resizing to 640 by 480

I captured a 320 by 240 uncompressed avi video clip from my tv. I
checked and its data rate is around 8 meg per second. I was reading
the states on dvd's and it said that most dvd mpeg-2 files at 740 by
480 have a data rate of around 8 meg per second. My first question
is, is 8 meg a second right for dvd's? My other question is, if I
were to convert my 320 by 240 uncompressed avi video clip into a
mpeg-2 video clip at a resolution of 740 by 480 would I wind up with
a clip the same quality as i would have gotten if I had captured in
mpeg-2 directly from the tv?


THanks a hole heap to any body willing to tackle this brain buster.

k

On Fri, 09 Jan 2004 00:02:33 -0800, k <> Gave us:

>I captured a 320 by 240 uncompressed avi video clip from my tv. I
>checked and its data rate is around 8 meg per second. I was reading
>the states on dvd's and it said that most dvd mpeg-2 files at 740 by
>480 have a data rate of around 8 meg per second. My first question
>is, is 8 meg a second right for dvd's? My other question is, if I
>were to convert my 320 by 240 uncompressed avi video clip into a
>mpeg-2 video clip at a resolution of 740 by 480 would I wind up with
>a clip the same quality as i would have gotten if I had captured in
>mpeg-2 directly from the tv?
>
>
>THanks a hole heap to any body willing to tackle this brain buster.
>
>
WRONG GROUP

DarkMatter

"k" <> wrote in message
news:...
> I captured a 320 by 240 uncompressed avi video clip from my tv. I
> checked and its data rate is around 8 meg per second. I was reading
> the states on dvd's and it said that most dvd mpeg-2 files at 740 by
> 480 have a data rate of around 8 meg per second. My first question
> is, is 8 meg a second right for dvd's? My other question is, if I
> were to convert my 320 by 240 uncompressed avi video clip into a
> mpeg-2 video clip at a resolution of 740 by 480 would I wind up with
> a clip the same quality as i would have gotten if I had captured in
> mpeg-2 directly from the tv?
>
>
> THanks a hole heap to any body willing to tackle this brain buster.

Resizing up from 320x240 to 720x480 will be horrible. Just try it with a
picture, now imagine that picture moving.

DVDs have around 6Mbit/s for the movie, usually less...somewhere in the
upper 4Mbit/s to middle 5Mbit/s region. Notice, that it is Megabits. Here,
it is refering to 1,000,000 BITS, not the conventional MB which is 1,024,576
BYTES. The MB would have over 8,000,000 BITS, so to use 1 Mbit is not using
much at all.

Since the source is uncompressed, this is the first compression and it will
turn out the best. Resizing up is bad, and doing it by 4x (320x240x4 =
720x480) is really bad. The most I would up-scale this AVI to is 480x480,
for a SVCD disc, or a 352x480 CVD disc. Oddly, you will probably end up
with left/right bars, not the standard top/bottom bars. This is mainly
because it should have been captured in 352x240. You could just resize it
to 352x240, changing the aspect, because that's all that setting does, I
think. Then again, if I capture VHS @ 352x240, the video is in a 320x240
box, so there are left/right bars....

Anonymous Joe

>Resizing up from 320x240 to 720x480 will be horrible. Just try it with a
>picture, now imagine that picture moving.
>
>DVDs have around 6Mbit/s for the movie, usually less...somewhere in the
>upper 4Mbit/s to middle 5Mbit/s region. Notice, that it is Megabits. Here,
>it is refering to 1,000,000 BITS, not the conventional MB which is 1,024,576
>BYTES. The MB would have over 8,000,000 BITS, so to use 1 Mbit is not using
>much at all.
>
>Since the source is uncompressed, this is the first compression and it will
>turn out the best. Resizing up is bad, and doing it by 4x (320x240x4 =
>720x480) is really bad. The most I would up-scale this AVI to is 480x480,
>for a SVCD disc, or a 352x480 CVD disc. Oddly, you will probably end up
>with left/right bars, not the standard top/bottom bars. This is mainly
>because it should have been captured in 352x240. You could just resize it
>to 352x240, changing the aspect, because that's all that setting does, I
>think. Then again, if I capture VHS @ 352x240, the video is in a 320x240
>box, so there are left/right bars....

But if I rescale a uncompressed avi at 320 by 240 with a 6 meg per
second data rate wouldn't I end up with a to 640 by 480 clip at 6 meg
per second. Which would be exactly that I would have gotten I
captured to mpeg2 in the first place?
>

k

On 1/9/04 8:16 PM, in article ,
"k" <> wrote:

>
>> Resizing up from 320x240 to 720x480 will be horrible. Just try it with a
>> picture, now imagine that picture moving.
>>
>> DVDs have around 6Mbit/s for the movie, usually less...somewhere in the
>> upper 4Mbit/s to middle 5Mbit/s region. Notice, that it is Megabits. Here,
>> it is refering to 1,000,000 BITS, not the conventional MB which is 1,024,576
>> BYTES. The MB would have over 8,000,000 BITS, so to use 1 Mbit is not using
>> much at all.
>>
>> Since the source is uncompressed, this is the first compression and it will
>> turn out the best. Resizing up is bad, and doing it by 4x (320x240x4 =
>> 720x480) is really bad. The most I would up-scale this AVI to is 480x480,
>> for a SVCD disc, or a 352x480 CVD disc. Oddly, you will probably end up
>> with left/right bars, not the standard top/bottom bars. This is mainly
>> because it should have been captured in 352x240. You could just resize it
>> to 352x240, changing the aspect, because that's all that setting does, I
>> think. Then again, if I capture VHS @ 352x240, the video is in a 320x240
>> box, so there are left/right bars....
>
> But if I rescale a uncompressed avi at 320 by 240 with a 6 meg per
> second data rate wouldn't I end up with a to 640 by 480 clip at 6 meg
> per second. Which would be exactly that I would have gotten I
> captured to mpeg2 in the first place?
>>
>


Rescaling up is bad because the software has to create information that
isn't there.

At 320x240, you've got 76,800 pixels of information in your image. At
640x480, you've got 307,200 pixels. The software's going to have to
interpolate 230,400 of those pixels. Sure, it uses special algorithms to
examine the visual information in an effort to determine what
color/brightness to make each of those new pixels but, in the end, it's just
guessing. You'll end up with a very soft image regardless of your data rate.
The data rate doesn't determine the detail in your image - it determines how
faithfully the image it has to work with is reproduced (as I understand it).

What you'll end up with is a very faithful rendition of a very fuzzy image.

Neal
--
"If morons could fly, it'd be pitch black." - Anonymous

Video Flyer

do you know where I can find a program that gives me the bit rate of a
video file?

k

I read on the web that a video at 640 by 480 running at 2 meg per
second would look the same as a video at 320 by 240 running a 2 meg
per second. Granted the web isn't always the most truthful source.

k

"k" <> wrote in message
news:...
> I read on the web that a video at 640 by 480 running at 2 meg per
> second would look the same as a video at 320 by 240 running a 2 meg
> per second. Granted the web isn't always the most truthful source.

Can you please stop using the word "meg"?

There's actually TWO meanings of it here!!

Meaning #1: 1,048,576 BYTES
Meaning #2 (as in video): 1,000,000 BITS

OK, let's convert so they're using the same unit here:

#1: 8,388,608 BITS
#2: 1,000,000 BITS

So...which one are you actually meaning?

Even if that statement means a 640x480 @ 2megs (#1) is equal to 320x240 @
2megs (#2), it's still wrong, because the 640x480 one is going to take up
2.1x more space per pixel, because it's using 8.4x more data (ie, a 100MB
320x240 = 840MB 640x480), but the actual area is only 4x larger, so
8.4/4=2.1.

Regardless, that statement is wrong, and if you re-encode something it will
always look worse, and it will never be equal. Even if I take a 320x240
Uncompressed AVI and encode it into an 8,000kbps MPEG-1 video at 320x240, it
will look worse than that Uncompressed AVI, not equal. Encoding brings in
new flaws in algorithms & even if you're giving it more bits to work with,
those errors which just naturally happen due to encoding will still happen.
Granted, you wouldn't notice the errors -- in *this* example -- unless you
magnify it a few times.

If I said I was going to convert a 3,000kbps Xvid to a 3,000kbps MPEG-2,
then to a 4,000kbps Xvid, which Xvid is going to look better, the 3000kbps
or the 4000kbps? [It's the 3000]

Anonymous Joe

On Fri, 09 Jan 2004 20:09:49 -0800, k <> Gave us:

>do you know where I can find a program that gives me the bit rate of a
>video file?


WRONG GROUP... DIPSHIT!

DarkMatter

On Fri, 09 Jan 2004 20:16:40 -0800, k <> Gave us:

>I read on the web that a video at 640 by 480 running at 2 meg per
>second would look the same as a video at 320 by 240 running a 2 meg
>per second. Granted the web isn't always the most truthful source.


WRONG GROUP, DIPSHIT!

DarkMatter