You have already seen how to store sound in memory -- in a
buffer~ -- by recording into it directly or by reading in a pre-recorded audio file. Once the sound is in memory, it can be accessed in a variety of ways with
cycle~,
lookup~,
index~,
play~,
groove~,
wave~, etc.
The main limitation of
buffer~ for storing samples, of course, is the amount of unused RAM available to the Max application. You can only store as much sound in memory as you have memory to hold it. For playing and recording very large amounts of audio data, it is more reasonable to use the hard disk for storage. But it takes more time to access the hard disk than to access RAM; therefore, even when playing from the hard disk, MSP still needs to create a small buffer to preload some of the sound into memory. That way, MSP can play the preloaded sound
while it is getting more sound from the hard disk, without undue delay or discontinuities due to the time needed to access the disk.
MSP has objects for recording directly into, and playing directly from, an AIFF file:
sfrecord~ and
sfplay~. Recording an audio file is particularly easy, you just open a file, begin recording, and stop recording. (You don't even need to close the file;
sfrecord~ takes care of that for you.) In the upper right corner of the Patcher window there is a patch for recording files.
Recording audio into an audio file on disk
sfrecord~ records to disk whatever signal data it receives in its inlets. The signal data can come directly from an
adc~ or
ezadc~ object, or from any other MSP object.
• Click on the
message box marked ‘Create an AIFF file’. You will be shown a Save As dialog box for naming your file. (Make sure you save the file on a volume with sufficient free space.) Navigate to the folder where you want to store the sound, name the file, and click Save. Turn audio on. Click on the
toggle to begin recording; click on it again when you have finished.
In the left part of the Patcher window there is a patch for playing audio files. The basic usage of
sfplay~ requires only a few objects, as shown in the following example. To play a file, you just have to open it and start
sfplay~. The audio output of
sfplay~ can be sent directly to
dac~ or
ezdac~, and/or anywhere else in MSP.
Simple implementation of audio file playback
• • Click on the
openmessage box marked ‘Set the current file’, and open the audio file you have just recorded. Then (with audio on) click on the
toggle marked ‘Play/Stop’ to hear your file.
Because
sfplay~ does not need to load an entire audio file into memory, you can actually have many files open in the same
sfplay~ object, and play any of them (or any portion of them) on cue. The most recently opened file is considered by
sfplay~ to be the ‘current’ file, and that is the file it will play when it receives the message
1.
• Click on the remaining
openmessage boxes to open some other audio files, and then click on the
message box marked ‘Define cues, 2 to 9’.
The
preload message to
sfplay~ specifies an entire file or a portion of a file, and assigns it a
cue number. From then on, every time
sfplay~ receives that number, it will play that cue. In the example patch, cues
2,
3, and
4 play entire files, cue
5 plays the first 270 milliseconds of
sacre.aiff, and so on. Cue
1 is always reserved for playing the current (most recently opened) file, and cue
0 is reserved for stopping
sfplay~.
Whenever
sfplay~ receives a cue, it stops whatever it is playing and immediately plays the new cue. (You can also send
sfplay~ a
queue of cues, by sending it a
list of numbers, and it will play each cue in succession.) Each
preload message actually creates a small buffer containing the audio data for the beginning of the cue, so playback can start immediately upon receipt of the cue number.
Now that cues 0 through 9 are defined, you can play different audio excerpts by sending
sfplay~ those numbers. The upper-left portion of the patch permits you to type those numbers directly from the computer keyboard.
ASCII codes from the number keys used to send cues to sfplay~
• Click on the toggle marked ‘Keyplay On/Off’. Type number keys to play the different pre- defined cues. Turn ‘Keyplay’ off when you are done.
Before you define a cue, you will probably need to listen to segments of the file to determine the precise start and end times you want. You can use the seek message to hear any segment of the current file.
• Open your own audio file again (or any other audio file) to make it the current file. In the right portion of this patch, enter an end time for the seek message. The excerpt you have specified will begin playing. Try different start and end times.
Once you find start and end times you like, you could use them in a
preload message to establish a cue. Because
sfplay~ can't know in advance what excerpt it will be required to play in response to a
seek message, it can't preload the excerpt. There will be a slight delay while it accesses the hard disk before it begins playing. For that reason,
seek is best used as an auditioning tool; preloaded cues are better for performance situations where immediate playback is more critical.
The patch in the lower right portion of the Patcher window demonstrates the use of the right outlet of
sfplay~. When a cue is done playing (or when it is stopped with a
0 message),
sfplay~ sends a
bang out the right outlet. In this example patch, the
bang is used to trigger the next (randomly chosen) cue, so
sfplay~ effectively restarts itself when each cue is done.
When a cue is completed, sfplay~ triggers the next cue
Note the importance of the
gate object in this patch. If it were not present, there would be no way to stop
sfplay~ because each
0 cue would trigger another non-zero cue. The
gate must be closed before the
0 cue is sent to
sfplay~.
• In the patch marked ‘Play random excerpts’, click on the
message box to preload the cues, then click on the
toggle to start the process. To stop it, click on the
toggle again. Turn audio off.
For large and/or numerous audio samples, it is often better to read the samples from the hard disk than to try to load them all into RAM. The objects
sfrecord~ and
sfplay~ provide a simple way to record and play audio files to and from the hard disk. The
sfplay~ object can have many audio files open at once. Using the
preload message, you can pre-define ready cues for playing specific files or sections of files. The
seek message to
sfplay~ lets you try different start and end points for a cue. When a cue is done playing (or is stopped)
sfplay~ sends a
bang out its right outlet. This
bang can be used to trigger other processes, including sending
sfplay~ its next cue.
See Also
Name |
Description |
sfplay~ |
Play audio file from disk
|
sfrecord~ |
Record to audio file on disk
|