[FFmpeg-devel] [PATCH v8 11/13] avfilter/stripstyles: Add stripstyles filter
Soft Works
softworkz at hotmail.com
Wed Sep 22 07:04:05 EEST 2021
> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Andreas
> Rheinhardt
> Sent: Wednesday, 22 September 2021 05:28
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH v8 11/13] avfilter/stripstyles: Add
> stripstyles filter
>
> Soft Works:
> >
> >
> >> -----Original Message-----
> >> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Andreas
> >> Rheinhardt
> >> Sent: Wednesday, 22 September 2021 04:48
> >> To: ffmpeg-devel at ffmpeg.org
> >> Subject: Re: [FFmpeg-devel] [PATCH v8 11/13] avfilter/stripstyles: Add
> >> stripstyles filter
> >>
> >> Soft Works:
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> Andreas
> >>>> Rheinhardt
> >>>> Sent: Wednesday, 22 September 2021 03:58
> >>>> To: ffmpeg-devel at ffmpeg.org
> >>>> Subject: Re: [FFmpeg-devel] [PATCH v8 11/13] avfilter/stripstyles: Add
> >>>> stripstyles filter
> >>>>
> >>>> Soft Works:
> >>>>>
> >>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> >> Andreas
> >>>>>> Rheinhardt
> >>>>>> Sent: Wednesday, 22 September 2021 03:06
> >>>>>> To: ffmpeg-devel at ffmpeg.org
> >>>>>> Subject: Re: [FFmpeg-devel] [PATCH v8 11/13] avfilter/stripstyles: Add
> >>>>>> stripstyles filter
> >>>>>>
> >>>>>> Soft Works:
> >>>>>>> - stripstyles {S -> S)
> >>>>>>> Remove all inline styles from subtitle events
> >>>>>>>
> >>>>>>> Signed-off-by: softworkz <softworkz at hotmail.com>
> >>>>>>> ---
> >>>>>>> libavfilter/Makefile | 1 +
> >>>>>>> libavfilter/allfilters.c | 1 +
> >>>>>>> libavfilter/sf_stripstyles.c | 211
> +++++++++++++++++++++++++++++++++++
> >>>>>>> 3 files changed, 213 insertions(+)
> >>>>>>> create mode 100644 libavfilter/sf_stripstyles.c
> >>>>>>>
> >>>>>>> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> >>>>>>> index e6fef97c08..309c404bf7 100644
> >>>>>>> --- a/libavfilter/Makefile
> >>>>>>> +++ b/libavfilter/Makefile
> >>>>>>> @@ -540,6 +540,7 @@ OBJS-$(CONFIG_NULLSINK_FILTER) +=
> >>>>>> vsink_nullsink.o
> >>>>>>> OBJS-$(CONFIG_CENSOR_FILTER) += sf_textmod.o
> >>>>>>> OBJS-$(CONFIG_SHOW_SPEAKER_FILTER) += sf_textmod.o
> >>>>>>> OBJS-$(CONFIG_TEXTMOD_FILTER) += sf_textmod.o
> >>>>>>> +OBJS-$(CONFIG_STRIPSTYLES_FILTER) += sf_stripstyles.o
> >>>>>>>
> >>>>>>> # multimedia filters
> >>>>>>> OBJS-$(CONFIG_ABITSCOPE_FILTER) += avf_abitscope.o
> >>>>>>> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> >>>>>>> index fc72858d18..e2e4deea22 100644
> >>>>>>> --- a/libavfilter/allfilters.c
> >>>>>>> +++ b/libavfilter/allfilters.c
> >>>>>>> @@ -528,6 +528,7 @@ extern const AVFilter ff_avf_showwavespic;
> >>>>>>> extern const AVFilter ff_vaf_spectrumsynth;
> >>>>>>> extern const AVFilter ff_sf_censor;
> >>>>>>> extern const AVFilter ff_sf_show_speaker;
> >>>>>>> +extern const AVFilter ff_sf_stripstyles;
> >>>>>>> extern const AVFilter ff_sf_textmod;
> >>>>>>> extern const AVFilter ff_svf_graphicsub2video;
> >>>>>>> extern const AVFilter ff_svf_textsub2video;
> >>>>>>> diff --git a/libavfilter/sf_stripstyles.c
> >> b/libavfilter/sf_stripstyles.c
> >>>>>>> new file mode 100644
> >>>>>>> index 0000000000..15c00e73b1
> >>>>>>> --- /dev/null
> >>>>>>> +++ b/libavfilter/sf_stripstyles.c
> >>>>>>> @@ -0,0 +1,211 @@
> >>>>>>> +/*
> >>>>>>> + * Copyright (c) 2021 softworkz
> >>>>>>> + *
> >>>>>>> + * This file is part of FFmpeg.
> >>>>>>> + *
> >>>>>>> + * FFmpeg is free software; you can redistribute it and/or
> >>>>>>> + * modify it under the terms of the GNU Lesser General Public
> >>>>>>> + * License as published by the Free Software Foundation; either
> >>>>>>> + * version 2.1 of the License, or (at your option) any later
> version.
> >>>>>>> + *
> >>>>>>> + * FFmpeg is distributed in the hope that it will be useful,
> >>>>>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> >>>>>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> >>>>>>> + * Lesser General Public License for more details.
> >>>>>>> + *
> >>>>>>> + * You should have received a copy of the GNU Lesser General Public
> >>>>>>> + * License along with FFmpeg; if not, write to the Free Software
> >>>>>>> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> >> 02110-
> >>>>>> 1301 USA
> >>>>>>> + */
> >>>>>>> +
> >>>>>>> +/**
> >>>>>>> + * @file
> >>>>>>> + * text subtitle filter which removes inline-styles from subtitles
> >>>>>>> + */
> >>>>>>> +
> >>>>>>> +#include <libavcodec/ass.h>
> >>>>>>
> >>>>>> This header and the API in it is not public.
> >>>>>
> >>>>> I'm not sure IIRC, but aren't there other cases where the ffmpeg libs
> >>>>> are accessing non-public symbols from each other?
> >>>>>
> >>>>
> >>>> Yes, there are via avpriv functions. Yet this is strongly discouraged,
> >>>> so the bar for new ones is pretty high.
> >>>>
> >>>>>
> >>>>>>> +
> >>>>>>> +#include "libavutil/avassert.h"
> >>>>>>> +#include "libavutil/opt.h"
> >>>>>>> +#include "avfilter.h"
> >>>>>>> +#include "internal.h"
> >>>>>>> +#include "libavcodec/avcodec.h"
> >>>>>>> +#include "libavcodec/ass_split.h"
> >>>>>>> +
> >>>>>>> +typedef struct StripStylesContext {
> >>>>>>> + const AVClass *class;
> >>>>>>> + enum AVSubtitleType format;
> >>>>>>> + int remove_animated;
> >>>>>>> +} StripStylesContext;
> >>>>>>> +
> >>>>>>> +typedef struct DialogContext {
> >>>>>>> + const AVClass *class;
> >>>>>>
> >>>>>> An AVClass is for options and logging (and would actually need an
> >>>>>> AVClass, which you didn't define); you are not using it for that, so
> >>>>>> just remove this.
> >>>>>
> >>>>> No I can't, because this is being passed to the
> >>>>> ff_ass_split_override_codes which expects an AVClass at the first
> >>>>> position of the struct.
> >>>>>
> >>>>>
> >>>>
> >>>> Why? The docs don't say so. And the opaque priv pointer is never used
> >>>> for logging. (Or did I miss something?)
> >>>
> >>> It crashed at some point, I don't remember where exactly, but the first
> >>> member of the struct got overwritten and invalidated. Then I realized
> that
> >>> it was assumed to have an AVClass.
> >>>
> >>
> >> This surprises me. Are you sure that you did not forget the AVClass from
> >> your private filter context (in this case, StripStylesContext)?
> >
> > That's something that happened as well, but at an earlier time and
> > with a different filter..
> >
> > I think I had some logging in the callback functions (ASSCodesCallbacks)
> > before, probably that's how it happened to crash.
> >
>
> That would make sense. If you want to have logging in these callbacks,
> you should probably move DialogContext into StripStylesContext and use
> the latter as opaque priv pointer.
StripStylesContext is the context of the filter and DialogContext has
a lifetime of a single execution of process_dialog()..
Sounds weird to me, probably because it's somewhat difficult for me
to switch off object-oriented thinking ;-)
> >>>>> If not, what would you suggest. Duplicate the ass code in avfilter,
> >>>>> move it to avutil and make it public, or any other idea?
> >>>>>
> >>>>
> >>>> Making it public? You know that your 10/13 would not be possible if this
> >>>> were public? (And it would also not work if it were avpriv; at least not
> >>>> without some versioning uglyness.)
> >>>> I don't like the idea of duplicating the code. The only vague suggestion
> >>>> that I have is that this might be more suitable for a bitstream filter.
> >>>
> >>> The ass subtitle format is used as the internal text subtitle format,
> >>> which means that those ass manipulation function are required to be
> >>> accessible by many other text subtitle filter in some way.
> >>> I'm using them in more filters already..
> >>>
> >>
> >> Then we have a problem. And I don't have a solution.
> >
> > Function prefixes per preprocessor defs to compile the same two source
> files
> > into both libs?
> >
>
> If we opt for duplicating, then it could be made in a way that it is
> only duplicated for shared builds; see
> https://github.com/mkver/FFmpeg/commits/avpriv (I finally need to get
> this patchset updated and sent before the next release while the ABI is
> still open.)
>
> > Moving into avutil would appear to make more sense to me. Anyway, it's
> exactly
> > that: utility functions. (it's not the ass encoder or decoder)
> >
>
> That has the compatibility problem I mentioned. Which is the reason why
> avpriv symbols are disliked.
> (Some devs (like Nicholas George) want to merge all the libraries or at
> least disallow using libraries from different commits together (I like
> the latter approach). This would automatically solve the compatibility
> issue.)
That's just one of the many things I don't understand - why there's a need
to allow different versions to interoperate, given that all of them are
having the same origin. Having one version for all libs that needs to match
seems to me just natural - even mandatory, but that's a discussion I
don't want to get involved.
Ok, while these things are pending, I suppose as a temporary solution
I'd just duplicate that code until a final solution can be found?
softworkz
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