a the beat detection engine · 2010. 9. 9. · 4. next, i’ll use the region menu’s create...

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}A The Beat Detection Engine

Digital Performer’s Beat Detection Engine (BDE), introduced in Version 4.5, is a sophisticated tran-sient detection engine that analyzes an audio file, or portions of audio files, and determines wherethe beats of the file or selection are located. Once beats are detected, DP can use this information tointuitively map out the tempo of a soundbite, quantize the beats that reside inside a soundbite,extract a “groove” from a soundbite, split a soundbite up into separate beats, copy the beat loca-tions into other soundbites, and so on. The Beat Detection Engine is a non-destructive beat analysistool that works in the background. When enabled, it looks for the transients within an audio file andmaps out the locations of each beat— that’s all it does. Sounds straightforward, doesn’t it? Well it is. Itonly gets complex or confusing when you start to use your analyzed beats to perform a specific task,such as beat quantization, tempo mapping, and so on.

DP’S BEAT DETECTION ENGINE VERSUS THE PRO TOOLS BEAT DETECTIVEThere seems to be much confusion on what BDE is and isn’t. Digital Performer’s Beat Detection Engine is

not Beat Detective, the feature that is embedded into Digidesign’s Pro Tools software, though they are sim-

ilar. As with BDE, Beat Detective finds beats or transients within an audio selection. Unlike DP’s Beat

Detection Engine, Beat Detective’s transient and beat analysis is a manual process. With Beat Detective,

after you adjust the beat detection settings, you tell Pro Tools what you want to do with the analyzed

audio (such as tempo mapping, quantizing the beats, groove extraction, and so on), and then Beat Detec-

tive goes to work, automatically splicing and dicing, time-stretching and crossfading as needed.

DP’s Beat Detection Engine, however, works in the background. It isn’t a menu command or specific win-

dow within DP; it’s simply a non-destructive algorithm built into Digital Performer that looks for beats

inside an audio file. You can have BDE set to automatically analyze your audio files in the background, or

you can choose to manually apply the process when needed. Once beats have been found and mapped

out, it’s up to you to decide how you wish to use this information. If you never use quantizing, never have

to meticulously edit performances, or never work with ADR material, you may never even know that BDE

is there, quietly mapping the beats of your audio files in the background.

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APPENDIX A} The Beat Detection Engine

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In this appendix, I’m going to demonstrate how to incorporate DP’s Beat Detection Engine to find thebeats of a soundbite, map its tempo, extract a groove from the mapped soundbite, and then apply itsextracted groove to another soundbite. This, of course, is one of the more practical applications ofBDE within the music production workflow—you have two tracks (or loops) and you want to take the“feel,” or groove, from one track and apply it to another track so that they are “locked” together.

Changing the Groove of a SoundbiteIn this example, I’ll be working with two soundbites—an acoustic rhythm guitar loop and a drum loop.Both soundbites have been imported into DP without tempo maps, and for demonstration purposes, Ihave DP’s preemptive beat analysis turned off.

The acoustic rhythm guitar loop is the focus of the song I’m working on, so I want to extract thegroove from the acoustic guitar and apply it to the drum loop. The drums are in the same meter andtempo and complement the acoustic guitar well, but something’s still lacking—the drums aren’t lockedto the acoustic rhythm guitar loop. So what I want to do is extract the groove from the acoustic guitarand then apply it to the drum track— locking the performance of the two soundbites together andimparting the “feel” of the acoustic rhythm guitar on the drums.

Before I dive into the groove extraction/application process, I’ll give a brief description of the stepsin this tutorial.

1. I’m going to start by manually analyzing the beats of each loop. I have DP’s preemptive beatanalysis turned off, so DP hasn’t mapped out any beats.

2. Next, I’ll have DP look at the analyzed beats and calculate the tempos for each soundbite.

3. As I want the acoustic guitar loop to be the focus of my song, I’ll use the Audio menu’s AdjustSequence to Soundbite command to copy the guitar loop’s tempo map into DP’s ConductorTrack.

4. Next, I’ll use the Region menu’s Create Groove command to extract the groove (or rhythmic“feel”) from the acoustic guitar.

5. Once the guitar loop’s groove is extracted, I’ll use the Groove Quantize command to applythe acoustic guitar’s groove to the drum loop. The result, hopefully, will be two tracks thatsound like they were performed together and recorded at the same time.

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Q Changing the Groove of a Soundbite

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Manually Analyzing Beats and Tempo As I have DP’s preemptive beat analysis turned off, I’ll need to manually find the beats in theacoustic guitar and drum soundbites.

Manually analyzing an audio file or soundbite for beats (and tempo) is a fairly straightforwardprocess. If you have Digital Performer set to preemptively analyze beats and your soundbite’s beatshave already been mapped out, feel free to skip forward to the “Working with Your AnalyzedBeats” section.

To manually start the beat detection process:

1. Start by opening the Waveform Editor by pressing Shift+B and selecting the Edit Pane.

TURNING ON PREEMPTIVE BEAT ANALYSISAs discussed earlier, the Beat Detection Engine can be set to automatically analyze audio files in the back-

ground, or you can turn preemptive beat analysis off and apply it manually as needed. The Background

Processing section of the Preferences and Settings window, shown in Figure A.1, provides options for con-

trolling how BDE works. Choose Digital Performer menu > Preferences and Settings and select Background

Processing from the list.

By default, BDE is set to automatically or preemptively analyze audio files within a new project (or proj-

ects created in the current DP version that you’re using) for beats. It will also attempt to determine the

tempo of any file that doesn’t already contain a tempo map. Even though BDE is on by default, you

should go ahead and confirm the Automatic Beat and Tempo Analysis settings within the Preferences and

Settings window.

If you would rather perform this analysis manually, turn off the Automatically analyze beats in this project

option. Just keep in mind that if you turn off DP’s automatic beat detection, you will have to perform any

beat analysis manually before you can use any of Digital Performer’s beat-related commands. See Chap-

ter 13 for a detailed look at the Automatic Beat and Tempo Analysis preferences.

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Figure A.1Preferences for controlling

the Beat Detection Engine

(BDE) are located in the

Background Processing

section of the Preferences

and Settings window.

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2. Next, select the soundbite you want to analyze from the list— in this case, that’s the acousticguitar soundbite. I could have selected both soundbites and analyzed them together, but fordemonstration purposes, I’ll have DP analyze them one at a time.

3. Select the entire soundbite by pressing Command+A. If I wanted to analyze a portion of theguitar loop instead, I would need to make a time-range selection.

4. Once you’ve defined theselection, click on the Beatsmode menu, as shown in Fig-ure A.2, and select the FindBeats In Selection optionfrom the drop-down menu,as shown in Figure A.3.

5. DP will begin the beat analy-sis process and display theFind Beats progress bar, asshown in Figure A.4. To stopthe Find Beats process, sim-ply click the Cancel button.Once beats are analyzed,DP will automatically closethe Find Beats progress bar.

6. To view the analyzedacoustic guitar beats, clickon the Beats tab, locatedabove the Waveform Edi-tor’s Selection End Timeinput field, as shown in Figure A.5.

Figure A.2The Waveform Editor’s

Beats mode menu.

Figure A.5Click the Waveform Edi-

tor’s Beats tab to display

a soundbite’s analyzed

beats.

Figure A.4The Find Beats progress

bar.

Figure A.3The Beats mode menu’s

Find Beats In Selection

option.

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Working with Your Analyzed Beats Once the Beat Detection Engine has analyzed a soundbite or a portion of a soundbite, beats willappear as vertical green lines within the Waveform Editor, as shown in Figure A.6.

Excluding Analyzed BeatsClicking on the Beats tab, I see DP has located and mapped the acoustic guitar’s beats. Besides plac-ing beats on the major downbeats, BDE has also mapped out the guitar’s rhythmic subdivisions. It’sgreat that DP has mapped all the beats, but I don’t want to include every one of them when I calcu-late the soundbite’s tempo—I only need the major beats to do that.

I can tell DP to look only at the significant beats in the soundbite with the Adjust Beat Sensitivityoption, located in the Waveform Editor’s Beats mode menu.

To adjust the sensitivity of the beats:

1. I’ll begin by opening the Adjust Beat Sensitivity command from the Waveform Editor’s Beatsmode menu. I could also use the default keyboard shortcut Control+D.

2. I want to exclude the secondary beats from the soundbite, so I’ll drag the Disabled BeatThreshold slider to the left, as shown in Figure A.7. If I want to include more beats in the selec-tion, however, I could drag the slider to the right.

3. Once I’m happy with the settings, I’ll click the Apply button. Beats that were excluded from theacoustic guitar soundbite now appear dimmed.

Figure A.6Beats are displayed as

green vertical lines within

the Waveform Editor.

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Figure A.7In this example, the Adjust

Beat Sensitivity window

has been used to include

only the major downbeats

of the acoustic rhythm gui-

tar performance.

MUTING AND UNMUTING BEATSWhen the Adjust Beat Sensitivity command is used to exclude analyzed beats, the

beats are not removed or deleted from the soundbite; they are muted instead. Once

muted, beats will appear dimmed (or light gray). DP’s Mute tool can be used to mute

and unmute beats.

If you can’t seem to find the appropriate setting when using the Adjust Beats Sensitivity

slider, you’ll need to compromise and find a slider position that has the lowest number

of stray beats. Once you decide on a setting, click the Apply button. Finally, use the

Mute tool to mute any unwanted beats or to unmute beats you wish to include.

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VELOCITY HANDLESThe small rectangle that appears on each active beat is called the Velocity Handle; it

displays the velocity of each beat, relative to the other beats in the soundbite. Beat

velocities are used when you extract a groove from a beat selection with the Region

menu’s Create Groove command. Drag vertically on a Velocity Handle to change the

velocity for that beat.

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Moving BeatsThere will be times when DP’s BeatDetection Engine incorrectly analyzesthe location of a beat. It may be a littlebehind the beat or a little ahead—orentirely in the wrong place. If I zoom inon the acoustic guitar soundbite, I cansee that one of the beats has beenplaced a little early (or ahead of thebeat), as shown in Figure A.8. It looksas if the guitarist put a heavy accent onthe pickup to the downbeat, fooling DPinto placing the beat there. To correctthis, I can manually change the positionof this beat by horizontally dragging it.

Figure A.8In this example, a beat

has been placed ahead of

the downbeat.

THE BEAT GRIDWhen dragging beats, be aware that, as with any edit operation, the Edit Grid (when

enabled) will constrain any movements to the specified time format in the main Time

Ruler. In addition to the standard Edit Grid, the Waveform and Sequence Editors con-

tain an additional grid, called the Beat Grid, shown in Figure A.9. When the Beat Grid

is enabled, movements or edits are constrained to locations of analyzed beats.

When you’re dragging beats in the Waveform Editor, beats will snap to a beat loca-

tion when you move a beat close to another beat.

If you want to temporarily override this feature and move beats freely, press and hold

the Command key while dragging any beats.

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Figure A.9The Beat Grid button.

Downbeat

Beat

Beat Grid button

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To change the position of a beat:

1. The beat in question is a little early,so I’m going to move it to the right inthe Waveform Editor with the Pointertool. Notice that when I place thePointer over a beat, as shown in Fig-ure A.10, it toggles the hand cursor.

2. Next, I’ll press and hold the Com-mand key to temporarily disable theBeat Grid. This will allow me to movethe beat freely within the WaveformEditor.

3. With the Beat Grid still disabled, I’llclick on the beat and drag it a coupleof milliseconds over so that it lines upwith the downbeat, as shown in Fig-ure A.11. Now there is no need toconfirm any changes, as the to moveis instantaneous.

Now that the acoustic guitar has been ana-lyzed and I have tweaked the beat posi-tions, I’ll go ahead and manually analyzethe remaining drum loop, repeating thesteps discussed in the previous section.

Analyzing a Soundbite’s TempoOnce I have analyzed the beats for both the drum and acoustic guitar loops, I’m ready to have DPcalculate the tempos for both soundbites.

To calculate the tempo of a soundbite(s):

1. First, I’ll Shift-click to select both soundbites in the Soundbite List.

2. Next, I’ll choose Analyze Soundbite Tempo to have DP calculate the tempo for each soundbite.

Figure A.10The Hand cursor.

Figure A.11In this example, the

beat has been manu-

ally moved later in

the soundbite by

approximately three

milliseconds.

Hand cursor

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3. The change is instantaneous. I can confirm the new soundbite tempo by selecting a soundbitein the Soundbite List and clicking on the Information Pane. The Soundbite section of the win-dow, shown in FigureA.12, displays the sound-bite’s information—includ-ing the new soundbitetempo.

Taking a look at the new tempo,I notice that DP has calculatedthe soundbite’s tempo as 80.90BPM. For convenience, I’ll goahead and round the number up to 81 BPM. The Audio menu’s Set Soundbite Tempo commandallows me to change (or set) the tempo for a selected soundbite.

To set a soundbite’s tempo:

1. First, I’ll select the soundbite.

2. Next, I’ll choose Audio menu > Set Soundbite Tempo.

3. In the Set Soundbite Tempo window, shown in Figure A.13, I’ll type in 8811..0000 for the tempo.

4. Finally, I’ll click OK to set the new tempo.

The tempo for the drum loop was calculated to exactly 80 BPM during the Analyze Soundbite Tempoprocess discussed earlier, so I don’t have to bother rounding off the tempo value for it—that’s purelyoptional, of course.

Figure A.12You can view the tempo of

a soundbite from the

Soundbite section of the

Soundbite window’s Infor-

mation Pane.

Figure A.13The Set Soundbite Tempo

window.

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Adjusting the Sequence to Match a Soundbite’s TempoNow that I have calculated and set the soundbite tempos for both loops, I’m going to take theacoustic guitar soundbite’s new tempo and apply that to the sequence’s Conductor Track. This way,any editing and recording (and mixing) I do will be aligned to DP’s Edit Grid. Before I start thisprocess, I’m going to drag both loops into audio tracks within the Sequence Editor. Once they are intheir respective tracks, I can see red vertical lines indicating that the soundbite tempos and thesequence’s tempo do not match, as shown in Figure A.14.

To apply a soundbite’s tempo to the sequence tempo:

1. First, I’ll select the acoustic guitar in the Sequence Editor.

2. Next, I’ll choose Audio menu > Adjust Sequence To Soundbite Tempo. Voila! The sequencetempo is changed to 81 BPM, as shown in Figure A.15. The Time Ruler is updated to reflect thenew project tempo and the red vertical lines have been removed.

Figure A.14In this example, the tem-

pos of each loop do not

match the tempo for the

sequence.

Figure A.15The tempo for the acoustic

guitar loop has been

applied to the sequence.

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Extracting and Applying GroovesWith the soundbite tempos and the project tempo matched, I begin playback of the tracks and cansee and hear the soundbites playing back, but they just aren’t locked together—the acoustic guitar isa little more laid back than the drums. This is where the Create Groove command comes in handy.The work I’ve done so far—mapping the beats and calculating and changing the tempos—was so thatDP could extract the rhythmic elements (including the velocity) from the acoustic guitar track. Oncethe groove is extracted, I can apply it to the drum track, locking the two performances together.

To extract a groove from a soundbite:

1. I’ll start by selecting the acoustic guitarsoundbite in the Sequence Editor.

2. Next, I’ll open the Create Groove com-mand from the Region menu, shown inFigure A.16.

3. Before I can save the new groove, I’llneed to specify where the new groovewill be saved. I can choose (or open)one of DP’s default groove files or Ican create a new one. I decide to cre-ate a new one, so I click the New Filebutton.

4. In the New Groove File window,shown in Figure A.17, I enter the name formy new groove and click OK. Once cre-ated, the new groove file will appear inthe groove list.

5. Next, I’ll select the groove file I created inStep 4 by clicking the Open button.This tells DP where to save the acousticguitar groove. Once the groove file isselected (or opened), the Open buttonwill change to the OK button, allowingme to save my new groove.

6. I name the new groove somethingappropriate, choose eighth notes forthe beat division, and then click OK tocreate (or extract) the acoustic guitargroove. The new groove appears inthe groove list, as shown in FigureA.18.

Figure A.16The Create Groove

window.

Figure A.18Extracted grooves will

appear in the groove

list.

Figure A.17The New Groove File

window.

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7. Once I’ve created the new groove, I’ll close the Create Groove window by clicking on itsClose button.

To apply a groove from a soundbite:

1. First, I’ll select the drum loop in theSequence Editor.

2. Next, I’ll choose Region menu > GrooveQuantize.

3. When the Groove Quantize windowopens, I’ll select the acoustic guitargroove I created in the previous section,as shown in Figure A.19.

4. I can tweak the groove parameters withadditional options by clicking on theMore Choices button. Once I’veselected desired options, the windowwill expand to display extra controls, asshown in Figure A.20.

5. I don’t want to include the velocity curve that was extracted from the acoustic guitar loop. Iwant the drum loop to retain its original volume curve, so I’ll lower the Velocity slider to Off.

6. I click OK to apply the groove. DP creates a new soundbite and processes it with the appliedgroove settings, as shown in Figure A.21.

Figure A.19The Groove Quantize

window.

Figure A.20Clicking the More Choices

button reveals additional

Groove Quantize options.

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Q Summary

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7. Once the processing has been completed and the groove has been successfully applied, I lis-ten to the tracks. The drums (with the applied groove) play back locked together with theacoustic guitar track. Crowds cheer!

SummaryOf course, this was a very simplified look at the groove extraction and application process using DP’sBeat Detection Engine. The soundbites that I was working with were recorded and played well, so itdidn’t take much effort for DP to lock the tracks together. Under less than ideal circumstances, how-ever, it might take some trial and error when adjusting the beats to achieve satisfying results.

The Beat Detection Engine is truly an incredible feature. With some practice and imagination, you’llbe using your analyzed beats in all types of production processes.

Figure A.21In this example, the

Groove Quantize com-

mand has been applied.

BEAT DETECTION ENGINE INTERACTIVE MOVIE TUTORIALSFor a more in-depth look at other creative uses for Digital Performer’s Beat Detection

Engine, be sure to check out the Cool School Interactus Series’ Digital Performer 4 Csi

Master Second Edition CD. The first edition of this CD contains over five hours of inter-

active QuickTime movie tutorials on Digital Performer 4.

To get a feel for what those CDs are like, take a look at the DP4 Csi LE CD included in

the back of this book. This CD contains over an hour of movie tutorials from the Digital

Performer 4 Csi Master and Digital Performer 4 Csi Starter CDs.

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a the beat detection engine · 2010. 9. 9. · 4. next, i’ll use the region menu’s create...

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