[opendtv] Re: 20040722 Thundering Thursday Thanks (Mark's Monday Memo)
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 22 Jul 2004 19:32:24 -0400
Ron Economos wrote:
> Since there are no real-time HD H.264 encoders, I'd say
> the "holdup" is a technical problem.
But not with the ATSC standard.
With A/90, ATSC "decoupled" (as Craig would say) synchronous
payload streams from the MPEG-2 compression algorithm. MPEG-2
TS was retained, I guess you might call that at OSI Layer 2,
but now, in principle, anything goes for image compression.
Actually there was a comment in another document, I'm too
lazy to search for it now, that stipulated use of MPEG-2
image compression for TV programs. But those are just words
that can be revised any old time, as indeed they have been
(or rather, are being).
Anyway, the only point I was trying to make is that use of
MPEG-4 AVC, or for that matter any other compression scheme,
does not depend on E-VSB. These newer algorithms could have
been introduced anytime after A/90 was written, which means
four years ago.
What has happened now is that AVC was added to the new
candidate standard, ammendment to A/53C,
http://www.atsc.org/standards/cs_documents/cs_t3-608.pdf
but AVC per se it isn't dependent on E-VSB. It's merely
added as another codec option. As the quote below
demonstrates. In other words, I don't take this document
as being *only* about E-VSB. It includes E-VSB.
Note that A/90 also shows the PID as being a possible
discriminator of payload types, and it provides other
payload identifying schemes as well (LLC/SNAP and IP).
Bert
-----------------------------------
6.7 Assignment of Identifiers
In this section, those identifiers and codes that shall
have a fixed value are summarized. These include PES Stream
IDs and Descriptors. Stream_type codes for program element
types managed by the ATSC Code Points Registrar (currently
assigned or available for future assignment) shall be in the
range 0x80 to 0xC3. Those descriptor_tag codes managed by
the ATSC Code Points Registrar (currently assigned or
available for future assignment) shall be in the range 0x40
to 0xEF.
6.7.1 AC-3 Audio Stream Type
The stream_type value for AC-3 audio program elements shall
be 0x81.
6.7.2 MPEG-2 Video Stream Type
The stream_type value for MPEG-2 video program elements shall
be as defined in ISO/IEC 13818-1 [C3] which is 0x02.
6.7.3 AVC Video Stream Type
The stream_type value for AVC video program elements shall be
as defined in ITU-T Rec. H.264 |ISO/IEC 14496-10 [C5] which is
0x1B.
6.7.4 Enhanced AC-3 Audio Stream Type
The stream_type value for the enhanced AC-3 audio program
element defined in A/52B [C1] Annex E shall be 0x87.
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