[linux-dvb] DVB-T card for PCI-X + Digital-RADIO-Linux-Questions

Jon Burgess jburgess at uklinux.net
Sat Oct 1 02:07:49 CEST 2005

Christoph Anton Mitterer wrote:
> What do you mean with "these kinds of cards",.. what other kinds of 
> cards are there?

Budget vs full-featured. The budget card has a tuner which provides the 
MPEG transports stream for software to decode and display. A full 
featured card has the same hardware as a budget card but also includes 
an embedded CPU and firmware on the card to decode the MPEG and send it 
to a TV-out connector on the card. This might be a helpful introduction

> And does this now mean,.. that those feature are only 
> boradcaster/software dependant?

The MPEG transport stream is very flexible any allows an almost infinite 
combination of multiple audio, video and other data streams.
- stereo audio
- 5.1 audio
- Standard definition video
- Other digital data e.g. electronic program guide.
... plus many more things.

All the above depend on the broadcaster sending the appropriate 
transmission and you having the appropriate software capable of decoding 
the stream.

> Uhm,.. if PCI/PCI-X bus is enough for the amount of data,.. I'd prefer 
> this in favour of PCIe (because I could save the PCIe for a 2nd videocard).

The data rate for a full transport stream from a budget card is in the 
order of ~30 Mbit/s. For a rough theorectical comparison USB2 manages 
480Mbit/s, PCI ~1000Mbit/s (=132MByte/s). PCI-X and PCIe go even faster. 
As you can see, a budget card going flat out doesn't begin to stretch 
them. You could attach multiple devices to a single USB2 port using a 
hub without wasting a single PCI clot.

> What other non-DVB-T-features could such a card have?

Some cards also include a composite / S-video analog input to allow 
recording from something like an analog camcorder. These streams tend to 
be a much higher data rate because they are uncompressed.


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