normalize amplitude modulation

[engartst]

I'm using ffmpeg-normalize on a .wav file to create a EBU Normalized .mp3.

Settings for ffmpeg-normalize:
target level = -16 LUFS
true peak = -0.1
audio codec = libmp3lame
audio bitrate = 320 k

I am having some issues that I am not having when I reproduce the settings through Steinburg's Wavelab . The sound seems to come and go instead of staying at a constant level (amplitude modulation).

Do you know why this might be happening? Is there an issue with window size of analysis/is there a way to set that? or are these peculiarities the results in running the script on a mono file vs. dual-mono?

Cheers,
Stewart

[slhck]

As mentioned by the OP in an email, adding --dual-mono seems to fix it, since the input files are mono, but I'm not sure if that is a proper workaround or if something else is going on. Stewart, would you have an example WAV file available for testing?

[engartst]

I have audio examples but cannot attach them here.

I could link to a GoogleDrive Folder but not sure if it is appropriate in the forum, let me know and I will.

Cheers,
Stewart

[ilessing]

go for it Stewart. I think a link to Google drive location is appropriate.

[engartst]

Hi all,

I have uploaded three mp3s here:
https://drive.google.com/drive/folders/1DC9PY-3wJTSsQVPvf-ipGV35CCCY1vIN?usp=sharing

wavelabEBU.mp3 is the output with the above settings through WaveLab 8.5
ffmpegEBU.mp3 is the output with the above settings through ffmpeg-normalize without the --dual-mono tag
ffmpegEBU_dualMono.mp3 is the output with the above settings through ffmpeg-normalize with the --dual-mono tag

The flag seemingly fixed the issue, let me know what you think

[slhck]

Thanks for sending these files. Since the file is indeed mono and meant to be played back on a stereo system, using the -dual_mono flag seems to be correct usage. I don't know the underlying reason for that. I briefly looked into the relevant recommendations:

• EBU R 128
• EBU Tech 3341
• EBU Tech 3342
• ITU-R BS.1770-4

But I can't find a passage dealing with this topic in particular.

Note that it's actually an “issue” with the loudnorm filter in ffmpeg itself, but I'll leave this open for the time being.

[sampumon]

I notice modulation in ffmpegEBU_dualMono.mp3 also, right in the beginning between 0:02…0:06. It's less, but still quite annoying.

I have a difficult file too: https://vimeo.com/292682053

Adobe Media Encoder EBU-normalized it correctly, or at least without sudden volume drop during the loudest part at 0:41. Loudnorm refuses to to linear normalization:

ffmpeg -i U48_2018_Her_Fish.mp4 -af loudnorm=i=-23.0:lra=7.0:tp=0.0:offset=0.0:measured_i=-14.04:measured_lra=25.7:measured_tp=0.01:measured_thresh=-30.84:linear=true:print_format=summary -c:v copy Her_Fish_loudnorm2passHandBrew.mp4
[…]
[Parsed_loudnorm_0 @ 0x7fb5e580ba80] 
Input Integrated:    -14.0 LUFS
Input True Peak:      +0.0 dBTP
Input LRA:            25.7 LU
Input Threshold:     -30.8 LUFS

Output Integrated:   -18.0 LUFS
Output True Peak:     -2.1 dBTP
Output LRA:           25.7 LU
Output Threshold:    -34.8 LUFS

Normalization Type:   Dynamic
Target Offset:        -5.0 LU

My guess is @engartst your input file also has true peak 0 dB? Mine actually has "+0.01 dB" with json output. Changing that to 0.0 in the above ffmpeg command does not fix the issue.

Who dares report this upstream? 😅

[kylophone]

Hi,

@engartst can you please share your source file. I'll take a look and see what's happening. It's possible that there's a bug in the ffmpeg filter, but I'd need the source file to dig in.

Thanks,
Kyle

[engartst]

@ilessing can you share this?

thanks

[slhck]

Closing for now. Please reopen if you have an original source file that you can share.

[engartst]

Hey @ilessing , can you share the source file?

[slhck]

@engartst, I think that Ian asked you for a source file since you were the one originally reporting the error? Ian never mentioned having issues.

[engartst]

Sorry for the miscommunication on my part!

I have added the original .wav to the google drive folder here (original.wav): https://drive.google.com/drive/folders/1DC9PY-3wJTSsQVPvf-ipGV35CCCY1vIN

Thanks all