I have a source video file in m2ts format with resolution 1440x1080 that I edited in another software and then I load it into AE to applied some effects and when I am rendering it and play it in a media player it lagging thru almost the hole video. The only thing that doesn´t lagg is the effects created in AE. What is the problem to all that? My computer is new with 6gb ram, ati radeon 2gb ram dual gpu and CPU Intel i7. Im kind a new to render in HD and has never rendering any HD projects yet (this is my first). I also tried different HD ouput format but it doesn´t help. The format I want to have it in is MPEG2 Blu-Ray. I am useing AE CS4.
Well, to what specs are you rendering? I hope you are not using the default Lossless output, which is uncompressed. Even the juiciest computer can't play that in realtime. The number of effects etc. don't have anything to do with that. M2TS is compressed, so naturally you will have to chose a compressed format as well to get the same playback performance. MPEG-2 BD would definitely work and AE spits it out (full version, noit trial), so try that. For desktop review, use H.264 or WMW or a compressed Quicktime format.
I found that the problem lays in the source file cause when I edited the source file and took a piece off from it then I got it to work. This problem is very strange and hard to explaine.