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Format tags represent the names of individual formats, such as PCM. Filter tags represent the names of individual filters. Typical ACM drivers support one or more types of format or filter, or a combination of both. A set of formats or filters is associated with each of an ACM driver's tags. For example, the sample IMAADPCM driver, a codec, supports the WAVE_FORMAT_PCM format tag for the PCM format type and WAVE_FORMAT_IMA_ADPCM for the IMAADPCM format type. For each format tag, the driver supports a set of individual formats, consisting of combinations of sample rates and sample sizes.
The main difference between codecs and converters is that codecs transform data from a format belonging to one format tag into a format belonging to another format tag, whereas converters transform data between two formats that belong to the same format tag.
The supported format tags and filter tags are declared in the Mmreg.h header file. If you write an ACM driver for a new format type or filter type, register your driver with Microsoft.
Last updated on Tuesday, July 13, 2004