L1 Ultramaximizer User Manual
Contents
1. The maximum level of a digital signal is governed by the highest peak in the file Simple normalization finds the highest peak then raises the entire signal so that this peak is at the maximum value However many of these peaks may be of very short duration and can usually be reduced in level by several dBs with minimal audible side effects Those familiar with digital editing systems may even have proved this for themselves by redrawing some trouble some peaks by hand By transparently controlling these peaks the entire level of the file can be raised several more dB than by simple normalization resulting in a higher average signal level The L1 Ultramaximizer avoids the possibility of overshoot by utilizing a lookahead technique that allows the sys tem to anticipate and reshape signal peaks in a way that produces the bare minimum of audible artifacts Because there is no possibility of overshoot L1 can be used with absolute confidence in situations where brickwall limiting is important N luti Any digital signal processing that alters the original digital data mixing gain changes EQ dynamic processing etc generally increases the number of bits required to represent the signal Conventional truncation results in a loss of signal resolution each time the signal is processed The human ear uses this low level information to construct a mental image of the stereo soundstage so any compromise in this area manifests itself as a l2. i Table of Contents Chapter Dvd cdeawacceeniaseeadersdeencaiasis About the L1 3 L1 component plug ins 0 0 3 Chapter gt 00 Some secrets of digital audio 4 About maximum level ssssssssssssssese 4 About maximum resolution 0 4 Why use them and what are they ssssessee 5 A bit about IDR Increased Digital Resolution 0 5 MVADOCE SS scecishesesacouanucetacnesasecsanesesses Using the L1 6 The peak limiter section scesseceee 6 The IDR section sseui 7 Basic control of IDR w ceesseessseeceee 8 An example of IDR resolution improvement uu 9 Ty pel TE 9 Typed 10 Noise shaping Options 10 Chapter 4 ssssssssssssssscsisedssssse Important IDR Info 11 Recommended IDR settings 0 0 12 Chapter 5 16 bit and higher mastering CD DAT 13 Chapter 6 8 bit multimedia mastering 14 PUPS scissc sscitiacieritsstiesreratansicans do all other processing including sample rate conversion u 14 Secondi sisirain N choose IDR settings 14 For lowest noise usses 14 For higher resolution ves 14 For highest resolution usss 14 Third sasen ii reduce the bitdepth 0 14 aA Ptee 7 sassceceniesnetevtnvenevietesvecsnupen Use the LI last 15 L1 Plug In Manual 1 Chapters Chapter9 Chapter 10 2 L1 Plug In Manual Important notes on digital clipping Peak normalized signals Practical Precau
3. MasterList CD is a form of editing playing regions songs with silence or splices between audio regions songs it is recommended to use Normal noise shaping with either Dither typel or type2 However thousands of L1 processed masters have been produced with typel Ultra with no unusual problems Ifyou must process or EQ any previously L1 processed file you will need to create headroom by lowering input on those later processes then probably re limit to restore the average level L1 Plug In Manual 15 Chapter 8 Important notes on digital clipping The digital words representing an audio signal at each moment have a maximum possible positive value and a minimum possible negative value defined by the bit depth of the file format Any attempt to force an audio signal beyond these maximum permitted values for example by applying excessive gain will result in the audio signal being clipped Clipping distortion generally sounds quite unpleasant and is to be avoided However there are other ways in which a signal can become clipped and some of these are far from obvious A Normalize process allows a file to be processed in such a way that the maximum peak level within the file just reaches but does not exceed the digital zero or clipping point This is obviously desirable as it means that the file is as loud as is possible without clipping and in turn this maintains the best signal to noise ratio especially at low bit word lengt
4. audible background crackles but most especially on very cheap CD players While these effects generally don t occur on the majority of mid or hi fi CD players they can be notice able on very cheap products The amount of such crackles on poor pressings is greatly reduced by the Normal noise shaping c If high gain treble boost is subsequently employed This can cause the strongly boosted higher frequencies used by Ultra noise shaping to become so high in level that they become unpleasantly audible or to feed excessive noise energy into loudspeakers Therefore Ultra shaping is best avoided in situations where subsequent heavy equalization may be used A much lower boost of high frequencies is used with the Normal and Moderate noise shapers Ultra will not affect Dolby or broadcast encoders Recommended IDR settings All of the Factory Presets in the Load menu are relatively self explanatory Keep in mind that any combination of dither and noise shaper can be used but the following settings are particularly recommended for different applications and bitdepths General Purpose high quality use including material liable to be edited and EQ ed typel Normal 24 20 16 12 Lowest Noise CD type2 Ultra 24 20 16 12 Low Noise Highest quality typel Ultra 24 20 16 12 Low noise while allowing editing EQ type2 Normal 24 20 16 12 8 excellent for 8 44 1 files High Quality with lowest risks of spurious noises
5. available audio frequency range is smaller at lower sampling rates Such filtering can increase peak sound levels in exactly the same way as attenuating equalizers can But even when increasing sampling rate an increase of peak level can occur This is because the continuous time audio waveform is represented in the digital domain only by its values at the sampling instants It is perfectly possible for the peak value of the continuous time audio waveform to occur at instants lying between two sam pling instants and thus to be higher than the peak value at any of the sampling instants When changing the sampling rate new sampling instants are chosen for the continuous time audio waveform and these new sampling instants may coincide with an increased peak lying between the original sampling in stants This is especially likely to occur with signals with a lot of high frequencies since such signal waveforms change more rapidly between the sampling instants Though artificially contrived signals can be created to really show up this problem in real life an attenuation of at least 0 3 dB or so prior to conversion should provide adequate protection against clipping You might expect sample rate converter designers to account for the possibility by designing in a small amount of attenuation and the cheap ones generally do not But can you safely normalize a file that you know is at the final sample rate Unfortunately not because many compact disc
6. bitdepth of a file is being reduced for example if you have a 16 bit file and need to create an 8 bit final output or if you have a 24 bit file and need a 16 bit final output 14 L1 Plug In Manual Chapter 7 Use the L1 last It is recommended that L1 be used as the final process after all dynamic and EQ adjustments have been made Only when all these processes are finalized should the question of peak level be addressed Instinctively it might seem appropriate to Normalize the file once all other processing has taken place but in practice it may be better to set the peak levels to around 1dB below clipping using L1 For an explanation of this reasoning see the notes on digital clipping The choice of IDR setting depends on the final use to which the file will be put Typel or 2 Normal is recommended for most work Type or 2 Ultra is considered best for final mass production of 16bit and greater masters and for producing a complete disc master which will undergo no further edits An example of this would be a production master DAT run off from a hard disk editing system in a single pass and where no further editing is anticipated all timing is finalized This DAT would then be transferred unchanged through to the glass master When using programs such as Jam MasterList or MasterList CD which in effect string together separate regions of the soundfile you must perform destructive processing with the L1 Since
7. for more information read the Peak Clipping section Factory Presets already set the Out Ceil control to the recommended value Leave the Release time set to the default 1 0 millisecond Set Quantize output for 16 bit for CD DAT or 20 24 for higher archival or mastering medium if your hardware supports the transfer of 16 bits Set Dither type typel or type2 IDR typel is recommended for most high resolution applications Set Shaping Moderate Normal Ultra non Ultra and Normal are recommended for most high resolution applications Select Digital or Analog Domain mode Analog domain is recommended for all final production masters as it gives a little more protection from clipping in poorly designed DA converters without compromising any L1 processes For more information see Digital Analog Domain paragraph in the IDR controls chapter L1 Plug In Manual 13 Chapter 6 8 bit multimedia mastering There is no single best way to process 8 bit files because each method has its strengths and weaknesses The best approach for any given project depends both on your tastes and on the use to which the finished audio file will be put In order to provide some practical guidelines three methods are described here which have been formulated by top beta testers and multimedia developers These techniques employ peak limiting with optional combinations of dithering and noise shaping It is essential that your host applic
8. now possible for the new DVD and other delivery media as well as for archives of masters By using the IDR implemented within the L1 Ultramaximizer optimum results may be achieved during final file preparation mastering and quantization or requantization The greatest possible implementation of IDR available is in the L2 hardware limiter from Waves and features 9th order noise shaping the L1 has 2nd order Therefore L1 can maximize the audio level then increase the perceived resolution of the resulting file L1 Plug In Manual 5 Chapter 3 Using the L1 Threshold rete fie Out Ceiling Hall 18 18 E a C41 5 The peak limiter of the L1 The peak limiter section 1 Open a soundfile in your host application Select part or all of the soundfile you wish to process with the L1 Pass audio through the L1 for more information see your host application system manual 2 Listen to the output of the L1 Set the threshold of the limiter by dragging the left triangle Threshold down Leave the Out Ceiling setting at the maximum value 0 0 dB 3 When the threshold is exceeded by the signal you will see the Gain Reduction indicated on the single Attenuation meter to the right Set the threshold about 4 to 6 dB lower than the peaks in the Threshold meters input You will see that you have from 4 to 6 dB of peak limiting indicated on the Attenuation meter output 4 You l
9. so that you may achieve the best processing for your application In the L1 there are two types of Increased Digital Resolution dither technology typel and type2 The differences between them will likely influence your choice for your project typel gives no nonlinear distortion type2 exhibits lower dither level It is up to you to choose no distortion or lower dither level for your soundfile More information is in the section called IDR Dither Type amp Noise shaping combinations ___ Basic control of IDR Select Quantize level for desired output 20 16 12 8 bit or no IDR by clicking the button to toggle through the choices Alternately if you option click hold on the Quantize button a popup menu will allow direct selection of bitdepth Select Dither typel type2 non by clicking the button Select the type of noise shaping Moderate Normal Ultra non by clicking the Shaping button The following chapter has extensive information on the combination of these 3 options For optimum results level maximization and at least normalization should also be done This is why the L1 includes both advanced peak controlling and IDR together one step maximizes both ect Rceeclunent To hear what truncation an extremely severe form of quantization error sounds like at the 1 bit level present in every signal no matter the bitdepth and how Waves IDR and Noise shaping works try this simple and exagger at
10. soundfile work then you should set the output to the appropriate bit depth 8 or 12 bit The file should be sample rate converted PRIOR to level maximization and dithering 20 bit If you are saving the final output to 20 bit storage medium set the Quantize to 20 bit 24 bit New feature Now the L1 works at 48 bit resolution and is dithered back to 24 bit when this option is chosen Ideal if you have a 24 bit archival medium or intend on a 24 bit file bounce for later work In previous versions the signal was not dithered with this selection and in very old versions of L1 the selection actually said no IDR Dither This controls the type of dithering process typel type2 non Please read the Important IDR Info section com pletely for better comprehension of the options that the two modes of IDR present In brief IDR dither typel yields lower distortion greater linearity IDR dither type2 yields lower dither level Shaping Noise shaping may be selected to suit your preference for each application Select from Moderate Normal Ul tra non Normal and Ultra are recommended for optimal result with typel Moderate and Normal are recom mended for optimal result with type2 however there are no specific restrictions Your preference is the most important factor Noise shaping may be used without IDR being engaged although it is not an optimal use of the technology For multimedia work it is a very good option fo
11. the end of the sound or tail it is during this time that quantization error is most audible although it is present on all low level signals such as elements that are soft in a mix etc Since the entire issue of dithering is a very subtle one we recommend you listen to a rather long piece of audio 2 3 minutes of high quality say 20 bits if possible with a good dynamic range Jazz and classical recordings are ideal If you don t feel you fully understand the trade offs between IDR and Noise shaping settings the option that will generally work well for CD mastering is typel with Normal noise shaping For minimum noise with 16 bit and greater files type2 Ultra maximum resolution typel Ultra IDR technology was designed by Michael Gerzon a Gold medal AES fellow and a world authority in psychoacoustics He also invented the SoundField microphone and was the major contributor to Ambisonics The design of IDR is a result of his long term researches dating back to 1982 with many of the other leading experts in digital resolution enhancement technologies 10 L1 Plug In Manual Chapter 4 Important IDR Info In L1 Waves provides users with three dither options 1 No dither lt non gt This is normal truncation and gives a high degree of nonlinear distortion at low levels This is what most signal processors do 2 IDR typel dither This dither adds a certain amount of noise causing a 5 dB increase in backgr
12. R s different noise shaping filters 6 For this example leave Dither set to non Audition the noise shaping settings to familiarize yourself with the distortion removing properties of IDR For 16 bit work the flexibility of the IDR implementation of L1 gives you the choice of dither and noise shaping Please read the following sections on typel type2 and Noise shaping For specific applications see the appropriate chapter 8 bit 216 bit etc Type This is the purist technology It is designed for no nonlinear distortion or modulation noise at low levels and combines optimal dither noise with psychoacoustic noise shaping When signals are subjected to several stages of higher resolution processing and re quantizing back to lower bitdepths the design of resolution enhancement must satisfy different requirements than a technology designed just for one stage use If applied several times in succession a digital resolution enhancement technology optimized for one stage CD mastering can produce unwanted side effects Waves typel technology however is the first optimized for use at every processing stage allowing for the effects of cascading and subsequent signal processing Typel is also optimized to cause minimal side effects when used with stereo signals Typel is the recommended choice for use with 20 and 16 bit files processing and other high quality mastering applications By combining level maximization peak controlling a
13. ation be able to write a physical 8 bit file on disk we assume you re working from 16 bit files there is very little improvement trying to use L1 on existing 8 bit files Consult your host application manual for details or their tech support staff First do all other processing including Sample Rate conversion Second choose IDR settings For lowest noise Regardless of sampling rate for the lowest level of background noise when working with an 8 bit file it is recom mended that you use the L1 s peak limiter but without dithering or noise shaping The appropriate IDR settings are Quantize 8 bit Dither non Shaping non For higher resolution When working with 22kHz sampling rate music files it is generally best to use Ultra noise shaping and peak limiting without dither typel or type2 The corresponding IDR settings are 8 bit non Ultra This processing approach yields good results for continuous signals such as music only or background files For highest resolution When working with 8 bit files with sampling rates of 22kHz or greater you can use Ultra noise shaping with IDR type2 dithering The appropriate IDR settings are 8 bit type2 Ultra However use will depend on the source material Third reduce the bitdepth Some applications require specific settings to write smaller bitdepth files Read your host application manual or contact their tech support staff for information The following observations are relevant when the
14. ded that the L1 be used last in the processing chain Failure to observe this will not prevent L1 from working but you should be aware that both the absolute brickwall limiting AND the benefits of IDR requantization will be compromised and will need re limiting to maintain the original level l1 component plug ins On most host applications and platforms you can select just the audio processing you need and use only the power necessary to do the job The L1 has several plug in components in the menu As of this printing here are the current components plus a few examples for each Ll limiter mono stereo wideband limiter without IDR track insert voice or instrument limiter SEX maximizer e L1 Ultramaximizer the full mastering plug in with limiter and all IDR options CD mastering multimedia authoring L1 Plug In Manual Ei Chapter 2 Some secrets of digital audio In order to make the best use of the L1 Ultramaximizer it is important that we explain some of the less obvious implications of digital audio Once these have been explained you will understand why Waves thought a product such as L1 was necessary and you will be a in a better position to make use of its powerful features The operation of the L1 breaks down into two main areas 1 maximum level of the digital signal through proprietary peak control 2 maximum resolution of the signal through dithering and noise shaping _ About maximum level
15. ed example NOTE L1 is currently optimized for 48 44 1 32 and 22kHz files 1 Using a 16 bit 44 1kHz soundfile select a desired region Select the L1 plug in within your application and set your system so you can monitor the L1 output 2 Set Dither Type to non and Shaping to non Set Quantize to 8 bit for easier auditioning of quantization distortion 3 Listen to the output of the L1 preview or realtime depending on your host application 4 To more easily hear the quantization error reduce the the input level at least 30dB until you hear the sound becoming distorted in a fuzzy way If necessary depending on the input level pull the Out Ceiling level down also to about 15dB Leave the Threshold at 0 0 You will have to raise your monitor levels quite a bit to hear the distortion noise so do NOT click Bypass until you turn your monitor level down This quantization distortion you are hearing is present in varying degrees in ALL digital signals at the 1 bit level 8 L1 Plug In Manual 5 Click Shaping twice It changes to Normal You will hear the music cleanly the nonlinear distortions are gone and that a steady hiss in the background is now present Of course since you have reduced the input level this hiss will be much more prominent than in actual work and is exaggerated just like the distortion You can cycle throughout the Shaping options to listen to the quantization error removing effects of ID
16. es of low level non linearity but at the expense of a very slightly increased background noise Obviously increased noise levels are not ideal in high quality audio applications but fortunately the perceived level of this dither noise can be greatly reduced by shaping the noise in such a way that it falls into an area of the audio spectrum where the human ear is least sensitive The main point of maximum resolution is simple to capture the best possible quality into a shorter wordlength smaller bitdepth from a longer wordlength higher resolution A bit about IDR IDR is a Waves proprietary noise shaping dither system developed by the late Michael Gerzon and Waves and signifies a major advance in preserving and actually increasing the resolution of the digital signal being processed You can utilize IDR each time during subsequent processes for 16 bit storage or once at the end of a high resolution chain say 24 bit in order to ensure that the final signal has the maximum resolution possible IDR is of particular benefit when data is deliberately requantized from 24 bit to 16 bit 16 bit to 8 bit and so on Dithered outputs of 20 16 12 and 8 bit are available The current version of L1 now features double precision resolution that is that for TDM systems all internal limiting and gains calculated with 48 bit fixed precision on native sys tems 64 bit floating precision is used Dithering back to 24 bit output is
17. f IDR technology Sample rates would include pull down pull up and other rates close to those mentioned here High resolution mastering no further digital editing Setting Dither typel Ultra 4 to 6 dB gain reduction default release time Bitdepth 16 20 24 Sample rates 48 44 1 32kHz Multimedia and low resolution mastering Setting Dither type non Moderate Normal shaping for music shaping non for voice only up to 15 dB gain reduc tion this heavy gain reduction may need longer release times such as 20 40ms Low peak rms ratio sounds such as synthesizers should not have very heavy gain reduction with short release times Bitdepth 8 and 12 Sample rates 22 and 32kHz and similar rates For 11kHz and below Set Dither to non set Shaping to non Use only the peak limiter with 8 bit Quantize setting 20 L1 Plug In Manual
18. he noise shaping options are re optimized for best results at the lower sampling rates and give smaller but still useful reductions of perceived noise If audibility of noise were the only factor the choice would almost always be to use Ultra noise shaping but in some situations heavy noise shaping of the Ultra kind can have some disadvantages and the alternate settings such as Normal or Moderate may be better As mentioned previously it is theoretically possible for any extreme noise shaper to cause trouble with cheap DA converters Therefore we want to include these small notes L1 Plug In Manual 11 Ultra shaping should be avoided in the following situations a Subsequent digital editing when the signal is subjected to later editing At the edit points an extreme noise shaping might cause audible clicks which may be disturbing An example application in which you would avoid use of Ultra shaping would be on CD s with production music or sound effects that would certainly be subject to further digital editing Use Normal for optimum compatibility b Poor Error Correction i e when a signal is destined for a carrier medium with poor error correction such as CDs pressed in pressing plants with poor quality control which are not so widespread these days When errors that are not properly corrected occur the Ultra setting like all forms of heavy noise shaping and other resolution enhancement technologies might cause
19. hs In situations where a higher average sound level is required L1 s peak limiter allows the typical level of signals to be even further increased by gently pulling down the gain without audible nonlinear distortion of waveform peaks L1 can simultaneously rescale the audio data so that the limited peak signals approach or just reach digital zero However by storing soundfiles at the maximum possible level there is a risk that any subsequent processing may take these peak levels too high resulting in clipping distortion Peak limiting to 0dB by whatever means leaves no margin for any subsequent increase in peak level Intuitively you might think that simple gain reduction could be applied without incurring the risk of clipping and equally that any increase in gain would be sure to cause clipping This is true You might also think that applying an EQ boost at any frequency might result in clipping depending on the peak energy level within the band being equalized Again this is true What is far less obvious is that applying an EQ cut also runs the risk of causing clipping To prove this would take a lot of math but the following description should help get the point across At any instant the peak level of a signal may be the result of several components at different frequencies and at different phases relative to each other Some components will add while others will subtract but what happens if you EQ out a frequency that w
20. ise shaping curves for optimal processing in a wide variety of applications and with a wide choice of source material While the operation of conventional limiters is well understood the limiter section of the L1 Ultramaximizer is capable of a very fast overshoot free response and once the limiter threshold has been set the user can then go on to define the actual peak level that the processed signal will reach Once set limiting and level rescaling becomes a one shot process For master ing purposes the peak level of the processed signal would normally be set to 0dB or just below OdB Because a typical digital audio file of music contains many high intensity short duration peaks simple normaliza tion of the file may still result in a low average signal level Using the L1 Ultramaximizer however it is generally possible to significantly increase the average signal level of a typical audio file without introducing any audible side effects In the event that a deliberately limited sound is required however there is more than adequate range of the limiter parameters to recreate vintage effects such as level pumping or severely limited dynamic range The Ultramaximizer is specifically designed for mastering digital editing multimedia and any application that requires limiting and or requantization of the digital signal with highest quality In order to ensure the maximum possible resolution of a processed signal it is very highly recommen
21. l notice that as you pull the Threshold down the output level goes up Leave the Out Ceiling setting at the maximum value 0 0 dB This is your maximum peak output Notice that you have significantly increased the output level If your threshold is at 12dB then you have pushed the signal up 12 dB not that this is recommended With moderate gain reduction the maxi mum level of a file can be significantly increased with minimal audible effect Only the signal above the threshold is limited all signal below the threshold has a constant gain change that Gi L1 Plug In Manual is controlled by the difference between the Threshold and the Out Ceiling It is this function of the L1 that allows you to maximize the level with the amount of headroom desired Release Aten 12 10 peN oO mw A 0 014 000 0 The release time and Attenuation meter 5 Adjust the Release time to suit the application For most sources leave the Release time set to 1 0ms mastering 3 to 7ms The release time controls how fast the L1 recovers to the constant gain after a peak is encountered The IDR section lt a Dither Shaping The IDR processor L1 Plug In Manual After reading this overview make sure to read the chapter Important IDR info which will offer you complete IDR technical information so that you may be able to better choose from the IDR options in L1 Take the time to read about this new technology
22. nd IDR processing 16 bit files created from 20 or 24 bit masters this way can have an apparent resolution of 19 bits an 18dB improvement Type2 Type2 also uses dither with a similar noise shaping curve but the dither is of a unique kind designed to minimize the amount of noise added thereby giving a lower noise level than the IDR typel process but at the expense of some low level distortion Type2 does have some advantages for high quality mastering as well and it is purely your choice whether the ultimate in low distortion of typel is preferred or the additional reduction in dither level of type2 It may be used for multimedia applications of all 8 bit 44 1kHz files and many 8 bit 22kHz files dependent on source material Type is black with no input signal that is there is no dither signal if there is no input See the 8 bit multimedia mastering chapter for more information E S l Another way to decrease the perceived amount of noise and increase perceived resolution is to shape the frequency content of the noise so it matches the ear s sensitivity curves In basic terms noise shaping shifts the energy of the L1 Plug In Manual 9 noise to the frequency ranges where we hear it the least The three options of Noise shaping provided in L1 s IDR section push more of the noise energy to higher frequen cies above 15 kHz where our ears are least sensitive and reducing the noise energy of lower frequencies The th
23. on edits or cheap CD players typel Moderate 24 20 16 12 8 excellent for 8 44 1 files Low noise with lowest risk of spurious noises on edits or cheap CD players type2 Moderate 24 20 16 12 8 excellent for 8 22kHz files Lowest Noise for Multimedia ideal for voice non non 8 excellent for 8 22 or 8 11 files Lowest Distortion for Multimedia music good for music or continuous sound non Normal excellent for 8 22 files not for use with 8 11 12 L1 Plug In Manual Chapter 5 16 bit and higher mastering Here are the basic steps of using L1 in a 16 bit 44 1 48kHz application These steps also apply to 24 and 20 bit mastering All processing EQ sample rate conversion dynamic changes etc MUST be done before L1 processing The L1 Ultramaximizer should be the last processing of the file Ideally dithering occurs only once Ifthe left and right channels need to be balanced adjust the Input levels separately or together by using the input faders Using a 16 or higher bit input file set the Threshold for desired peak limiting For suggestions on how much limiting to do for certain applications see the Specific Applications chapter In general set Threshold for about 4 6 dB of Gain Reduction in the Atten meter e Now take the Output Ceiling up to the maximum peak output you desire You can take this Output all the way to 0 0 dB without any clipping For CD s a recommended setting is 0 3dB
24. oss of spaciousness and transparency Waves IDR prevents this loss of critical low level detail Even when processing 16 bit signals it is normal to process with at least 24 bits resolution or more as in the L1 which is now double precision However as soon as the resolution is pulled back down to 16 bits by rounding or truncation by removing the bottom 8 bits the resulting rounding error produces an audible distortion at low signal levels and a permanent loss of digital resolution that can never be recovered If the audio signal is repeatedly processed and truncated back to 16 bits the losses accumulate causing a significant loss of fidelity most evident as a loss of the tonal subtleties of low level sounds within a mix The human ear uses such low level information to construct a mental image of the stereo soundstage so any compromise in this area manifests itself as a loss of spaciousness and transparency The solution is to properly dither and noise shape a signal each time the wordlength is increased then reduced such as nearly every digital signal process will require 4 L1 Plug In Manual Why use them and what are they Proper dithering is simply this before the requantization reduction of the wordlength a precisely controlled amount of noise termed dither is added to the signal This can convert the low level nonlinear distortion caused by truncation into a simple steady hiss thereby removing all trac
25. ould otherwise be subtracting from the peak level by virtue of its phase The peak is now higher than it was For most audio material this effect will be relatively small typically increasing peak levels of the order of 0 3 dB but is possible that under unfavorable circumstances or with nontypical signals the peak level could increase signifi cantly more than this If an effective peak limiter like the L1 is used because it forces the signal to skim the peak level more often this likelihood of clipping in this way is further increased In practice filters attenuating mid or high frequency components tend to cause the kind of increase in peak level 16 L1 Plug In Manual described but high pass filters that attenuate the bass can sometimes cause much larger increases of peaks of the order of several dBs on heavily limited signals The phase response of certain high or low pass filter types can also increase peak levels by up to 4 dB or thereabouts Bearing in mind what s just been said it might seem logical to keep the signal peaking a few dB below digital zero until all processing has been carried out After that you can safely normalize the signal or can you A related problem with peak clipping can arise when a normalized soundfile or signal is converted to a new sampling rate The reason has to do with the sample rate conversion process itself and during sample rate reduc tion the signal is effectively being filtered the
26. ound noise compared to no dither but completely eliminates all low level distortion and signal dependent modulation effects The result is a very transparent and clean low level sound with a very high resolution 3 IDR type2 dither This dither adds virtually no audible noise and so is 5 dB quieter than typel but it still gives some low level distortion However this distortion is generally much lower than with no dither at all There are four Noise shaping options 1 None No noise shaping resulting in high audible hiss levels and high distortion levels when used without dither 2 Moderate This typically reduces perceived noise by around 6 dB and slightly reduces audible distortion when no dither is used 3 Normal This typically reduces perceived noise by around 8 5 dB and somewhat reduces audible distortion when no dither is used 4 Ultra This gives the greatest perceived noise reduction typically 10 5 dB The noise shaping options of Waves IDR differ from those in most commercial noise shapers by avoiding shapes of noise that sound colored to the ear While this gives less perceived noise reduction than in some of the most extreme shapers on the market the resulting sound is more pleasant less colored and takes more kindly to several generations of processing of sound files The noise reduction figures given here apply to sampling rates of 44 1 or 48 kHz At the lower sampling rates of 22 or 32 kHz t
27. players and some other digital consumer equipment use oversampling digital to analog converters DACs to produce the analog signal fed to the amplifier Such oversampling converters involve a sampling rate conversion process which can and does cause audible peak clipping Once again some designers appear to have overlooked this problem although not as widely as they did in earlier DAC designs Practical P L1 incorporates an analog domain processing mode that estimates the between sample peak levels to reduce the clipping risk but even here the process is not foolproof so that some headroom to avoid clipping may still be needed If you want to normalize and avoid clipping normalize your files after all other processing including sample rate conversion However if you re going to use L1 limiting normalization may be completely redundant In all cases the L1 should be used last L1 Plug In Manual 17 Chapter 9 L1 Controls descriptions ___Quantize This controls the final bit depth 8 12 16 20 24 of the output of L1 It is not related to the input bitdepth 16 bit If you are saving the final output to DAT or CD recorder then set the Quantize to 16 bit Waves plug ins work at an internal resolution of 24 bits or higher during all processing The Quantize setting captures the best data possible for the selected bitdepth 8 and 12 bit If you are saving the final output for low resolution multimedia
28. r music files For complete information read the Important IDR Info section 18 L1 Plug In Manual __Digital Analog Domain When in the Digital Domain position absolutely no sample will be over the Out Ceiling value However after analog conversion it is possible to have peaks higher than in the digital domain This is due to very complex digital audio issues involving peaks between the samples Almost all quality made digital to analog converters have at least 3 dB headroom to allow for these peaks many have at least 12dB headroom You would want to use the Analog Domain position when you wish to have absolute control over any peak that occurs in both the analog and digital domains Some examples as mentioned previously in the manual you wish to accommodate poorly designed DACs the file will undergo further modification such as ADPCM data reduc tion or you wish to have a signal that can be broadcast without further peak controlling In these cases brickwall limiting is desired in both domains and you should put L1 in the Analog Domain mode L1 Plug In Manual 19 Chapter 10 Recommended settings These are intended as a few guidelines for use of L1 Of course your preferences will be based on your experiences the settings here are suggested just for quick reference or as beginning points for your session The Important IDR Info section contains critical information for you concerning all of the choices in the use o
29. ree Noise shaping options differ in the amount of this shifting action Moderate is provided for 8 12 bits files but also is completely usable for 16 bit files Normal is the recommended option for use under most conditions for all bitdepths Ultra is a very high quality setting suitable only for use at the very last stage of mastering high resolution files 16 bit and higher targeted for high quality digital media It is theoretically possible that the relatively high amount of high frequency energy could cause undesirable side effects if the signal is going to be processed or digitally edited again Therefore it is best that Ultra is used in the last stage of file preparation However with many thousands of L1 processed products no such situations have been reported Since it is theoretically possible we wish to inform you of it Most companies do not These theoretical side effects might cause clicks at later edit points if Ultra noise shaping was used if played back on poorly designed D A converters However state of the art designs rarely have these troubles anymore Of course the effect of Noise shaping is even greater when used with typel or type2 dithering since Noise shaping reduces the audibility of the added dither noise Now try the full effect of IDR technology by listening to the same material with both IDR types and different kinds of noise shaping The most obvious places to examine are notes or reverb during
30. tions ee EEA L1 Controls descriptions Quantize 16 bit 8 and 12 bit 18 20 and 22 bit 24 bit Dither Shaping Digital Analog Domain Chapter 1 About the L1 The L1 Ultramaximizer is a highly sophisticated audio processing tool kit combining an advanced peak limiter a level maximizer and a high performance re quantizer based on the implementation of Michael Gerzon s IDR Increased Digital Resolution noise shaped re dithering process Why do we call it the Ultramaximizer Because it maximizes both the level of the digital signal and the resolution of the final file working on both ends of the digital word output New in the L1 is 48 bit double precision processing offering improvements for all resolutions and the opportu nity to dither to a 24 bit output for archives and DVD The L1 offers superb requantization for all bitdepths includ ing 24 20 16 12 and 8 bit outputs The development of L1 s lookahead peak limiter provides the mastering engineer with the capability to increase soundfile resolution and production master levels with precise control and dithering options The algorithms are carried out to their fullest potential in the L2 hardware from Waves although they have their roots in the L1 Waves IDR process brings more choices greater control and unmatched compatibility to the mastering environment whether for high resolution CD or low resolution multimedia IDR offers two dither types and three no
Download Pdf Manuals
Related Search