[FFmpeg-trac] #10137(avcodec:open): hevc_nvenc [Clipping lookahead depth] and surfaces

[FFmpeg]

#10137: hevc_nvenc [Clipping lookahead depth] and surfaces
-------------------------------------+-------------------------------------
             Reporter:  colemarc     |                    Owner:  (none)
                 Type:  defect       |                   Status:  open
             Priority:  normal       |                Component:  avcodec
              Version:  unspecified  |               Resolution:
             Keywords:  hevc_nvenc   |               Blocked By:
  scenecut lookahead clipping        |
  surfaces                           |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Comment (by quinkblack):

 From "NVIDIA VIDEO CODEC SDK - ENCODER Programming Guide",
 ```
 The number of frames to be looked ahead should be set in
 NV_ENC_INITIALIZE_PARAMS::encodeconfig->rcParams.lookaheadDepth which can
 be up to 32.
 ```

 From nvEncodeAPI.h:
 ```
     uint16_t                        lookaheadDepth;
 /**< [in]: Maximum depth of lookahead with range 0-(31 - number of B
 frames).
 lookaheadDepth is only used if enableLookahead=1.*/

 ```

 You don't need a super large lookahead to enable scenecut. -rc-lookahead 1
 works for scenecut. You can verify it by a super large gop size, for
 example,
 ```
 ffmpeg -hwaccel cuda -i ~/video/cctv.mp4 -an -c:v hevc_nvenc -rc-lookahead
 1 -b:v 3M -t 60 -g 2500 /tmp/test.mp4
 ```
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10137#comment:2>
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