This is a National Stage application of PCT/SG2007/000319, filed Sep. 19, 2007. The foregoing application is incorporated by reference herein in its entirety.
The invention relates to an apparatus and method for transforming an input sound signal. At least one of the disclosed techniques can be used for synthesising a scratched sound, such as a disc jockey (DJ) could produce.
In a basic DJ's setup, two turntables connect to a DJ mixer which pre-amplifies the turntable outputs and mixes them according to the position of a slide controller on the turntable crossfader. During a typical scratch, the DJ controls one turntable with one hand to change its playback rate and the crossfader with his other hand to fade in and out this turntable output. The remaining turntable usually plays some backing music.
Scratching is considered by many as the primary technique for playing the turntable as a musical instrument making “new” sounds from recorded sounds on vinyl records by altering the way they are played. The term “turntablism” is loosely defined as the act of performing on the turntable. Some consider turntablism to be a musical genre in its own right. Turntablists—that is, DJs who practice turntablism—change the rate of playing records with hand movements to produce scratched sounds. Many DJs play as expressively as any traditional instrumentalist, with control of the duration, loudness, articulation, and timbre of individual scratched sounds.
Turntablists produce different types of scratched sound with different scratching techniques; that is, the techniques implemented when the DJ moves the record on the turntable and/or the crossfader slide. The techniques for three fundamental types of scratches [1] are as follows:
Recently DJing software has allowed DJs to extend their scratching techniques to manipulation of digital sound files. Broadly speaking, current DJing systems are able to generate time-varying rates of play back of sound files based on gestural data, graphical representations or stored patterns. Gestural—e.g. hand movement—data is captured by controllers such as control records (on ordinary turntables) [7], computer mice [4, 6], and optical sensors and accelerometers [3]. Graphical representations involve plotting changes in the playback rate over time [5].
Other systems store patterns of these changes for common scratching techniques [4, 6], and among them Skipproof allows limited modifications to the patterns [4]. However, it is possibly true to say that not even a proficient turntablist knows the exact changes in the playback rates for different scratches. This makes graphical representations of scratches not intuitive. Further, it makes synthesis/reproduction of scratches particularly difficult, especially for the unskilled DJ—i.e. DJs with minimal or no DJing/turntablist skills.
Further, there is no standard scratching notation. Though not in wide use, the Turntablist Transcription Methodology is a comprehensive grid system where changes in the playback position in the record are written [2]. An illustration of such notation is given in
Although gestural data preserves expressiveness, it is hard for musicians without DJing skills to execute the correct movements. Pattern-based systems such as those described above, do not require any DJing skills but in their current form these systems provide no means of allowing a DJ to create expressive turntablism performances.
Known techniques such as additive analysis/resynthesis are disclosed in, for example, [9]. Such known techniques as those typified by [9] use linear analysis which is particularly unsuitable for scratching techniques.
The invention is defined in the independent claims. Some optional features of the invention are defined in the dependent claims.
An apparatus incorporating the features of the independent claims may allow synthesis of scratched sounds by musicians, thereby enabling the musicians to describe scratches, scratch strokes and their acoustic characteristics in a musical, concise and reproducible notation. Such an apparatus is capable of producing a minimum of three types of scratches. With this repertoire, it is possible for musicians to create realistic and expressive performances. Further, the disclosed techniques allow users without a DJing skillbase to create realistic scratched sounds from and for music production, allowing creation of new sounds beyond simple stored patterns. In one implementation, the techniques may be used in a personalisable ringtone generator for mobile telephone ringtones.
The present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:
An apparatus for transforming an input sound signal (usable to provide an output or “scratched” sound) is illustrated in
In one implementation the apparatus 10 is a computer apparatus which implements the disclosed techniques either in hardware, software or in a combination thereof. The apparatus may be configured to read, from a computer readable medium, executable code for implementing the disclosed techniques. In another example, the apparatus 10 is a mobile telephone apparatus where memory 20, GUI 22 (mobile telephone display and keypad), recorder module 24 (mobile telephone microphone and processing circuitry) and speaker 26 (mobile telephone earpiece and/or speaker and processing circuitry) are readily available standard mobile telephone features.
For the purposes of the following description, some definitions are now made:
A second apparatus (not shown) for transforming an input sound signal comprises a synthesiser for manipulating, in accordance with a manipulation parameter, a pitch deviation envelope selected with reference to the manipulation parameter to derive a manipulated pitch deviation envelope. The manipulation techniques of this apparatus may be as for synthesiser 12 of
Referring now to
At step 54, synthesiser 12 makes reference to a user-selected manipulation parameter. This may be received from the user at receiver module 14. The process is discussed in further detail below, but in one implementation, the manipulation parameter is a user-defined peak pitch deviation of an output sound signal defined by the user through GUI 22. That is, the user defines the desired peak pitch deviation of the output scratched sound.
At step 56, synthesiser 12 manipulates the pitch deviation envelope in accordance with the user-defined manipulation parameter, e.g. the desired peak pitch deviation of the output scratched sound.
At step 58, filter 18 resamples the input sound signal with respect to the manipulated pitch deviation envelope.
At step 60, the transformed input signal—i.e. the scratched sound—is output as the desired output sound signal by the apparatus 10 from speaker 26.
In one implementation, the manipulation at step 56 takes the form of a shift of the pitch deviation envelope in accordance with the peak pitch deviation of the (desired) output sound signal. That is the envelope of the pitch deviation envelope is shifted in accordance with the user-defined peak pitch deviation of the desired output sound signal. The shift corresponds to a peak pitch difference between a peak pitch of the pitch deviation envelope and a peak pitch deviation of the desired output sound signal. The pitch deviation envelope may comprise at least one of an attack portion and a decay portion, and the synthesiser is configured to stretch or trim the at least one of the attack portion and the decay portion when shifting the pitch deviation envelope. Signal processing algorithms for these operations are described in greater detail with respect to
Prior to its manipulation, the pitch deviation envelope is selected from a library of pitch deviation envelopes by synthesiser 12. The plurality of pitch deviation envelopes are defined by a respective plurality of stroke tables (discussed below) and synthesiser 12 makes the selection from a comparison of the user-defined peak pitch deviation of the output sound signal with respective peak pitch deviation values of the pitch deviation envelopes in the library.
As noted above, a scratched sound comprises one or a sequence of stroke sounds, each of which is determined by at least a pitch deviation envelope and, optionally, an amplitude envelope. Specifying the acoustic details of a number of strokes tends not to be intuitive and can also be tedious. A better representation would allow DJs and computer musicians alike to describe strokes (and scratches) on a musical level. It would also be concise and express main acoustic characteristics of the strokes.
From a technical perspective, scratching is the result of playing back a recording at a time-varying rate. The rate of playback is expressed as pitch deviation ρ. The higher the pitch deviation, the faster the recording plays. ρ=1 when the playback rate is normal, ρ=2 when it is twice the normal speed, and so on. If the recording is digital, the period (in number/amount of samples) between a time it is sampled and the time it is next sampled is equal to the value of ρ. Resampling of the digital signal allows for it to be reproduced at different playback rates. The value of ρ is equal to the original sampling rate divided by the new rate. The resampling process is described in greater detail below with respect to
Taking into account a DJ's mental model of scratches and possible pitch deviation and amplitude envelopes for human performances, a stroke may be synthesised from the following parameters:
Receiver module 14 is configured to receive any one or more of the above parameters as the user-defined manipulation parameter for manipulation of the input sound signal by synthesiser 12.
A stroke corresponds to a hand movement in either a forward or backward direction. There can be silence between strokes, but each of the strokes is usually continuous. Playback of a scratched sound starts at its beginning, where the previous stroke ends, or at an arbitrary position. The peak pitch deviation of the stroke is related to the speed of the hand: the faster the hand, the higher the pitch. The attack and decay times of the stroke define the shapes of the pitch deviation and amplitude envelopes. For example, a simple stab scratch with one forward stroke is specified by a user as follows:
(The Lines Beginning with Semicolons are Comments.)
The first line of code is a scratch statement, and it begins the description of the stab scratch. The last line is a stroke statement, which specifies the acoustic parameters of an individual stroke. If a scratch includes several strokes, the DJ user may insert multiple stroke statements under the same scratch statement.
Turning to
The upper pitch deviation envelope 100 of
It is these pitch deviation envelopes—stored as stroke tables—which are selected and manipulated with reference to the manipulation parameter discussed above to provide the manipulated pitch deviation envelope for use in resampling the input sound signal. The pitch deviation envelope 100 is manipulated/shifted according to the user's definition of the desired peak pitch deviation of the output sound signal.
That is, synthesiser 12 modifies the parameters of the stroke table for the specified scratch type and direction. Synthesiser 12 shifts the entire pitch deviation envelope 100 by the difference between the peak of the selected pitch deviation envelope and the peak of the specified output signal. The attack and decay sections 106, 108 of the envelopes 100 are trimmed/shortened if they are too long or stretched if too short.
Referring now to
Like acoustic musical instrument tones, scratched sounds in the same “register” have a similar timbre. It is possible to synthesise strokes of close peak pitch deviations and the same scratch type and direction using a stroke table. Several strokes may be recorded at different peak pitch deviations (usually 2-3 per octave) to allow variation in the timbre over the full range from −24 to 24 semitones.
One technique for deriving the plural pre-determined pitch deviation envelopes at step 156 comprises conducting a spectral analysis of the template input signal and one or more of the plural recordings of the template input signal (of time-varying speeds of playback). An alignment of the respective spectra is carried out and from this the pitch deviation envelopes are derived. The pitch deviation envelopes are stored in a library of stroke tables in, e.g., memory 20 at step 158. The process of
The low-pass filter has a cutoff frequency dependent on the pitch deviation, and a kaiser-windowed sinc kernel with stopband attenuation of −80 dB. The output 206 of filter 204 is multiplied by multiplier 208 with an amplitude envelope 210, which is as long as the pitch deviation envelope. The scratched sound is then output (step 60 of
When a new sampling point falls between the original points, the new sample value can be obtained by the bandlimited interpolation technique. Based on Shannon's sampling theorem, bandlimited interpolation reconstructs missing sample values by convolving the original samples with the sinc function. The sinc function serves as the impulse response of a low-pass filter whose cutoff frequency is half of the lowest of the original and the new sampling rates.
In summary, the described scratched sound synthesiser allows synthesis of a sound clip for playback at different time-varying rates specified by a user to imitate the sounds a DJ produces on a turntable with different scratching techniques. The sound clip, called a scratchable unit, is usually speech with a single syllable. The scratched sound synthesiser turns the scratchable unit into a scratch with one or more strokes (e.g., a chirp scratch with a forward and a back strokes).
The invention has been described by way of example only and it will be appreciated that various modifications in detail may be made to the described embodiments above without departing from the spirit and scope of the claims. Features presented in one aspect of the invention may be combined with another aspect of the invention.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/SG2007/000319 | 9/19/2007 | WO | 00 | 10/12/2010 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2009/038539 | 3/26/2009 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5512704 | Adachi | Apr 1996 | A |
6011212 | Rigopulos et al. | Jan 2000 | A |
6025552 | Mukaino et al. | Feb 2000 | A |
6150598 | Suzuki et al. | Nov 2000 | A |
7041892 | Becker | May 2006 | B2 |
20010017076 | Fujita et al. | Aug 2001 | A1 |
Number | Date | Country | |
---|---|---|---|
20110023692 A1 | Feb 2011 | US |