About the video_codec_sdk jpeg dec

hi all,i want to know why i use AppDec sample will have the following decode errors in the video_codec_sdk ? when i sent the same one frame jpeg data to decoder to dec Continuously for 100 times
max—>nFrameReturned=1
Decode Error occurred for picture 92
max—>nFrameReturned=1
max—>nFrameReturned=1
max—>nFrameReturned=1
Decode Error occurred for picture 95
max—>nFrameReturned=1
Decode Error occurred for picture 96
max—>nFrameReturned=1
max—>nFrameReturned=1
Decode Error occurred for picture 98
max—>nFrameReturned=1

i know that if i want to stop the dec i have to set the nVideoBytes = 0,and sent to the decoder