FilterAudioStream does not provide Input Preset of the underlying stream in case of fallback

[rpattabi]

When a specific InputPreset is specified in Audio Stream Builder, oboe may choose to fallback to a different preset if it's unavailable on a device. For instance, when opening OpenSLES stream, if setting a given preset fails, it falls back to Voice Recognition. Similarly, the recently introduced Voice Performance preset fallsback to Voice Recognition on older devices.

When such fallback happens, FilterAudioStream still has the input preset as provided in the builder, but not the actual one in the underlying stream. This is misleading for the developers to think that the requested input preset is available on the device.

The following code may have to copy input preset as well to address this problem.

oboe/src/common/FilterAudioStream.h

Lines 55 to 57 in 9a62b97

	// Copy parameters that may not match builder.
	mBufferCapacityInFrames = mChildStream->getBufferCapacityInFrames();
	mPerformanceMode = mChildStream->getPerformanceMode();

Additionally, the following sections in AudioStreamBuilder.cpp may also need to consider InputPreset as it can also be left kUnspecified:

oboe/src/common/AudioStreamBuilder.cpp

Lines 82 to 87 in 9a62b97

	bool AudioStreamBuilder::isCompatible(AudioStreamBase &other) {
	return (getSampleRate() == oboe::Unspecified || getSampleRate() == other.getSampleRate())
	&& (getFormat() == (AudioFormat)oboe::Unspecified || getFormat() == other.getFormat())
	&& (getFramesPerCallback() == oboe::Unspecified || getFramesPerCallback() == other.getFramesPerCallback())
	&& (getChannelCount() == oboe::Unspecified || getChannelCount() == other.getChannelCount());
	}

oboe/src/common/AudioStreamBuilder.cpp

Lines 124 to 136 in 9a62b97

	// Build a stream that is as close as possible to the childStream.
	if (getFormat() == oboe::AudioFormat::Unspecified) {
	parentBuilder.setFormat(tempStream->getFormat());
	}
	if (getChannelCount() == oboe::Unspecified) {
	parentBuilder.setChannelCount(tempStream->getChannelCount());
	}
	if (getSampleRate() == oboe::Unspecified) {
	parentBuilder.setSampleRate(tempStream->getSampleRate());
	}
	if (getFramesPerCallback() == oboe::Unspecified) {
	parentBuilder.setFramesPerCallback(tempStream->getFramesPerCallback());
	}

[philburk]

Thanks! I reproduced this on an S10e running P.

1. launch OboeTester
2. tap TEST INPUT
3. select InPreset = Performance
4. select SRATE 44100
5. select SRC Quality "Medium"
6. tap OPEN

EXPECT
Actual InPreset = VoiceRec

ACTUAL
Actual InPreset = Performance

The same problem occurs with OpenSL ES but for a different reason.

[philburk]

Fixed as you suggested. Thanks.

By the way, isCompatible() does not check InputPreset because the FilterAudioStream does not provide a conversion for that InputPreset. It only converts data rates, formats, channels and callback sizes. So it is OK.