audio_io_h
andle_t AudioPolicyManager::getOutputForDevices
(
const DeviceVector &devices,
audio_session_t session,
const audio_attributes_t *attr,
const audio_config_t *config,
audio_output_flags_t *flags,
bool *isSpatialized,
sp<PreferredMixerAttributes
Info> prefMixerConfig
Info,
bool forceMut
ingHaptic
)
{
audio_io_h
andle_t output = AUDIO_IO_H
ANDLE_NONE;
// Discard haptic
channel mask when forc
ing mut
ing haptic
channels.
audio_
channel_mask_t
channelMask = forceMut
ingHaptic
? static_cast<audio_
channel_mask_t>
(config->
channel_mask & ~AUDIO_
CHANNEL_HAPTIC_ALL
)
: config->
channel_mask;
// open a direct output if required by specified parameters
//force direct flag if offload flag is set: offload
ing implies a direct output
stream
//
and all common behaviors are driven by check
ing only the direct flag
// this should normally be set appropriately
in the policy configuration file
if
((*flags & AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD
) != 0
) {
*flags =
(audio_output_flags_t
)(*flags | AUDIO_OUTPUT_FLAG_DIRECT
);
}
if
((*flags & AUDIO_OUTPUT_FLAG_HW_AV_SYNC
) != 0
) {
*flags =
(audio_output_flags_t
)(*flags | AUDIO_OUTPUT_FLAG_DIRECT
);
}
audio_
stream_type_t
stream = mEng
ine->get
StreamTypeForAttributes
(*attr
);
// only allow deep buffer
ing for music
stream type
if
(stream != AUDIO_
STREAM_MUSIC
) {
*flags =
(audio_output_flags_t
)(*flags &~AUDIO_OUTPUT_FLAG_DEEP_BUFFER
);
} else if
(/*
stream == AUDIO_
STREAM_MUSIC && */
*flags == AUDIO_OUTPUT_FLAG_NONE && mConfig->useDeepBufferForMedia
()) {
// use DEEP_BUFFER as default output for music
stream type
*flags =
(audio_output_flags_t
)AUDIO_OUTPUT_FLAG_DEEP_BUFFER;
}
if
(stream == AUDIO_
STREAM_TTS
) {
*flags = AUDIO_OUTPUT_FLAG_TTS;
} else if
(stream == AUDIO_
STREAM_VOICE_CALL &&
audio_is_l
inear_pcm
(config->format
) &&
(*flags & AUDIO_OUTPUT_FLAG_
INCALL_MUSIC
) == 0
) {
*flags =
(audio_output_flags_t
)(AUDIO_OUTPUT_FLAG_VOIP_RX |
AUDIO_OUTPUT_FLAG_DIRECT
);
ALOGV
("Set VoIP
and Direct output flags for PCM format"
);
}
// Attach the Ultrasound flag for the AUDIO_CONTENT_TYPE_ULTRASOUND
if
(attr->content_type == AUDIO_CONTENT_TYPE_ULTRASOUND
) {
*flags =
(audio_output_flags_t
)(*flags | AUDIO_OUTPUT_FLAG_ULTRASOUND
);
}
// Use the spatializer output if the content can be spatialized, no preferred mixer
// was specified
and offload or direct playback is not explicitly requested,
and there is no
// haptic
channel included
in playback
*isSpatialized = false;
if
(mSpatializerOutput != nullptr &&
canBeSpatialized
Int
(attr, config, devices.toTypeAddrVector
()) &&
prefMixerConfig
Info == nullptr &&
((*flags &
(AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD | AUDIO_OUTPUT_FLAG_DIRECT
)) == 0
) &&
checkHapticCompatibilityOnSpatializerOutput
(config, session
)) {
*isSpatialized = true;
return mSpatializerOutput->mIoH
andle;
}
audio_config_t directConfig = *config;
directConfig.
channel_mask =
channelMask;
status_t status = openDirectOutput
(stream, session, &directConfig, *flags, devices, &output,
*attr
);
if
(status != NAME_NOT_FOUND
) {
return output;
}
// A request for HW A/V sync cannot fallback to a mixed output because time
// stamps are embedded
in audio data
if
((*flags &
(AUDIO_OUTPUT_FLAG_HW_AV_SYNC | AUDIO_OUTPUT_FLAG_MMAP_NOIRQ
)) != 0
) {
return AUDIO_IO_H
ANDLE_NONE;
}
// A request for Tuner cannot fallback to a mixed output
if
((directConfig.offload_
info.content_id || directConfig.offload_
info.sync_id
)) {
return AUDIO_IO_H
ANDLE_NONE;
}
// ignor
ing
channel mask due to downmix capability
in mixer
// open a non direct output
// for non direct outputs, only PCM is supported
if
(audio_is_l
inear_pcm
(config->format
)) {
// get which output is suitable for the specified
stream. The actual
// rout
ing change will happen when startOutput
() will be called
SortedVector<audio_io_h
andle_t> outputs = getOutputsForDevices
(devices, mOutputs
);
if
(prefMixerConfig
Info != nullptr
) {
for
(audio_io_h
andle_t outputH
andle : outputs
) {
sp<SwAudioOutputDescriptor> outputDesc = mOutputs.valueFor
(outputH
andle
);
if
(outputDesc->mProfile == prefMixerConfig
Info->getProfile
()) {
output = outputH
andle;
break;
}
}
if
(output == AUDIO_IO_H
ANDLE_NONE
) {
// No output open with the preferred profile. Open a new one.
audio_config_t config = AUDIO_CONFIG_
INITIALIZER;
config.
channel_mask = prefMixerConfig
Info->getConfigBase
().
channel_mask;
config.sample_rate = prefMixerConfig
Info->getConfigBase
().sample_rate;
config.format = prefMixerConfig
Info->getConfigBase
().format;
sp<SwAudioOutputDescriptor> preferredOutput = openOutputWithProfile
AndDevice
(
prefMixerConfig
Info->getProfile
(), devices, nullptr /*mixerConfig*/,
&config, prefMixerConfig
Info->getFlags
());
if
(preferredOutput == nullptr
) {
ALOGE
("%s failed to open output with preferred mixer config", __func__
);
} else {
output = preferredOutput->mIoH
andle;
}
}
} else {
// at this stage we should ignore the DIRECT flag as no direct output could be
// found earlier
*flags =
(audio_output_flags_t
) (*flags & ~AUDIO_OUTPUT_FLAG_DIRECT
);
if
(com::
android::media::audioserver::
fix_concurrent_playback_behavior_with_bit_perfect_client
()) {
// If the preferred mixer attributes is null, do not select the bit-perfect output
// unless the bit-perfect output is the only output.
// The bit-perfect output can exist while the passed
in preferred mixer attributes
//
info is null when it is a high priority client. The high priority clients are
// r
ingtone or alarm, which is not a bit-perfect use case.
size_t i = 0;
while
(i < outputs.size
() && outputs.size
() > 1
) {
auto desc = mOutputs.valueFor
(outputs[i]
);
// The output descriptor must not be null here.
if
(desc->isBitPerfect
()) {
outputs.removeItemsAt
(i
);
} else {
i += 1;
}
}
}
output = selectOutput
(
outputs, *flags, config->format,
channelMask, config->sample_rate, session
);
}
}
ALOGW_IF
((output == 0
), "getOutputForDevices
() could not f
ind output for
stream %d, "
"sampl
ing rate %d, format %#x,
channels %#x, flags %#x",
stream, config->sample_rate, config->format,
channelMask, *flags
);
return output;
}
本文介绍了Java NIO的核心技术，包括文件与设备的I/O操作、对象序列化、原生态数据缓存、字符集编码与解码、新的I/O抽象通道、支持锁和内存映射的文件接口以及用于编写可伸缩服务器的多分复用非阻塞I/O设备。
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