I don't have a facecam.....yet, but when I livestream I use my Elgato game capture card. I've never heard of OBS, but I'll totally be checking that out when I get home this evening. I like free because it's....well.....free.
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Like Zac_Suma and Reallti Virtualski said it's definitely easy to stream from your PS4. I use to do it all the time before I got my Elgato game capture card. The only thing with using the PS4 is that the maximum output resolution is 720p. Using a game capture card, and likely even OBS, streaming your video through HDMI to your PC will be at 1080p resolution. Also, if you stream through the PS4 there isn't a way, that I know of, to link the live stream up to a live stream event that you may have scheduled on your YouTube channel. If none of that really matters to you then live streaming through the PS4 is definitely the easiest way to go.
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One advantage to streaming through the PS4 is that the stream is simultaneously sent to the Playstation Network's list of live streams so gamers on their PS4s can watch your stream AND it also sent to YouTube gaming so you may be able to reach a wider audience that way. Just make sure to mention your YouTube channel to viewers on the stream if you do things this way 'cause some of them maybe watching through their PS4s and not realize you have a YouTube channel.
I hope this helps.
This thread has also helped me. I gots to go home and check out OBS.
Later my gaming dudes!
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