1.avc转hevc转码默认带B帧
# ffmpeg -i guomei_avc.mp4 -c:v libx265 has_b_frame.h265
# ffmpeg -i guomei_avc.mp4 -c:v libx265 has_b_frame.mp42.avc转码hevc去掉B帧
# ffmpeg -i guomei_avc.mp4 -c:v libx265 -preset ultrafast -x265-params "bframes=0"  no_b_frame.h2653.avc去掉B帧
# ffmpeg -i guomei_avc.mp4 -vcodec libx264 -x264opts "bframes=0" h264_no_b.h264
# ffmpeg -i guomei_avc.mp4 -vcodec libx264 -x264opts "bframes=0" h264_no_b.mp4