Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

John wrote:
On Fri, 21 Oct 2005 11:33:39 GMT, "DAB sounds worse than FM"
wrote:

John wrote:
On Fri, 21 Oct 2005 10:11:26 GMT, "DAB sounds worse than FM"
wrote:

Then they must be about the same average bit rate:

165 MB = 165 x 2^23 bits

165 x 2^23 / (30 x 60) = 769 kbps

Really? I'm not an expert but I would have thought that the
compression and encoding used would have a significant positive
impact on that figure.


769kbps is the average bit rate for a 165 MB file for a 30 minute
programme. Compression can't alter the file size of a file that
already exists, if you know what I mean.

I've just seen your signature and your web site so you must be an
expert in this area but you have me completely flummoxed! Am I
operating under some terrible fallacy or are we talking at cross
purposes? At the risk of teaching grandmother to suck eggs:

You have taken the file size in the above calculation and the length
of the clip and from that (and that alone) you have calculated the bit
rate but have made no reference to the compression used.


Correct.


My logic
tells me that the bit rate of a 165 Mb uncompressed video clip is
going to be the same as the bit rate of that same file when it is
compressed (using a non-lossy compression mechanism) to, lets say, 150
Mb.


By definition, the size of a video clip file will be different before
and after compression, no?


So you can't tell what the bit rate of a video clip is simply from
the size of the file and the length of the video clip.


Yes, that is what I'm telling you.

It's no different from one of those simply maths question type thingies:

Jim runs 5 miles in one hour. What is the average speed at which Jim
runs? It's obviously 5 miles per hour. Same goes for a video or an audio
file.

Firstly, uncompressed video is 270 Mbps, so a 30 minute programme would
end up being

270 Mbps x 30 minutes x 60 seconds = 4.86 x 10^11 bits

The number of bits in 1 MB = 2^23, so a 30 minute programme at 270 Mbps
would be:

4.86 x 10^11 / 2^23 = 57936 MB, or around 58 GB

The 30 minute programme files you're downloading have been 165 MB, so
you can use the following to work out the average bit rate:

file size in number of bits / time of programme = average bit rate

so

165 MB x number of bits in 1 MB = total number of bits in file

165 MB x 2^23 = 1.3841 Gbits

1.3841 Gbits / number of seconds in programme = bit rate

1.3841 Gbits / (30 x 60) = 769 kbps


The only hole I can see in my logic is that your definition of bit
rate and my definition are different. I define 'bit rate' as the
frequency of bits passing a defined point and in the case of video
that point is AFTER the point of decompression.


That's wrong. Bit rate is not limited to being before or after
compression, bit rate just /is/.


Otherwise 'bit rate'
would be virtually useless as a measure of quality.


Why would bit rate be useless as a measure of quality?

For a bit rate to be used as a measure of quality for video or audio
coding it does have to be combined with the video or audio format,
because otherwise things would get pretty meaningless. For example, say
if you just said "the audio is 128kbps" without saying what format the
audio is in, then if it was using MP2 the audio quality would be crap,
whereas the format used was AAC then the audio quality would be very
good.


Am I really wrong?


'Fraid so.

Now, as I've explained all that, could you do me a favour and look at
what bit rate is being used for Radio 1 files in iMP? Cheers.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

":::Jerry::::" wrote in message
eenews.net...

"Heracles Pollux" wrote in message
...

":::Jerry::::" wrote in message
eenews.net...
snip

You wouldn't be a 'publisher' for very long then, after people
just
started to copy your one and only book sale (of that title)...


Wrong. People return to the source, not the copy, as the "work"
develops.


You really are a clueless ****, or a troll.





Right. Tell that to Mozart, Beethoven, Spielberg or Lucas.

No need for abuse, other than to signify you inability to cope with
civilised discussion, or has someone "stolen" your supply of intellect so
that there is none left?


A suit like you asks "how much profit can we make?"

A creative asks "how much good can I do in the world?"

The Accountancy crap is not an issue to me providing we get by.

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

John wrote on Fri, 21 Oct 2005 14:15:26 +0100:

The only hole I can see in my logic is that your definition of bit
rate and my definition are different. I define 'bit rate' as the
frequency of bits passing a defined point and in the case of video
that point is AFTER the point of decompression. Otherwise 'bit rate'
would be virtually useless as a measure of quality.

Am I really wrong?

Using "bit rate" to describe the rate of the uncompressed video would
be virtually useless as a measure of quality.

There is a bit rate for uncompressed digital video. For (say)
640x480 pixels at 25 frames per second with 24 bits of colour information
per pixel: 640x480x25x24 = ~175Mb/s or ~22MB/s.

That's the same whether the data was previously compressed to the point
that the entire screen is blank, or whether its raw digital video.

The important bit is how much information was kept when it was
compressed. A higher bit rate means more information per second
(assuming some ideal compression algorithm). Since we don't yet
have an ideal compression algorithm, better codecs can get
better quality from the same bitrate. But in general, the
important thing is the compressed bit rate, since that's
what changes.

Also, low bit-rates don't necessarily reduce the quality of the
video -- they only reduce the amount of information that can
be in the video. There's not a lot of information in a static white
screen, so that can easily be encoded perfectly at a very low bit rate.

A picture of completely random "noise" OTOH, contains basically
1 bit of information per bit of data, so needs close to that 22MB/s
data rate, to be perfectly represented.

I've tried a couple times to improve this explanation, but now I
think I'll just accept I'm not too good at explaining this...

--
David Taylor

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

"Heracles Pollux" wrote in message
...

snip clap-trap

Just **** off troll.

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

Working in an industry where bandwidth is a commodity and statistical
multiplexing is a black art, your explanation makes perfect sence to me

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

On Fri, 21 Oct 2005 15:36:17 GMT, "DAB sounds worse than FM"
wrote:



For a bit rate to be used as a measure of quality for video or audio
coding it does have to be combined with the video or audio format,
because otherwise things would get pretty meaningless. For example, say
if you just said "the audio is 128kbps" without saying what format the
audio is in, then if it was using MP2 the audio quality would be crap,
whereas the format used was AAC then the audio quality would be very
good.

Ah ok......I think we were talking at cross-purposes and maybe a
little ignorance on my part. I assumed that when people speak of bit
rates they mean it the sense of trying to define a continious curve by
a set of points joined together (or extrapolated); the more points you
have, the closer the curve resembles the original. Under that
interpertation you would measure the bit rate AFTER decompression of
the source file if you wanted to measure the closeness (i.e quality)
of the new curve to the original.

I need to read up a bit more on this but at the moment it makes no
sense to me that bit rates need to be defined along with the
compression technology used in order to makes sense. Why not measure
the number of bits being supplied to the video/sound card after the
file has been decompressed?

Anyway.......thanks a lot for your time. I think its time for me to
RTFM as they say! And.............

Now, as I've explained all that, could you do me a favour and look at
what bit rate is being used for Radio 1 files in iMP? Cheers.

Sure thing :-)

I downloaded three programmes from BBC Radio 1 for you and they all
seem to have the same bit rates of 128kbps (wma files):

The Chris Moyles Show 7am 19/10 172,506k 3:03:00
Zane Low 7pm 19/10 112,973k 1:59:50
oneclick/film 3am 20/10 56,581k 1:00:00


John

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

On Fri, 21 Oct 2005 17:26:57 +0100, "Heracles Pollux"
wrote:


Right. Tell that to Mozart, Beethoven, Spielberg or Lucas.

No need for abuse, other than to signify you inability to cope with
civilised discussion, or has someone "stolen" your supply of intellect so
that there is none left?

He could just be effected (sic) ?


John

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

John wrote:
On Fri, 21 Oct 2005 15:36:17 GMT, "DAB sounds worse than FM"
wrote:



For a bit rate to be used as a measure of quality for video or audio
coding it does have to be combined with the video or audio format,
because otherwise things would get pretty meaningless. For example,
say if you just said "the audio is 128kbps" without saying what
format the audio is in, then if it was using MP2 the audio quality
would be crap, whereas the format used was AAC then the audio
quality would be very good.

Ah ok......I think we were talking at cross-purposes and maybe a
little ignorance on my part. I assumed that when people speak of bit
rates they mean it the sense of trying to define a continious curve by
a set of points joined together (or extrapolated); the more points you
have, the closer the curve resembles the original.


Do you mean a curve as in a signal? If so, then you're talking about the
digital signal that goes into the DAC (digital to analogue converter),
and that's the decompressed version. But as I said, uncompressed video
is 270 Mbps, and Freeview as a whole only has a bandwidth of 120 Mbps,
so you have to compress very heavily.


Under that
interpertation you would measure the bit rate AFTER decompression of
the source file if you wanted to measure the closeness (i.e quality)
of the new curve to the original.


Uncompressed bit rates aren't of much interest, because video and audio
is always compressed prior to transmission.


I need to read up a bit more on this but at the moment it makes no
sense to me that bit rates need to be defined along with the
compression technology used in order to makes sense. Why not measure
the number of bits being supplied to the video/sound card after the
file has been decompressed?


Because it's not of any interest, because it's always the same for a
given mode. For example, CD audio uses 16-bits per sample, 2 channels
(stereo) and uses a sampling frequency of 44.1 kHz, so the bit rate is:

16 x 2 x 44,100 = 1411.2 kbps

and it's always 1411.2 kbps, so it's not very interesting to quote it.
Audio is now virtually always (or should be) compressed, and you can
achieve virtually CD-quality using a bit rate of 128kbps using the AAC
audio codec. In comparison, at the same 128kbps, MP3 can't achieve as
high an audio quality as AAC can, thus the reason why it's important to
quote the codec as well as the bit rate, because different bit
rate/codec combinations provide different levels of audio quality.


Anyway.......thanks a lot for your time.


I charge £20 per post. ;-)


I think its time for me to
RTFM as they say! And.............

Now, as I've explained all that, could you do me a favour and look at
what bit rate is being used for Radio 1 files in iMP? Cheers.

Sure thing :-)

I downloaded three programmes from BBC Radio 1 for you and they all
seem to have the same bit rates of 128kbps (wma files):


Right, thanks.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

On Fri, 21 Oct 2005 23:44:50 GMT, Edster wrote:


The TV shows I've seen on usenet (I don't know about P2P, etc) average
350mb for a 40 minute show. Which would be about 525 mb if they were
an hour long. So the 330 mb per hour would be quite a lot lower than
what you are used to.

Of course one difference between the average posting on Usenet and
those offered by the BBC is that the source material and the encoding
equipment is likely to be of a significantly higher quality in the
BBC's case.


John

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

"Edster" wrote in message
...
":::Jerry::::" wrote in message


"John" wrote in message
.. .
On Thu, 20 Oct 2005 11:55:55 +0100, ":::Jerry::::"
wrote:


"John" wrote in message
.. .
snip details of a crime
been successful. Hopefully someone will eventually put a
proper
one-click application together.



Hopefully criminals like you will be publicly flogged to an
inch
of
your life...


And hopefully some day the human race will rid itself of the
'holier
than thou' brigade that insists on preaching their dubious moral
attitudes about unenforceable (and therefore 'bad') laws at
others.
snip the rest of your clap-trap

Oh right, so just because someone thinks the laws that prevent
theft
are 'bad law' you wouldn't object to them breaking into your house
and stealing your earnt income then?


If you think wanting to watch something 9 days after it was
downloaded, or forgetting to blank a video tape after you've
watched
something is the same as breaking into someone's house and stealing
their money you're obviously off your trolley. Either you're the
troll
that you accuse more rational people of being, or you seriously
need
to get a grip on reality. Nobody is losing any money over
timeshifted
recordings that still exist in millions of homes across the
country.

The problem is that some people don't just time-shift their
recordings, when boot legers are using camcorders in cinemas etc what
do you think they will do with (possibly) high quality downloads?...

The problem is not the time-shifting viewer who keeps a programme
longer than needed but those who aim to abuse the system, as always
the few selfish t*ssers who spoil it for the many - just as the OP of
this thread is, what do you think programme rights holders think
about allowing the BBC to make their content available via iMP with
subject lines such as in this thread. Remember, bit rates might well
be low ATM but that is likely to change in the not to distance
future.

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

Edster wrote:
Roger Wilmut wrote in message

before you mention public libraries,
there is a payment to authors from borrowings as well)

How does that work? Does each author get a few pence every time one of
his books i borrowed,

Correct.

(Wow. Shortest post ever?)

--
Carl Waring
http://getdigiguide.com/?p=1&r=1495

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

:::Jerry:::: wrote:

Remember, bit rates might well
be low ATM but that is likely to change in the not to distance
future.


Really? If I said that you would accuse me of not understanding the
broadcasting / media industries. Why is it so different for you to say
such things?


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Please sign the petition asking the BBC to provide better audio quality
on its radio stations on DAB, Freeview, satellite and cable:
http://tinyurl.com/a68e4

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

In article , Carl Waring wrote:
Edster wrote:
Roger Wilmut wrote in message
before you mention public libraries,
there is a payment to authors from borrowings as well)
How does that work? Does each author get a few pence every time one of
his books i borrowed,

Correct.

(Wow. Shortest post ever?)

No.

:)

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

--
Stuart @ SJW Electrical

Please Reply to group

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

"Edster" wrote in message
...
snip

What are you expecting people to do with them once they have been
hacked? They will just file them away somewhere and probably forget
about them. Without people like that, where will the BBC's next
generation of lost recordings be found?

Hmm, I suggest you find out why those 'lost recordings' were still
around - considering that most people had no means to record a radio
programme let alone a TV programme at the time...

AIUI most of them were either official or semi-official recording
that were saved before they were destroyed.

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

"DAB sounds worse than FM" wrote in message
...
:::Jerry:::: wrote:

Remember, bit rates might well
be low ATM but that is likely to change in the not to distance
future.


Really? If I said that you would accuse me of not understanding the
broadcasting / media industries. Why is it so different for you to
say
such things?


For someone who says they are a communications engineer I'm amazed
that you even need to ask...

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

"Edster" wrote in message
...
":::Jerry::::" wrote in message


"Edster" wrote in message
...
snip

What are you expecting people to do with them once they have
been
hacked? They will just file them away somewhere and probably
forget
about them. Without people like that, where will the BBC's next
generation of lost recordings be found?

Hmm, I suggest you find out why those 'lost recordings' were still
around - considering that most people had no means to record a
radio
programme let alone a TV programme at the time...

AIUI most of them were either official or semi-official recording
that were saved before they were destroyed.


People have been recording the radio since the 1950s. The BBC were
still "losing" radio programmes in the 90s.

People were recording radio in the 1930's, what was your point
exactly?...

Update: The BBC Intergrated Media Player trial and DRM......how to hack?
 

":::Jerry::::" wrote:

The problem is not the time-shifting viewer who keeps a programme
longer than needed but those who aim to abuse the system, as always
the few selfish t*ssers who spoil it for the many - [...]

So get out of the way of the time-shifters and use better methods
to track down the "selfish t*ssers". It's never made sense to
build a house in the middle of a motorway and then pass a law
against people crashing into it, yet that is exactly what F*CT
friends support, using bad technical measures and then passing
laws against people fixing that error. The bugfixers are not the
"selfish t*ssers" you are looking for.