Video ADC...

[Clifford Heath]

<https://www.cirrus.com/products/wm8234/>

Why make a 16-bit ADC that only has circa 8-10-bit linearity? I mean
granted, video doesn\'t need much linearity, but then video doesn\'t need
16 bits either.

See Page 8, Differential/integral non-linearity,

Or am I reading the data sheet wrongly?

There has to be some quid pro quo for a sub-$20 chip that claims 70MSPS
and 16 bits, given that the nearest similar credible chips are over $100
from TI or Linear/AD. But still...

I\'m a bit shy of Cirrus anyway given the propensity of their audio ADCs
to randomly melt after 12 months continuous use, unrelated to any actual
abuse. We had some in a fleet of SoftRock SDRs and got tired of
replacing the chips after the third time. The entire fleet dies at
around 12-14 months.

Clifford Heath.

 

[Clifford Heath]

On 11/04/23 15:51, Clifford Heath wrote:

I\'m a bit shy of Cirrus anyway given the propensity of their audio ADCs
to randomly melt after 12 months continuous use

Ahh wait, I maligned Cirrus unnecessarily. It\'s the C-Media ADCs that melt.

Is AKM back from the dead yet?

 

[Phil Hobbs]

On 2023-04-11 03:01, Clifford Heath wrote:

On 11/04/23 15:51, Clifford Heath wrote:
I\'m a bit shy of Cirrus anyway given the propensity of their audio
ADCs to randomly melt after 12 months continuous use

Ahh wait, I maligned Cirrus unnecessarily. It\'s the C-Media ADCs that melt.

Is AKM back from the dead yet?

My #2 daughter works for Cirrus in Austin. I\'m generally a fan of theirs.

It looks like the strange ADC is meant to be run mostly in 10-bit mode,
which as you say is generally lots for video.

It also runs CID chips, though, which are mostly used in machine vision
and other such applications, where there are lots of bright glints and
where blooming is very bad news. (CCDs tend to dump charge into a whole
line of pixels when one gets overdriven.)

CIDs work oppositely to CCDs: the wells start out full, and the
photocurrent empties them. Thus there\'s no blooming.

So the extra bits may be intended for things such as flat-fielding,
where you want to do a bunch of averaging to get lower noise. (You
compute the gain and offset frames occasionally, and then use them for
many data frames, so calibration errors give rise to fixed-pattern noise.)

Or it may have been a design blunder that didn\'t affect the main
operation of the chip and so wasn\'t worth fixing.

I agree that it\'s weird, though.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[server]

On Fri, 14 Dec 2012 18:36:52 +0100, h200 <hubler@net.com> wrote:

On 12/14/2012 05:37 PM, Mike Perkins wrote:
On 14/12/2012 14:20, h200 wrote:
Hi.

I\'m planning to build one simple schematics / device which will convert
analog video signal to digital. The analog video signal comes from
camera over bnc and it has PAL / RGB format.

Do you mean PAL or RBG format? Most cameras produce composite video ie
PAL or NTSC and not RGB.

If the former there are many cheap decoders. Digkey has the TVP5150 at
£4.47 for one-off though I have never used it. I currently use a
Techwell TW9900.

Decoders accepting RGB inputs are less common, probably since they
require 2 ADCs like the ones you mention.



Could this kind of chip do the job :

http://www.ti.com/lit/gpn/tvp7000

or

http://www.analog.com/en/analog-to-digital-converters/video-decoders/adv7181c/products/product.html#product-samples



---------------
You are correct, PAL is mostly used and I will take this as base.
I was thinking to take any analog camera, maybe some cctv camera,
connect the BNC output of this camera to my portable device and transfer
the data over rf. Maximum distance is around 20 meters.

Camera --> video ADC ---> RF transfer ---> video DAC ----> monitor/ TV.

Is this an outdoor or indoor application ?

If outdoor condition and such short distance a simple analog system
will do. Just get base band composite video and feed it to an
FM-modulator. For reception get an old analog satellite-TV receiver.

However, if this is an indoor application, the reflections from the
walls will cause a lot of multi path (ghosting),

With some primitive digital signal with much higher bit rates, the
nultipath is going to be a severe issue. You might have to feed the
digital data stream into a DVB-T modulator and receive it with a DVB-T
tuner (available as USB sticks).

DVB-T with suitable parameters is very robust against multipath.

I can not use USB because this should be some kind of camera adapter an
it has to be portable.

TW9900 looks like very good solution.
What do you think, can i use it in my project ?

 

[DemonicTubes]

On Tuesday, April 11, 2023 at 11:28:23 AM UTC-6, upsid...@downunder..com wrote:

On Fri, 14 Dec 2012 18:36:52 +0100, h200 <hub...@net.com> wrote:

On 12/14/2012 05:37 PM, Mike Perkins wrote:
On 14/12/2012 14:20, h200 wrote:
Hi.

I\'m planning to build one simple schematics / device which will convert
analog video signal to digital. The analog video signal comes from
camera over bnc and it has PAL / RGB format.

Do you mean PAL or RBG format? Most cameras produce composite video ie
PAL or NTSC and not RGB.

If the former there are many cheap decoders. Digkey has the TVP5150 at
£4.47 for one-off though I have never used it. I currently use a
Techwell TW9900.

Decoders accepting RGB inputs are less common, probably since they
require 2 ADCs like the ones you mention.



Could this kind of chip do the job :

http://www.ti.com/lit/gpn/tvp7000

or

http://www.analog.com/en/analog-to-digital-converters/video-decoders/adv7181c/products/product.html#product-samples



---------------
You are correct, PAL is mostly used and I will take this as base.
I was thinking to take any analog camera, maybe some cctv camera,
connect the BNC output of this camera to my portable device and transfer
the data over rf. Maximum distance is around 20 meters.

Camera --> video ADC ---> RF transfer ---> video DAC ----> monitor/ TV.
Is this an outdoor or indoor application ?

If outdoor condition and such short distance a simple analog system
will do. Just get base band composite video and feed it to an
FM-modulator. For reception get an old analog satellite-TV receiver.

However, if this is an indoor application, the reflections from the
walls will cause a lot of multi path (ghosting),

With some primitive digital signal with much higher bit rates, the
nultipath is going to be a severe issue. You might have to feed the
digital data stream into a DVB-T modulator and receive it with a DVB-T
tuner (available as USB sticks).

DVB-T with suitable parameters is very robust against multipath.
I can not use USB because this should be some kind of camera adapter an
it has to be portable.

TW9900 looks like very good solution.
What do you think, can i use it in my project ?

You are replying to a post from over 10 years ago!

 

[Clifford Heath]

On 11/04/23 23:54, Phil Hobbs wrote:

On 2023-04-11 03:01, Clifford Heath wrote:
On 11/04/23 15:51, Clifford Heath wrote:
I\'m a bit shy of Cirrus anyway given the propensity of their audio
ADCs to randomly melt after 12 months continuous use

Ahh wait, I maligned Cirrus unnecessarily. It\'s the C-Media ADCs that
melt.
My #2 daughter works for Cirrus in Austin.  I\'m generally a fan of theirs.

It looks like the strange ADC is meant to be run mostly in 10-bit mode,
which as you say is generally lots for video.

Thanks for your thoughtful response Phil.

I guess I could ask Cirrus. But I wonder if your daughter might be more
likely to get an honest answer, if you feel you could request that?

> I agree that it\'s weird, though.

Clifford Heath

 

[Rich S]

On Friday, April 14, 2023 at 3:45:20 AM UTC, Clifford Heath wrote:

On 11/04/23 23:54, Phil Hobbs wrote:
On 2023-04-11 03:01, Clifford Heath wrote:
On 11/04/23 15:51, Clifford Heath wrote:

It looks like the strange ADC is meant to be run mostly in 10-bit mode,
which as you say is generally lots for video.

10-bit processing isnt peculiar at all for standard 8-bit video
signals (ITU Rec 709, etc), since some LSB errors may accumulate
with subsequent signal processing (which there will be, much of,
in typical consumer video products). Moreso, HDR or High-
dynamic range, video products & content are in the marketplace
associated with \"4K\" UHD TV, where 10-bit video is the standard
(ITU Rec 2020). So > 10bit digital video is internal to the product.

Almost all 4K UHD TVs claim HDR capability (10-bit disaplys, >1000:1
contrast ratios), but still fall short (mostly because of low luminance
output range, rather than visible D/A artifacts.)

regards, RS

 

[Clifford Heath]

On 15/04/23 10:39, Rich S wrote:

On Friday, April 14, 2023 at 3:45:20 AM UTC, Clifford Heath wrote:
On 11/04/23 23:54, Phil Hobbs wrote:
On 2023-04-11 03:01, Clifford Heath wrote:
On 11/04/23 15:51, Clifford Heath wrote:

It looks like the strange ADC is meant to be run mostly in 10-bit mode,
which as you say is generally lots for video.

10-bit processing isnt peculiar at all for standard 8-bit video
signals (ITU Rec 709, etc), since some LSB errors may accumulate
with subsequent signal processing (which there will be, much of,
in typical consumer video products). Moreso, HDR or High-
dynamic range, video products & content are in the marketplace
associated with \"4K\" UHD TV, where 10-bit video is the standard
(ITU Rec 2020). So > 10bit digital video is internal to the product.

Almost all 4K UHD TVs claim HDR capability (10-bit disaplys, >1000:1
contrast ratios), but still fall short (mostly because of low luminance
output range, rather than visible D/A artifacts.)

Yes. The real question is why are there 16 bits, and how many of them
can you actually use? I\'m not interested in video, but inexpensive SDR.

Clifford Heath