problem in video reconstruction after splitting it into audio and frames File size is more than the original?

i am tried to hide data in LSB of audio in video after extracting audio from video data hide in audio successfully but when video reconstructed its size becomes 99 MB from 302 Kb and hidden data are not found in video.While data is still present in audio and extracted successfully... my video writing code is:

VidObj=VideoReader(path);

n=VidObj.NumberOfFrames;

videoFReader = vision.VideoFileReader(path);

videoFWriter = vision.VideoFileWriter(fnn,... 'AudioInputPort',1,'AudioDataType','int16','VideoCompressor','ffdshow video encoder','FileFormat','avi',... 'FrameRate',videoFReader.info.VideoFrameRate);

[audio,fs]=wavread(Fn);

op=floor(fs/videoFReader.info.VideoFrameRate);

for i=1:n

    videoFrame= step(videoFReader);

    audios=audio( (i-1)*op + 1 : i*op , : );

    step(videoFWriter, videoFrame,audios);

end