bsf 'rotate' seemingly not doing anything

[geegee]

FFMPEG is not changing the rotation matrix when asked to like when for example using either of the two sample commands provided below. The two output files will be identical to each other and even to a third simple output made with ffmpeg -i input.mp4 -c copy outputx.mp4, meaning -bsf:v h264_metadata=rotate=90.0 and -metadata:s:v:0 rotate=90 aren't doing anything at all. This can be further verified by opening the output file(s) in a hex editor and checking the values of the rotation matrix as specified in this external post: ​https://superuser.com/a/1307206/580856

Outputs will lack the line displaymatrix: rotation of 90.00 degrees when analized with ffprobe, but this line will be displayed when the mp4 is edited manually with a hex editor as specified in the superuser link.

How to reproduce:

% ffmpeg -i input.mp4 -c copy -metadata:s:v:0 rotate=90 output2.mp4

or

% ffmpeg -i input.mp4 -c copy -bsf:v h264_metadata=rotate=90.0 output1.mp4
ffmpeg version 2024-04-04-git-478d97f303-full_build-www.gyan.dev Copyright (c) 2000-2024 the FFmpeg developers
  built with gcc 13.2.0 (Rev5, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libaribcaption --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libxevd --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxeve --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-libharfbuzz --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-dxva2 --enable-d3d11va --enable-d3d12va --enable-ffnvcodec --enable-libvpl --enable-nvdec --enable-nvenc --enable-vaapi --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libcodec2 --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      59. 13.100 / 59. 13.100
  libavcodec     61.  5.101 / 61.  5.101
  libavformat    61.  3.100 / 61.  3.100
  libavdevice    61.  2.100 / 61.  2.100
  libavfilter    10.  2.101 / 10.  2.101
  libswscale      8.  2.100 /  8.  2.100
  libswresample   5.  2.100 /  5.  2.100
  libpostproc    58.  2.100 / 58.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf59.27.100
  Duration: 00:10:50.38, start: 0.000000, bitrate: 1830 kb/s
  Stream #0:0[0x1](eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 888x1920 [SAR 1:1 DAR 37:80], 1691 kb/s, 43.14 fps, 43 tbr, 15360 tbn (default)
      Metadata:
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
        encoder         : Lavc59.37.100 libx264
  Stream #0:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
      Metadata:
        handler_name    : SoundHandler
        vendor_id       : [0][0][0][0]
[h264_metadata @ 0000012096b317c0] 4 bytes left at end of AVCC header.
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Output #0, mp4, to 'output1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf61.3.100
  Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 888x1920 [SAR 1:1 DAR 37:80], q=2-31, 1691 kb/s, 43.14 fps, 43 tbr, 15360 tbn (default)
      Metadata:
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
        encoder         : Lavc59.37.100 libx264
  Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
      Metadata:
        handler_name    : SoundHandler
        vendor_id       : [0][0][0][0]
Press [q] to stop, [?] for help
[out#0/mp4 @ 0000012096b53900] video:134242KiB audio:10163KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead: 0.634229%
size=  145321KiB time=00:10:50.27 bitrate=1830.7kbits/s speed= 881x

[mkver]

The h264_metadata bsf modifies the bitstream (i.e. it adds a SEI message that indicates the rotation), not the displaymatrix as used by mov/mp4.

The metadata rotate tags have been removed (after having been deprecated for ages). Use the display_rotation ffmpeg option instead.