bitstream encoder to RF modulator (ATSC/8-VSB)

Archived from groups: alt.tv.tech.hdtv (More info?)

In analog, the normal input to an RF modulator would a baseband
video input (75 ohm), and 1 or 2 audio inputs (various impedance).
Digital adds a new twist because there is a digital step added.
What I am interested in finding is what is used to pass the digital
bit stream from the encoder/multiplexer (after the R-S encoding is
included) to the RF modulator (before Trellis encoding, etc).

Is there any chance this "baseband ATSC" would become the new form
of baseband for digital TVs? Or would it be done strictly by things
like SDI and SDI/HD?

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------

Archived from groups: alt.tv.tech.hdtv (More info?)

On Fri, 05 Aug 2005 03:50:23 GMT numeric <numeric@att.net> wrote:

| phil-news-nospam@ipal.net wrote:
|> In analog, the normal input to an RF modulator would a baseband
|> video input (75 ohm), and 1 or 2 audio inputs (various impedance).
|> Digital adds a new twist because there is a digital step added.
|> What I am interested in finding is what is used to pass the digital
|> bit stream from the encoder/multiplexer (after the R-S encoding is
|> included) to the RF modulator (before Trellis encoding, etc).
|>
|> Is there any chance this "baseband ATSC" would become the new form
|> of baseband for digital TVs? Or would it be done strictly by things
|> like SDI and SDI/HD?
|
|
| Not sure what you are asking, but baseband ATSC is contained in a
| bandwidth of 5.38 MHz. I would think that a standard baseband video

Given the bit rate is higher than 19 Mhz, there must be some kind of
baseband symbol coding going on to get the bandwidth under 6 Mhz.
Do you know what it is? Is there a document that describes how they
chose to pass the 19+ Mhz in 5.38 Mhz? Obviously it isn't NRZI.
Are they leaving it multi-level Trellis encoded (that would get down
to almost the bandwidth you mention).


| linear amplifier parameters would also be sufficient for baseband ATSC.
| The bandwidth should be wide enough so that the higher frequencies are
| not attenuated to a point where too much pulse rounding would result.

Of course. How about an amplifier intended for SDI?


| You also have to consider cascaded stages which would have a
| multiplicative effect in the frequency domain. Point to point transfer
| using standard 75 ohm coax would easily handle baseband ATSC. Going one
| step further, a modulated RF ATSC protocol could easily handle all
| current DTV interconnection needs on a single coaxial cable. A DVD

What interconnection needs are you referring to? Just multiple channels
of separate ATSC streams?


| player, as an example, with a modulated an ATSC 8VSB RF output could
| easily interconnect with a simple RF distribution system. Dish Network
| provided an HDTV modulator to interconnect to an 8VSB tuner with their
| 5000 satellite receiver system. Unfortunately, interconnection
| convenience is not what Hollywood wants to permit and Dish Network no
| longer provides or supports the RF digital modulator system for HDTV.

So how do they connect it? (FYI, I don't have Dish Network)

Do any separately purchasable receivers work with Dish Network or Direct TV?

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------

Archived from groups: alt.tv.tech.hdtv (More info?)

In article <dcvniq0i0j@news2.newsguy.com> phil-news-nospam@ipal.net writes:

>Given the bit rate is higher than 19 Mhz, there must be some kind of
>baseband symbol coding going on to get the bandwidth under 6 Mhz.

The bit rate is higher than 19 megabits/second. You have the units
wrong.

>Do you know what it is? Is there a document that describes how they
>chose to pass the 19+ Mhz in 5.38 Mhz?

Yes there is a document that tells how ATSC codes several bits per
Hz of bandwidth. It was easy to find in the specifications for 8-VSB
online.

>Do any separately purchasable receivers work with Dish Network or Direct TV?

Yes.


For both of these, the details are readily available with a quick web
search.


Alan

Archived from groups: alt.tv.tech.hdtv (More info?)

On Sat, 06 Aug 2005 04:17:33 GMT numeric <numeric@att.net> wrote:

| See ATSC a_54a.pdf section 8. This section shows the data bandwidth
| derivation, but is not very clear and can lead to much confusion.
|
| Look at the section for the explanation for the constants. Basically (my
| current understanding) the 5.35 MHz bandwidth is as follows:
|
| The raw data rate is 4.5Mhz/286 * 684 * 3 = 32.287... megabits/second.
| This includes the data overhead of trellis encoding and other overhead.
| Since there is one symbol for 3 databits (3 data bits yield 8 levels,
| hence the 8 in 8VSB)
| the raw data rate = 4.5Mhz/286 * 684 = 10.762.. mega symbols/second
| equation (8.1).
|
| The key is to realize that for every bandwidth cycle there is actually 2
| symbols.
| The data bandwidth then is 4.5Mhz/286 * 684/2 = 5.35.. Mhz.

You're talking about the RF output side. What I am concerned with is
the binary input side ... before the trellis encoder. I want to get
this bit stream from a demodulator, and provide it to a modulator, with
the binary data staying in digital form.

Yes, I could also do this with an RF to IF downconversion, and IF to RF
upconversion. But I want to do things with the binary data, too, such
as storing it, delaying it, etc.


|> | linear amplifier parameters would also be sufficient for baseband ATSC.
|> | The bandwidth should be wide enough so that the higher frequencies are
|> | not attenuated to a point where too much pulse rounding would result.
|>
|> Of course. How about an amplifier intended for SDI?
|
| I assume SDI is standard definition interface?

Serial Data Interface. I have not found a complete specification for it
on the web, but I have found a few articles mentioning some flaws in its
design due to cases of pathological video causing long sequences of 1's
or 0's despite SDI having a CRC scrambler to try and avoid such cases.
I think there is a non-free SMPTE document for it.


| Just a guess, but I would think that a video amplifier with a bandwidth
| of 30 Mhz or more would be sufficent for a baseband ATSC interface.
| Shouldn't matter what definition is transmitted.

For the raw data rate you describe, minimally 17 Mhz would be needed, but
50 Mhz would be needed for nice clean digital transitions. SDI has a much
higher rate since it is uncompressed video.

What I was wondering is if the binary side of an ATSC modulator would use
the same electrical specifications as SDI, but at a lower bit rate.


|> | multiplicative effect in the frequency domain. Point to point transfer
|> | using standard 75 ohm coax would easily handle baseband ATSC. Going one
|> | step further, a modulated RF ATSC protocol could easily handle all
|> | current DTV interconnection needs on a single coaxial cable. A DVD
|>
|> What interconnection needs are you referring to? Just multiple channels
|> of separate ATSC streams?
|
| The output of one device connected into the input of another device will
| reduce the output bandwidth bandwidth in a predictable way. Since you
| mentioned an ATSC baseband interface, connecting devices together might
| be a consideration; ie connecting a DVD to a digital TV via an ATSC
| baseband interface.

If I get raw bit stream out of a demodulator, I should be able to put raw
bit stream back into a modulator. That would work if the bit stream
transport specifications are the same.

Note, I only want to get ATSC down to the bit level ... not deal with raw
video. E.g. a demodulator would leave all video compressed, and a
modulator would require compressed video in.


|> | player, as an example, with a modulated an ATSC 8VSB RF output could
|> | easily interconnect with a simple RF distribution system. Dish Network
|> | provided an HDTV modulator to interconnect to an 8VSB tuner with their
|> | 5000 satellite receiver system. Unfortunately, interconnection
|> | convenience is not what Hollywood wants to permit and Dish Network no
|> | longer provides or supports the RF digital modulator system for HDTV.
|>
|> So how do they connect it? (FYI, I don't have Dish Network)
|
| MY HDTV set included a built in ATSC digital tuner; but no HD component,
| DVI or derivatives of DVI interface for external HD input. This was a
| typical for HDTV sets built about 7 years ago. Dish Network solved the
| interface problem by providing an ATSC HDTV modulator that encoded the
| MPEG data stream from the Dish receiver to an RF digital signal on
| either channel 3 or 4 to the TV antenna connector. The result was a pure
| digital connection from the provider to the TV set.

So although it would not give me what I wanted, they certainly were dealing
with modulating an ATSC compliant signal all the way from MPEG to RF.


|> Do any separately purchasable receivers work with Dish Network or Direct TV?
|
| Yes, but I think that you will only be able to receive channels that are
| not encrypted. I do not have any specific details on receivers.

Unless they have the decryption circuit included and the appropriate key
setup is done through that provider (unless they strictly do that only
through the boxes they provide, which would be annoying if I wanted an
all-in-one box they don't provide).

The really NICE receiver would have, all in ONE BOX, with appropriate ability
to decrypt when subscribed, these:

- OTA analog NTSC
- OTA analog FM radio
- OTA 8-VSB on US channeling
- Cable QAM on US cable channeling (including IRC and HRC)
- DirectTV
- Dishnet
- Sirius radio
- XM radio
- C-band and Ku-band clear and encrypted satellite

or is that too much of a dream?

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------

Archived from groups: alt.tv.tech.hdtv (More info?)

phil-news-nospam@ipal.net wrote:

nonesense snipped.

> - OTA analog NTSC
> - OTA analog FM radio
> - OTA 8-VSB on US channeling
> - Cable QAM on US cable channeling (including IRC and HRC)
> - DirectTV
> - Dishnet
> - Sirius radio
> - XM radio
> - C-band and Ku-band clear and encrypted satellite
>
> or is that too much of a dream?
>

You really are a moron, aren't you?

It's not a dream, it is insane. Name one good reason that the owners of
proprietary formats should support the owners of other proprietary
formats (DiSH and DirecTV, Sirius and XM)

Anyone who knows anything about this industry is having a laughing fit
after reading your post.

Matthew