cherry picked from commit 8e50557707d2ec11ccad657470b2e140f314348e
7cf6a67 avcodec/hevc: adding support for monochrome sequences in hevc
libavcodec/hevc.c | 73 ++++++++++++++++------------
libavcodec/hevc_filter.c | 118 +++++++++++++++++++++++-----------------------
libavcodec/hevc_ps.c | 11 ++---
3 files changed, 107 insertions(+), 95 deletions(-)