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MP3 (and All “Lossy” Digital Compression) Sound Enhancement
and Restoration Getting Nice Vacuum Tube Sound out of Digital
Compression
BBE MP (Minimized Polynomial Non-Linear Saturation) Process
improves digitally compressed sound, such as MP3, by restoring
and enhancing the harmonics lost through compression. BBE MP
works by re-generating harmonics from the source material, effectively
recovering warmth, details and nuance.
BBE MP extends the upper frequency range of MP3/WMA files to
CD-range and a CD’s frequency range to Super Audio CD or DVD
audio range. This is accomplished through over-sampling. |
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MP3 Player, MD Player, CD Player, Headphone Stereo, Mini-Component
Stereo, Portable Stereo, Car Stereo, TV, Satellite Radio (XM,
Sirius),
Internet Radio,Telephone, etc. |
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All Digitally Compressed (Lossy Compression) Audio and CD
(PCM) MPEG Layer Audio (MP1, MP2, MP3), mp3PRO, MPEG4 Audio,
AAC, ATRAC (MD),
AC-3, DTS, Sirius, XM, IBOC, CD (PCM), Telephone, etc. |
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Restores and enhances harmonics lost through compression.
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Restores harmonics’ phase alignment. |
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Restores stereo image reduced by compression, and regain
full-stereo performance. |
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Reveals the delicate and aesthetically delightful details
in the music. |
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Restores warmth to the spoiled digitally compressed sound.
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Expands the upper frequency range by over-sampling |
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Very Simple Digital Software (1/10 to 1/100 of comparable
processes) |
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| The digital compression is mainly performed in frequency
domain. The above left waveform is sound wave seen on a scope. Sampled
at the instant “A”, the spectrum of the sound is mapped like the above
right, indicated as “Original”. This is essentially the sampling process.
The sampled spectrum appears to be very complex. However, it is generally
accepted that smoothing this complex curve does not greatly affect
the sound, while reducing substantial amount (more than 90%) of data.
The result is a smooth curve indicated as “Compression”. This is the
core of digital compression. The sampling continues in the time domain
at about 40KHz, generating the series of spectrum datum displayed
below. |
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| Besides the main frequency domain compression, the
digital compression is performed in the time domain as well. After
the both frequency and time domain compression processes, the spectrum
datum are simplified as illustrated below. (Note: The illustration
is overly simplified for easier understanding.) Thus, a huge amount
of information is removed and permanently lost. (This is the reason
why this type of compression is called “Lossy” Compression.) Moreover,
MP3 often uses a lower sampling rate than a CD, which creates a total
loss of information above the specific frequency (1/2 of the sampling
frequency). Note the sudden information loss over the specific frequency
in the illustration below. The specific frequency also varies depending
on the contents of frequency spectrum. |
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| The sound reproduced from this data file sounds okay,
a piano still sounds like a piano and a trumpet sounds like a trumpet,
but the details, nuance, and musicality are lost. The sound becomes
rather dull. BBE helps to restore and enhance the sound by detecting
the reduced harmonics, boosting them and correcting the time alignments.
However, if the harmonics are completely lost, they must be regenerated.
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| The MP (Minimized Polynomial Non-Linear Saturation) Process effectively
generates harmonics indicated as “ Generated Harmonics by MP Process
” from a “ Fundamental ” note in the illustration below. The even
order harmonics create harmonized, warm and comfortable sound, while
the right amount of odd order harmonics makes the sound brighter and
sharper, when they are added to the original sound. The result is
a warm and comfortable, yet distinguished sound. [This mechanism is
similar to a vacuum tube amplifier, which also tends to generate even-order
and odd-order harmonics, which is why a vacuum tube amplifier sounds
warmer and more comfortable than more advanced modern solid state
amplifiers. |
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| This MP process performance covers the entire audio
bandwidth, evenly from low to high frequencies, without enhancing
or coloring any particular frequency range. The spectrum file, after
adding the regenerated harmonics, is shown below. By using a higher
sampling rate, the MP process can even regenerate audio signals to
fill the once completely-lost high-frequency range. |
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| The BBE Process, which provides a linear phase advance in proportion
to the frequency, is placed before the MP process. The MP process
evenly generates higher harmonics from the entire audio bandwidth.
Since the BBE-processed sound has a tapered time alignment (the higher
the frequency, the more time advance), the generated harmonics are
time-advanced in the higher frequencies. This allows the brain to
analyze the sound more easily with the least amount of added harmonics.
(It is common knowledge in the psycho-acoustic studies that time-advanced
harmonics, compared to fundamentals, make the brain's interpretation
of sound easier.) |
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The BBE process progressively enhances the higher frequencies.
The harmonics generated by the MP process tends to have more elements
in the higher frequencies compared to the lower frequencies. The degree
of this contrast is optimized by the BBE process gain.
The BBE MP process turns digitally compressed and spoiled sound into
a warmer and richer sound with more details, clarity and sharpness.
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| MP3 data contains a minimum amount of information attempting to
reproduce the sound in an acceptable quality. A mere 1/20 of the original
information is kept and the rest is permanently discarded. (Instead,
you can store 20 times more music in the same media.) The narrowed
frequency range is another tactic to compress the file size. It is
noticeable that the MP3 music obviously has less high-frequency information
compared to CD music. This is a common problem to any digitally compressed
audio including WMA. |
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| The BBE MP process not only restores the harmonics within the
band but also extends the high frequency bandwidth up to 24KHz or
48KHz, as shown below, through over-sampling at 48KHz and 96KHz respectively.
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| The pictures below show a part of the frequency spectrum of “I
Remember You” by Dianna Krall, illustrating the effect of the BBE
MP process. The upper picture shows the test material with no information
above 16KHz. The higher frequencies were removed by down-sampling
the original CD at 32KHz. The lower picture illustrates the BBE MP
process regenerating the harmonics over 16KHz when it is applied to
the frequency-limited test material. The effect is obvious at the
beginning of every beat. The center of the picture indicates a large
amount of harmonics over 16KHz being generated from the 6KHz-8KHz
information. |
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| The pictures on this page are details (one beat) of the previous
illustrations. Although it is not clearly visible (due to display
and/or print quality), even the darker regions of the lower illustration
have very subtle regenerated harmonics. This is true throughout the
entire song. |
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| The following three pictures, corresponding with the pictures
on the previous page, show the frequency analysis at the same time-position.
The first picture shows the frequency response of the original CD
in which the upper frequency limit is 22KHz. The second picture is
the frequency limited MP3 test material which contains no information
over 16KHz. |
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| The third picture (below) shows the result of the BBE MP process.
All signals over 16KHz have been regenerated by the MP process. The
upper frequency is thus extended to 24KHz which is even higher than
the original CD's 22KHz limit. In respect to the original CD, the
frequency response is well restored. |
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| This result is similar to mp3PRO decoding. The difference is that
the mp3PRO decoder works only on its own encoded materials whereas
the MP process works on both MP3 and mp3PRO materials, as well as
on all digital audio formats including WMA and AAC. |
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| The CD provides good quality sound for normal audio applications.
However, the new Super Audio CD or DVD audio exceeds the CD's quality
by far. This is because of its higher sampling rate (wider bandwidth)
and greater number of audio bits. |
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BBE MP extends the high frequency response of CDs to the level
of Super Audio CD or DVD audio. This is realized by over-sampling.
The figure above shows the CD's upper limit of 22KHz being extended
to 48KHz by over-sampling at 96KHz. The sound becomes smoother with
the increased details.
The waveforms on the next page are details from Emmylou Harris's “I
Still Miss Someone.” The upper picture shows a WAV file obtained by
re-sampling the CD at 44KHz ? an exact copy of the original CD. The
bottom picture shows the result of the BBE MP process, slightly over-sampled
at 48KHz. Quite a few high frequency elements (small vibrations) are
seen riding on the large waves. These are the harmonics generated
by the BBE MP process. |
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| This is an example of vintage recording restoration using the
BBE MP process. The first picture is Peggy Lee's 1941 original recording
(recently digitally re-mastered for CD) “On the Sunny Side of the
Street.” The part in detail is a few beats of Benny Goodman's clarinet.
This old SP recording has absolutely no information above 10KHz. The
second picture illustrates the BBE MP process generating the higher
harmonics all the way up to 20KHz. Perhaps Benny Goodman's clarinet
sounded like this originally, but it had never been recorded. |
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| The following two pictures, corresponding with the pictures on
the previous page, show the frequency analysis at the same time-location.
The first picture shows the frequency response of the original recording.
No information above 10KHz were recorded. The second picture shows
the result of the BBE MP process. All signals over 10KHz have been
regenerated by the MP process. The upper frequency is extended to
20KHz. |
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| The distinctive sound of a telephone is caused by its narrow bandwidth,
especially by its relatively low 4KHz frequency limit which degrades
its clarity. |
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| The MP process extends the 4KHz upper frequency limit through
over-sampling. The figure above illustrates the 4KHz upper limit being
extended to 8KHz by re-sampling the signal at 16KHz instead of the
normal 8KHz. The normal 300Hz ? 4KHz bandwidth is expanded to 300Hz
? 8KHz. By combining the MP process with the BBE T2 (Telephone Technology)
process, both clarity and intelligibility are dramatically improved.
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