I am trying to achieve the lowest latency possible using the Microphones and audio output from the built-in PMIC on the Dragon Board. However, I have run into a wall trying to do this. I tried using Jackd and it errors out saying that it cannot set the buffer size. I also used PortAudio and it would silently fail for the same reason as not being able to set the buffer size. Given that I2S is supposed to have one of the lowest latencies, I am not able to set the period size below 2048 and buffer size of 4096 which is a latency of 85.3333 ms using the latency.c test code. It seems like the period_min and period_max has been hardcoded in Alsa driver for the PMIC to be 2048.
But here is the kicker when I use alsaloop code that is part of the alsa utils, I am able to set the period at 48 and buffer size of 96 giving us a latency of 2 ms.
Has anyone played around with this and figured out a way to use Jackd and/or PortAudio with a latency of less than 10 ms on the DragonBoard 410c or if anyone has an insight in this problem?