Webm's (vp8 and vp9) encode at extremely low bitrates when speed is adjusted

[Mojavve]

OS: Arch Linux
WmG Version: Freshly downloaded repo
ffmpeg Version: n7.0.1
Freshly made venv

When encoding with vp8 or vp9 at an adjusted speed (I adjusted it to 0.5, with interpolation checked OFF ) the video that outputs is extremely low bitrate.

This result is extremely similar to what was experienced when the -psnr flag was initially updated here

---

1st pass:
Ffmpeg command: ffmpeg -y -i tempVideoFiles/0_testmp4_4.799347826086956_7.790701394585724_c0a5150cb0_1724365552_0.mp4 -filter_complex_script tempVideoFiles/filters_6.txt -map [outvfinal] -pass 1 -passlogfile tempVideoFiles/encoder_6.log -shortest -copyts -start_at_zero -c:v libvpx-vp9 -c:a libopus -stats -pix_fmt yuv420p -threads 4 -auto-alt-ref 6 -lag-in-frames 25 -quality good -flags +psnr -row-mt 1 -tile-columns 2 -tile-rows 0 -arnr-maxframes 7 -arnr-strength 5 -aq-mode 0 -tune-content film -enable-tpl 1 -frame-parallel 0 -metadata Title=test WmG -b:v 10240000.0 -an -sn -f null /dev/null

2nd pass:
Ffmpeg command: ffmpeg -y -i tempVideoFiles/0_testmp4_4.799347826086956_7.790701394585724_c0a5150cb0_1724365552_0.mp4 -filter_complex_script tempVideoFiles/filters_6.txt -map [outvfinal] -pass 2 -passlogfile tempVideoFiles/encoder_6.log -shortest -copyts -start_at_zero -c:v libvpx-vp9 -c:a libopus -stats -pix_fmt yuv420p -threads 4 -auto-alt-ref 6 -lag-in-frames 25 -speed 1 -quality good -flags +psnr -row-mt 1 -tile-columns 2 -tile-rows 0 -arnr-maxframes 7 -arnr-strength 5 -aq-mode 0 -tune-content film -enable-tpl 1 -frame-parallel 0 -metadata Title=test WmG -b:v 10240000.0 -an -sn tempVideoFiles/test_6.webm

filters_6.txt:

[0:v]tpad=stop=100:stop_mode=clone,trim=end=2.991353568498768[0vsc],[0vsc][0:a]concat=n=1:v=1:a=1[outvconcat][outaconcat],[outvconcat]setpts=2.0*PTS[outvpre],[outaconcat]atempo=0.5[outapre],[outvpre]null[outv],[outapre]anull[outa],[outv]null,null[outvfinal],[outa]anullsink

ffprobe test_6.webm:

ffprobe version n7.0.1 Copyright (c) 2007-2024 the FFmpeg developers
  built with gcc 14.1.1 (GCC) 20240522
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-amf --enable-avisynth --enable-cuda-llvm --enable-lto --enable-fontconfig --enable-frei0r --enable-gmp --enable-gpl --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libdav1d --enable-libdrm --enable-libdvdnav --enable-libdvdread --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libharfbuzz --enable-libiec61883 --enable-libjack --enable-libjxl --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libplacebo --enable-libpulse --enable-librav1e --enable-librsvg --enable-librubberband --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpl --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxml2 --enable-libxvid --enable-libzimg --enable-mbedtls --enable-nvdec --enable-nvenc --enable-opencl --enable-opengl --enable-shared --enable-vapoursynth --enable-version3 --enable-vulkan
  libavutil      59.  8.100 / 59.  8.100
  libavcodec     61.  3.100 / 61.  3.100
  libavformat    61.  1.100 / 61.  1.100
  libavdevice    61.  1.100 / 61.  1.100
  libavfilter    10.  1.100 / 10.  1.100
  libswscale      8.  1.100 /  8.  1.100
  libswresample   5.  1.100 /  5.  1.100
  libpostproc    58.  1.100 / 58.  1.100
Input #0, matroska,webm, from 'test_6.webm':
  Metadata:
    title           : test WmG
    COMPATIBLE_BRANDS: isomiso2avc1mp41
    MAJOR_BRAND     : isom
    MINOR_VERSION   : 512
    ENCODER         : Lavf61.1.100
  Duration: 00:00:05.94, start: 0.000000, bitrate: 44 kb/s
  Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv, bt709, progressive), 1920x1080, SAR 1:1 DAR 16:9, 14.99 fps, 14.99 tbr, 1k tbn
      Metadata:
        ENCODER         : Lavc61.3.100 libvpx-vp9
        DURATION        : 00:00:05.939000000

[dfaker]

Yeah this is a bug caused by using setpts with vp9 and vp8

https://trac.ffmpeg.org/ticket/11126

The previous workaround for this was able to remove setpts in most cases, in this one however it's central to the speed adjustment.