MP3 coding (was Current trends in audio)
 

If you'd excuse a thread-swerve, while the subject's mp3 - I'm not familiar
with the internals of mp3, and there's a thing I've never been sure of.
Namely, what happens if you do the compression twice ? I mean, if you
convert an mp3 file back into something lossless, then recode that as mp3,
what gets lost on the second compression ? Does it only throw away what was
already thrown away on the first compression (ie the quality of the second
generation isn't much worse than the first), or do you lose the same amount
of 'quality' all over again ? (I'm guessing somewhere between the 2, but I
have nothing much to go on except masculine intuition).

This could get all kinds of "subjective" (see other subthread blind
testing), but I was wondering if anybody can comment on the software side of
it, how the algorithms work ? (and worrying that I won't understand if they
do, but I'll have a go :-)

--
Richard Robinson
"The whole plan hinged upon the natural curiosity of potatoes" - S. Lem

My email address is at http://www.qualmograph.org.uk/contact.html

Current trends in audio
 

In article ,
wrote:
But often is not, as one clearly see when the director cuts from one
camera to another. In this situation, makeup and lighting are unchanged.

Sounds like very inexperience racks engineers. Or, more likely these days
on a low budget production, non at all.

Or, of course, just your TV.

--
*IS THERE ANOTHER WORD FOR SYNONYM?

Dave Plowman London SW
To e-mail, change noise into sound.

Current trends in audio
 

In article ,
Don Pearce wrote:
On Sun, 22 Jan 2017 12:03:01 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Don Pearce wrote:
White balance - and particularly skin tone balance on TV suffered with
the shift from illuminant C (the standard for the delta tube) and
illuminant E which came in with the PIL tube.

But even that is pretty good compared with that of the typical flat
screen.

It's the reason CRT monitors (delta gun) were used in racks long after
LCDs arrived.

Indeed, when I retired some 8 years ago, they were still in use for
location drama, by the lighting director.

But I dunno what is used these days.

I believe there are still delta tubes in use in critical situations.
They remain the standard against which everything must be judged - but
still come up short.

Well, yes. Rather the same as a loudspeaker. A perfect one is yet to be
invented.

It's odd that so many go on and on about poor digital audio - like DAB is
at worst - but put up with modern TV where so much is inferior picture
wise to what was possible 30 odd years ago. Apart from display size and
cost.

I suppose it's like CD - everything downhill since.

--
*CAN VEGETARIANS EAT ANIMAL CRACKERS?

Dave Plowman London SW
To e-mail, change noise into sound.

Current trends in audio
 

On 22/01/2017 13:30, Dave Plowman (News) wrote:

It's odd that so many go on and on about poor digital audio - like DAB is
at worst - but put up with modern TV where so much is inferior picture
wise to what was possible 30 odd years ago. Apart from display size and
cost.

So why are all the 1980's shows (on DVD) in soft focus and pastel colours?

--
Eiron.

MP3 coding (was Current trends in audio)
 

On 22-01-17 13:57, Richard Robinson wrote:

If you'd excuse a thread-swerve, while the subject's mp3 - I'm not familiar
with the internals of mp3, and there's a thing I've never been sure of.
Namely, what happens if you do the compression twice ? I mean, if you
convert an mp3 file back into something lossless, then recode that as mp3,
what gets lost on the second compression ? Does it only throw away what was
already thrown away on the first compression (ie the quality of the second
generation isn't much worse than the first), or do you lose the same amount
of 'quality' all over again ? (I'm guessing somewhere between the 2, but I
have nothing much to go on except masculine intuition).

Yes, "somewhere between the 2" is pretty much the same answer.

Double compression degrades the result a bit further, but not much
as long as you use the same mp3 encoder and the same bit rate. Changing
encoder and/or bit rate might result in different decisions about
what to discard, thus degrading the result further.

Julf

Current trends in audio
 

In article ,
Eiron wrote:
On 22/01/2017 13:30, Dave Plowman (News) wrote:

It's odd that so many go on and on about poor digital audio - like DAB
is at worst - but put up with modern TV where so much is inferior
picture wise to what was possible 30 odd years ago. Apart from display
size and cost.

So why are all the 1980's shows (on DVD) in soft focus and pastel
colours?

All of them? The problem with old TV shows (on tape) is they may have been
copied many times - and even if the original tapes exist and are in good
condition, the machine to replay them may not be so hot.

Then add in that they may have been transferred by inexperienced people.
The type who think everything can be sorted in software afterwards.

FFS, they can't even get the audio levels approximately right. Analogue
video has a lot more than that to cock up.

--
*You! Off my planet!

Dave Plowman London SW
To e-mail, change noise into sound.

MP3 coding (was Current trends in audio)
 

In article , Johan Helsingius
wrote:
On 22-01-17 13:57, Richard Robinson wrote:

If you'd excuse a thread-swerve, while the subject's mp3 - I'm not
familiar with the internals of mp3, and there's a thing I've never
been sure of. Namely, what happens if you do the compression twice ? I
mean, if you convert an mp3 file back into something lossless, then
recode that as mp3, what gets lost on the second compression ? Does it
only throw away what was already thrown away on the first compression
(ie the quality of the second generation isn't much worse than the
first), or do you lose the same amount of 'quality' all over again ?
(I'm guessing somewhere between the 2, but I have nothing much to go
on except masculine intuition).

Yes, "somewhere between the 2" is pretty much the same answer.

Double compression degrades the result a bit further, but not much as
long as you use the same mp3 encoder and the same bit rate. Changing
encoder and/or bit rate might result in different decisions about what
to discard, thus degrading the result further.

Anyone interested can probably do an analogous experiment by repeatedly
jpeg encoding and rendering an image though a series of sucessive cycles.
The image will tend to degrade after each cycle. But the rate at which it
does so will vary with factors like the amount of data reduction used and
the 'rules' being employed. Some encoders may be better than others.

Thus it becomes obvious that for any 'chain' where end-quality matters
you'd avoid data reduction (aka lossy compression) until the last lap!

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Current trends in audio
 

On Sun, 22 Jan 2017 13:30:33 +0000 (GMT), "Dave Plowman (News)"
wrote:


Well, yes. Rather the same as a loudspeaker. A perfect one is yet to be
invented.

It's odd that so many go on and on about poor digital audio - like DAB is
at worst - but put up with modern TV where so much is inferior picture
wise to what was possible 30 odd years ago. Apart from display size and
cost.


I think that's rather an exaggeration. Yes, early flat screen displays
were terrible in many ways (but popular with the public despite that),
but I think you'll find the picture quality of recent ones, even cheap
ones, is pretty good, once you've adjusted them away from the eyeball
searing defaults - but you had to do that with CRT TVs as well. And in
some respects they have always been better than CRTs; perfect
geometry, no convergence errors and no visible flicker (for LCDs
anyway).

You can buy Grade 1 LCD monitors if you have deep enough pockets, so
they must be getting close to CRTs in colourimetry.

I always find these "everythings deteriorating" arguments amusing,
AFAICS many things are improving by and large.

The premise of this thread, that sound quality available to the
general public is poor, is also wrong. A run of the mill smart phone
with decent headphones/earbuds can have very high quality sound, and
that's the way many people listen to music. They'ld rather have the
constant availabilty and convenience of that than a room full of
expensive equipment that will sound no better.

Current trends in audio
 

In article ,
Bill Taylor wrote:
The premise of this thread, that sound quality available to the
general public is poor, is also wrong. A run of the mill smart phone
with decent headphones/earbuds can have very high quality sound, and
that's the way many people listen to music. They'ld rather have the
constant availabilty and convenience of that than a room full of
expensive equipment that will sound no better.

If listening on headphones is your thing, it's a long time since you
needed a room full of equipment to do this.

Much the same as a TV. You don't need to have a 60" screen for simply
watching pictures.

However, I don't want either a personal sound system or viewing one in the
comfort of my own house.

--
*The problem with the gene pool is that there is no lifeguard *

Dave Plowman London SW
To e-mail, change noise into sound.

Current trends in audio
 

On 22/01/2017 12:51, Iain Churches wrote:
"Graeme Wall" wrote in message
...
On 22/01/2017 09:52, Iain Churches wrote:
"Brian Gaff" wrote in message
...
Bit unfair on des. I used to see him live and most of the time he looked
better than on the screen. I strongly dispute this old thing of the
camera
never lies. I think that very much depends on how its adjusted in the
first place.
Brian

Yes. White balance.


More to do with make-up and lighting, the white balance on the camera
should be neutral.


It should be, but often is not, as one clearly sees
when the director cuts from one camera to another.
In this situation, makeup and lighting are unchanged.


I'm referring to the era when Des was (dis)gracing our screens when
line-ups were done properly and cameras matched on cuts (also mixes and
wipes!)


--
Graeme Wall
This account not read.