Go to the 4PDA forum thread for "Allwinner H313/H616" and filter for your specific box name (e.g., "Tanix TX3 H313 slimBOXtv"). Download the .img file (usually compressed in .7z or .rar ).
The most popular and stable options for H313 devices focus on replacing the clunky stock launcher and removing bloatware: Allwinner H313 Custom Rom
A: On stock, no. On custom ROMs like CoreELEC or slimBOXtv with Viper4Android, you can force AC3 (Dolby Digital) passthrough via HDMI. Go to the 4PDA forum thread for "Allwinner
: The most technical "paper" for H313 is the Armbian Allwinner H313 Forum Thread . It contains detailed discussions on: Allwinner H313 Custom Rom