Even the fastest computers will have trouble playing back uncompressed data. Its not your processor thats the cause as this decodes most video easily in real time during all video playback. The problem is most likely the transfer rate from your hard drive as it streams the file.
To overcome this some editors have whats called a RAM disk. Computer memory is allocated and the frames are pre loaded there. Playback is then smooth as its arriving at the processor from RAM. Adobe After Effects has such a setup as do others. It enables playback of short sections without problems even with high resolution uncompressed frames.
If your captured frames are Bitmaps, you can also convert them to high quality jpegs before importing them to your editor. you wont notice the quality difference, but the file size is much smaller and helps playback speed. The file sizes can be about 5% of the size.
If your importing video into an editor you could also try lossless compression to reduce the file sizes. HuffYuv is a free one thats quite good (Just Google for it)
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