Open Sound System
OSS 4.x Programmer's Guide

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PCM_CAP_BATCH audio device capability

The device may have some extra latencies


Some devices have additional FIFO type buffers in addition to the driver level (DMA) buffer in the main memory. This means that the latencies of this kind of devices may be slightly larger than with "normal" devices.

This some kind of nice to know information. It doesn't have any practical meaning for normal applications (including games) so it doesn't make any sense to check for it. In particular no application should refuse to work with this kind of devices since they are very common

The only case where this capability is usefull is applications that need to know what the exact latencies are. This kind of operation is needed for example when doing multi track hadt disk recordings. The application plays the earlier recorded tracks and records some new instrument at the same time. It's possible to align the recorded track with the previous ones if the exact latencies are known in both directions. The application may need to use some manually measured delay constants with devices that have additional buffers.

Audio device capabilities like PCM_CAP_BATCH can be checked using the SNDCTL_AUDIOINFO or SNDCTL_DSP_GETCAPS ioctl calls.

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