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• avcodec : Add explicit capability flag for encoder flushing

  10 avril 2020, par Philip Langdale

  avcodec : Add explicit capability flag for encoder flushing
  Previously, there was no way to flush an encoder such that after
  
  draining, the encoder could be used again. We generally suggested
  
  that clients teardown and replace the encoder instance in these
  
  situations. However, for at least some hardware encoders, the cost of
  
  this tear down/replace cycle is very high, which can get in the way of
  
  some use-cases - for example : segmented encoding with nvenc.
  To help address that use case, we added support for calling
  
  avcodec_flush_buffers() to nvenc and things worked in practice,
  
  although it was not clearly documented as to whether this should work
  
  or not. There was only one previous example of an encoder implementing
  
  the flush callback (audiotoolboxenc) and it's unclear if that was
  
  intentional or not. However, it was clear that calling
  
  avocdec_flush_buffers() on any other encoder would leave the encoder in
  
  an undefined state, and that's not great.
  As part of cleaning this up, this change introduces a formal capability
  
  flag for encoders that support flushing and ensures a flush call is a
  
  no-op for any other encoder. This allows client code to check if it is
  
  meaningful to call flush on an encoder before actually doing it.
  I have not attempted to separate the steps taken inside
  
  avcodec_flush_buffers() because it's not doing anything that's wrong
  
  for an encoder. But I did add a sanity check to reject attempts to
  
  flush a frame threaded encoder because I couldn't wrap my head around
  
  whether that code path was actually safe or not. As this combination
  
  doesn't exist today, we'll deal with it if it ever comes up.
  

  • [DH] doc/APIchanges
  • [DH] libavcodec/audiotoolboxenc.c
  • [DH] libavcodec/avcodec.h
  • [DH] libavcodec/decode.c
  • [DH] libavcodec/nvenc_h264.c
  • [DH] libavcodec/nvenc_hevc.c
  • [DH] libavcodec/version.h

• lavc/libopenh264enc : add default gop size and bit rate

  29 avril 2020, par Linjie Fu

  lavc/libopenh264enc : add default gop size and bit rate
  It would be 200kbps bitrate with gop size = 12 by default
  
  which generated too many IDR frames in rather low bit rate.
  
  The quality would be poor.
  Set these default values to -1 to check whether it's specified
  
  by user explicitly.
  Use 2Mbps bitrate as nvenc sugguested, and leave gop size
  
  untouched in libopenh264.
  Signed-off-by : Linjie Fu <linjie.fu@intel.com>
  
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavcodec/libopenh264enc.c

• lavc/libopenh264enc : Add qmin/qmax support

  29 avril 2020, par Linjie Fu

  lavc/libopenh264enc : Add qmin/qmax support
  Clip iMinQp/iMaxQp to (1, 51) for user specified qp range.
  If not set, leave iMinQp/iMaxQp untouched and use the values (0, 51)
  
  initialized in FillDefault(), and the QP range would be adjusted to the
  
  defaults inside libopenh264 library according to the iUsageType, (12, 42)
  
  for iUsageType == CAMERA_VIDEO_REAL_TIME which is default.
  <https://github.com/cisco/openh264/blob/master/codec/encoder/core/src/encoder_ext.cpp#L375> ;
  Signed-off-by : Linjie Fu <linjie.fu@intel.com>
  
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavcodec/libopenh264enc.c