I use gst-launch to play mp4 files, use following commandline:
gst-launch filesrc location=/1.mp4 ! ffdemux_mov_mp4_m4a_3gp name=d d.video_00!
{queue ! ffdec_mpeg4 ! sdlvideosink } d.audio_00! {queue ! ffdec_mpeg4aac ! 
osssink } ,
but the decoded picture stop after played the first several frames and No 
sound .

It seems that the video and audio not sync ,Is the command right ?

But following command can play a mpeg-1 files ,it is right :)

gst-launch filesrc location=/1.mpg ! ffdemux_mpeg name=d d.video_00!
{queue ! ffdec_mpegvideo ! sdlvideosink } d.audio_00! {queue ! ffdec_mp3 ! 
osssink }

Please tell me how to play a mp4 file (mpeg4video + mpeg4aac audio). Thanks