2-hour length, 148.50 Mhz, 1920 x 1080 progressive scan image, 1-bit object data, 193 bits of file s

[Radium]

Michael Walraven wrote in
http://groups.google.com/group/sci.electronics.basics/msg/67ea1a75d326e0f8?hl=en&
:

An empty wma file will have some overhead even if there is no 'data' within
it.
WMA files are wrapped in a ASF file structure which has the format:

Object GUID 16 Bytes (128 bits)
Object Size 8 Bytes (64 bits)
Object data {as many as needed}

so as a minimum, not knowing what type of WMA file is involved 192 bits (24
bytes) are required. (probably somewhat more)

So is it possible to exist for the following to exist:

A WMV file of 2-hour length, 148.50 Mhz, 1920 x 1080 progressive scan
image, whose object data is only 1-bit in size due to massive
compression of color-depth? [this file would be 193 bits in size
because the the "object size" is 64 bits, the GUID is 128 bits, and the
object data is only 1-bit]?

If such a WMV file can exist, how would its video look like?


Thanks,

Radium

 

[Bob Myers]

So is it possible to exist for the following to exist:

A WMV file of 2-hour length, 148.50 Mhz, 1920 x 1080 progressive scan
image, whose object data is only 1-bit in size due to massive
compression of color-depth? [this file would be 193 bits in size
because the the "object size" is 64 bits, the GUID is 128 bits, and the
object data is only 1-bit]?

You still don't get it. A one-bit "file," no matter how it
was produced, can provide only one bit of information.
That SHOULD be obvious, but you're not thinking about
what it means. A single bit can convey what amounts to ONE
answer to a yes/no, or true/false sort of question - in other
words, just enough information to permit one to decide
between two and only two possible answers. That's why
people have been, in jest, talking about the multi-gigabyte
"decompression" routines your supposed "one bit" file would
require - what they really mean is that the "decompression"
program itself would have to contain all of the information
required to reconstruct either of two (and not more than two)
possible videos. Or in other words, you've just shifted the
burden of providing the information from the "video file" to
the "decompressor" - in effect, the "file" you're talking about
is just identifying which of two videos (contained elsewhere)
you want to see.

As usual, you need to learn a LOT more about the fields you're
trying to discuss (in this case, information theory and data
compression) before you leap to these absurd notions.

Bob M.

 

[Radium]

You still don't get it. A one-bit "file," no matter how it
was produced, can provide only one bit of information.

I never said the file size is 1 bit. The file size is 193 bits.

 

[Bob Myers]

I never said the file size is 1 bit. The file size is 193 bits.

Radium, old chap, here's exactly what you said:

"So is it possible to exist for the following to exist:

A WMV file of 2-hour length, 148.50 Mhz, 1920 x 1080 progressive scan
image, whose object data is only 1-bit in size due to massive
compression of color-depth? [this file would be 193 bits in size
because the the "object size" is 64 bits, the GUID is 128 bits, and the
object data is only 1-bit]?

If such a WMV file can exist, how would its video look like?"

You're clearly talking about the "object data" - i.e., all of the data
outside of the required overhead - being just a single bit. That's
the data that actually carries the video information, right? If not,
then what exactly DID you mean by "the object data is only
1 bit"?

And given THAT, the analysis I gave you is both correct and
relevant. You simply have no idea what you're talking about
here - once again.

Bob M.

 

[Radium]

You're clearly talking about the "object data" - i.e., all of the data
outside of the required overhead - being just a single bit. That's
the data that actually carries the video information, right?

Yes. The "object data" is the video signal. So I just got the point. As
you say, one-bit would not work for this video. Then what is the
minimum bit required?

 

[Martin Heffels]

Yes. The "object data" is the video signal. So I just got the point. As
you say, one-bit would not work for this video. Then what is the
minimum bit required?

Do yourself a favour, and play with the bit-depth of your computer-screen
and then play a movie. You will find the answer yourself.....
If the video is compressed down to 1 bit, it will be black or white, no
colour, no grey, no nothing. It's as simple as that

cheers

-martin-
--

 

[Bob Masta]

Yes. The "object data" is the video signal. So I just got the point. As
you say, one-bit would not work for this video. Then what is the
minimum bit required?

I have the distinct impression that you are new to the concepts of
compression. Here's a thumbnail sketch: All compression schemes
can be divided into lossless and lossy. Lossless compression
works by analyzing the data and replacing large redundant areas
with smaller versions. For example, in a text file you might replace
each occurence of 'the' with a single byte or symbol. The compressor
also creates a "dictionary" table that allows you to determine the
long form from the symbol. Then the decompressor reads a symbol
and recreates the original.

If you think about it, you should realize that there is no way to
predict ahead of time how much compression is possible with
this scheme. If your source has a lot of redundancy, the compression
ratio is high. If the source is random data with no patterns, then
no compression is possible (by defininition). So if you had a video
taken with the lens cap on (all black) the compression would be
extremely high... just a symbol for "black" and a run length. If
you had a video of a swirling snowstorm (random black and white
dots) the compression might be non-existent.

But many real-world things like video and audio contain a lot
more information than most people want. For example, in an
audio recording, you probably don't care if the background hiss
is *exactly* the same waveform as the original. You can't really
tell one run of random hiss from another with the sme spectrum
and level. Similarly, human ears are really bad at detecting
absolute phase, or a soft sound in the presence of a loud one
at a similar frequency, and a whole lot of other stuff. So lossy
compression says, essentially, "if you can't tell the difference,
don't bother to save the details". In the hiss case, for example,
it could encode a few symbols to specify the spectrum, level,
and duration. A program of pure background hiss that could
not be compressed at all with lossless compression would
thus compress down to a few symbols. In the real world, of
course, we don't care about such cases. In concept, lossy audio
compression works by looking at the spectrum of sound snippets
and deciding which sounds would be masked by louder sounds
in the same frequency region, and trims those out. Then it
only has to store the frequencies and levels of the components
you can actually hear.

Another concept is to store only *changes* from one frame
to the next, whether we are talking about audio or video.
If everything is the same as the last frame, store a "ditto"
symbol and run length for the total number of frames that
are the same. If there is a small change, store only the
part that is changed.

So once again, you should see that there is no way to
predict maximum compression for a real-world case.

Hope that helps!


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

 

[Quanta]

I never said the file size is 1 bit. The file size is 193 bits.

Radium, old chap, here's exactly what you said:

"So is it possible to exist for the following to exist:

A WMV file of 2-hour length, 148.50 Mhz, 1920 x 1080 progressive scan
image, whose object data is only 1-bit in size due to massive
compression of color-depth? [this file would be 193 bits in size
because the the "object size" is 64 bits, the GUID is 128 bits, and the
object data is only 1-bit]?

If such a WMV file can exist, how would its video look like?"

You're clearly talking about the "object data" - i.e., all of the data
outside of the required overhead - being just a single bit. That's
the data that actually carries the video information, right? If not,
then what exactly DID you mean by "the object data is only
1 bit"?

And given THAT, the analysis I gave you is both correct and
relevant. You simply have no idea what you're talking about
here - once again.

Bob M.

A-men and Bravo!

 

[Ken Maltby]

I have the distinct impression that you are new to the concepts of
compression. Here's a thumbnail sketch: All compression schemes
can be divided into lossless and lossy. Lossless compression
works by analyzing the data and replacing large redundant areas
with smaller versions. For example, in a text file you might replace
each occurence of 'the' with a single byte or symbol. The compressor
also creates a "dictionary" table that allows you to determine the
long form from the symbol. Then the decompressor reads a symbol
and recreates the original.

If you think about it, you should realize that there is no way to
predict ahead of time how much compression is possible with
this scheme. If your source has a lot of redundancy, the compression
ratio is high. If the source is random data with no patterns, then
no compression is possible (by defininition). So if you had a video
taken with the lens cap on (all black) the compression would be
extremely high... just a symbol for "black" and a run length. If
you had a video of a swirling snowstorm (random black and white
dots) the compression might be non-existent.

But many real-world things like video and audio contain a lot
more information than most people want. For example, in an
audio recording, you probably don't care if the background hiss
is *exactly* the same waveform as the original. You can't really
tell one run of random hiss from another with the sme spectrum
and level. Similarly, human ears are really bad at detecting
absolute phase, or a soft sound in the presence of a loud one
at a similar frequency, and a whole lot of other stuff. So lossy
compression says, essentially, "if you can't tell the difference,
don't bother to save the details". In the hiss case, for example,
it could encode a few symbols to specify the spectrum, level,
and duration. A program of pure background hiss that could
not be compressed at all with lossless compression would
thus compress down to a few symbols. In the real world, of
course, we don't care about such cases. In concept, lossy audio
compression works by looking at the spectrum of sound snippets
and deciding which sounds would be masked by louder sounds
in the same frequency region, and trims those out. Then it
only has to store the frequencies and levels of the components
you can actually hear.

Another concept is to store only *changes* from one frame
to the next, whether we are talking about audio or video.
If everything is the same as the last frame, store a "ditto"
symbol and run length for the total number of frames that
are the same. If there is a small change, store only the
part that is changed.

So once again, you should see that there is no way to
predict maximum compression for a real-world case.

Hope that helps!


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

Great intro./basic description to this issue. It serves well as
a means to address a needed common level of understanding.
It covers all that most well need, to allow their use of
compressed video in most commercial products. Well done!

There is a great deal more in the way of using the "limitations"
of human perception, that goes into modern compression schemes
and the whole use of sophisticated algorithms to detect and
address/exploit such opportunities, would be next. Then the "Eyes
glazing over" would reach a level that causes most to stop reading.

I wouldn't have posted to this ridiculous thread but for your
reply.

Luck;
Ken

------------------------------------

To the rest of the thread:

While you can have a logical data of 1-bit, the computer has to
read data from a Byte. It can throw away the rest of the bits in a
Byte, but they must have existed. In fact, to have a usable data
structure will require more than one Byte, for an addressable data
element. Your 193 bits could be addressing some of that, but even
if it covered it all, there is still another factor.

Any program that might be expected to work with video "object
data" would require more than that "1-bit" of it, to function.

 

[Bob Myers]

Yes. The "object data" is the video signal. So I just got the point. As
you say, one-bit would not work for this video. Then what is the
minimum bit required?

There's no way of giving a single, absolute answer here - the
minimum "file size" or "object data" size for any compressed
information depends on the size, etc., of the original data, and
the nature of the compression and the desired quality of the
uncompressed result. Compression methods broadly fall into
two categories - "lossless," in which case the compression itself
does not degrade the data in any way (but it removes redundancy,
making the data more vulnerable to loss through noise in the
transmission channel), and "lossy," in which case you know there's
going to be some loss of quality no matter what - the question is
how much of a hit you're willing to take (which in turn often has
to do with what can reasonably be expected to be heard/seen
by the human user of this data).

Bob M.

 

[Richard Crowley]

"Radium" wrote...

Yes. The "object data" is the video signal. So I just got the point. As
you say, one-bit would not work for this video.

One bit would not work for ANY video.
One bit would not work for any AUDIO.
One bit would not work for any TEXT.

One bit could tell you whether the porch light is on.
One bit could tell you if you left the fridge door open.
One bit could tell you if it is night or day.

One bit = Yes or No. Nothing beyond that.

Then what is the minimum bit required?

How may frames per sec? 30? 24? 15? 6? 2? 1? 1 per minute?
How much image degradation is acceptable?

You might even be able to get it down to several MB,
but nobody would want to watch it (or likely even
recognize it.)

Do you understand that your question is not answerable?
Or are you just trolling us?

 

[Frank]

2-hour length, 148.50 Mhz, 1920 x 1080 progressive
scan image, 1-bit object data, 193 bits of file size>,

There's no way of giving a single, absolute answer here - the
minimum "file size" or "object data" size for any compressed
information depends on the size, etc., of the original data, and
the nature of the compression and the desired quality of the
uncompressed result. Compression methods broadly fall into
two categories - "lossless," in which case the compression itself
does not degrade the data in any way (but it removes redundancy,
making the data more vulnerable to loss through noise in the
transmission channel), and "lossy," in which case you know there's
going to be some loss of quality no matter what - the question is
how much of a hit you're willing to take (which in turn often has
to do with what can reasonably be expected to be heard/seen
by the human user of this data).

Bob M.

For anyone who's interested, Microsoft offers as a free download
(sorry, I don't have the URL handy) a program called Windows Media ASF
View 9 Series (asfview.exe).

To see just how much overhead a Windows Media Video (.wmv) file has, I
just took a look at a typical 21,211,084 byte .wmv file with the
following results.

Header Object (2744 bytes)

Data Object (21,208,050 bytes)

Simple Index Object (290 bytes)

The program breaks down each of the above categories of data types
into as many as 13 subtypes, displaying the contents of each field,
and also offers the ability to display the raw contents of each
subtype in hex.

 

[Radium]

"Radium" wrote...

One bit would not work for ANY video.
One bit would not work for any AUDIO.
One bit would not work for any TEXT.

One bit could tell you whether the porch light is on.
One bit could tell you if you left the fridge door open.
One bit could tell you if it is night or day.

One bit = Yes or No. Nothing beyond that.

Okay. I understand.

How may frames per sec? 30? 24? 15? 6? 2? 1? 1 per minute?

Frames per sec should not be decreased at all. The sample rate should
still be 148.50 mhz.

How much image degradation is acceptable?

Infinite, as long as as the sample-rate [148.50 mhz], the frame-rate
[60 hz], and the pixel-resolution [1920 X 1080 progressive] are not
decreased. As for the color-depth, compress it as much as you want.

You might even be able to get it down to several MB,
but nobody would want to watch it (or likely even
recognize it.)

Well, as long as the sample-rate, frame-rate, and pixel-resolution are
not decreased, I don't mind maximum WMV compression of color-depth.

Do you understand that your question is not answerable?

Now I do.

Or are you just trolling us?

No.

 

[Dave Martindale]

Do yourself a favour, and play with the bit-depth of your computer-screen
and then play a movie. You will find the answer yourself.....
If the video is compressed down to 1 bit, it will be black or white, no
colour, no grey, no nothing. It's as simple as that

Well, not, it's not. When someone is discussing image or video
compression, and they refer to "one bit per pixel", they are almost
certainly *not* talking about bilevel black&white display. Instead,
they are talking about either a greyscale or colour image that has been
sufficiently compressed that the *average* bit rate is 1 bit per
pixel. But when the image is decompressed, it returns to some wider
format; usually 8 bits for greyscale and 24 bits for colour.

Dave

 

[Ken Maltby]

Well, not, it's not. When someone is discussing image or video
compression, and they refer to "one bit per pixel", they are almost
certainly *not* talking about bilevel black&white display. Instead,
they are talking about either a greyscale or colour image that has been
sufficiently compressed that the *average* bit rate is 1 bit per
pixel. But when the image is decompressed, it returns to some wider
format; usually 8 bits for greyscale and 24 bits for colour.

Dave

Could you provide a reference to where such discussions
are going on? A paper perhaps, a journal?

Luck;
Ken

 

[Pete Fraser]

Could you provide a reference to where such discussions
are going on? A paper perhaps, a journal?

Looks at the documantation of almost any video or image
compression tool.

For example, the usage example for Kakadu (JPEG2000):

a) kdu_compress -i image.pgm -o out.j2c -rate 1.0
-- irreversible compression to 1 bit/sample.

 

[Ken Maltby]

Looks at the documantation of almost any video or image
compression tool.

For example, the usage example for Kakadu (JPEG2000):

a) kdu_compress -i image.pgm -o out.j2c -rate 1.0
-- irreversible compression to 1 bit/sample.

Even I could do better than that, but the point was that if
this annoying OP could be lead to such material he might
have a chance of gaining some better understanding of the
situation where a reference to a standard bitrate/color depth
like "one bit per pixel" doesn't mean "1-bit object data".

It took a series of threads by the OP before he was able to
post this thread with his still refusal to comprehend that you
can't create a *FILE* compressed to just one bit of "object
data" and some overhead. Not for 2 hours of video, not for
2 seconds, not for HD, not for SD. Not a WMV, or AVI,
or MPEG. Not with wavelet compression, or any other way.
You can't have:
"A WMV file of 2-hour length, 148.50 Mhz, 1920 x 1080
progressive scan image, whose object data is only 1-bit in size
due to massive compression of color-depth? [this file would be
193 bits in size because the the "object size" is 64 bits, the
GUID is 128 bits, and the object data is only 1-bit]?"

This FILE wouldn't be 193 bits in size. This FILE couldn't
exist. Too suggest otherwise, is only encouraging this folly. I
fully expect this OP to keep up his series of incremental
postings, on this matter, rather than crack a book, or even
Google for a published reference, but we need not waste
too much time trying to straighten out his misconceptions.
The information is out there for OP to find with a little real
effort on his part.

Luck;
Ken

 

[Bob Myers]

Frames per sec should not be decreased at all. The sample rate should
still be 148.50 mhz.

Why are you hung up on sample rate per se? Question:
if I could decrease the sample rate by eliminating "dead"
time in the original video signal (for instance, by cutting out
excess blanking time in which no image information was
being transmitted), would you find that acceptable?

How much image degradation is acceptable?

Infinite, as long as as the sample-rate [148.50 mhz], the frame-rate
[60 hz], and the pixel-resolution [1920 X 1080 progressive] are not
decreased. As for the color-depth, compress it as much as you want.

Oh, OK - in that case, I can give you an infinitely-degraded
image in no bits at all!

And why do you think that "color depth" is something
you can compress the daylights out of, but by Gawd, don't
touch there OTHER things?

Bob M.

 

[Bob Myers]

Could you provide a reference to where such discussions
are going on? A paper perhaps, a journal?

Consider the following - the average data rate of an ATSC
digital television broadcast cannot exceed about 19.4 Mbits/sec.
In one second, a 1920 x 1080, 60 Hz (2:1 interlaced) HDTV
source generates at least:

1920 x 1080 x 30 = 62.2 million pixels.

So we have a data stream giving us under 20 million bits
each second, which we're going to have to turn into over
60 million pixels. That's under 3 bits/pixel, on average.
Ain't compression wonderful? (And it often gets down
to an average rate of around a bit per pixel...)

Bob M.

 

[Pasi Ojala]

So we have a data stream giving us under 20 million bits
each second, which we're going to have to turn into over
60 million pixels. That's under 3 bits/pixel, on average.

Or rather, 0.33 bits/pixel..

-Pasi