RGB waveforms don't show graticules

[cepesh]

Summary of the bug: RGB waveforms don't show graticules

How to reproduce:

% ffplay -f lavfi -i "smptebars=duration=5:size=1280x720:rate=30" -vf "format=pix_fmts=rgb24,waveform=g=orange"

compare to:

% ffplay -f lavfi -i "smptebars=duration=5:size=1280x720:rate=30" -vf "format=pix_fmts=yuv422p10le,waveform=g=orange"

ffplay version

ffplay version N-91626-gf631c328e6 Copyright (c) 2003-2018 the FFmpeg developers
built with gcc 8.2.1 (GCC) 20180813
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. 19.100 / 56. 19.100
libavcodec     58. 23.100 / 58. 23.100
libavformat    58. 17.101 / 58. 17.101
libavdevice    58.  4.101 / 58.  4.101
libavfilter     7. 26.100 /  7. 26.100
libswscale      5.  2.100 /  5.  2.100
libswresample   3.  2.100 /  3.  2.100
libpostproc    55.  2.100 / 55.  2.100

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

[Elon Musk]

Fixed in d94d2527317dc0e22bc3e1d135a0362ba796bf95.