Hello everyone,
I'm using loudnorm with two passes on various FLAC music files.
By applying the filter, files will also change bit depth from 16 to 24 bit.
What is the reason for this change in bit depth? The documentation on
loudnorm only mentions upsampling to 192 kHz when dynamic mode is used.
(https://ffmpeg.org/ffmpeg-filters.html#loudnorm)
I'm certain I'm using linear scaling as all parameters necessary are
specified and required criterea are also met. Linear scaling is also
confirmed by ffmpeg when running the command.
Ideally I'd like to keep the original bit depth without manually
specifying it for each file.
First pass:
`ffmpeg -i "Ad Infinitum - 02 Marching on Versailles.flac" -pass 1
-filter:a loudnorm=print_format=json -f null /dev/null`
Output:
```
ffmpeg version n6.1.1 Copyright (c) 2000-2023 the FFmpeg developers
built with gcc 13.2.1 (GCC) 20230801
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-gnutls --enable-gpl --enable-ladspa --enable-libaom
--enable-libass --enable-libbluray --enable-libbs2b --enable-libdav1d
--enable-libdrm --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-nvdec --enable-nvenc
--enable-opencl --enable-opengl --enable-shared --enable-vapoursynth
--enable-version3 --enable-vulkan
libavutil 58. 29.100 / 58. 29.100
libavcodec 60. 31.102 / 60. 31.102
libavformat 60. 16.100 / 60. 16.100
libavdevice 60. 3.100 / 60. 3.100
libavfilter 9. 12.100 / 9. 12.100
libswscale 7. 5.100 / 7. 5.100
libswresample 4. 12.100 / 4. 12.100
libpostproc 57. 3.100 / 57. 3.100
Input #0, flac, from 'Ad Infinitum - 02 Marching on Versailles.flac':
Metadata:
TITLE : Marching on Versailles
ARTIST : Ad Infinitum
DATE : 2020-04-03
ALBUM : Chapter I - Monarchy
track : 2
album_artist : Ad Infinitum
ISRC : ATN261993602
GENRE : Rock;Power Metal;Heavy Metal
PUBLISHER : Napalm Records
WWWAUDIOSOURCE :
https://adinfinitummusic.bandcamp.com/album/chapter-i-monarchy-2
SOURCEMEDIA : Bandcamp
Duration: 00:03:50.92, start: 0.000000, bitrate: 1277 kb/s
Stream #0:0: Audio: flac, 44100 Hz, stereo, s16
Stream #0:1: Video: mjpeg (Baseline), yuvj444p(pc,
bt470bg/unknown/unknown), 3000x3000, 90k tbr, 90k tbn (attached pic)
Metadata:
comment : Cover (front)
Stream mapping:
Stream #0:1 -> #0:0 (mjpeg (native) -> wrapped_avframe (native))
Stream #0:0 -> #0:1 (flac (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
Output #0, null, to '/dev/null':
Metadata:
TITLE : Marching on Versailles
ARTIST : Ad Infinitum
DATE : 2020-04-03
ALBUM : Chapter I - Monarchy
track : 2
album_artist : Ad Infinitum
ISRC : ATN261993602
GENRE : Rock;Power Metal;Heavy Metal
PUBLISHER : Napalm Records
WWWAUDIOSOURCE :
https://adinfinitummusic.bandcamp.com/album/chapter-i-monarchy-2
SOURCEMEDIA : Bandcamp
encoder : Lavf60.16.100
Stream #0:0: Video: wrapped_avframe, yuvj444p(pc,
bt470bg/unknown/unknown, progressive), 3000x3000, q=2-31, 200 kb/s, 90k
fps, 90k tbn (attached pic)
Metadata:
comment : Cover (front)
encoder : Lavc60.31.102 wrapped_avframe
Stream #0:1: Audio: pcm_s16le, 192000 Hz, stereo, s16, 6144 kb/s
Metadata:
encoder : Lavc60.31.102 pcm_s16le
[out#0/null @ 0x5d755b580380] video:0kB audio:173190kB subtitle:0kB
other streams:0kB global headers:0kB muxing overhead: unknown
frame= 1 fps=0.2 q=-0.0 Lsize=N/A time=00:03:48.10 bitrate=N/A
speed=51.3x
[Parsed_loudnorm_0 @ 0x5d755b5aaa40]
{
"input_i" : "-9.37",
"input_tp" : "-0.24",
"input_lra" : "5.00",
"input_thresh" : "-19.62",
"output_i" : "-23.22",
"output_tp" : "-8.59",
"output_lra" : "3.20",
"output_thresh" : "-33.30",
"normalization_type" : "dynamic",
"target_offset" : "-0.78"
}
```
Second pass
`ffmpeg -i "Ad Infinitum - 02 Marching on Versailles.flac" -pass 2
-filter:a
loudnorm=measured_I=-9.37:measured_LRA=5.00:measured_tp=-0.24:measured_thresh=-19.62:print_format=json
-c:a flac -y out.flac`
Output:
```
ffmpeg version n6.1.1 Copyright (c) 2000-2023 the FFmpeg developers
built with gcc 13.2.1 (GCC) 20230801
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-gnutls --enable-gpl --enable-ladspa --enable-libaom
--enable-libass --enable-libbluray --enable-libbs2b --enable-libdav1d
--enable-libdrm --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-nvdec --enable-nvenc
--enable-opencl --enable-opengl --enable-shared --enable-vapoursynth
--enable-version3 --enable-vulkan
libavutil 58. 29.100 / 58. 29.100
libavcodec 60. 31.102 / 60. 31.102
libavformat 60. 16.100 / 60. 16.100
libavdevice 60. 3.100 / 60. 3.100
libavfilter 9. 12.100 / 9. 12.100
libswscale 7. 5.100 / 7. 5.100
libswresample 4. 12.100 / 4. 12.100
libpostproc 57. 3.100 / 57. 3.100
Input #0, flac, from 'Ad Infinitum - 02 Marching on Versailles.flac':
Metadata:
TITLE : Marching on Versailles
ARTIST : Ad Infinitum
DATE : 2020-04-03
ALBUM : Chapter I - Monarchy
track : 2
album_artist : Ad Infinitum
ISRC : ATN261993602
GENRE : Rock;Power Metal;Heavy Metal
PUBLISHER : Napalm Records
WWWAUDIOSOURCE :
https://adinfinitummusic.bandcamp.com/album/chapter-i-monarchy-2
SOURCEMEDIA : Bandcamp
Duration: 00:03:50.92, start: 0.000000, bitrate: 1277 kb/s
Stream #0:0: Audio: flac, 44100 Hz, stereo, s16
Stream #0:1: Video: mjpeg (Baseline), yuvj444p(pc,
bt470bg/unknown/unknown), 3000x3000, 90k tbr, 90k tbn (attached pic)
Metadata:
comment : Cover (front)
Stream mapping:
Stream #0:1 -> #0:0 (mjpeg (native) -> png (native))
Stream #0:0 -> #0:1 (flac (native) -> flac (native))
Press [q] to stop, [?] for help
[swscaler @ 0x5ee2dc47e1c0] deprecated pixel format used, make sure you
did set range correctly
[swscaler @ 0x5ee2dc48ddc0] deprecated pixel format used, make sure you
did set range correctly
[swscaler @ 0x5ee2dc48cc40] deprecated pixel format used, make sure you
did set range correctly
Last message repeated 1 times
[flac @ 0x5ee2dbc8a040] encoding as 24 bits-per-sample, more is
considered experimental. Add -strict experimental if you want to encode
more than 24 bits-per-sample
Output #0, flac, to 'out.flac':
Metadata:
TITLE : Marching on Versailles
ARTIST : Ad Infinitum
DATE : 2020-04-03
ALBUM : Chapter I - Monarchy
track : 2
album_artist : Ad Infinitum
ISRC : ATN261993602
GENRE : Rock;Power Metal;Heavy Metal
PUBLISHER : Napalm Records
WWWAUDIOSOURCE :
https://adinfinitummusic.bandcamp.com/album/chapter-i-monarchy-2
SOURCEMEDIA : Bandcamp
encoder : Lavf60.16.100
Stream #0:0: Video: png, rgb24(pc, gbr/unknown/unknown, progressive),
3000x3000, q=2-31, 200 kb/s, 90k fps, 90k tbn (attached pic)
Metadata:
comment : Cover (front)
encoder : Lavc60.31.102 png
Stream #0:1: Audio: flac, 44100 Hz, stereo, s32 (24 bit), 128 kb/s
Metadata:
encoder : Lavc60.31.102 flac
[flac @ 0x5ee2dbc8fac0] Picture block too big 19237006 >= 16777216=
0.0kbits/s speed= 228x
[out#0/flac @ 0x5ee2dbc5c380] video:18786kB audio:41876kB subtitle:0kB
other streams:0kB global headers:0kB muxing overhead: unknown
frame= 1 fps=0.0 q=-0.0 Lsize= 41884kB time=00:03:50.92
bitrate=1485.9kbits/s speed= 235x
[Parsed_loudnorm_0 @ 0x5ee2dcb1a4c0]
{
"input_i" : "-9.33",
"input_tp" : "-0.25",
"input_lra" : "5.00",
"input_thresh" : "-19.53",
"output_i" : "-23.96",
"output_tp" : "-14.88",
"output_lra" : "5.00",
"output_thresh" : "-34.14",
"normalization_type" : "linear",
"target_offset" : "-0.04"
}
```
Thanks a lot for your help
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