blog/data/2015-06-11-frikanalen-loadness.txt

   1 Title: Measuring and adjusting the loudness of a TV channel using bs1770gain
   2 Tags: english, video, frikanalen, multimedia
   3 Date: 2015-06-11 13:40
   4
   5 <p>Television loudness is the source of frustration for viewers
   6 everywhere.  Some channels are very load, others are less loud, and
   7 ads tend to shout very high to get the attention of the viewers, and
   8 the viewers do not like this.  This fact is well known to the TV
   9 channels.  See for example the BBC white paper
  10 "<a href="http://downloads.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP202.pdf">Terminology
  11 for loudness and level dBTP, LU, and all that</a>" from 2011 for a
  12 summary of the problem domain.  To better address the need for even
  13 loadness, the TV channels got together several years ago to agree on a
  14 new way to measure loudness in digital files as one step in
  15 standardizing loudness.  From this came the ITU-R standard BS.1770,
  16 "<a href="http://www.itu.int/rec/R-REC-BS.1770/en">Algorithms to
  17 measure audio programme loudness and true-peak audio level</a>".</p>
  18
  19 <p>The ITU-R BS.1770 specification describe an algorithm to measure
  20 loadness in LUFS (Loudness Units, referenced to Full Scale). But
  21 having a way to measure is not enough.  To get the same loudness
  22 across TV channels, one also need to decide which value to standardize
  23 on.  For European TV channels, this was done in the EBU Recommondaton
  24 R128, "<a href="https://tech.ebu.ch/docs/r/r128.pdf">Loudness
  25 normalisation and permitted maximum level of audio signals</a>", which
  26 specifies a recommended level of -23 LUFS.  In Norway, I have been
  27 told that NRK, TV2, MTG and SBS have decided among themselves to
  28 follow the R128 recommondation for playout from 2016-03-01.</p>
  29
  30 <p>There are free software available to measure and adjust the loudness
  31 level using the LUFS.  In Debian, I am aware of a library named
  32 <a href="https://tracker.debian.org/pkg/libebur128">libebur128</a>
  33 able to measure the loudness and since yesterday morning a new binary
  34 named <a href="http://bs1770gain.sourceforge.net">bs1770gain</a>
  35 capable of both measuring and adjusting was uploaded and is waiting
  36 for NEW processing.  I plan to maintain the latter in Debian under the
  37 <a href="https://qa.debian.org/developer.php?email=pkg-multimedia-maintainers%40lists.alioth.debian.org">Debian
  38 multimedia</a> umbrella.</p>
  39
  40 <p>The free software based TV channel I am involved in,
  41 <a href="http://www.frikanalen.no/">Frikanalen</a>, plan to follow the
  42 R128 recommondation ourself as soon as we can adjust the software to
  43 do so, and the bs1770gain tool seem like a good fit for that part of
  44 the puzzle to measure loudness on new video uploaded to Frikanalen.
  45 Personally, I plan to use bs1770gain to adjust the loudness of videos
  46 I upload to Frikanalen on behalf of <a href="http://www.nuug.no/">the
  47 NUUG member organisation</a>.  The program seem to be able to measure
  48 the LUFS value of any media file handled by ffmpeg, but I've only
  49 successfully adjusted the LUFS value of WAV files.  I suspect it
  50 should be able to adjust it for all the formats handled by ffmpeg.</p>