[FFmpeg-devel] [PATCH v1 2/6] avfilter/af_silencedetect: document metadata

[Limin Wang]

On Tue, Oct 08, 2019 at 02:21:06PM +0200, Moritz Barsnick wrote:
> On Mon, Oct 07, 2019 at 22:23:21 +0800, Limin Wang wrote:
> > On Tue, Oct 01, 2019 at 09:40:45AM +0200, Moritz Barsnick wrote:
> > > On Mon, Sep 30, 2019 at 21:36:43 +0800, lance.lmwang at gmail.com wrote:
> > > > -The printed times and duration are expressed in seconds.
> > > > +The printed times and duration are expressed in seconds. The @code{lavfi.silence_start}
> > > > +or @code{lavfi.silence_start.X} metadata key is set on the first frame whose timestamp
> > > > +equals or exceeds the detection duration and it contains the timestamp of the first
> > > > +frame of the silence.
> > > > +
> > > > +The @code{lavfi.silence_duration} or @code{lavfi.silence_duration.X} and
> > > > + at code{lavfi.silence_end} or @code{lavfi.silence_end.X}metadata keys are set on the
> > > > +first frame after the silence. Where @code{X} is the channel number and .X is used
> > > > +if @option{mono} is enabled.
> > >
> > > I don't understand. Literal ".X" (which you should write as
> > > "@code{.X}", by the way)? And if not mono, it's ".0", ".1"? And when is
> > > ".N" completely omitted?
> > By the code,  if it's mono mode, it'll output lavfi.silence_duration metadata, if not mono,
> > it'll output lavfi.silence_duration.0, lavfi.silence_duration.1(0, 1 is the channel number).
> > Please advise how to describe this clearly.
> 
> Well, I must say I was confused by the option "mono", because it does
> the opposite in my opinion[*].
> 
> Anyway, since it's technically correct, I would rearrange or explain as
> such:
> 
> The @code{lavfi.silence_duration} or @code{lavfi.silence_duration.X}
> and @code{lavfi.silence_end} or @code{lavfi.silence_end.X} metadata
> keys are set on the first frame after the silence. If @option{mono} is
> enabled, and each channel is evaluated separately, the @code{.X}
> suffixed keys are used, and @code{X} corresponds to the channel number.

OK, I'll update it by your description, it's more native to understand.

> 
> [*] In "mono" mode, from its name, I would have expected all the
> channels to be mixed down and interpreted as a monaural signal. But
> this is actually what happens if "mono" mode is *not* selected,
> apparently. In reality, in "mono" mode, each channel is interpreted
> separately, but that doesn't make these mono, in my opinion. But
> there's nothing we can change about that now. ;-)

Yes, the mono mode make the metadata difficult to process also.

> 
> Cheers,
> Moritz
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