[FFmpeg-devel] [PATCH] avfilter: add loudnorm

[Kyle Swanson]

On Wed, Apr 6, 2016 at 10:02 AM, Clément Bœsch <u at pkh.me> wrote:
> On Wed, Apr 06, 2016 at 09:52:51AM -0500, Kyle Swanson wrote:
>> On Wed, Apr 6, 2016 at 12:45 AM, Clément Bœsch <u at pkh.me> wrote:
>> > On Tue, Apr 05, 2016 at 07:01:14PM -0500, Kyle Swanson wrote:
>> >> Here's another audio filter. I hinted at this a few months ago, but I found out that
>> >> finishing the last 5% took almost as long as the first 95%. This is an EBU R128
>> >> dynamic loudness normalization filter. This filter uses libebur128 v1.1.0[1] and must be
>> >> configured with `--enable-libebur128'. Please also see the accompanying blog post[2]
>> >> which has an algorithm description, as well as some usage instructions.
>> >>
>> >> [1] https://github.com/jiixyj/libebur128
>> >> [2] http://k.ylo.ph/2016/04/04/loudnorm.html
>> >>
>> >> Thanks!
>> >> Kyle
>> >>
>> >> Signed-off-by: Kyle Swanson <k at ylo.ph>
>> >> ---
>> >>  Changelog                 |   1 +
>> >>  MAINTAINERS               |   1 +
>> >>  configure                 |   5 +
>> >>  doc/filters.texi          |  42 +++
>> >>  libavfilter/Makefile      |   1 +
>> >>  libavfilter/af_loudnorm.c | 905 ++++++++++++++++++++++++++++++++++++++++++++++
>> >>  libavfilter/allfilters.c  |   1 +
>> >>  libavfilter/version.h     |   4 +-
>> >>  8 files changed, 958 insertions(+), 2 deletions(-)
>> >>  create mode 100644 libavfilter/af_loudnorm.c
>> >>
>> >
>> > Mmh. That's nice and all but... why not use/adjust the native ebur128
>> > filter we have instead of relying on an external library?
>> >
>> > [...]
>> >
>> > --
>> > Clément B.
>>
>> This could be an option for the future. We'll need to break all the
>> EBU R128 logic out into utility functions
>
> why? what do you need exactly from the filter? The meta are exported in
> each audio frame.

That could work, but in this filter there is a second internal
loudness measurement. Frame meta would only work for the input stream.

>
>> and update it to use the newest version BS.1770 so it can be used by
>> both filters. Using libebur128 is a
>> good option because it is widely used, actively developed, and updated
>> whenever the spec changes.
>
> except it's an external dependency and we have code builtin available,
> doing the same thing, and with no open issue (afaik).
>
> --
> Clément B.
>
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