Hi,
I am developing an audio conferencing application with 5 way
conference that will be part of Android firmware,.
Could you please let me know what is the best way to leverage Android
audio framework for this.
as of now I am considering this doing on AudioTrack level only. but have
feeling that this is not the best way.
appreciate your help.
Thanks
On Friday, September 7, 2012 9:14:29 PM UTC+5:30, Glenn Kasten wrote:
>
> 1. You didn't mention if you're developing Android apps or the platform.
> If you're an Android app developer, you should be using only documented
> public APIs. For audio output, that's Java language
> android.media.AudioTrack in SDK and C language OpenSL ES AudioPlayer with
> PCM buffer queue in NDK. The AUDIO_OUTPUT_FLAG_FAST is an internal symbol
> that's used only at the AudioTrack C++ level, and that's not a documented
> public API. So you should not need to deal with AUDIO_OUTPUT_FLAG_FAST.
>
> But if you're doing platform development such as porting, it can be
> helpful to understand the internal implementation in JB ...
> AUDIO_OUTPUT_FLAG_FAST is a hint from the API level that this application
> would like to use a lower latency, fewer feature, audio track if one is
> available. The request is not guaranteed to be accepted by the audio
> server (AudioFlinger). The fewer features that are not available include
> effects, as you said, and also sample rate conversion. If AudioFlinger
> can handle the request it will create a "fast track", otherwise a normal
> track.
>
> 2. The "fast" in FastMixer means that it executes more often, and that it
> uses less CPU time each time it runs, than the normal mixer thread. The
> normal mixer thread runs about once every 20 ms, and the FastMixer thread
> runs at rate of once per HAL buffer (which is ideally less than 20 ms). The
> FastMixer thread supports up to 7 fast tracks, and does not support sample
> rate conversion of effects. So it uses a limited amount of CPU each time it
> runs. The normal mixer thread supports more tracks (up to 32), and supports
> sample rate conversion and effects. So it can use more CPU each time it
> runs. The main purpose of FastMixer design was not to take advantage of
> multi-core.
>
> On Tuesday, September 4, 2012 6:59:27 PM UTC-7, big_fish_ wrote:
>>
>> I am a android developer, I just read the FastMixer code of Jellybean.
>>
>> I have some questions,
>>
>> 1, If submit AudioTrack with AUDIO_OUTPUT_FLAG_FAST flag, then this Track
>> can't do AudioEffect handle, right?
>>
>> I noticed that FastMixer thread handle all FastTacks without
>> AudioEffect. Except mFastTracks[0], because the zero FastTrack is passed
>> from MixerThread which was already through mixer and effect handled. right?
>>
>> 2, About the performance, why FastMixer is faster then before?
>>
>> If we have 20 tracks, we set 8 tracks as FastMixer, and 12 as normal tracks,
>> then there are two threads to do mixer. So if we run on dual core CPU, then
>> we have multithreading adventage.
>>
>> But if we have 32 tracks are all as FastTrack, then MixerThread will not
>> do mixer. then there will have no multithreading adventage.
>>
>>
>>
>>
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