[FFmpeg-trac] #9363(avfilter:new): loudnorm does not allow a loudness range beyond 20 LU

FFmpeg trac at avcodec.org
Thu Aug 5 16:40:49 EEST 2021


#9363: loudnorm does not allow a loudness range beyond 20 LU
-------------------------------------+-------------------------------------
             Reporter:  Llyw         |                     Type:
                                     |  enhancement
               Status:  new          |                 Priority:  normal
            Component:  avfilter     |                  Version:
             Keywords:  loudnorm     |               Blocked By:
  loudness range lra                 |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 The loudnorm filter provided with FFmpeg 4.4 does not allow a loudness
 range (LRA) parameter beyond 20.

 I would like to request for that limit to be extended and, if possible,
 allow the value inf such that no compression is enforced based on the
 loudness range of the input file.

 I am not sure why the current limit of at most 20 LU of LRA is currently
 being imposed, but my reasoning for my request is that certain movies
 easily exceed an LRA of 20 LU such as The Matrix as shown in
 [https://tech.ebu.ch/docs/tech/tech3343.pdf], section 11.2.2. According to
 the AES presentation
 [https://www.aes.org/technical/documentDownloads.cfm?docID=521], section
 "Loudness vs. Speech: Transparency", feature films can more generally
 easily reach a LRA ranging from 16-30 LU.

 Additionally, both the EBU R 128 guideline (near the end of section
 11.2.2) and [https://auphonic.com/blog/2019/08/19/dynamic-range-
 processing/] in section "Where LRA falls short" explain that the LRA value
 should at least in general not be used for specifying a dynamic range
 target value. (The EBU R 128 guideline goes on to suggest that the Maximum
 Short-term Loudness Level should be used instead but this clearly goes
 beyond this request for enhancement.)

 So the first observation gives justification of an increase of the upper
 limit of loudnorm's LRA parameter, the second observation gives
 justification for also making the LRA constraint optional when using
 loudnorm.

 I am looking forward to getting feedback from you concerning this request.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9363>
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