When loading textures there are trade offs. When you use an uncompressed file format like for example tga you'll get the best quality but of course also larger files. The performance bottleneck is most likely going to be the speed of your HD/SSD.
With compressed formats like jpg you can save diskspace and therefore "io-duration" at the cost of cpu performance for decompressing/decoding the image. Also when using jpg the compression and thus the needed performance varies with the image content. So some files may play just fine but others don't.
Your textures are 640x360 px (for 24bit textures / no Alpha) that should be approx. 0,7 MB uncompressed.
Multiplied by 24 Videos and 60 FPS you'll get about 1GB/sec that need to be loaded from disk. That is easily possible with newer m2 / pcie SSDs.
IIRC BC7 has a compression ratio of 4:1, so you'll need only to load 250MB/sec which should be possible with any evo, m2 or sata.
Woei's player has outputs for disk-loading-time, cpu and gpu usage, use those to find your bottleneck.