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Plugins:PepperAudioAPI: Difference between revisions
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→Problem Summary
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with both input channel(s) and output channel(s), audio can stream | with both input channel(s) and output channel(s), audio can stream | ||
isochronously on the same callback. | isochronously on the same callback. | ||
</pre> | |||
=====queryCapability() Details===== | |||
This section goes into more detail on what queryCapability() returns based on the input | |||
enum. | |||
<pre> | |||
notes: | |||
queryCapability() can be called before initializeContext to probe | |||
capabilities of the audio device. queryCapability() should only be | |||
called from the NPAPI thread. If the output parameter is NULL, | |||
queryCapability will return NPERR_INVALID_PARAM. | |||
queryCapability(npp, NPAudioCapabilitySampleRate, &value) | |||
output value: | |||
Current 'native' sample rate of the underlying audio system. If an | |||
application can use this rate, less upsampling/downsampling is | |||
likely to occur at the driver level. | |||
NPAudioSampleRate44100Hz | |||
NPAudioSampleRate48000Hz | |||
NPAudioSampleRate96000Hz | |||
notes: | |||
Both NPAudioSampleRate44100Hz and NPAudioSampleRate48000Hz are | |||
always available, and will be upsampled/downsampled as needed. By | |||
querying for the native sample rate, an application can avoid | |||
implicit sample rate conversion. | |||
queryCapability(npp, NPAudioCapabilitySampleType, &value) | |||
output value: | |||
Native sample format of the underlying audio system | |||
NPAudioSampleTypeInt16 | |||
NPAudioSampleTypeFloat32 | |||
notes: | |||
NPAudioSampleTypeInt16 will always be available. By querying for | |||
the sample format, an application may be able to discover higher | |||
quality output formats. | |||
queryCapability(npp, NPAudioCapabilitySampleFrameCount, &value) | |||
Query the audio system for the sample buffer frame count recommended by | |||
NPAudioQuerySampleRate. | |||
output value: | |||
Native sample buffer size of the underlying audio system ranging | |||
from NPAudioMinSampleFrameCount...NPAudioMaxSampleFrameCount. | |||
This sample buffer frame count relates to the sample rate returned | |||
by queryCapability(npp, NPAudioCapabilitySampleRate, &sampleRate) | |||
notes: | |||
Upon successful initialization of the audio system, an application | |||
will always be able to request and obtain the native sample buffer | |||
frame count when specifying the sample frequency returned by | |||
NPAudioQuerySampleRate. | |||
queryCapability(npp, NPAudioCapabilitySampleFrameCount44100Hz, &value) | |||
Query the audio system for the sample buffer frame count to use for | |||
44.1kHz output. | |||
output value: | |||
Recommended sample buffer frame count ranging from | |||
NPAudioMinSampleFrameCount...NPAudioMaxSampleFrameCount. | |||
notes: | |||
Upon successful initialization of the audio system at 44.1kHz, an | |||
application will always be able to request and obtain this sample | |||
buffer frame count. | |||
queryCapability(npp, NPAudioQuerySampleFrameCount48000Hz, &value) | |||
Query the audio system for the sample buffer frame count to use for | |||
48kHz output. | |||
output value: | |||
Recommended sample buffer frame count ranging from | |||
NPAudioMinSampleFrameCount...NPAudioMaxSampleFrameCount. | |||
notes: | |||
Upon successful initialization of the audio system at 48kHz, an | |||
application will always be able to request and obtain this buffer | |||
frame count. | |||
queryCapability(npp, NPAudioCapabilitySampleFrameCount96000Hz, &value) | |||
Query the audio system for the sample buffer frame count to use for | |||
96kHz output. | |||
output value: | |||
Recommended sample buffer frame count ranging from | |||
NPAudioMinSampleFrameCount...NPAudioMaxSampleFrameCount. | |||
notes: | |||
Upon successful initialization of the audio system at 96kHz, an | |||
application will always be able to request and obtain this buffer | |||
frame count. | |||
queryCapability(npp, NPAudioCapabilityOutputChannelMap, &value) | |||
Query the audio system for the output/speaker arrangement. | |||
output value: | |||
NPAudioChannelNone | |||
NPAudioChannelMono | |||
NPAudioChannelStereo | |||
NPAudioChannelThree | |||
NPAudioChannelFour | |||
NPAudioChannelFive | |||
NPAudioChannelFiveLFE | |||
NPAudioChannelSeven | |||
NPAudioChannelSevenLFE | |||
notes: | |||
Upon successful initialization of the audio system, an application | |||
will always be able to request and obtain this channel setup. | |||
Additionally, NPAudioChannelMono and NPAudioChannelStereo will | |||
always be available, regardless of physical speaker configuration: | |||
mono output -> mono speaker, or | |||
mono output -> center speaker, or | |||
mono output -> left & right speakers | |||
stereo output -> left & right speakers, or | |||
stereo output -> mono speaker | |||
queryCapability(npp, NPAudioCapabilityInputChannelMap, &value) | |||
Query the audio system for the input/microphone arrangement. | |||
output value: | |||
NPAudioChannelNone | |||
NPAudioChannelMono | |||
NPAudioChannelStereo | |||
NPAudioChannelThree | |||
NPAudioChannelFour | |||
NPAudioChannelFive | |||
NPAudioChannelSeven | |||
notes: | |||
Upon successful initialization of the audio system, an application | |||
will always be able to request and obtain this channel setup. If | |||
NPAudioChannelNone is returned, either the device has no input, or | |||
the implementation doesn't support audio input. | |||
</pre> | </pre> | ||