To convert and reduce GoPro Hero 5 4K video to 1080P, you need a 4K video converter in the first place. There is a dozen of 4K video converters in the market and most of them claimed that they are the fastest, but it is usually just advertisement, not the fact. Here according to the feedbacks of dozens of users, they unanimously recommend the award-winning 4K video compressor - GoPro Compression Software.
Additinal Knowledge:
1. 4K resolution- Wikipedia: The name "4K resolution" refers to a horizontal resolution of approximately 4,000 pixels.
2. High-definition video - Wikipedia:High-definition video is video of higher resolution and quality than standard-definition. While there is no standardized meaning for high-definition, generally any video image with considerably more than 480 horizontal lines (North America) or 576 horizontal lines (Europe) is considered high-definition.
source from http://mediaconverti...5-4k-to-hd.html
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