WEBm chunking fails as it reports that ffmpeg requires the HEADER to have a %d (even when added) and appears to ignore 'channel_layout' regardless of where placed. and windows builds lack libvpx-vp9

[Andy]

ffmpeg.exe -f dshow -i video="USB Capture HDMI":audio="HDMI (USB Capture HDMI)" -rtbufsize 6082560 -channel_layout mono -ac 1 -map 0:0 -pix_fmt yuv420p -c:v libvpx-vp9 -s 768X576 -keyint_min 60 -g 60 -speed 6 -tile-columns 4 -frame-parallel 1 -threads 8 -static-thresh 0 -max-intra-rate 300 -deadline realtime -lag-in-frames 0 -error-resilient 1 -b:v 360K -f webm_chunk -header "webm_live_video_360_%d.hdr" -chunk_start_index 1 "webm_live_video_360_%d.chk" -map 0:1 -c:a libvorbis -b:a 48k -ar 44100 -f webm_chunk -audio_chunk_duration 2000 header "webm_live_audio_48_%d.hdr" -chunk_start_index 1 "webm_live_audio_48_%d.chk"
ffmpeg version 2023-11-02-git-4dbfb52230-full_build-www.gyan.dev Copyright (c) 2000-2023 the FFmpeg developers

built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
configuration: --enable-gpl --enable-version3 --enable-static --pkg-config=pkgconf --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-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --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-ffnvcodec --enable-nvdec --enable-nvenc --enable-dxva2 --enable-d3d11va --enable-libvpl --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 58. 31.100 / 58. 31.100
libavcodec 60. 32.102 / 60. 32.102
libavformat 60. 17.100 / 60. 17.100
libavdevice 60. 4.100 / 60. 4.100
libavfilter 9. 13.100 / 9. 13.100
libswscale 7. 6.100 / 7. 6.100
libswresample 4. 13.100 / 4. 13.100
libpostproc 57. 4.100 / 57. 4.100

[aist#0:1/pcm_s16le @ 000001e0ef7d4840] Guessed Channel Layout: stereo
Input #0, dshow, from 'video=USB Capture HDMI:audio=HDMI (USB Capture HDMI)':

Duration: N/A, start: 22379.144186, bitrate: N/A
Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422(tv, bt709/bt709/unknown), 768x576, 25 fps, 25 tbr, 10000k tbn
Stream #0:1: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s

[out#1/webm_chunk @ 000001e0ef6f8900] Output filename 'header' does not contain a numeric pattern like '%d', which is required by output format 'webm_chunk'.
Error opening output file header.
Error opening output files: Invalid argument

[mkver]

Your second output uses "header", where "-header" is meant. The result is that 'header' is interpreted as output filename which is of course lacking a numeric pattern.

The issue regarding the lack of libvpx-vp9 should be directed to the provider of your builds. Anyway, libvpx is enabled in the build used for your bug report.