[FFmpeg-devel] [PATCH v8 11/13] avfilter/stripstyles: Add stripstyles filter
Soft Works
softworkz at hotmail.com
Wed Sep 22 05:11:05 EEST 2021
> -----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.
>
> >
> >>> + const StripStylesContext* ss_ctx;
> >>> + AVBPrint buffer;
> >>> + int drawing_scale;
> >>> + int is_animated;
> >>> +} DialogContext;
> >>> +
> >>> +static void dialog_text_cb(void *priv, const char *text, int len)
> >>> +{
> >>> + DialogContext *s = priv;
> >>> + if (!s->drawing_scale && (!s->is_animated || !s->ss_ctx-
> >>> remove_animated))
> >>> + av_bprint_append_data(&s->buffer, text, len);
> >>> +}
> >>> +
> >>> +static void dialog_new_line_cb(void *priv, int forced)
> >>> +{
> >>> + DialogContext *s = priv;
> >>> + if (!s->drawing_scale && !s->is_animated)
> >>> + av_bprint_append_data(&s->buffer, forced ? "\\N" : "\\n", 2);
> >>> +}
> >>> +
> >>> +static void dialog_drawing_mode_cb(void *priv, int scale)
> >>> +{
> >>> + DialogContext *s = priv;
> >>> + s->drawing_scale = scale;
> >>> +}
> >>> +
> >>> +static void dialog_animate_cb(void *priv, int t1, int t2, int accel,
> char
> >> *style)
> >>> +{
> >>> + DialogContext *s = priv;
> >>> + s->is_animated = 1;
> >>> +}
> >>> +
> >>> +static void dialog_move_cb(void *priv, int x1, int y1, int x2, int y2,
> int
> >> t1, int t2)
> >>> +{
> >>> + DialogContext *s = priv;
> >>> + if (t1 >= 0 || t2 >= 0)
> >>> + s->is_animated = 1;
> >>> +}
> >>> +
> >>> +static const ASSCodesCallbacks dialog_callbacks = {
> >>> + .text = dialog_text_cb,
> >>> + .new_line = dialog_new_line_cb,
> >>> + .drawing_mode = dialog_drawing_mode_cb,
> >>> + .animate = dialog_animate_cb,
> >>> + .move = dialog_move_cb,
> >>> +};
> >>> +
> >>> +static int query_formats(AVFilterContext *ctx)
> >>> +{
> >>> + AVFilterFormats *formats;
> >>> + AVFilterLink *inlink = ctx->inputs[0];
> >>> + AVFilterLink *outlink = ctx->outputs[0];
> >>> + static const enum AVSubtitleType subtitle_fmts[] = {
> >> AV_SUBTITLE_FMT_ASS, AV_SUBTITLE_FMT_NONE };
> >>> + int ret;
> >>> +
> >>> + /* set input subtitle format */
> >>> + formats = ff_make_format_list(subtitle_fmts);
> >>> + if ((ret = ff_formats_ref(formats, &inlink->outcfg.formats)) < 0)
> >>> + return ret;
> >>> +
> >>> + /* set output video format */
> >>> + if ((ret = ff_formats_ref(formats, &outlink->incfg.formats)) < 0)
> >>> + return ret;
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +static char *ass_get_line(int readorder, int layer, const char *style,
> >>> + const char *speaker, const char *effect, const
> >> char *text)
> >>> +{
> >>> + return av_asprintf("%d,%d,%s,%s,0,0,0,%s,%s",
> >>> + readorder, layer, style ? style : "Default",
> >>> + speaker ? speaker : "", effect, text);
> >>> +}
> >>> +
> >>> +static char *process_dialog(StripStylesContext *s, const char *ass_line)
> >>> +{
> >>> + ASSDialog *dialog = ff_ass_split_dialog(NULL, ass_line);
> >>> + char *result = NULL, *text;
> >>> + DialogContext dlg_ctx = { 0 };
> >>> +
> >>> + if (!dialog)
> >>> + return NULL;
> >>> +
> >>> + dlg_ctx.ss_ctx = s;
> >>> +
> >>> + av_bprint_init(&dlg_ctx.buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
> >>> +
> >>> + ff_ass_split_override_codes(&dialog_callbacks, &dlg_ctx, dialog-
> >>> text);
> >>
> >> This function is in libavcodec and is not public; it is not available
> >> when using shared linking. The same goes for all the other ff_ass_*
> >> functions. Generally, the ff-prefix denotes something that is library
> >> internal, but is not static, i.e. not confined to one translation unit.
> >
> > I thought this could be ensured by having something like this in
> > configure:
> >
> > overlay_textsubs_filter_deps="avcodec libass"
> >
>
> This won't work (as it won't make libavcodec export these functions).
>
> >
> > 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..
Kind regards,
sw
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