Î'm trying to play some videos which were encoded using the x264 video codec with 1080p but using vlc it plays like a slideshow.
Do you think that the cause of this problem is because of my low-spec laptop? (intel core duo T5800 @ 2GHZ)
If you have an Nvidia card, make sure you're using VDPAU off-loading. In mplayer, this is done with the
Without VDPAU, you'll need a lot more CPU horsepower to play the stream smoothly. For example, a E4500 @ 2.20GHz cannot keep up with heavily encoded x264 1080p streams without VDPAU. An Intel video card on a 2GHz system isn't going to work, I don't think. :(
Maybe your laptop has a weak graphics card or heat problems. What does totem do?
Even when there is no such a "Minimal requirements" for h264 video playback (the audio is not your problem at this time), you should consider using a high performance GPU in order to experience the best results on your playback.
Information provided in the answers to this question may give you an idea of what a hardware I am talking about. Of course, I am for nVidias (1GB or more) but you can choose a different brand name. Anyway, Intel embedded graphic cards won't achieve a smooth playback for high demanding video codecs (like h264).
Your microprocessor is good enough for a smooth playback but you may be experiencing an issue at the moment that your computer needs to "draw" the things on screen. Task that is normally achieved by the GPU, not the CPU itself. When I answered this question I was using a microprocessor similar to yours, with a PhysX SPARKLE GeForce 9500GT 1024MB/DDR2/CRT/DVI-I/HDCṔ/SLI/PCI Express 2.0 and experiencing no problems during the playback.
Placed here for your convenience:
Additionally, the comments on the original answer will be very illustrative also.