I checked a couple local news sources, it seems that at least some Chinese airlines have started to use a system called "X-CVR", which can record up to 8000hrs of cockpit voice recordings with "quality higher than MP3".
It has also been suggested that the so-called X-CVR system supports downloading the recordings directly to USB drive, and can even transmit the recordings via 3G/4G wireless network automatically to specific servers.
Reports say Hainan Airlines has started to fit its 737 and A320 fleets with X-CVR as early as 2018. So it looks like such technology already exists in China, although it's unclear whether MU has started to fit their 737s with the system.