Quantcast Putting the DPS/Leitch DPS-235 TBC to the test - digitalFAQ Forum
  #1  
09-09-2012, 11:00 PM
NJRoadfan NJRoadfan is offline
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I just won a few of these units on ebay cheap. I bought them mainly for genlocking purposes for the Video Toaster, but will also test their suitability for video tape-to-DVD transfers and the effectiveness of their built in proc-amps. The DPS-235 is nothing more then a DPS ES-2200T expansion chassis/controller with one or two "Personal TBC IV" ISA expansion cards installed. I don't know if it includes the "Plus" variant of the card which has a 3D Y/C adaptive comb filter. These cards were popular with Video Toaster uses and only used the ISA slot for power. DPS provided software to control the card's procamp and phase controls in addition to the front panel.

Personal TBC-IV spec sheet: http://www.broadcaststore.com/pdf/mo..._VT-2600WB.pdf
Highres photos and the Amiga control software: http://amiga.resource.cx/exp/personaltbc4
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  #2  
09-10-2012, 04:00 AM
robjv1 robjv1 is offline
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Looking forward to hearing your impressions! I love these sorts of test threads.
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  #3  
09-10-2012, 07:32 AM
NJRoadfan NJRoadfan is offline
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I'm hoping they at least do something to correct jittery tape. DPS marketed these cards to folks to integrate VTRs into their Video Toaster setups in an era where TBC equipped decks were rare. All too often these cards were used just as frame syncs.
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  #4  
09-12-2012, 11:04 AM
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Quote:
Originally Posted by robjv1 View Post
Looking forward to hearing your impressions! I love these sorts of test threads.
Same here.

I used to do these years ago, but have been lazy in more recent ones. Need to reverse myself. At least I've been hacking again. I found a way to use ATI AIW cards in Windows Vista and Windows 7 now. So I've not been totally useless. In my defense, I spend most of my time helping others on this forum and a couple of others -- doesn't leave me much time for original research.

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  #5  
09-12-2012, 11:38 AM
NJRoadfan NJRoadfan is offline
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The price was right. Assuming the lot I'm getting tests and works correctly, there may be extra units available.

The units arrived today, and I have run them through a very basic test with color bars. I will be posting video clips of each unit (5 total) later on.

My first test was to see how "transparent" each TBC was to video. To test this I first recorded the color bars generated by the AVT-8170 TBC when hooked up directly to my ATI All-in-Wonder. I connected it up to each TBC channel using strictly S-Video input and output. I than reset the internal proc-amp on the TBC cards to their default or unity setting. To check levels without a real scope, I used the Video Tools Virtualdub plug-in on each clip I captured. There is quite a bit of variation on output to say the least!

Results:
Unit 1, Channel 1: Levels way too hot, this was evident in the video preview
Unit 1, Channel 2: (no card installed)

Unit 2, Channel 1: Levels about right, color balance correct
Unit 2, Channel 2: Same as channel one. Note that this is the newest unit of the bunch as its labeled Leitch instead of DPS

Unit 3, Channel 1: Levels are low, video is slightly "dull", color balance is slightly off
Unit 3, Channel 2: Levels are low like above, color balance is slightly off

None of the units introduce RF interference into the video path. There is no pulsing or herringbone noise. The proc-amp controls are about "medium" in their correction range. More then the AVT-8710's proc-amp, but less then a Elite Video BVP4+. In addition to linear hue adjustment, there is a "color balance" to adjust R-Y and B-Y levels. I can easily compensate for the output problems in the units using the built in proc-amp. Optionally there is a serial interface that can be utilized with PC or Amiga based software to adjust all the parameters on these units. There are also pots on the cards themselves to adjust static calibration. Of course I would need a real vectorscope and waveform monitor to do the calibration. That is if one even notices the color or level changes to begin with. Of the tests, I only noticed the one with the hot video levels. The rest were mostly correct to my eye.

This leads to an answer to the question on why old professional TBCs aren't good for VHS-to-DVD work. These older units are very fickle. They are affected by temperature changes and require adjustment from time to time. This was expected for this equipment as its target market was to be installed in an equipment rack in a studio with the proper scopes and where procedure dictated regular calibration checks. To put it simply, they aren't idiot proof "plug it in and forget it" devices like the Datavideo TBC-1000 and AV Tool AVT-8710.

Expect to see more tests in the coming days of this unit's ability to actually time-base correct video(line TBC functionality). I'll also try and stress its composite comb filtering ability as the daughter card for the function is present.
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  #6  
09-14-2012, 04:20 PM
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Quote:
Originally Posted by NJRoadfan View Post
They are affected by temperature changes
... and were designed for temperature controlled studios not too different from modern internet datacenters. For example, rack heat is exhaust-vented out of the facility, and not recycled into the room. Even low-rent community colleges sometimes have exhausted racks.

Quote:
where procedure dictated regular calibration checks.
... using special tools and documentation as thick and cumbersome as a NASA preflight check manual. Quite often, servicing and maintenance required the special training you only receive from broadcast engineering education. It requires a special technical understanding that even those well-versed in certain aspects of video (like editing or transfer) would find challenging to master. The person using the equipment was rarely the same one who fixed it.

Quote:
Expect to see more tests in the coming days
Looking forward to it.

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  #7  
09-14-2012, 04:37 PM
NJRoadfan NJRoadfan is offline
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I want to add that reading the manual revealed a few more "uncommon" features.

-3:2 pulldown conversation: The manual says its "simulated", but one is likely better off using computer software for this these days.
-Y/C horizontal delay: This can adjust for chroma shift common on multi generation tapes.

I have attached the manual for the generic ES-2200 expansion chassis. The TBC control section applies to these units.

Quote:
... using special tools and documentation as thick and cumbersome as a NASA preflight check manual. Quite often, servicing and maintenance required the special training you only receive from broadcast engineering education. It requires a special technical understanding that even those well-versed in certain aspects of video (like editing or transfer) would find challenging to master. The person using the equipment was rarely the same one who fixed it.
Whats funny is that the DPS Personal TBC IV cards that are in these units were marketed to Video Toaster users to install in their Amigas. Those folks didn't have the kind of tools to do calibration. Reading period reviews, video pros warned that these cards direct from the factory needed some sort of adjustment as they were rarely correct out of the box! Considering these cards cost folks $1200-1500 new, it was a bit of a shock to those users.

Some background reading on how to buy a TBC 20 years ago: http://www.execulink.com/~impact/tbc_gen.htm
A review of the older DPS Personal TBC II card: http://www.execulink.com/~impact/dpstbc.htm


Attached Files
File Type: pdf es2200manual.pdf (275.6 KB, 38 downloads)
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  #8  
09-14-2012, 06:03 PM
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I remember reading that TBC guide about 10 years ago.

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  #9  
09-14-2012, 06:35 PM
juhok juhok is offline
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Quote:
Originally Posted by NJRoadfan View Post
To put it simply, they aren't idiot proof "plug it in and forget it" devices like the Datavideo TBC-1000 and AV Tool AVT-8710.
OT: these don't always seem so idiot proof either.
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  #10  
09-19-2012, 10:44 AM
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Originally Posted by juhok View Post
OT: these don't always seem so idiot proof either.
Yes, but they usually work. The downside is if they screw up, they aren't as tweakable or easy to fix. I just picked up a DPS "Personal V-Scope" card to put in one of the units. Its a combination color bar generator/vectorscope/waveform monitor. It displays the scopes as a video overlay or on a dedicated monitor. It was also advertised as coming with a floppy of test patterns in Video Toaster framestore format.

http://img526.imageshack.us/img526/9...copebrouj6.jpg

The Personal V-Scope card came today. It came with a a bunch of instructions, and a photocopy of a 1995 article from AV Video magazine on calibrating video equipment with a waveform monitor and vectorscope. I'll be scanning these in and posting them here for general interest in the next day. The card came with some Amiga software to generate all the industry standard test patterns as Video Toaster format frame stores along with a blue gel eye piece to calibrate monitors.
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