[FFmpeg-devel] [PATCH] lavfi: add asendcmd and sendcmd filters

[Stefano Sabatini]

On date Monday 2012-09-03 03:36:24 +0200, Clément Bœsch encoded:
> On Sun, Sep 02, 2012 at 06:18:42PM +0200, Stefano Sabatini wrote:
> > On date Wednesday 2012-08-15 10:20:33 +0200, Nicolas George encoded:
> > > Le nonidi 29 thermidor, an CCXX, Nicolas George a écrit :
> > > > I do not believe having a solution for that problem right now is mandatory,
> > > > but having a syntax that be extended to implement a solution would be
> > > > better.
> > > 
> > > I suggest the following syntax:
> > > 
> > > 0:05:00-0:15:00         delogo set 10:10:160:120
> > > +               [leave] delogo set 0
> > > 
> > > In other words:
> > > 
> > > - command timestamps can be intervals, with the end defaulting to infinity
> > >   (INT64_MAX should be infinite enough);
> > > 
> > > - these intervals can have several associated commands, using a '+' instead
> > >   of the timestamp to add to the current interval;
> > 
> > What about:
> > 
> > 0:05:00-0:15:00 [enter] delogo set 10:10:160:120
> >                 [leave] delogo set 0;
> > 
> > ?
> > 
> > Basically this is setting several commands in a given interval (so the
> > primitive will be parse_interval_commands()), possibly with different
> > targets.
> >  
> > > - flags can be set between the timestamp and target using brackets, and some
> > >   of these flags can specify when the corresponding command is sent
> > >   depending on the evolution of the current timestamp with regard to the
> > >   interval (default: "enter").
> > > 
> > > I believe this syntax could cover most reasonable needs without being too
> > > much trouble to implement.
> > > 
> > > And if we agree that the target of a command can not have brackets in its
> > > name (or that they must be escaped), it is completely compatible with what
> > > you already wrote, so you can go ahead with it.
> > 
> > Updated WIP patch with token escaping (for the old syntax), and
> > command terminator.
> > -- 
> > FFmpeg = Fierce & Frenzy Monstrous Plastic Evil Geisha
> 
> > From 362b7ee4dfa0a4d2d78a6baf3ab7b7d8287fe0c0 Mon Sep 17 00:00:00 2001
> > From: Stefano Sabatini <stefasab at gmail.com>
> > Date: Mon, 13 Aug 2012 20:13:26 +0200
> > Subject: [PATCH] lavfi: add asendcmd and sendcmd filters
> > 
> > ---
> >  doc/filters.texi         |   70 +++++++++
> >  libavfilter/Makefile     |    2 +
> >  libavfilter/allfilters.c |    2 +
> >  libavfilter/f_sendcmd.c  |  369 ++++++++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 443 insertions(+), 0 deletions(-)
> >  create mode 100644 libavfilter/f_sendcmd.c
> > 
> > diff --git a/doc/filters.texi b/doc/filters.texi
> > index 712936d..938758c 100644
> > --- a/doc/filters.texi
> > +++ b/doc/filters.texi
> > @@ -4176,6 +4176,76 @@ tools.
> >  
> >  Below is a description of the currently available multimedia filters.
> >  
> > + at section asendcmd, sendcmd
> > +
> > +Send commands to filters in the filtergraph.
> > +
> > +These filters read commands to be sent to other filters in the
> > +filtergraph.
> > +
> > + at code{asendcmd} must be inserted between two audio filters,
> > + at code{sendcmd} must be inserted between two video filters, but apart
> > +from that they act the same way.
> > +
> 
> nit: I think something like this would be more obvious for users:
> 
>   @code{sendcmd} must be inserted between two video filters.
>   @code{asendcmd} works the same way as sendcmd but for audio.

Fixed.
 
> > +The specification of commands can be specified in the filter arguments
> > +with the @var{commands} option, or in a file specified with the
> > + at var{filename} option.
> > +
> > +Commands are sent the first time when a frame with time greater or
> > +equal to the specified command time is processed by the filter.
> > +
> > +These filters accept the following options:
> > + at table @option
> > + at item commands, c
> > +Set the commands to be read and sent to the other filters.
> > + at item filename, f
> > +Set the filename of the commands to be read and sent to the other
> > +filters.
> > + at end table
> > +
> > + at subsection Commands syntax
> > +
> > +Commands are specified one per line. Empty lines or lines starting
> > +with @code{#} are ignored.
> > +
> > +A command line has the syntax:
> > + at example
> > + at var{target} @var{time} @var{command} @var{arg}
> > + at end example
> > +
> > + at var{target} specify the target of the command, usually the name of
> > +the filter class or of the specific filter instance.
> > +
> 
> Here and below, "specifies"? (it appears like a sentence to me, not an
> itemized thing like the other entries)

Changed.
 
> Even if "filter class" and "specific filter instance" sounds more correct
> from a developer perspective, would it make more sense to say that it's
> just the filter name?
> 

> And by the way, how do you identify the different target instances of the
> same filter? ("volume", "volume1", "volume2", ...?)

Different filters have different instance name (parsed_...), it is not
still possible to specify the name of an instance in the filter graph.

> > + at var{time} specify the time when the filter command is sent, expressed
> > +as a time duration.
> > +
> 
> Note: as I said on IRC, I really think this should allow frame accurate
> timing range at some point.

Mixing times and frames is really hard if not impossible.
 
> > + at var{command} specify the name of the command, and depends on the
> > +target filter.
> > +
> 
> How does it "depends" on the target filter? Wouldn't it be more obvious to
> say that it is a "specific command for the @var{target} filter"?

Changed.
 
> > + at var{arg} specify the optional list of argument for the given command.
> > +
> > + at subsection Examples
> > +
> > + at itemize
> > + at item
> > +Specify audio tempo change at second 4:
> > + at example
> > +asendcmd=c='atempo 4 tempo 1.5',atempo
> > + at end example
> > +
> > + at item
> > +Specify a list of drawtext commands in a file.
> > + at example
> > +drawtext 5 reinit fontsize=25:fontfile=FreeSerif.ttf:x=100+30*(t-5):text='hello world 5'
> > +drawtext 10 reinit fontsize=25:fontfile=FreeSerif.ttf:x=100+30*(t-10):text='hello world 10'
> > + at end example
> > +
> > +The file containing the list of commands can be specified with:
> > + at example
> > +sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='hello world 0'
> > + at end example
> > + at end itemize
> > +
> 
> I didn't really follow the evolution of the talk about the time range, but
> would it be possible to have something like:
> 
>     % cat timeline
>     drawtext 00:01:02.123 start
>     drawtext 00:05:23.435 stop
>     %
>
> Using the following filtergraph:
> 
>     sendcmd=f=timeline,drawtext=fontfile=FreeSerif.ttf:x=10*t:text='hello world'
> 
> the text would start appearing at 01:02.123 and be removed at 05.23.435
> 
> Would that be allowed?

This is already supported:
00:01:02.123-00:05:23.435 [enter] drawtext reinit ...,
                          [leave] drawtext reinit ...;
  
> [...]
> 
> Anyway, sorry for commenting only from a user perspective, but I believe
> this filter will be intensively (ab)used by users so I'd like to see it
> kind of well designed. That filter really is very welcome, thanks!

Updated work in progress, this also exposed a bunch of bugs in the
various components I used to test it.
-- 
FFmpeg = Frightening and Faithless Murdering Pure Enlightened Gladiator
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