hi, Nhoj.
happy new year.
i have sony dcr-trv740. like you i transfer Di8 using the firewire.
what i've found out is what Dafydd said. it will not capture Hi8 videos; however, it'll capture Di8 videos. as you know our camcorders will play Hi8 tapes.
i have panasonic DMR-E85H, DMR-EZ475, and Toshiba RD-XS35 DvD recorder player. i transfer Hi8 tape using S-video, if you don't have then you can use RCA connectors. after that you can transfer to pd v9 through your computer's DvD recorder player.
i've transferred all my home movies that was recorded in Beta, Super Beta, VHS, S-VHS, Hi8, and Di8. yes over 40 years of analog videos into digital.
pd v9 puts those videos some spices and zing! also transforms to HD & Blu-Ray; however, don't expect too much for it is Garbage In Garbage Out...
hope this helps and put some hope in your endeavours.
PepsiMan
'no bridge too far'
Yashica Electro 8 LD-6 Super 8mm
Asrock TaiChi X470, AMD R7 2700X, W7P 64, MSI GTX1060 6GB, Corsair 16GB/RAM
Dell XPS L702X i7-2860QM, W7P / W10P 64, Intel HD3000/nVidia GT 550M 1GB, Micron 16GB/RAM
Samsung Galaxy Note3/NX1