In the mid-2000s, many cheap Chinese portable media players were labeled "MP4" (even if they just played video). "Viola" and "SS" are not known brands in that space (unlike Archos, iRiver, or Sony). If this is an old device, expect: very low storage (e.g., 2-4GB), a tiny low-resolution screen, poor battery life, and low audio quality compared to any modern smartphone. I cannot recommend buying one today.
While this specific name is likely a hoax, the underlying threat——is real. To stay safe: ss viola mp4
There are other minor possibilities for the keywords: In the mid-2000s, many cheap Chinese portable media
"MP4" is a container format. "SS Viola" might be a fan edit, a fansub group's tag, or a specific encode of a show or anime. If so, this is not a hardware review. The quality would depend entirely on the encoder's settings. I cannot recommend buying one today