[FFmpeg-trac] #6477(undetermined:new): NVENC: Warn explicitly when specific bit rate is out of range

[FFmpeg]

#6477: NVENC: Warn explicitly when specific bit rate is out of range
-------------------------------------+-------------------------------------
             Reporter:  alexpigment  |                     Type:
               Status:  new          |  enhancement
            Component:               |                 Priority:  normal
  undetermined                       |                  Version:
             Keywords:               |  unspecified
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
-------------------------------------+-------------------------------------
 Summary of the enhancement:

 Give an informative error when the user specifies a bit rate that is out
 of the encoder's range. NVENC appears to cap out at 144Mbps for
 progressive encoding and 37.5Mbps for interlaced encoding.

 Currently, there is a generic "InitializeEncoder failed: invalid param
 (8)" message that is given. This can cause (and has caused, in my case)
 the user to waste a considerable amount of time trying to change various
 parameters in the command line when the actual failure is the result of an
 invisible bit rate ceiling (which is especially low for interlaced).

 How to reproduce:

 Progressive FAILURE:
 {{{
 % ffmpeg -f lavfi -i smptebars -c:v h264_nvenc -s 1920x1080 -aspect 16:9
 -profile:v high -r 29.97 -t 5 -rc cbr_hq -b:v 144.1M 1080p.mp4
 }}}

 Progressive SUCCESS:
 {{{
 % ffmpeg -f lavfi -i smptebars -c:v h264_nvenc -s 1920x1080 -aspect 16:9
 -profile:v high -r 29.97 -t 5 -rc cbr_hq -b:v 144M 1080p.mp4
 }}}

 Interlaced FAILURE:
 {{{
 % ffmpeg -f lavfi -i smptebars -c:v h264_nvenc -s 1920x1080 -aspect 16:9
 -profile:v high -r 29.97 -t 5 -rc cbr_hq -flags ildct -b:v 37.6M 1080i.mp4
 }}}

 Interlaced SUCCESS:
 {{{
 % ffmpeg -f lavfi -i smptebars -c:v h264_nvenc -s 1920x1080 -aspect 16:9
 -profile:v high -r 29.97 -t 5 -rc cbr_hq -flags ildct -b:v 37.6M 1080i.mp4
 }}}


 ffmpeg version N-86330-gbd1179e
 built on 2017-06-01

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Ticket URL: <https://trac.ffmpeg.org/ticket/6477>
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