Your computer can't preview your comp at the real time frame rate. You can reduce the comp's resolution to half (bottom of the comp window), render every other frame (shift-zero [numeric keypad]), or both. AE gives you many ways to ret real time previews.
I tried these but still same. Nothing changed.
Playing From RAM 748 of 748
fps 25 (realtime)
at Info screen at top right.
But when i'm at 30th second it tooks 37 sec in my cell phone stopwatch
It might be the audio files you use. After Effects needs uncompressed audio. Mp3 and AC3 audio is compressed. Convert such files to aiff or wav files.
yea already tried it.
Project 30sec but when i preview it took 37 sec to watch it.
But i hear the audio real time thats why it stops at 23s at Time Ruler.
Preview too slow
i need to watch preview at real time
Do you actually know how to do a proper RAM Preview? Are you hitting the zero on the numeric kaypad? Sorry to be so blunt, but there just aren't many ways to mess up a RAM preview.
You set the comp window SIZE to 50%. The comp RESOLUTION is still at FULL. Set it to half.
What does this tell you about your machine?
We've exhausted all the easy responses to your woes. It's time that you provided additional information.
Furthermore, I really think you need to spend a lot of quality time visiting here and following the links: http://blogs.adobe.com/aftereffects/2010/01/getting-started-with-after-eff.html.
Start with the top few links. Memorize them.