The ATEM Television Studio Pro HD has a dedicated multi view output, 4 SDI and 4 HDMI inputs with re-sync on all inputs so you can use it with non-synchronous video sources.
Specifications:
SD Video Standards: 525i59.94 NTSC 4:3 or 16:9, 625i50 PAL 4:3 or 16:9
HD Video Standards: 720p50, 720p59.94, 1080p23.98, 1080p24, 1080p25, 1080p29.97, 1080p50, 1080p59.94, 1080i50, 1080i59.94
Frame Rates: 720 x 480i 59.94Hz. 720 x 576i 50Hz. 1280 x 720p 59.94Hz 50Hz. 1920 x 1080p 23.98, 24, 25, 29.97,30, 50, 59.94. 1920 x1080i 50 and 59.94Hz 60Hz.