Dependencies and Prerequisites

Directly Playing Sounds to Hardware

When a media engine integration is not used Qt Extended requires that either:

1. A OSS Linux sound driver is used
2. A ALSA sound support with OSS compatibility

In addition Qt Extended requires that /dev/dsp is writable and supports the following ioctls:

• SNDCTL_DSP_SETFRAGMENT - Qt Extended will set this to 0x4000c.
• SNDCTL_DSP_SETFM - Qt Extended will set this to AFMT_S16_LE
• SNDCTL_DSP_STEREO - Qt Extended will set this to 1/true.
• SNDCTL_DSP_SPEED - Qt Extended will set this to 44100.
• SNDCTL_DSP_GETOSPACE.

Qt Extended also requires that /dev/dsp can be opened as both blocking and non-blocking. The values set above are the Qt Extended preferred settings for the audio device, and some deviation is allowed. However smooth playing of audio is not guaranteed if the above ioctls cannot be set to the Qt Extended preferred settings.

For example your device only plays at 22500 speed, then it is required to report this when the SNDCTL_DSP_SPEED ioctl is called and should not result in a drop in audio quality. However not supporting GETOSPACE, non-blocking write or SNDCTL_DSP_SET_FRAGMENT will almost certainly result loss of audio quality.