#8559: Windows: EBU R128 filter lag when capturing from sound card
-------------------------------------+-------------------------------------
Reporter: | Type: defect
chrisdoernen |
Status: new | Priority: normal
Component: | Version: git-
undetermined | master
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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== Summary of the bug: ==
When capturing from a sound card on windows, the EBU R128 filter does not
print it's metadata continuously as it is calculated (every 100ms) but
rather in "chunks" every 500ms or so. This does not happen when specifying
a mp3 file with the realtime flag (-re). Please see the corresponding
commands below.
On Ubuntu, both variations (capturing from sound card and file) produce
the same continuous output. Also, live streaming the mp3 encoded audio
works fine (the commands below are shortened for the purpose of
demonstration). So I think it is not a problem with my sound card/sound
system.
== How to reproduce: ==
Compare the output over time of this command
{{{
ffmpeg.exe -re -i test.mp3 -filter_complex
ebur128=metadata=1,ametadata=print:key=lavfi.r128.M:file=-:direct=1 -f
null -
}}}
with the output over time of the following command (adapting the input
parameter)
{{{
ffmpeg.exe -y -f dshow -i audio="Mikrofonarray (Realtek High Definition
Audio)" -filter_complex
ebur128=metadata=1,ametadata=print:key=lavfi.r128.M:file=-:direct=1 -f
null -
}}}
Observe that the output of the first command is printed smootly, one frame
at a time, the output of the second command gives multiple frames at once.
== Ffmpeg version: ==
20200306-cfd9a65 (Windows Build from Zeranoe, Static linked, 64bit)
Background info about the use case:
I am building an audio streaming application where I want to display the
momentary loudness in real time as a volume meter.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8559>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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