. Processors : Useful hi-fi features
For the hifi enthousiast seeking high-end stereo performance, the following features on some pre/pro’s come quite handy :
Upsampling : some examples
16/88.2 (#sample redbook *2) greatly improves high frequencies : block wall filter outside audible range
24/88.2 further improves dynamics : a larger range of the DAC is used by scaling
Good anti-jitter design
With a good anti-jitter design, the sound is less dependent on the source
E.g. 300 CD carousel on Meridian pre
5.1 analog bypass for those who can’t wait

33. Building blocks : D/A + analog

34. Digital to analog conversion
Current processors are equipped with 24/96 to 24/192 D/A converters
Given the current formats, 24/96 is the most useful
24/192 should be useful in a pre/pro when MLP streams (or after decoding) can be sent digitally to the processor, but …
But Warner is about to give up DVD-A ...
So, except for upsampling 44.1 * 4, those 24/192 DAC’s will never be used native in their full resolution.
Some 24/192 DACs are hybrid DSD, such as those inside the Pioneer 747A.
Note that the Tag 5.1 upgrade board also has 5 new 192/24 dacs onboard

35. Analog stages : double costs ?
Without a high-res interconnect format for SACD, what is the customer paying extra for 5.1 bypass?
Tag asks about 1000 EUR for the av192r upgrade, which makes the av32r a high-end 5.1 analog pre-amp with 192K dacs. This is a fair price, given the RRP for the TAP9000ESN is even higher, Sony’s 5.1 bypass pre-amp
The customer at least pays that amount twice when investing in a high-end multichannel SACD player, such as the SCDXA777ESN
Keep attention to 3 extra interconnect pairs
TAP9000ESN
SACDXA777ESN

36. Hot formats Dolby Pro-Logic 2
Extract 5.1 from 4:2 encoded pro-logic material
Less collapse of front stage towards center
Music and movie modes
Ideal for TV & Satellite owners
Not yet used by HP : almost all movies we watch are DVD sourced, no cable or sat

37. Hot formats 6.1 formats, 7.1 speakers
Extra channel : discrete or matrixed
Dolby : Dolby Digital Surround-EX
DTS : DTS-ES, DTS-ES Discrete
THX : THX-EX (post processing, collaboration with Dolby)
Two pairs of surrounds are required

38. Example : a 7.1 ready CRT room

39. Initially :full towers as surround
The initial surrounds were B&W Matrix 802 S2 towers, which were always too close to the couch and the rear wall.
Furthermore, the back port of the old 803 resulted in some boom.
At that moment, EX came on the market but we thought the idea could also help us solve the 6dB attenutation rule …

40. The 7.1 ready room : full towers as surround : wrong choice
Suppose a couch that’s 2m wide. Place the left and right 803’s at each side, let’s say at about 50cm. What happens when we sit in one corner ??
When we’re seated in the middle of the couch, we are 150cm away from each speaker : sweet spot OK
When we’re seated in the left corner, one speaker is only 50cm away, while the other is 250cm away.
SPL from left corner : -6dB from reference SPL (at 1m)
SPL from right corner : (log 2.5 / log 2)*6dB = 7.9dB
We can never get a two persons sweet spot …
A lot of inexperienced users are still placing speakers like this … it can never work this way, not with 5.1, 7.1 …
It doesn’t matter how many speakers you buy !

41. The 7.1 ready room : dipoles
As you may remember, the room is very high. We can exploit the height to solve the big difference which was almost 14 dB !
Furthermore, dipoles cancel out on the perpendicular line.
B&W SCM-8

42. The 7.1 ready room : dipoles
The dipoles greatly reduced the surround hot spotting.
We still were not 100% happy with the phantom center
Adding a single center in the back gave strange results
Adding another pair of dipoles in the back solved it. From the couch, our ears are inline with only one side of the rear dipoles and not the perpendicular line …

43. Setup of the av32r What is required ?
Distance between each speaker and the defined hot spot.
S-Video cable to Barco for menu setup
Analog or Digital SPL meter
THX test disc for reference SPLs