14 Bit/ 216mhz

Discussion in 'Blu-ray & DVD Players & Recorders' started by williamtassone, Jun 11, 2005.

  1. williamtassone

    williamtassone
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    We've all seen that in suceeding generations of DVD players the "specs" have gradually increased.First there were the 8bit/27mhz DACs then 8bit/54mhz then 12bit/108mhz DAC's. Now all the high end gear sport 14bit/216 DACs

    What exactly does the "bit" and Mhz" refer to as relates to the original DVD recording (which I understand is recorded at 8bit/27mhz)

    Are these newer DACs producing a sharper picture? I've scoured the net for an explanation and asked the sales reps and no-one seems to be sure :smashin:
     
  2. Thunder

    Thunder
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    In the main my opinion is that its just marketing. A lot of people tend to fall for the quoting of figures which don't always relate to the performance of a piece of equipment. In my experience a more powerful chip very rarely guarantees better performance ;) Whats far more important is the way the silicon is implemented, ie the way its used, what its coupled with and the circuit design. I would willingly and confidently compare the quality of the video output of my Tag DVD player to any of the new bread. Its output measures about as perfect as it gets and it uses what would be considered relatively old silicon :smashin:
     
  3. chambeaj

    chambeaj
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    Background notes (simplified) which might help towards answering your question:-

    27MHz - 27 million samples p/sec - A to D (analogue to digital). In otherwords the original analogue video signal was sampled (i.e. a measurement of the video signals voltage level taken) at a rate of 27 million times per second.

    Likewise the output voltage (i.e. signal level) of a D to A (digital to analogue) convertor (DAC) can be updated/changed 27 million times per second.

    A 216MHz/14-bit DAC can therefore produce a more accurate representation of the original analogue signal with respect to time when compared with a 27MHz/8-bit DAC.

    14bit sample - i.e. a 14-bit binary value (base 2 arithmatic) which represents the voltage level measured for a given sample. The more bits used (quantisization) the greater the granularity. For instance, 8-bit allows the values 0 to 255 (base 10/decimal), whereas 16-bits allows for the values 0-65,535. If your video signals voltage range was say from 0 to 1 volt then obviously taking 16-bit sample allows for a more precise representation of the analogue signals amplitude (i.e. 0 - 1 volt can be divided up into 65,535 possible sample values).....
     
  4. williamtassone

    williamtassone
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    Jesus! No wonder I failed physics at high school...

    I gather then that THEORETICALLY the newer DACs would produce a better image than the 1st generation video dacs. I remember years ago a Krell DVD player had a 10bit/54mhz dac and slaughtered some of the oppostion that boasted 12bit/108 fare.

    Its got me stuffed cause I walk into an AV shop to pick up a DVD player costing $thousands weighs 4 kilos and I wonder if it will outperform (video wise) my old player (which was 12bit/108).

    I remember a year ago asking industry reps from all the major cities of Australia what mass-produced player produced the best picture.

    They were all unanimous: The toshiba SD 9500.

    Yet the tosh scored poorly on some Objective testing (eg:chroma delay)

    That's why Im a bit wary about buying a player that "top scored" on the "secrets" website. :confused:
     
  5. bonzobanana

    bonzobanana
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    14bit refers to the colour sampling of the player. If the original dvd is 8bit giving 256 levels of brightness for each colour (R, G, B) then 9bit gives 512, 10bit gives 1024, 11bit gives 2048, 12bit 4096, 13bit 8192 and 14bit 16384 levels of intensity for each of the three colours. If your viewing on a plasma,LCD or digitally stored processed 100hz/progressive CRTs with a limited colour palette then for analogue connections (composite, VGA, s-video, RGB scart etc) it can have a real advantage in preventing colour stepping effects especially for images that are mainly only one colour like a blue sky.

    The thing is the colour resolution of dvds is not as good as the picture detail so colour sampling works to falsely improve colour resolution. a dvd player with 10bit colour sampling has 4x the colour resolution of a first generation 8bit dvd player. Interpolating does soften detail. I.e. if you had a black vertical line and next to it a white vertical line and a dvd player was interpolating that image you would get a thin grey line inbetween possibly depending on the processing used.

    The Mhz figure as far as I know simply refers to the speed of the dvd processing section involved in interpolating/processing the dvd image. For 10bit processing you want about 54mhz and for 12bit you want 108mhz approx. If you get 12bit at 54mhz its probably only doing 12bit in interlace mode and falls back to 10bit for progressive. However it all depends on the actual circuitry used. I don't know the full technical story but I do know that ARM designed a lot of the risc engines for many dvd processing chips. They do them for mediatek, zoran, sigmatel and loads of others. I think the arm based designs simply multitask doing all three colours interpolating within one actual unit but companies like sony and panasonic might actually have 3x embedded cores with each working on one colour.

    As you can imagine a 14bit DAC stage not only has to process a lot more data but it needs far more storage too.

    On a traditional 50hz CRT set which has a true linear/analogue RGB connection I don't think 14bit is necessary. 14bit is more for high end flat screen technology or dlp/lcd projectors in my opinion.
     
  6. williamtassone

    williamtassone
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    Thanks guys.

    I often wonder; the engineers at Denon, Arcam etc have known for a few years which are the best de-interlacers and MPEG-2 decoders. They know this. Yet it took a lowly chinese company, Oppo digital, to produce a $300 dvd player that worldwide could only be beaten by the Denon A1-XV (5910 in USA).

    Mind you the Denon costs about $3500 us dollars.

    As consumers are we being had? :mad:
     
  7. vonhosen

    vonhosen
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    Here is a post with what John Dawson (Arcam) said on this subject some time ago.

     
  8. williamtassone

    williamtassone
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    A magnificent article by John Dawson. Certainly shed a bit of light on the subject.
     
  9. Thunder

    Thunder
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    I would pit CRT against Plasma/DLP/LCD technology any day and be quite confident of it being superior in subjective results nearly every time :)

    I have to agree with John from Arcam and go back to what I said earlier. If the output stage isn't correctly buffered and you don't have a good clean linear power supply then it doesn't matter a hoot how powerful your video DAC is ;) The Pantera MPEG decoder in my DVD32R when coupled to the extremely stable power supply and extremely accurately buffered analogue 75ohm BNC outputs is a killer :smashin: And as John says its only a 10 bit device :) In fact the most renowned scalers I know, e.g Lumagen and Crystalio both use 10 bit technology :thumbsup:
     
  10. williamtassone

    williamtassone
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    Its an interesting point made regarding the crystalio scaler. From memory, when I was reading the Teranex website, their video processors use 10 bit processing as well.

    Which brings me to my next point: a cursory look at the "secrets" shootout will demonstrate, time and again, companies like Sony that use substandard MPEG 2 decoders on their flagship units and the picture quality was bettered by predesessors that used lower spec video DACS.

    Conclusion? I think one should be wary of the marketing B**lls**t about the new 14bit/216 mhz dacs that is used to help us part with $2000 for a dvd player. The filters/ power supply/ circuit layouts etc are just as important in rendering a great picture.

    And yes in 2003 I saw the Tag Mclaren in action and wouldn't be surprised if it was still competitive today
     
  11. bonzobanana

    bonzobanana
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    Nice to see the Zoran Vaddis 5 getting a mention. I don't own a Arcam but have two players based on this chipset and both give the most realistic and appealing image of any of the many dvd players I've seen and purchased. The mediatek based players just don't seem as natural to me. Yet the Toshiba 340 and Pioneer 575 both scored very highly for picture quality and are based on these. The Toshiba 330 also scored very highly for picture quality and yet worked very poorly on my projector setup.

    I suspect there are a lot of dvd player cons with regard electronics. I know there are cheap mediatek based players that have a 12bit DAC equipped DVD logic chip like the MT1379 or MT1389 but don't have enough onboard memory to actually do 12bit interpolation yet still claim 12bit in their specification.

    Also I've seen mediatek based players that seem to work very nicely until you get to panning shots and they have more noticable judder on players with a 12bit claimed DAC compared to a 10bit DAC. I can only assume the greater interpolation and detail is causing the player to struggle. Its obvious 12bit interpolation creates a far greater workload for the player especially in progressive mode.

    If you want a nice, well built zoran based dvd player with superb audio and a decent progressive mode you could do worse than the cyrus tuned Limit 900SE here;

    http://www.play.com/play247.asp?pa=srmr&page=title&r=ELEC&title=509316

    At £50 delivered you can't really go wrong.
     
  12. williamtassone

    williamtassone
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    Yet did you see the lowish score given to the Arcam DV79 by the yanks on the secrets website? Apparently Arcam dumped the silicon image de-interlacer in favour of the Zoran. If the Zoran chipset was as sub-standard as the yanks said it was why would Arcam do this?

    That's why I'm a bit dubious about "shootout scores"

    I remember the tosh sd9500 was found to have some problems like chroma delay, luminance filter problems etc when scrutinised by some whizz bang computer but christ the picture quality was the best thing since sliced bread.

    I don't know much but if your Arcam DV79 gives you a great picture lets not worry too much about the shootout score.

    Interesting comments you have made about the mediatek de-interlacer as the boys at "secrets' seem to be in love with that one ?!?!



    "...I went down that river once when I was a kid"
     
  13. bonzobanana

    bonzobanana
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    As far as I know the mediatek chips are the most embedded chips out there which is why they are used in the very, very cheapest players. They have little scope for customising the pcb because of this. May be the de-interlacer is good in them but I believe the main risc cpu engine struggles at times and audio quality is generally poor especially for audio cds. Its my experience of trying various mediatek based players including the Toshiba 330, 340, AMW P80L, Skyworth 3650, prism and a few others. I'm not knocking the players but I personally find the visuals more realistic and cleaner on the zoran based players generally. Maybe the zoran players might have less detail fractionally but the images just seem more natural. I use a Panasonic AE100 projector I might add. Not a high resolution projector but capable of good colour and fluid animation. The mediatek players just don't seem as good with it.
     

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