[FFmpeg-user] Trying to use 'ebur128' results to set up 'loudnorm'

[Mark Filipak]

(Intentionally top-posted)

Thank you, Paul. Thank you so much.

I used your command with some needed modifications: Copying existing DTS, coding to ac3, 
'-disposition' to change the default soundtrack, and all the '-map'ping and codec '-copy'ing.

I've always thought that people learn more from success than from failure, and you made it happen.

--Mark.


On 21/05/2024 16.04, Paul B Mahol wrote:
> On Tue, May 21, 2024 at 10:52 AM Mark Filipak <markfilipak.imdb at gmail.com>
> wrote:
> 
>> Attachments:
>> 1. original ebur128.jpg
>> 2. loudnorm-thresh=-85 pan ebur128.jpg
>> 3. what I want ebur128.jpg
>>
>> ___1. The original
>> has a 'shelf' just below LU = -13. That's soft speech.
>> The peak is at LU = +9. That's shouting.
>> So the transform I want goes like this:
>> LU = -18..-14 gets no boost.
>> LU = -14..+9 gets a linear boost to -11..+9.
>> I assume 'LU' is Loudness Unit', eh? What is a loudness unit?
>>
>> Now, the range of 'loudnorm=measured_thresh' is -99..0, so 100 steps.
>> Heaven knows what the scale is
>> and whether it's linear. No matter: Pressing on...
>>
>> If LU = -18..9 maps linearly to 'measured_thresh' = -99..0, then Lu = -14
>> is 'measured_thresh' =
>> -85. I use "-85" in the next step.
>>
>>
>> ___2. This command:
>>
>> ffmpeg -i "original.mp4" -map 0:a -filter_complex
>> "[0:a]loudnorm=measured_thresh=-85,
>> pan=stereo|FL<FL+0.5*FC+0.6*BL+0.6*SL|FR<FR+0.5*FC+0.6*BR+0.6*SR,ebur128=video=1:peak=true[a]"
>> -map
>> "[a]" -c:v libx265 -x265-params crf=16 -c:a ac3 "loudnorm-thresh=-85 pan
>> ebur128.mp4"
>>
>> maps LU = -13..+9 to -11..-7. That brings the soft speech up wonderfully,
>> but the shouting is dead.
>>
>>
>> ___3. What I want maps LU = -14..+9 to -11..+9.
>> But to map linearly with 'loudnorm' I need to specify 4 parameters:
>> measured_I = -99..0
>> measured_LRA = 0..99
>> measured_TP = -99..99
>> measured_thresh = -99..0
>> I sorta know what 'thresh' is and I think it is '-85'. But I have no idea
>> what 'I' and 'LRA' and
>> 'TP' are. I have no idea how to measure them. I have no idea what the
>> measurement units are. And I
>> have no idea what their physical meanings are.
>>
>> Is there a way to measure the source video to determine these numbers? I'm
>> partway there, but the
>> rest of the way seems impossibly difficult; there's just too many unknowns.
>>
>> Help! Please! I thank you,
>>
> 
> ffmpeg -i input.video -af
> "aformat=fltp,pan=stereo|FL=FL+FC+LFE+SL+BL|FR=FR+FC+LFE+SR+BR,alimiter"
> -c:v copy output.video
> 
> Loudnorm filter in ffmpeg codebase is bad and ugly especially in dynamic
> mode.
> 
> The best output is using limiter after just summing all channels, and not
> scaling channels prior to summing at all.
> This depends on quality of limiter filter, there are many alternative
> limiters like with effects within ladspa, lv2 and clap (only in Librempeg).