On Friday 01 February 2008 18:26, Alberto Hernando wrote:
> Hi.
>
> I have a dvb related question. Not directly related to freevo, but,
> depending on the answer, it might be in the future. I'm doing this question
> here because some people might now and, who knows, depending on the country
> it might be important.
>
> My question is about dvb-t, the standard behind digital terrestril tv, the
> new tv in Europe. In every analog channel, there is a stream containing up
> to 4 digital channels (that is, audio+video, what you see), and perhaps
> some data or some more audio channels. It is an mpeg2 strean, and the cards
> used in computers can tune a channel, extract the stream and decode it. So,
> the question:
>
> What if the stream isn't in mpeg2 but in mpeg4 (for example)? I think that,
> at least in Spain, some tests have been done to increase quality with the
> same bitrate. What I want to know is if the same cards will work in this
> case. Will they still capture the stream and let the cpu (mplayer rocks)
> decode it? Or the signal will just be ignored? The modulation won't change,
> so the card should see the signal and, at least, the receiver should see
> the bitstream, but if someone knows for sure, I'd like to know. It would be
> great to know that even if dvb-t changes this, we won't need a new
> receiver.
>
> Alberto
>
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Hi,
I don't know about all the DVB cards, but according to what I know about the
mpeg2 definition, there is quite a difference between the transport stream
and the elementary streams. The transport stream of DVB-S/T/C/H should always
refer to the mpeg2 specification. However, the single elementary streams
embedded in such a transport stream can have multiple formats, like mpeg2,
mpeg4, different audio formats and even "private" data formats with special
provider dependend coding (like e.g. the infosat epg). I.e. the mpeg4 only is
about the format of the elementary stream.
A (full featured?) DVB-card seems only to do the tuning into one transponder
(bouquet) and (maybe) filter which elementary streams to send (by the id of
the elementary stream). The decoding of these elementary streams is done by
software like mplayer.
At the end, I am pretty sure that mplayer can play this.
On the other hand, there is HDTV (where I do not really believe that HDTV is
transmitted via DVB-T). It seems that for HDTV, a higher bandwidth is used
and you need special receivers.
Just my 2c...
Regards,
Thorsten
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