MPEG2 MP@LL and MPEG1?

Hi all,

I heard that MPEG2 and MPEG1 use same compression methods.

MPEG2's MP@LL and MPEG1 are all 4:2:0, 352*288*30. But MPEG2's MP@LL is
4Mbit/s and MPEG1 is 1.5Mbit/s. Why they have different bit rates?

And if I want to do 352*288*30 video compression. Shall I choose MPEG2
or MPEG1?? 

Any suggestions will be appreciated!

Best regards,
Davy

Davy wrote:
> Hi all,
>
> I heard that MPEG2 and MPEG1 use same compression methods.
>
> MPEG2's MP@LL and MPEG1 are all 4:2:0, 352*288*30. But MPEG2's MP@LL is
> 4Mbit/s and MPEG1 is 1.5Mbit/s. Why they have different bit rates?
>
> And if I want to do 352*288*30 video compression. Shall I choose MPEG2
> or MPEG1??

You've got a few things confused.  First of all, MPEG can use any
bitrate you want, so that's why the bitrates are different in your
samples.  Secondarly, 352x288@30 isn't typical; I think you're thinking
of VCD PAL which is 352x288 @ 25fps.  If that's your target, VCD PAL
MPEG-1 would give you the most compatibility across platforms.

Hi Jim,

Thank you for your help!

Do you mean when I use the same compression parameter to generate MPEG1
or MPEG2, the compression ratio will be the same?

My target is PC. And can MPEG1 be expanded to  720*480*30?

All the best,
Davy

"Davy" <zhushenli@gmail.com> a &#4294967295;crit dans le message de news: 1125844327.579957.139370@g47g2000cwa.googlegroups.com...
| Hi all,
|
| I heard that MPEG2 and MPEG1 use same compression methods.
|
| MPEG2's MP@LL and MPEG1 are all 4:2:0, 352*288*30. But MPEG2's MP@LL is
| 4Mbit/s and MPEG1 is 1.5Mbit/s. Why they have different bit rates?

4 Mbit/s is probably the maximum bitrate allowed in MP@LL. You can't
compare it to the 1.5 Mbit/s of mpeg1

|
| And if I want to do 352*288*30 video compression. Shall I choose MPEG2
| or MPEG1??

Mpeg2 because it is more powerfull than mpeg1


| Any suggestions will be appreciated!
|
| Best regards,
| Davy
| 

Davy wrote:
> Do you mean when I use the same compression parameter to generate MPEG1
> or MPEG2, the compression ratio will be the same?

I'm saying that MPEG encoders by nature usually allow either
quality-based encoding (constant quality throughout the file), or
bitrate-based encoding (constant bitrate/size per second throughout the
file), or both.  So it doesn't matter what size you're working with, if
you want a file that doesn't chew up more than 150KB/s then that's what
you set the bitrate to.

Of course, larger bitrates result in larger files, but the larger the
file is the better it looks.

> My target is PC. And can MPEG1 be expanded to  720*480*30?

MPEG-1 can indeed be encoded at 720x480 but if you're working with
interlaced material you should be using MPEG-2.  MPEG-1 has no
provisions for working with interlaced source material and the output
is worse.

Is there a minimum bitrate constraint in MPEG2?
For I want to generate bitrate as low as possible.

Any suggestions will be appreciated!
Best regards,
Davy