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Ultimedia Services Version 2 for AIX: Programmer's Guide and Reference


The 16-bit PCM format used by the objects is 16-bits per sample, PCM, twos complement format with the most-significant byte (MSB) first. The 16-bit PCM format is the easiest to manipulate when converting sampling rates or adding other special effects, so many of the audio filter objects either have 16-bit PCM as a source or destination format. The following diagram illustrates how the audio data flows through the audio filter objects:

For example, to convert audio data from A-law to 16-bit PCM, do the following:

  1. Create an UMSALAWtoPCM16 object.
  2. Use this object and an input buffer size with the calculate_output_size method to determine the minimum output buffer size needed to hold the converted data.
  3. Pass the A-law data to filter.

Sample programs using filter objects are located in UMS install directory.

For introductory information, see Programming with Audio Filter Objects.

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