Main Concept MPEG1 - allows non-NTSC 720x480 ???

[Guest]

Archived from groups: rec.video.desktop (More info?)

In the Main Concept export settings, the display size by default is
set to the same size as my input AVI DV captured file - at 720x480.
This far exceeds the NTSC standard max display size for MPEG1, which
is 352x240.

I went ahead and made the video to see if it would work, and it did,
and I was able to play it just fine. Is this "max" display size of
MPEG1 just something that is written in the standards - and not an
actual max at all?

 

[Guest]

Archived from groups: rec.video.desktop (More info?)

lifeson@earthlink.net wrote:

> Is this "max" display size of [352x240 for] MPEG1 just something
> that is written in the standards - and not an actual max at all?

See <http://bmrc.berkeley.edu/frame/research/mpeg/faq/mpeg1.html>
and the section titled "Can MPEG-1 encode higher sample rates than
352x240x30?". It says, and I quote:

"Yes. The MPEG-1 syntax permits sampling dimensions as high as
4095 x 4095 x 60 frames per second. The MPEG most people think
of as "MPEG-1" is actually a kind of subset known as Constrained
Parameters Bitstream (CPB)."

(The fiqures quoted seem to be a bit off. Maybe I am wrong and
someone will correct me, but I would _believe_ the correct number
is 4096, not 4095.)

One of the obvious drawbacks of using MPEG-1 for full-frame 720×480
video is that (unlike the MPEG-2 format) MPEG-1 does not have any
special support for interlaced video.

--
znark

 

[Guest]

Archived from groups: rec.video.desktop (More info?)

"Jukka Aho" <jukka.aho@iki.fi> wrote in news:cjoma3$gr2$1
@plaza.suomi.net:

> lifeson@earthlink.net wrote:
>
>> Is this "max" display size of [352x240 for] MPEG1 just something
>> that is written in the standards - and not an actual max at all?
>
> See <http://bmrc.berkeley.edu/frame/research/mpeg/faq/mpeg1.html>
> and the section titled "Can MPEG-1 encode higher sample rates than
> 352x240x30?". It says, and I quote:
>
> "Yes. The MPEG-1 syntax permits sampling dimensions as high as
> 4095 x 4095 x 60 frames per second. The MPEG most people think
> of as "MPEG-1" is actually a kind of subset known as Constrained
> Parameters Bitstream (CPB)."
>
> (The fiqures quoted seem to be a bit off. Maybe I am wrong and
> someone will correct me, but I would _believe_ the correct number
> is 4096, not 4095.)
>

I like to speculate, so here goes.

The binary value for 4095 just fits into 12 bits. To go to 4096
would require going to 13 bits to express the value.

Nobody wants to deal with 13 bit numbers, especially just to add one
more value to the data range. (Nobody wants to deal with 12 bit
numbers either, but that's a whole 'nother story.)

An alternative could be to encode a data value x as x-1, so 0 means
1, ..., 4095 means 4096. That gets 4096 into 12 bits, but it doesn't
let you use data value 0 for a special purpose. Well, it could, by
making the data value 1 illegal, so its encoded value 0 represents
the special value. After all, 1x1 is a very small picture

Who knows?

> One of the obvious drawbacks of using MPEG-1 for full-frame 720×
480
> video is that (unlike the MPEG-2 format) MPEG-1 does not have any
> special support for interlaced video.
>

Gino

--
Gene E. Bloch (Gino) phone 650.966.8481
Call me letters find me at domain blochg whose dot is com