胡斌 / merge_av

1.修改老师和学生视频大小不一致，老师的视频小于320x240时，老师背景有花屏
2.修改老师和学生视频都为240x180视频时，视频宽度仍为240, 且有花屏
3.只有一路视频时，默认合成为上下布局

but at present,only support landscape layout

parse width and height in record info file

adjust the layout of one to many layout

improved adding new file when start time reached

print and return error if no paramter after "-t"

for 0,layout is decided by audio detect
for 1,using one2one layout
for 2,using one2many layout

2.flip image when retote 180
3.save record info as m_*
4.use stream time base when decode,don't use decode codec time base,because it is varied in some mp4 file

fix the bug for RGB2YUV

save output info

because the time offset is not begin from the recordinfo file,but maybe from the last recordinfo file with same uid.

2.add macro to support using ffmpeg codec version 58,which need pcm format using AV_SAMPLE_FMT_FLTP when encoding aac

one2one transcode works,need add still frame when one parter has no video but has audio
add some code about swscale,unfinished

fix bug for finished transcoding without all files transcoded