[AGL6.x][4a-softmixer]Question about high latency of audio playback

Hello,

I understood that AGL is using the ALSA loopback driver to create a virtual sound card to abstract underlying real sound cards. Softmixer capture audio from the loopback in user-space, and then subsequently playback to a real sound card.

So there must be a latency introduced. I want to measure how much this latency is.

I recorded the time stamp that aplay  invoked the snd_pcm_writei for the first time. And recorded the time stamp that write thread in softmixer invoked the snd_pcm_writei for the first time. The difference of these two time stamps should be the latency introduced.

But the measurement result of latency is extremely high, which is nearly 1.4 second.

1. I am wondering that if the approach of measurement is wrong.

2. I am wondering that if anyone has measured this latency. Would it be possible for you to share the approach and result with me? 

Thank you , and I look forward to hearing from you.

Best Regards

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Frank Luo(罗鹏)

Neusoft Automotive Solution Business Unit

Neusoft Corporation

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