[opendtv] Re: Confusion about MPEG-4 AVC within MPEG-2 TS
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 11 Feb 2005 16:48:25 -0500
Prashant Desai wrote:
> thanks a lot , it's pretty clear now except the
> things that i was not able to understand that
> incase if a provider uses MPEG-2 to encapsulate
> and thus transport the MPEG-4 part 10 content then
> does the IP STB require both MPEG-2 and MPEG-4
> part 10 decoders ?
Prashant,
Let me try this. MPEG-2 TS is exactly analogous to
Ethernet. It is merely a frame structure used to carry
payload.
Yes, MPEG-2 TS *can* carry IP frames. However, most
IPTV schemes I've read about, actually all, use
something like IP over PPP (see RFCs 1661 and 1662)
over ADSL, or IP (maybe over PPP) over Fast Ethernet,
or IP over Gigabit Ethernet. The Link Layers used by
IPTV are schemes other than MPEG-2 TS. It *is*
possible to transmit IP over MPEG-2 TS, but it's not
necessary.
Functionally, MPEG-TS is really nice, because it
supports synchronous payload streams (which Ethernet
does not do). But that means nothing over a switched
IP/Ethernet infrastructure. So there's no reason for
an IPTV system to use MPEG-2 TS, unless you're using
IPTV over a broadcast infrastructure.
(For example, *if* you wanted to implement IPTV over
a cable network, MPEG-2 TS would be a very nice way
to go. It would allow you to implement IPTV and
non-IP stuff over the common broadcast cable
infrastrucrture. Cool. But over a switched Ethernet
infrastructure, it makes no sense.)
> so that both the royalties should be paid or only
> MPEG-4 part 10 royalty needs to be paid ?
The latter, as far as I know. If you just want to
carry H.264/AVC compressed frames over an IPTV
system, there's no reason to necessarily use MPEG-2
TS, or to pay any royalties. (The details of
royalties are a mystery to me, though.)
All you care about, I believe, is the codec itself,
right? Just the H.264. Forget about the rest. Unless
you really want to use the MPEG-4 tool set for some
reason?
Bert
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