DVB-S & DVB-T Questions

[Mahoney]

Hi All,

I *think* I've got a handle on DVB-S and how it works, but I'd really appreciate it if some knowledgeable person could confirm my understanding and/or point me at a really good source of info - I seem to have been reading and googling on this for days now and I'm still not 100%.

My understanding is that both DVB-S and DVB-T transmit MPEG Transport Streams over Multiplexes. Sound right?

My understanding is that a single Multiplex contains a single Transport Stream. Sound right?

My understanding is that a single Transport Stream can contain multiple Program Streams (and other data). Sound right?

My understanding is that a single "tuner" DVB-S or DVB-T capture card can only tune to a single multiplex and so can only make a single Transport Stream available to software at a time. Sound right?

I do not know whether dual (or more) tuner DVB-S or DVB-T cards exist - does anyone? If they don't, does anyone know if they are in the pipeline?

Does anyone know if multiple DVB-S cards can be supported in a single system? Can they use the same Common Interface, and hence the same CAM?

Does anyone have a recommendation for DVB-S and DVB-T cards? At the moment I'm leaning towards the Hauppuage Nexus-S and the BlackGold DVB-T tuners, but more on gut instinct than anything else!

I *presume* that an existing DVB-S card can happily receive MPEG-4 HDTV Program Streams (and deencrypt them with a CAM if an appropriate CAM exists). Is that a reasonable assumption?

I presume that the Universal Network Encode can work with basically any DVB-S or DVB-T card as they will all make the digital stream available to graph edit or whatever it is called. Is this true?

Grateful if someone could confirm or deny these qestions, as I'm really struggling to get the necessary info on this.

[Mahoney]

OK, I might be getting a litle bit further...

My current understanding is that a Satellite dish receives a vast quantity of data and uses an LNB to pick a particular bit of that data to return to the receiver. I presume then that the receiver can tell the dish which LNB to use. I think you have one multiplex (and so one transport stream) per LNB. So a receiver can only get one transport stream at a time. Am I close?

So I would need a dual receiver, and a dish that can apply more than one LNB at a time, to get two transport streams at the same time. Right? Or am I still confused?

[insomniac]

I will answer the ones that I know

I did quite a bit of reading, and found that for what I wanted, the SS2 was the best card for me. Software , but works great with SDVBREcorder

UNE is only necessary for HDTV tuners, although they are essentially the same thing. SDVBrecorder (by Anders) is specifically for DVB (for DVB-s, you would use Yoja's version).


I.

Originally Posted by Mahoney

Does anyone have a recommendation for DVB-S and DVB-T cards? At the moment I'm leaning towards the Hauppuage Nexus-S and the BlackGold DVB-T tuners, but more on gut instinct than anything else!


I presume that the Universal Network Encode can work with basically any DVB-S or DVB-T card as they will all make the digital stream available to graph edit or whatever it is called. Is this true?

.

[insomniac]

Ok, I wil take a stab at this too...

If you use dishpro, it supports Bandstacking. Therefore allowing for multiple transport streams. I have 3 devices sharing 2 LNB's without issue. This is done with a DP34 switch.

did that help?

Originally Posted by Mahoney

OK, I might be getting a litle bit further...

My current understanding is that a Satellite dish receives a vast quantity of data and uses an LNB to pick a particular bit of that data to return to the receiver. I presume then that the receiver can tell the dish which LNB to use. I think you have one multiplex (and so one transport stream) per LNB. So a receiver can only get one transport stream at a time. Am I close?

So I would need a dual receiver, and a dish that can apply more than one LNB at a time, to get two transport streams at the same time. Right? Or am I still confused?

[Mahoney]

If you use dishpro, it supports Bandstacking. Therefore allowing for multiple transport streams. I have 3 devices sharing 2 LNB's without issue. This is done with a DP34 switch.

did that help?

Not sure :grin:. Does that mean you have 3 separate PCI cards in your system? Each able to record a separate transport stream?

I'm basically trying to understand what the limitations are in satellite TV. Most PCI cards are trying to tell me I can only record two shows (or more) at once if they are on the same transponder, and a transponder seems to carry a single MUX with a single Transport Stream from a single LNB. So if I want to record a show from one transponder at the same time as a show from a different transponder, I presume I need two PCI DVB-S cards? Or does bandstacking offer a route round this limitation with a single card? If not, can you have two PCI DVB-S cards in the same system?

What if I want to get legitimate encrypted content via a legit smart card in a CAM in a CI, and the provider uses two transponders - can two separate PCI DVB-S cards share a CI, so I can record channels from both transponders at the same time?

I can't find answers to these questions anywhere! Perhaps I just haven't understood enough to ask the right questions. I'm a total beginner at satellite digital TV.

[insomniac]

Nope, my other devices are dish IRD's. I capture the content from them via svideo to pvr250's.

im not sure, but there may be a limitation on how many dvb cards that can go in a machine, but if there was, im sure its just a driver issue. search the sdvbrecorder thread on this. I believe foolio might have more than one working together. there is no limitation on regular capture cards per machine. I have 7 in my server now.

in short, one card=one recording,2 cards=2 recordings, and so on. Bandstacking only allows you to be able to get more than one stream from the same lnb/transponder.


EDIT:

"Most PCI cards are trying to tell me I can only record two shows (or more) at once if they are on the same transponder"

nope, unless ive been missing out on a great thing, each card can only capture one stream at a time. Hence my above interpretation.
I.

[Mahoney]

"Most PCI cards are trying to tell me I can only record two shows (or more) at once if they are on the same transponder"

nope, unless ive been missing out on a great thing, each card can only capture one stream at a time. Hence my above interpretation.

I'm pretty sure on this one - an MPEG-2 Transport Stream can carry multiple Program Streams, and since it is the transport stream you are getting from the DVB-S card you can simply record that and then demux it to get the individual program streams out. Of course, it depends on the channels on that transponder being ones you want! And it depends on the software you are using.

[Mahoney]

Incidentally, some more Googling suggests that a CAM can only operate on one program stream at a time, so for each encrypted program stream you wanted to record you would need a separate CAM. .

[insomniac]

It would of been a shot in the dark anyway...

Originally Posted by Mahoney

Incidentally, some more Googling suggests that a CAM can only operate on one program stream at a time, so for each encrypted program stream you wanted to record you would need a separate CAM. .