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LAME conversion to MP3



 
 
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  #21  
Old February 21st 20, 11:45 PM posted to rec.audio.pro,uk.rec.audio
geoff
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Posts: 1,597
Default LAME conversion to MP3

On 22/02/2020 8:38 am, lid wrote:
> On 21 Feb 2020 12:33:06 -0500,
(Scott Dorsey) wrote:
>
>>> I would keep the oriiginal WAV file, but web browsers can't play this
>>> particular type of WAV file.

>>
>> Have you considered retracking this with proper encoding and microphone
>> placement?
>> --scott

>
> The recording device only produces WAV files with sample rate 48 KHz
> and bit rate 192 kb/s. The WAV files it produces cannot be read by MS
> Edge and other web browsers.
>
> Can you download and unzip the file
>
>
http://c-compiler.com/myfiles/a-mp3.zip
>
> and listen to the files x.wav and x.mp3 ? Are they similar?


Yes they are similar, almost if not totally indistinguishable, not
helped by of the overall clutter or extraneous sounds.

>
> The audio files are 4 seconds each, and to my untrained ear they sound
> much the same.
>
> What do you think, is the encoding scheme I chose for conversion from
> WAV to MP3 fit for purpose?


Kind of depends what your purpose is. The only unsatisfactory part is
the incredibly poor recording.

geoff

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  #22  
Old February 22nd 20, 12:08 AM posted to rec.audio.pro,uk.rec.audio
Andy Burns[_2_]
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Posts: 3
Default LAME conversion to MP3


Scott Dorsey wrote:

> since you refuse to explain why you want to do any of this, it's hard
> to know.


I suspect the answer to that is somewhere between "prove that
mindcontrol is real" and "show that MI5 are out to get me"
  #23  
Old February 22nd 20, 05:02 AM posted to rec.audio.pro,uk.rec.audio
Trevor
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Posts: 2,777
Default LAME conversion to MP3

On 22/02/2020 4:33 am, Scott Dorsey wrote:
> > wrote:
>>
>> You are correct. The file uses ADPCM compression, I believe, so it is
>> not CD quality. It uses a bit depth of 4 bits, which is de-compressed
>> when playing to 16 bit.

>
> ADPCM is not lossy compression at all, it is a sort of encoding method
> intended to get more usable dynamic range with fewer bits but it's still
> straight PCM... just not linear PCM. I had no idea you could do it with
> as few as 4 bits, but 8-bit u-law encoding is typical telephone quality
> today.


Yes, and he never said "lossy compression". However there is plenty of
loss already inherent in those low bit encoding schemes anyway. The
whole point of MP3 etc was to *reduce* the audible loss at low data
rates. I'm sure you know this, but the old compression Vs compression Vs
compression linguistic problem raises it's head once again.

  #24  
Old February 22nd 20, 05:09 AM posted to rec.audio.pro,uk.rec.audio
Trevor
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Posts: 2,777
Default LAME conversion to MP3

On 22/02/2020 4:30 am, Scott Dorsey wrote:
> If I were you I'd try to do some processing to improve intelligibility rather
> than worrying about fidelity. High pass everything below 200 Hz or so,
> then low-pass everything above maybe 6KHz, and consider sticking a presence
> boost in there. You might then consider an expander and fiddling with the
> threshold on the expander to try and boost the voice out of the noise.
>
> I think you are worried about entirely the wrong thing here.
> --scott


Yes he seems to keep ignoring the fact the recording is lousy in the
first place and therefore worrying so much about MP3 settings is rather
pointless.
  #25  
Old February 22nd 20, 05:45 PM posted to rec.audio.pro,uk.rec.audio
[email protected]
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Posts: 24
Default LAME conversion to MP3

On Sat, 22 Feb 2020 16:02:44 +1100, Trevor > wrote:

>On 22/02/2020 4:33 am, Scott Dorsey wrote:
>> > wrote:
>>>
>>> You are correct. The file uses ADPCM compression, I believe, so it is
>>> not CD quality. It uses a bit depth of 4 bits, which is de-compressed
>>> when playing to 16 bit.

>>
>> ADPCM is not lossy compression at all, it is a sort of encoding method
>> intended to get more usable dynamic range with fewer bits but it's still
>> straight PCM... just not linear PCM. I had no idea you could do it with
>> as few as 4 bits, but 8-bit u-law encoding is typical telephone quality
>> today.

>
>Yes, and he never said "lossy compression". However there is plenty of
>loss already inherent in those low bit encoding schemes anyway. The
>whole point of MP3 etc was to *reduce* the audible loss at low data
>rates. I'm sure you know this, but the old compression Vs compression Vs
>compression linguistic problem raises it's head once again.


Can you download and unzip the file

http://c-compiler.com/myfiles/a-mp3.zip

and listen to the files x.wav and x.mp3 ? Are they similar?

They are only 4 seconds in length, there is very little work involved
in listening to these two files.

I am looking for one or two more opinions as to whether the source WAV
file and destination MP3 file are similar to the ear. You might try
listening through earphones, for better clarity.

Sorry to keep harping on about this, but I am trying to obtain
re-assurance that the conversion to MP3 gives a file which is
effectively the same to the ear as the source WAV.
  #27  
Old February 22nd 20, 07:02 PM posted to rec.audio.pro,uk.rec.audio
[email protected]
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Posts: 24
Default LAME conversion to MP3

On 21 Feb 2020 16:24:46 -0500, (Scott Dorsey) wrote:

> > wrote:
>>On 21 Feb 2020 12:30:08 -0500,
(Scott Dorsey) wrote:
>>
>>>If I were you I'd try to do some processing to improve intelligibility rather
>>>than worrying about fidelity. High pass everything below 200 Hz or so,
>>>then low-pass everything above maybe 6KHz, and consider sticking a presence
>>>boost in there. You might then consider an expander and fiddling with the
>>>threshold on the expander to try and boost the voice out of the noise.
>>>
>>>I think you are worried about entirely the wrong thing here.

>>
>>The actions on the source WAV file must be such as to maintain
>>authenticity. If I start changing and deleting parts of the audio
>>file, that would render the output file as different from the source
>>file, and make it untrustworthy.

>
>I don't know about UK law, but as soon as you have made a transfer to
>MP3, or even a transfer to flat PCM, your file is no longer admissible in
>court. Rules of evidence in the UK are likely different but you can hire
>any one of a number of excellent forensic audio people there who can create
>an audition file which is separate from the traceable reference file (which
>is what is normally done for courtroom proceedings in the US).


I need this audio file for two purposes.

1) to present to a court or tribunal in support of proceedings, as
evidence. For this I would submit the source WAV file, unedited, apart
from being clipped.

2) to post to a web page in a public-facing role. This should be an
MP3 file, preferably indistinguishable to the average human ear from
the WAV,

Thank you for your advice re US law. I don't know what the situation
is in the UK regarding this sort of evidence.


>>Sorry to bug you, but; I've used the source WAV parameters; sample
>>rate 48,000 Hz and bit rate 192 kb/s; when converting to the MP3. I
>>don't know if this is proper for the destination MP3 file. What is
>>your view?


If you could provide some advice regarding parameters for the target
MP3 file, as in the above quoted paragraph, it would be appreciated.
  #29  
Old February 22nd 20, 10:11 PM posted to rec.audio.pro,uk.rec.audio
geoff
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Posts: 1,597
Default LAME conversion to MP3

On 23/02/2020 8:02 am, lid wrote:
> On 21 Feb 2020 16:24:46 -0500,
(Scott Dorsey) wrote:
>
>> > wrote:
>>> On 21 Feb 2020 12:30:08 -0500,
(Scott Dorsey) wrote:
>>>
>>>> If I were you I'd try to do some processing to improve intelligibility rather
>>>> than worrying about fidelity. High pass everything below 200 Hz or so,
>>>> then low-pass everything above maybe 6KHz, and consider sticking a presence
>>>> boost in there. You might then consider an expander and fiddling with the
>>>> threshold on the expander to try and boost the voice out of the noise.
>>>>
>>>> I think you are worried about entirely the wrong thing here.
>>>
>>> The actions on the source WAV file must be such as to maintain
>>> authenticity. If I start changing and deleting parts of the audio
>>> file, that would render the output file as different from the source
>>> file, and make it untrustworthy.

>>
>> I don't know about UK law, but as soon as you have made a transfer to
>> MP3, or even a transfer to flat PCM, your file is no longer admissible in
>> court. Rules of evidence in the UK are likely different but you can hire
>> any one of a number of excellent forensic audio people there who can create
>> an audition file which is separate from the traceable reference file (which
>> is what is normally done for courtroom proceedings in the US).

>
> I need this audio file for two purposes.
>
> 1) to present to a court or tribunal in support of proceedings, as
> evidence. For this I would submit the source WAV file, unedited, apart
> from being clipped.
>
> 2) to post to a web page in a public-facing role. This should be an
> MP3 file, preferably indistinguishable to the average human ear from
> the WAV,
>


Thanks for finally explaining the context.

But careful - Surely # 2) would compromise # 1) ?

geoff
  #30  
Old February 23rd 20, 12:14 AM posted to rec.audio.pro
[email protected]
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Posts: 1,718
Default LAME conversion to MP3

Trevor wrote:


>I'm sure you know this, but the old compression Vs compression Vs
>compression linguistic problem raises it's head once again.



That's why, in both professional and layman circles, I refer to compression
ONLY in the context of dynamics and dynamics processing, and 'data size
reduction' or 'data reduction' in the context of lossy file conversion.

If someone else uses the term 'compression' or 'compressed', I automatically
ask what threshold, ratio, and attack and release speeds they used. When they
say 'No, I mean compressed down to a smaller file size' I respond, 'Oh, you mean
data-reduced, or data reduction. When they ask me why I don't use 'compression
to mean the same thing, I just look at them, expressionless and tell them:

Think about why.

That usually convinces them.
 




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