Signal Viewing and Buffering

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Signal Viewing and Buffering            

• Week 13
• IAT-204, Spring 2007SFU Surrey

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Todays topics

• Viewing Signal Data
• Buffering and Saving
• Playback and Loop

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Learning Objectives

• Describe different objects for signal viewing
• Explain how to read from /write into file to
  build/save buffered sound signals
• Elaborate on how to play or loop buffered sound
  signals

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Viewing Signal Data

• MSP objects for viewing signal data
• meter
• Display/send peak amplitude
• levelmeter signal level meter
• Display signal level with optional ballistics
• number signal monitor / converter
• Display/send the instantaneous amplitude of an
  input signal, or convert floats into output
  signal
• capture
• View a signal excerpt
• spectroscope
• Display spectrogram or sonogram

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meter signal level meter

• Also sends the peak signal value out its outlet
  as a float.

• Displays the peak amplitude it has received
  since the last display

• The output value is always a positive number,
  even if the peak value was negative

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levelmeter signal level meter

• Display signal level with optional ballistics,
  which can be set up by setting its attack/release
  (in ms) properties

• Output signal levels in dB

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number signal monitor / converter

• Input monitor display the current value of the
  signal coming in at specified time interval
  snapshot

• Output converter
• Converts any float it receives into a signal
  sent out the left outlet floating-point number
  box

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number as line objects

• If number receives a non-zero number in its
  right
• inlet, it uses that number as an amount of time
  to
• interpolate linearly to the new value whenever
  it
• receives a number in the left inlet
• Equivalent to sending a list to line.

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capture View a signal excerpt

• Collect samples from a signal and examine them in
  a text window

• Useful for seeing precisely what has occurred in
  a signal over time
• It stores signal samples (4096 by default),

• You can type in an argument to specify how many
  samples you want to view

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spectroscope

• Spectrogram mode displays signal spectrum in two
  dim mode frequency vs. amplitude

• Allow you to display signals in modes
  Spectrogram or sonogram

• Sonogram mode displays graph of
• the spectrum over time, with amplitude displayed
  as grayscale or color
• depth

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Build and Save Buffer

• buffer multichannel sample buffer, works in
  conjunction with many different objects
• play/groove (to play the buffer)
• record (records into the buffer)
• peek (to write into/read from the buffer like
  the table object)
• How to work with buffer?

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Build and Save Buffer

• Build buffer object by reading files

• Arguments are buffer name, optional filename to
  read or optional initial length, and optional
  number of channels (1, 2, or 4)

• read message \
• filename
• an offset into the file (ms)
• the size to read in (ms)
• the number of channels to read from the file

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Buffered Signal Playback

• Two major objects
• play simply play back signals from a buffer
• groove variable-rate looping sample playback
  from a buffer

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Use play to play back

• Specify the buffer object name accurately

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Use groove to loop

• Turn on the loop attribute
• Set up the min/max loop points

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Summary of Todays Topics

• Different objects for signal viewing
• How to read from /write into file to build/save
  buffered sound signals
• How to play or loop buffered sound signals