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LAME conversion to MP3



 
 
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  #11  
Old February 20th 20, 05:12 PM posted to rec.audio.pro,uk.rec.audio
Andy Burns[_2_]
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Posts: 3
Default LAME conversion to MP3

John Williamson wrote:

> I just opened your original .wav file in Adobe Audition, and it was a
> compressed file anyway before you started processing it.
>
> Filename:*** x.wav
> Folder:*** F:\Downloads\a-mp3 (1)
> File Type:*** 48000Hz, 16-bit, Mono
> Uncompressed Size:*** 374.71 KB (383,708 bytes)
> File Format:*** ACM Waveform
> ****Microsoft ACM: IMA ADPCM


Maybe it was originally recorded with ATRAC compression, if originated
on Mike's minidisc recorder?
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  #12  
Old February 20th 20, 08:23 PM posted to rec.audio.pro,uk.rec.audio
[email protected]
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Default LAME conversion to MP3

On Thu, 20 Feb 2020 15:36:51 +0000, John Williamson
> wrote:

>On 20/02/2020 12:00, lid wrote:
>
>> Do the two files sound the same? Can you detect any loss of quality
>> between the source WAV and destination MP3?
>>

>They sound as near to identical as makes no difference on these speakers.


Good. Thank you for the re-assurance.

When I listen to the audio file in WAV and MP3, on earphones, it
sounds exactly the same. I am unable to detect any loss of quality.

Perhaps we could have one or two more people offering opinions on
this?

>For a conversion that is as close to the original as possible, I use
>320kbps as the MP3 bit rate, starting with 24 or 16 bit depth .wav
>files, and most people can't tell the difference even when the original
>contains noise sources such as cymbals as well as musical instruments.
>
>192 kbps is good enough for normal listening on domestic equipment or in
>a car, in my experience.


The bit rate of the source file is 192 Kbps, and the source file has
sample rate 48,000 Hz. I have kept the same parameters when converting
to MP3, so the MP3 file has bit rate 192Kbps and sample rate 48 KHz.

Is this the right approach to take with the conversion? Intuitively I
would think the bit rate and sample rate should be the same for both,
but my intuition may be wrong.

>> You might try using earphones, that will aid comprehension.


I can hear more clearly through earphones than laptop speakers.
  #13  
Old February 20th 20, 08:40 PM posted to rec.audio.pro,uk.rec.audio
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Default LAME conversion to MP3

On Thu, 20 Feb 2020 15:35:35 +0000, John Williamson
> wrote:

>By the way, I just opened your original .wav file in Adobe Audition, and
>it was a compressed file anyway before you started processing it.
>
>Filename: x.wav
>Folder: F:\Downloads\a-mp3 (1)
>File Type: 48000Hz, 16-bit, Mono
>Uncompressed Size: 374.71 KB (383,708 bytes)
>File Format: ACM Waveform
> Microsoft ACM: IMA ADPCM
>Size on Disk: 94.05 KB (96,316 bytes)
>Last Written (local): 2/20/2020 12:53:29.780
>Length: 0:03.996
> 191,854 samples
>
>This page explains what it has already done to your original recording.
>
>https://docs.microsoft.com/en-us/win...ession-manager
>
>Not all .wav files are uncompressed, or even the same format if not
>compressed.


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.

It's really just a practical question, is the MP3 audio quality as
good as the (compressed) source WAV.

I would keep the oriiginal WAV file, but web browsers can't play this
particular type of WAV file.
  #14  
Old February 21st 20, 06:30 PM posted to rec.audio.pro,uk.rec.audio
Scott Dorsey
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Posts: 16,701
Default LAME conversion to MP3

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
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #15  
Old February 21st 20, 06:33 PM posted to rec.audio.pro,uk.rec.audio
Scott Dorsey
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Posts: 16,701
Default LAME conversion to MP3

> 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.

>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
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #16  
Old February 21st 20, 08:38 PM posted to rec.audio.pro,uk.rec.audio
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Default LAME conversion to MP3

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?

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?
  #19  
Old February 21st 20, 10:24 PM posted to rec.audio.pro,uk.rec.audio
Scott Dorsey
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Posts: 16,701
Default LAME conversion to MP3

> 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).

>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?


My view is that you are looking at totally the wrong thing, but since you
refuse to explain why you want to do any of this, it's hard to know.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #20  
Old February 22nd 20, 12:41 AM 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 6:30 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
>


Yeah, the source media content is the only thing getting in the way of
intelligibility. Unfortunately most of the extraneous clutter is not too
far removed from the vocal frequencies.

Looks like more of a job for Spectral Layers, or a Mac or Linux
equivalent, to edit out the unwanted noises. Arduous fiddly work, but if
the content is really that important ....

geoff
 




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