Are standalone DVD Recorders effectively TBC's?

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It occurred to me yesterday when I had just TV static feeding into the DVDR
(Panasonic DMR-E20) and it looked "digitized" out the other end just like it
does through a TBC. Presumably the framebuffer is always active and not just
when it's recording. Interesting. Of course there's no way to "house-sync" it,
but it might be useful for cleaning up old, wavy VHS output.

....Sean.

 

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"CheetoDust" <Stalky14@synonymforenthuse.com> wrote in message
news:slrncrbmi5.9n.Stalky14@thehill.comcast.net...
> It occurred to me yesterday when I had just TV static feeding into the
> DVDR
> (Panasonic DMR-E20) and it looked "digitized" out the other end just like
> it
> does through a TBC. Presumably the framebuffer is always active and not
> just
> when it's recording. Interesting. Of course there's no way to "house-sync"
> it,
> but it might be useful for cleaning up old, wavy VHS output.

Don't confuse digitization with temporal compensation.

 

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"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:10rdeo1io3dke47@corp.supernews.com...
>
> "CheetoDust" <Stalky14@synonymforenthuse.com> wrote in message
> news:slrncrbmi5.9n.Stalky14@thehill.comcast.net...
> > It occurred to me yesterday when I had just TV static feeding into the
> > DVDR
> > (Panasonic DMR-E20) and it looked "digitized" out the other end just
like
> > it
> > does through a TBC. Presumably the framebuffer is always active and not
> > just
> > when it's recording. Interesting. Of course there's no way to
"house-sync"
> > it,
> > but it might be useful for cleaning up old, wavy VHS output.
>
> Don't confuse digitization with temporal compensation.

Why not? TBCs temporally compensate by digitizing the image and reclocking
it out with a stable sync.

 

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"FLY135" wrote ...

> "Richard Crowley" <rcrowley7@xprt.net> wrote in message

>> Don't confuse digitization with temporal compensation.
>
> Why not?

Because they are independent functions.

> TBCs temporally compensate by digitizing the image and
> reclocking it out with a stable sync.

Yes, they do. But not every video A/D converter does inter-
line (and even intra-line) adjustment of the sample points as
a TBC does. In fact, *only* the A/D converters in TBCs act
that way. Perhaps you are confused because with a reasonably
clean video signal you can get away without TBC functionality.

 

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"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:10re6rrsq7cvi44@corp.supernews.com...
> "FLY135" wrote ...
>
> > "Richard Crowley" <rcrowley7@xprt.net> wrote in message
>
> >> Don't confuse digitization with temporal compensation.
> >
> > Why not?
>
> Because they are independent functions.
>
> > TBCs temporally compensate by digitizing the image and
> > reclocking it out with a stable sync.
>
> Yes, they do. But not every video A/D converter does inter-
> line (and even intra-line) adjustment of the sample points as
> a TBC does. In fact, *only* the A/D converters in TBCs act
> that way. Perhaps you are confused because with a reasonably
> clean video signal you can get away without TBC functionality.
>
>

Yes, you could digitize video with a clock frequency that is not related to
the incoming video, but I don't think you could do mpeg conversion without
the clock locked to the incoming video. If the A/D clock was not related to
incoming video, then the video from line to line and field to field woud not
be aligned and mpeg encoding would be very difficult. I believe the A/D
conversion for these DVD recorders would provide a form of TBC. The real
question is how they handle compressed sync and tape drop-outs and other
noise problems that we had to try to accept when designing TBC's.

Most devices that digitize the video do not try to correct for line to line
step errors as this is not usually a problem with most video sources. This
is why that it takes several lines of video to correct for the head switch
step error in the VHS playback.

Mike T

 

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Richard Crowley wrote:

>> TBCs temporally compensate by digitizing the image and
>> reclocking it out with a stable sync.

> Yes, they do. But not every video A/D converter does inter-
> line (and even intra-line) adjustment of the sample points as
> a TBC does. In fact, *only* the A/D converters in TBCs act
> that way. Perhaps you are confused because with a reasonably
> clean video signal you can get away without TBC functionality.

What would you define as TBCs? For instance, many, many, many cheap PC
video capture cards are based on the Conexant (formerly Brooktree) BT878
chip. This chip has something called Ultralock(TM), a marketing name for
a feature which practically means that the card may internally capture a
variable number of samples for each scanline, then rescale/interpolate
them on the fly (or whatever is needed) to get them to the target
sampling rate. This is done specifically to combat the problem of
digitizing from unstable sources such as VHS VCRs. Sounds a lot like a
TBC to me.

--
znark

 

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"Jukka Aho" <jukka.aho@iki.fi> wrote in message
news:n5yud.57$lk6.13@reader1.news.jippii.net...
> Richard Crowley wrote:
>
>>> TBCs temporally compensate by digitizing the image and
>>> reclocking it out with a stable sync.
>
>> Yes, they do. But not every video A/D converter does inter-
>> line (and even intra-line) adjustment of the sample points as
>> a TBC does. In fact, *only* the A/D converters in TBCs act
>> that way. Perhaps you are confused because with a reasonably
>> clean video signal you can get away without TBC functionality.
>
> What would you define as TBCs? For instance, many, many, many cheap PC
> video capture cards are based on the Conexant (formerly Brooktree) BT878
> chip. This chip has something called Ultralock(TM), a marketing name for a
> feature which practically means that the card may internally capture a
> variable number of samples for each scanline, then rescale/interpolate
> them on the fly (or whatever is needed) to get them to the target sampling
> rate. This is done specifically to combat the problem of digitizing from
> unstable sources such as VHS VCRs. Sounds a lot like a TBC to me.

I would call that "TBC-like functionality" Certainly a very nice
feature useful to people capturing from lousy VHS sources, etc.
Clearly a step above crystal-locked sampling rate of a simple
A/D converter.

 

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Richard Crowley wrote:

>> What would you define as TBCs? For instance, many, many, many cheap
>> PC video capture cards are based on the Conexant (formerly
>> Brooktree) BT878 chip. This chip has something called Ultralock(TM),
>> a marketing name for a feature which practically means that the card
>> may internally capture a variable number of samples for each
>> scanline, then rescale/interpolate them on the fly (or whatever is
>> needed) to get them to the target sampling rate. This is done
>> specifically to combat the problem of digitizing from unstable
>> sources such as VHS VCRs. Sounds a lot like a TBC to me.

> I would call that "TBC-like functionality" Certainly a very nice
> feature useful to people capturing from lousy VHS sources, etc.
> Clearly a step above crystal-locked sampling rate of a simple
> A/D converter.

What additional features would you require to the above for being able
to call it a true TBC?

--
znark

 

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"Jukka Aho" <jukka.aho@iki.fi> wrote in message
news:yENud.261$b84.160@reader1.news.jippii.net...
> Richard Crowley wrote:
>
>>> What would you define as TBCs? For instance, many, many, many cheap
>>> PC video capture cards are based on the Conexant (formerly
>>> Brooktree) BT878 chip. This chip has something called Ultralock(TM),
>>> a marketing name for a feature which practically means that the card
>>> may internally capture a variable number of samples for each
>>> scanline, then rescale/interpolate them on the fly (or whatever is
>>> needed) to get them to the target sampling rate. This is done
>>> specifically to combat the problem of digitizing from unstable
>>> sources such as VHS VCRs. Sounds a lot like a TBC to me.
>
>> I would call that "TBC-like functionality" Certainly a very nice
>> feature useful to people capturing from lousy VHS sources, etc.
>> Clearly a step above crystal-locked sampling rate of a simple
>> A/D converter.
>
> What additional features would you require to the above for being able to
> call it a true TBC?

The traditional standalone TBC functionality/adjustment
features as on any commercial unit. And frequently TBCs/
framesync units include proc amp functionality thrown in
for grins.

But I'm from the old school where video started out long
before computers were ever dreamed of for video processing.

 

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Richard Crowley wrote:

>> What additional features would you require to the above for being
>> able to call it a true TBC?

> The traditional standalone TBC functionality/adjustment
> features as on any commercial unit.

I am not familiar with those. Could you please enlighten me and name
some examples of the most important ones? Or is there a web site
somewhere where I could learn more about it?

> And frequently TBCs/framesync units include proc amp functionality
> thrown i for grins.

I believe many of the cheap PC video decoder/digitizer chips - such as
the aforementioned BT878 [1] - have various adjustments: coring, gain
for Y, Cb and Cr channels separately (contrast and saturation), hue,
brightness, adjustable filters (notch, low-pass etc.), some switchable
and adjustable AGC functionality, adjustable gamma correction,
switchable comb filter etc. Probably not in any way up to the standards
of a professional proc amp, but still - these commonly used cheap chips
are not your simple, straightforward run-of-the-mill A/D converters any
more, either.

Also note that any functionality which does not serve the main purpose
of these chips - of being able to capture and digitize the active area
of the signal the best way possible - is left out. These are not meant
to be part of a video processing chain, but at the very end of the
chain, and the "end product" is captured, digitized images of the active
area. Everything else (areas of vertical and horizontal blanking in the
signal) is discarded in the end [2], and not retained, since that
information is not needed.

_____

[1] A data sheet / register reference for BT878 can be downloaded here:
<http://www.conexant.com/products/entry.jsp?id=404> (100119A.pdf).

[2] An exception: some chips may have a Teletext or CC decoder as well,
in which case you may retain this (decoded) data if you will.

--
znark

 

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"Jukka Aho" wrote ...
> I am not familiar with those. Could you please enlighten me and name some
> examples of the most important ones? Or is there a web site somewhere
> where I could learn more about it?

There is likely more information out on the internet than you care
to read. I don't feel compelled to promote or support timebase
correctors, I just use them when necessary. I only entered this
conversation to correct the misconception that any A/D conversion
is synonymous with timebase correction.

 

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Richard Crowley wrote:

> I only entered this conversation to correct the misconception
> that any A/D conversion is synonymous with timebase correction.

I don't see that particular statement expressed in this thread.
Do you?

--
znark

 

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"Jukka Aho" <jukka.aho@iki.fi> wrote in message
news:0WYud.378$ok2.101@reader1.news.jippii.net...
> Richard Crowley wrote:
>
>> I only entered this conversation to correct the misconception
>> that any A/D conversion is synonymous with timebase correction.
>
> I don't see that particular statement expressed in this thread.
> Do you?

Yes. The subject line and the very first posting.

 

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Richard Crowley wrote:

>>> I only entered this conversation to correct the misconception
>>> that any A/D conversion is synonymous with timebase correction.

>> I don't see that particular statement expressed in this thread.
>> Do you?

> Yes. The subject line and the very first posting.

I don't see that being said in the first post or on the subject line,
either. I think you are reading too much into it.

--
znark

 

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"Jukka Aho" <jukka.aho@iki.fi> wrote in message
news:R4%ud.422$oF6.226@reader1.news.jippii.net...
> Richard Crowley wrote:
>
>>>> I only entered this conversation to correct the misconception
>>>> that any A/D conversion is synonymous with timebase correction.
>
>>> I don't see that particular statement expressed in this thread.
>>> Do you?
>
>> Yes. The subject line and the very first posting.
>
> I don't see that being said in the first post or on the subject line,
> either. I think you are reading too much into it.

If we encourage the thought that anything that does A/D
conversion is a TBC, then what do we call A/D conversion
that does NOT have TBC functionality? It is called dilution
of meaning. (In any language.) We clearly read the OP
differently.

 

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In article <3T7vd.622$Or5.464@reader1.news.jippii.net>,
"Jukka Aho" <jukka.aho@iki.fi> writes:
> Richard Crowley wrote:
>
>> If we encourage the thought that anything that does A/D
>> conversion is a TBC,
>
> My take on this question is: yes, these days most digital video
> recorders with analog inputs are likely to have TBC(-alike)
> functionality, effectively making them TBC's of some sort. Why is this
> so?
>
One note -- my D9 decks DO NOT LIKE UNSTABLE VIDEO!!! They use
straightforward DV25-like technology (but multiplied by two), and
even LD isn't stable enough for them!!! (Well, if I am very
careful and don't disturb the LD player, then it works okay (usually.))

The only way that I can record from LD to D9 is to use a TBC (DPS290).

John

 

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Richard Crowley wrote:

> If we encourage the thought that anything that does A/D
> conversion is a TBC,

No such thought was expressed. The original poster asked "Are standalone
DVD Recorders effectively TBCs" [for the purposes of digitizing video
before storing it on the disc, or recording through the device]. He
based this assumption on the looks of static on screen: to him, it
looked similar as if it had been routed through a TBC - but this
observation, despite prompting the original question, was _not_ the gist
of the matter. The gist of the matter is the original question stated on
the subject line: do commonly available stand-alone DVD recorders
generally have TBC-alike synchronizing capabilities? Can TBC-alike
functionality be reasonably expected from them?

My take on this question is: yes, these days most digital video
recorders with analog inputs are likely to have TBC(-alike)
functionality, effectively making them TBC's of some sort. Why is this
so? Because inexpensive video decoder/digitizer chips with built-in
line-by-line synchronization and reclocking (such as the BT878 with its
Ultralock(TM) capability mentioned earlier in the thread) have been
available for a long time now. These kind of chips are mature technology
already; over the last few years, they have been used on myriads of
ordinary cheap tv tuner / video capture cards. As such, it is in no way
implausible that they would also have found their way inside consumer AV
devices, such as DVD recorders, as a standard - or at least semi -
standard - feature.

And actually, they have: Some Sony consumer DV/D8 camcorders with
analog-in functionality (video digitizing through the analog terminals)
are even _advertised_ as having a TBC:

<http://www.gearpreview.com/film/digi8/trv350.html>

<http://www.220-electronics.com/camcorder/sonydcrtrv320.htm>

Finally, Googling a bit more reveals there are dozens of DVD recorders
that claim TBC functionality:

<http://www.unbeatable.co.uk/CatalogueItem_17593.html>

<http://www.av-sales.com/html/panasonic_dmr-e55ebs.html>

<http://www.plasma.com/dvdrecorders/DMRE100HS.htm>

<http://www.rcaaudiovideo.com/Cultures/en-US/ModelDetail.html?PCI=DVD+Recorders&ProductID=DRC8040N>

<http://www.pioneerelectronics.com/pna/product/detail/0,,2076_4139_98124086_tab=B,00.html>

<http://www.tacp.toshiba.com/dvd/product.asp?model=d-r2>

<http://www.sonystyle.com/is-bin/INTERSHOP.enfinity/eCS/Store/en/-/USD/SY_DisplayProductInformation-Start?ProductSKU=RDRVX500&Dept=hav&CategoryName=hav_DVD_DVDPlayers#specs>

<http://www.sonystyle.com/is-bin/INTERSHOP.enfinity/eCS/Store/en/-/USD/SY_DisplayProductInformation-Start?ProductSKU=RDRHX900&Dept=hav&CategoryName=hav_DVD_DVDPlayers#specs>

It seems it is kind of a standard feature by now.

To add the icing on the cake, the OP's own DVD recorder, Panasonic
DMR-E20, seems to be advertised as having TBC too:

<http://www.dvnation.com/dmrspecs.html>

It says, and I quote:

--- 8< ---

More detailed specs for the Pioneer DVR-7000 DVD Recorder

[...]

Improved Video Quality in Analog-to-Digital Transfer

* Input TBC, 3D Y/C separation circuitry, and 3D digital noise reduction
are particularly effective when recording from analog video sources such
as conventional VHS or S-VHS VCRs. Input TBC is a built-in time base
corrector that delivers highly stable, natural images. The 3D Y/C
Separation Circuitry minimizes the dot crawl and color smearing caused
by interference between the video signal's Y and C color subcomponents.
And, 3D Digital Noise Reductioneffectively removes noise components from
the signal during playback.

--- 8< ---

> then what do we call A/D conversion that does NOT have TBC
> functionality?

Why would we want to discussa plain A/D conversion without TBC
functionality (much less invent new names for it) as the devices which
the original poster asked about - including his _own_ DVD recorder -
_do_ seem to have TBC functionalty?

--
znark

 

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John S. Dyson wrote:

>> these days most digital video recorders with analog inputs
>> are likely to have TBC(-alike) functionality, effectively
>> making them TBC's of some sort.

> One note -- my D9 decks DO NOT LIKE UNSTABLE VIDEO!!!

I should have added "consumer-level" somewhere between the words "most"
and "digital". My bad.

If you buy professional gear (such as D9), all bets are off. They
probably don't think a simple consumer-level, non-user-adjustable TBC
solution would suffice your needs at that level, and expect you to have
a separate TBC unit somewhere in your toolchain, anyway. (Or maybe they
would like to _sell_ you one separately.

--
znark

 

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In article <8k9vd.628$wB.110@reader1.news.jippii.net>, Jukka Aho wrote:
> If you buy professional gear (such as D9), all bets are off. They
> probably don't think a simple consumer-level, non-user-adjustable TBC
> solution would suffice your needs at that level, and expect you to have
> a separate TBC unit somewhere in your toolchain, anyway. (Or maybe they
> would like to _sell_ you one separately.

Maybe he should put his D9 on the other side of a consumer DVD recorder
from his LD and see how it records. 8^)

....Sean.