[FFmpeg-trac] #7591(avcodec:new): h264_amf encoder: target bitrate increase results in real bitrate decrease

[FFmpeg]

#7591: h264_amf encoder: target bitrate increase results in real bitrate decrease
----------------------------------+---------------------------------------
             Reporter:  skaron    |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  avcodec   |                  Version:  unspecified
             Keywords:  h264_amf  |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
----------------------------------+---------------------------------------
 Summary of the bug:

 I performed convertations with different bitrates using AMF encoder
 (Radeon RX 560, 24.20.13017.1009 driver version)
 {{{
 % ffmpeg.exe -i <input_file> -b:v 30M -c:v h264_amf test_30.mp4
 % ffmpeg.exe -i <input_file> -b:v 45M -c:v h264_amf test_45.mp4
 % ffmpeg.exe -i <input_file> -b:v 72M -c:v h264_amf test_72.mp4
 }}}
 The bitrate in results files (from ffprobe output, mediainfo gives same
 values):
 test_30.mp4 - bitrate: 29765 kb/s
 test_45.mp4 - bitrate: '''5474''' kb/s - artifacts
 test_72.mp4 - bitrate: '''3693''' kb/s - artifacts

 Before 30 Mbps there is no problem. The boundary after that real bitrate
 decrease depends on frame resolution and FPS.

 {{{
 ffmpeg version 4.1 Copyright (c) 2000-2018 the FFmpeg developers
 built with gcc 8.2.1 (GCC) 20181017
 configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-
 fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-
 libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-
 amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus
 --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora
 --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp
 --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg
 --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-
 libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex
 --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-
 ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec
 --enable-dxva2 --enable-avisynth
 libavutil      56. 22.100 / 56. 22.100
 libavcodec     58. 35.100 / 58. 35.100
 libavformat    58. 20.100 / 58. 20.100
 libavdevice    58.  5.100 / 58.  5.100
 libavfilter     7. 40.101 /  7. 40.101
 libswscale      5.  3.100 /  5.  3.100
 libswresample   3.  3.100 /  3.  3.100
 libpostproc    55.  3.100 / 55.  3.100
 }}}

 Full ffprobe output for one of test files
 {{{
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test_30.mp4':
 Metadata:
   major_brand     : isom
   minor_version   : 512
   compatible_brands: isomiso2avc1mp41
   encoder         : Lavf58.20.100
 Duration: 00:03:44.35, start: 0.000000, bitrate: 29765 kb/s
   Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv),
 1280x720 [SAR 1:1 DAR 16:9], 29639 kb/s, 23.98 fps, 23.98 tbr, 24k tbn,
 47.95 tbc (default)
   Metadata:
     handler_name    : ISO Media file produced by Google Inc. Created on:
 02/08/2018.
   Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo,
 fltp, 127 kb/s (default)
   Metadata:
     handler_name    : ISO Media file produced by Google Inc. Created on:
 02/08/2018.
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7591>
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