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Topic: Sample loops often disappointing.

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  1. #1

    Sample loops often disappointing.

    The best sample loops are of course these of which you don\'t hear they are looped. Unfortunately lots of times you can hear the sample loop. The volume of the sound becoming softer at the end of a loop, or clicks and pops.

    For example at sampled church organs, or violins etc. When the note is held, often you can hear the loop, sometimes hardly noticable, sometimes very clear.

    Is it actually possible to get loops which you don\'t notice, as if there\'s no loop. That is of course the best loop you can get.

  2. #2
    Senior Member Bruce A. Richardson's Avatar
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    Re: Sample loops often disappointing.

    Theoretically, perfect loops are possible with any waveform that repeats itself perfectly.

    But that\'s the ideal, and the real world situations of space, acoustic phenomena, players\' tone shifts, subtle changes in directionality, low freqency rumble, traffic, and other anomalies make the perfect loop difficult to obtain.

    The longer you wish to loop an evolving sound (like pipe organ, wind instrument, string section) the less static the loop will be tonally. The tradeoff is that the longer you loop, the less likely you\'ll find a \"perfect\" transition. The \"room\" will change, saturating and desaturating over certain frequencies and over time, not to mention the added factors above.

    So the choice is to balance the loop point somewhere between \"perfect, but static,\" which is essentially creating a wave-based oscillator, or on the other extreme, very long loops that may have a noticeable loop point, but which may be less detectable within a full mix than the static \"oscillating\" loop.

    Sometimes you do get great loop points on long loops, but the longer the loop and the more \"interesting\" the timbre, the more variables stack up against it.

  3. #3

    Re: Sample loops often disappointing.

    The older sample libraries were looped pretty much by ear. Later people were aided by visual fedback from the PC. Even later some excellent looping programs were made which automatically detect possible loop points based on zero crossing points and audio content around your suggested loop areas.

    Years ago, there was a Mac program developed by Jupiter Systems (now Antares) called Infinity Looping Tools, which apparently made impossible loops childs play. This became pretty popular with serious sample developers of the time.

    These days most good audio editors have very good loooping aids. You still have to have loopable material and a focussed ear.

    Of course, many libraries are now being made without loops at all. Thankyou disk streaming!

  4. #4

    Re: Sample loops often disappointing.

    I\'ve played toccatas on the church organ with notes held for minutes.
    If the samples aren\'t looped the sound will suddenly stop after a while. So looping certainly is necessairy.

  5. #5

    Re: Sample loops often disappointing.

    One of the main problems in creating my up and coming library of a Romantic Pipe Organ has been the looping. Initially I did it by sight and ear plus at times, redrawing the loop join which was very time consuming (like a day or two to do 61 samples).

    The wonderful Zero X looper sorted that and has proved to be a total Godsend. However, good as it may be, sometimes it just isn\'t possible to find a loop regardless of crossfading or length and if it can’t find a loop, I doubt that anything can.

    As Bruce will know - being in receipt of several disks of my initial tryouts that the individual notes of single stops in my samples are pretty good for their lack of any audible loops and the odd one that is noticable is more down to a tired ear and/or carelessness at the time of creating the loop. Even so, the current results although “acceptable” still need much work and reworking before I will be happy.

    However, on the combinations of several stops played together it becomes more and more difficult;- small combinations of 2-3 stops will generally loop pretty much OK on up to about 10-20 secs but as the stop number increases it becomes far more difficult and with something like 10 stops or more playing, even with loops of 30 and 60 secs or longer it is impossible to find any valid loop within them even with multiple crossfading.

    An alternative is to take a very, very short loop of a few cycles but this then results in a cheesy lifeless sound reminiscent of the very worst examples of electronic church organs – perfectly in tune, no irregularities and also no character or valid tonal qualities whatsoever.

    It doesn’t matter how well in tune the pipes or individual samples are, the very nature of so many pitches and harmonics playing together along with the idiosyncrasies of the instrument itself create horrendous problems since their inter-reaction can and does create beats and cross beats and thus changes in amplitude which last for many seconds.

    Another problem that arises is phase cancellation and thus the benefits of the extension/duplex pipe organ are nullified – ie- in that sort of instrument, a single pipe may do the job of many but in itself, it can only speak once and if it is already speaking, the fact that it is re-switched in another pitch is irrelevant- it has absolutely no effect. However, in sampling, it does and as a result, phase cancellation problems become intolerable and result in a total lack of power where they occur (Bruce, if you are reading this, you will probably notice this in the tenor octave of the Full Great to mixtures plus 16,8,4,reeds combination on quite a few notes).

    Thus I can understand why Peter Ewers just allows a 30 sec sample instead of any attempt at looping – it just is not possible to obtain an acceptable loop.

    There is also the added problem of waiting for any click, volume change or anomaly at the loop point to become apparent when the loop is several seconds long. For one or two notes it might be acceptable but for 61/32 individual samples per combination it just isn\'t a feasible excercise.

  6. #6

    Re: Sample loops often disappointing.

    When will your Romantic Pipe Organ library come out? I\'m very interested. [img]images/icons/smile.gif[/img]

  7. #7

    Re: Sample loops often disappointing.

    SO, have you considered alternate looping instead of straight forward to help get around the \'impossible\' loops?

    It may also be possible to do something like Michiel\'s Grandioso FX to aid situations where you want a single instance of a sample no matter how many notes you play (a bit like adding a single instance of string resonance when you put lift the damper on the piano)

  8. #8
    Senior Member Bruce A. Richardson's Avatar
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    Re: Sample loops often disappointing.

    Looping is easier than people tend to make it. The harder lesson is that nothing can be sacred in sampling.

    If you cannot find a loop point in even a lengthy sample, you can still achieve a loop. It requires a little different approach. First, you must create a loop in the actual waveform via crossfading. This is a lot easier than a \"hard loop\" because you can stretch the crossfade over several samples. This can cure a world of hurts. And now that you have a truly repeating section in the waveform, you can go back into the sample editing process and achieve a perfect \"hard loop.\"

    Vegas is the best tool I\'ve found for this kind of sample editing, because of its fabulous timeline editing. You can see exactly what you\'re doing every step of the way, which is of absolute importance. For instance, in building a loop like we\'re describing, your ability to \"cheat\" a crossfade loop into the equation is still dependent upon keeping the overall waveform in phase, on a similar waveshape within the overall timbre, etc. These things will still create anomolies even over time, not the least of which is the solo to ensemble to solo sound you\'ll get if you land an edit off-phase (or if you crossfade for too long in the wrong spot).

    Once you\'ve gotten the repeat into the sample, setting a hard loop is just a matter of looping to the exact match. You don\'t even have to hit a zero-crossing if there\'s a bunch of low material--as long as you match to the exact sample (which you will have now that you\'ve \"cheated\" it in) the loop will be perfectly silent and musical.

    Of course, some waveforms morph so much they\'ll defy all attempts at looping, because the sound four seconds down the timeline is just completely evolved. Even the crossfade cheat won\'t help this kind of situation too much, since the loop point will just be a \"softer\" glitch. The jump will still be timbrally obvious.

    Sometimes air handlers or electronic phenomena can introduce subsonics into material recorded for samples, and those frequency components really hurt the ability to loop. Good quality EQ should be used to clear away unwanted subsonics. Of course, some instruments\' timbres have subsonic components, but on a case-by-case basis, one must determine the best compromise. DC offset, where the whole waveform is skewed with its phase off-center, can be removed by a simple process.

    Wind instruments are sometimes hard to loop, because it\'s hard to keep the players really still. For instance, a trumpet player might move his bell one inch while playing. That\'s actually very conservative, because even the most stoic players move more than that. But say your microphone array is ten feet from the player. The \"tone\" moves a lot more than an inch at ten feet. So, you are in the editing booth, busily looping your trumpet sample three months later, and you notice you can\'t get a loop, because the trumpet keeps walking across the room and back...even if you don\'t hear a \"pop\" or even identify that it\'s moving, the waveform has changed enough where the imaging is now weird. This is the same phenomenon that causes samples to have those aggravating \"panning\" issues, where one note jumps around. People often assume that this resulted from re-takes or different sessions, when in fact, it\'s just the subtle movements of the human body, multiplied by the distance from which the sample is recorded. In a performance, this moves like a sine wave, gently, and it\'s unnoticeable. When you cut up a recording into samples, your granularity attaches to the note, and it\'s as if you\'ve created the antiphonal orchestra from hell.

    Sorry, I am now sufficiently off topic and will shut up.

  9. #9

    Re: Sample loops often disappointing.

    Hi, Bruce:

    Sorry, I am now sufficiently off topic and will shut up.
    <font size=\"2\" face=\"Verdana, Arial\">No! No! Don\'t shut up quite yet. Can you continue on a bit longer and give some comment with respect to reverse looping and it merits, strengths and weaknesses?

    John

  10. #10
    Senior Member Bruce A. Richardson's Avatar
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    Re: Sample loops often disappointing.

    I think whatever gets the job done the most musically wins. Some sounds will take more kindly to reversing than others. Any of the looping techniques are case by case. Sample by sample, really.

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