I downloaded MPEG_Streamclip1.2 from
Squared 5 - MPEG Streamclip video converter for Mac and Windows and I use it with the following settings to get the HQ playback option on my videos on YT.
FILE->Export to MPEG4
Compression->H.264
Quality->Move the slider to 100%
Limit Data Rate to->2500kbps (minimum)
Sound-> MPEG4/Stereo/Auto/256kbps
Frame Size->640 x 360
Field Dominance->Lower Field First (I don't see any difference in using one or the other)
Frame Rate->25fps or 30fps
Deinterlace Video (Ticked)
Click on the Adjustments button and in the Watermark box type something like a copyright notice or a contact email address.
Then click on the Make MP4 button.
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Download QuickTimeAlt181 first and install it as it needs to be on your computer before you can use Streamclip.