Following up with a previous answer.

There was research being done in 2018 on forwarding custom audio to the Xiaomi Redmi Note 3:

https://xdaforums.com/t/direct-audio-playback-through-alsa.3806297/

More info can be found there.

First of all, you need your card name. You can get it from /proc/asound/cards. For example:

0 [msm8976tashalit]:
msm8976-tashali - msm8976-tashalite-snd-card
                  msm8976-tashalite-snd-card

card name will be "msm8976-tashalite-snd-card". Next thing is paths. You need to figure out how codec needs to be prepared. This info lies in mixer_paths.xml in /system/etc or /vendor/etc. Search for paths called deep-buffer-playback, low-latency-playback, compress-offload-playback, etc. Put values from there to "device" section. And a device number. See /proc/asound/pcm. Example:

00-09: (Compress1) :  : playback 1

Device number is 9. Volume is hard one because android changes it with software, so you can't see any difference when dumping control vars (at least in my case). Use AlsaMixer and guess... This blog post can help you: https://arunraghavan.net/2016/01/audio-devices-and-configuration/