Hi, Comments on DVB in general: On Tue, 22 Jan 2002, Brian J. Murrell wrote: > I use mpeg1 to but at 320x240 due to my standard being NTSC over here. > I do want to jump to 640x480 using mp1e (FFMPEGrec cannot capture > 640x480 on my Athlon TB 800, mp1e does it at less than 50% CPU!) but > it is still causing me problems. As you know, I used to use mp1e with good results except for a gradual drift of AV sync. I changed to FFMPEGrec with some patches now because that gives really solid sync. I'd prefer to use MP1Erec but the MP1E library interface has lockup problems with the interface that Justin uses for NVrec. > The latest is mp1e locking up and > not writing the file anyomre. There is a fix checked in that I have > to test still though. Perhaps this fix will sort out MP1Erec - did you ask Justin Schoeman to try it out? > OK. I have been thinking about DVB. From what I understand and you > seem to be confirming... that what you actually receive from the > broadcast source is an MPEG2 compressed stream. This is sweet. Way > nicer than having to receive uncompressed and then compress one's > self. Fundamentally DVB sends an MPEG2 transport stream over the air. The principle is the same for cable, over the air and satellite (though details of modulation vary). Within the transport stream are multiplexed various different streams - several video streams, one or more audio tracks for each video stream, teletext etc. Some special streams provide info on what is what, programs showing now and next and suchlike. Streams can be encrypted. Some DVB cards provide an interface to a so-called "CAM", which will decrypt a particular encryption with the help of a smart card containing decrypt keys. Within the UK DVB is used for all of terrestrial, cable and satellite. But only terrestrial, as far as I know, provides unencrypted content. The cable and satellite broadcasters do not provide CAMs for their encryptions: you must use their closed receiver boxes. > So DVB is the "digital" interoperable standard which broadcasters and > receivers can transfer MPEG2 streams right? So if one's provider is > DVB compliant, one can go out and buy any old DVB compliant "cable > converter" and not have to buy the one the provider rents or sells > you. Well - read all that about encryption. You'll need to research whether your cable provider uses standard DVB, and whether they encrypt. If they do, is a CAM available? > Would I be correct in parallelizing that situation to the status of > DVB right now? Soon(ish) televisions (and other devices, like capture > cards, one of which you seem to have now) will be created following > the DVB standard and therefore will work on any DVB compliant > provider? Yes - DVB is a standard. However - encryption may be used may limit your ability to decode on an open platform. In the UK you can already buy television sets with integrated DVB decoders, by the way. The BBC and others are promoting a migration to digital transmission, though BSkyB, the main multi-channel satellite provider in the UK, are winning majority market share with a "DVB-based but closed through encryption" platform. > It sure seems like the right way to go. Get the compressed stream > from the source and save it as you get it instread of everybody from > source to destination doing their own compression and decompression. Yes - I like the quality and simplicity very much. > How big is an hour of DVB MPEG2? Various rates are used depending on the channel. In the UK rates are adjusted depending on the content. Say 4 up to 15 Mbits/sec. Hope that helps, Steve
