filesrc: num-buffers only produces N-1 buffers

Submitted by Ullysses A Eoff @ullysses.a.eoff

Link to original bug (#796345)

Description

Steps

gst-launch-1.0 videotestsrc num-buffers=100 ! video/x-raw,format=NV12,width=176,height=144 ! rawvideoparse format=nv12 width=176 height=144 ! filesink location=./src.yuv

gst-launch-1.0 filesrc location=./src.yuv num-buffers=100 ! rawvideoparse format=nv12 width=176 height=144 ! videoconvert ! video/x-raw,format=YV12 ! filesink location=./out.yuv

Expected

src.yuv and out.yuv should be the same size (3801600 bytes)

Actual

out.yuv size is 3763584 (i.e. missing 38016 bytes which is the size of one NV12/YV12 frame - 176x144*1.5)