Having read at least a dozen other answers, it seems that the b:a 96k parameter should be producing a MP3 with a constant bitrate (CBR), yet I can only get Variable bitrates.
The latest variation of ffmpeg that comes closest is below. I don't believe I'm missing anything, so are the other values interfering?
UPDATE: replace input/output with the latest results.
From MediaInfo:
General
Complete name : C:\3024.mp3
Format : MPEG Audio
File size : 124 MiB
Duration : 2 h 59 min
Overall bit rate mode : Variable
Overall bit rate : 96.0 kb/s
Track name : My Title
Writing library : LAME3.100
major_brand : mp42
minor_version : 0
compatible_brands : mp42mp41
Audio
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 3
Duration : 2 h 59 min
Bit rate mode : Variable
Bit rate : 96.0 kb/s
Channel(s) : 1 channel
Sampling rate : 44.1 kHz
Frame rate : 38.281 FPS (1152 SPF)
Compression mode : Lossy
Stream size : 124 MiB (100%)
Writing library : LAME3.100
ffmpeg -i 3024.mp4 -metadata title="My Title" -vn -ar 44100 -ac 1 -b:a 96k 3024.mp3
ffmpeg version 4.1.1 Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 8.2.1 (GCC) 20190212
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
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '20221011_regular_3024.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: mp42mp41
creation_time : 2022-10-12T06:53:10.000000Z
Duration: 02:59:59.36, start: 0.000000, bitrate: 1297 kb/s
Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720 [SAR 1:1 DAR 16:9], 1198 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 60k tbc (default)
Metadata:
creation_time : 2022-10-12T06:53:10.000000Z
handler_name : ?Mainconcept Video Media Handler
encoder : AVC Coding
Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 93 kb/s (default)
Metadata:
creation_time : 2022-10-12T06:53:11.000000Z
handler_name : #Mainconcept MP4 Sound Media Handler
Stream mapping:
Stream #0:1 -> #0:0 (aac (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, mp3, to '20221011_regular_3024.mp3':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: mp42mp41
TIT2 : Regular Meeting on Tuesday, October 11th, 2022
TSSE : Lavf58.20.100
Stream #0:0(eng): Audio: mp3 (libmp3lame), 44100 Hz, mono, fltp, 96 kb/s (default)
Metadata:
creation_time : 2022-10-12T06:53:11.000000Z
handler_name : #Mainconcept MP4 Sound Media Handler
encoder : Lavc58.35.100 libmp3lame
size= 126556kB time=02:59:59.36 bitrate= 96.0kbits/s speed= 126x
video:0kB audio:126555kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000393% ```
