Soft Works:
> Signed-off-by: softworkz <softwo...@hotmail.com>
> ---
> doc/filters.texi | 64 +++++++
> libavfilter/Makefile | 3 +
> libavfilter/allfilters.c | 1 +
> libavfilter/sf_textmod.c | 381 +++++++++++++++++++++++++++++++++++++++
> 4 files changed, 449 insertions(+)
> create mode 100644 libavfilter/sf_textmod.c
>
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 1d76461ada..9fd2876d63 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -25024,6 +25024,70 @@ existing filters using @code{--disable-filters}.
>
> Below is a description of the currently available subtitle filters.
>
> +@section textmod
> +
> +Modify subtitle text in a number of ways.
> +
> +It accepts the following parameters:
> +
> +@table @option
> +@item mode
> +The kind of text modification to apply
> +
> +Supported operation modes are:
> +
> +@table @var
> +@item 0, leet
> +Convert subtitle text to 'leet speak'. It's primarily useful for testing as
> the modification will be visible with almost all text lines.
> +@item 1, to_upper
> +Change all text to upper case. Might improve readability.
> +@item 2, to_lower
> +Change all text to lower case.
> +@item 3, replace_chars
> +Replace one or more characters. Requires the find and replace parameters to
> be specified.
> +Both need to be equal in length.
> +The first char in find is replaced by the first char in replace, same for
> all subsequent chars.
> +@item 4, remove_chars
> +Remove certain characters. Requires the find parameter to be specified.
> +All chars in the find parameter string will be removed from all subtitle
> text.
> +@item 5, replace_words
> +Replace one or more words. Requires the find and replace parameters to be
> specified. Multiple words must be separated by the delimiter char specified
> vie the separator parameter (default: ',').
> +The number of words in the find and replace parameters needs to be equal.
> +The first word in find is replaced by the first word in replace, same for
> all subsequent words
> +@item 6, remove_words
> +Remove certain words. Requires the find parameter to be specified. Multiple
> words must be separated by the delimiter char specified vie the separator
> parameter (default: ',').
> +All words in the find parameter string will be removed from all subtitle
> text.
> +@end table
> +
> +@item find
> +Required for replace_chars, remove_chars, replace_words and remove_words.
> +
> +@item replace
> +Required for replace_chars and replace_words.
> +
> +@item separator
> +Delimiter character for words. Used with replace_words and remove_words-
> Must be a single character.
> +The default is '.'.
> +
> +@end table
> +
> +@subsection Examples
> +
> +@itemize
> +@item
> +Change all characters to upper case while keeping all styles and animations:
> +@example
> +ffmpeg -i "https://streams.videolan.org/ffmpeg/mkv_subtitles.mkv";
> -filter_complex "[0:s]textmod=mode=to_upper" -map 0 -y out.mkv
> +@end example
> +@item
> +Mark the 100-pixel-wide region on the left edge of the frame as very
> +uninteresting (to be encoded at much lower quality than the rest of
> +the frame).
> +@example
> +addroi=0:0:100:ih:+1/5
> +@end example
> +@end itemize
> +
> @section graphicsub2video
>
> Renders graphic subtitles as video frames.
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index 0e752c5bf9..5a5a4be47e 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -534,6 +534,9 @@ OBJS-$(CONFIG_YUVTESTSRC_FILTER) +=
> vsrc_testsrc.o
>
> OBJS-$(CONFIG_NULLSINK_FILTER) += vsink_nullsink.o
>
> +# subtitle filters
> +OBJS-$(CONFIG_TEXTMOD_FILTER) += sf_textmod.o
> +
> # multimedia filters
> OBJS-$(CONFIG_ABITSCOPE_FILTER) += avf_abitscope.o
> OBJS-$(CONFIG_ADRAWGRAPH_FILTER) += f_drawgraph.o
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index 77463aa4c8..6d7a535ee8 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -524,6 +524,7 @@ extern const AVFilter ff_avf_showvolume;
> extern const AVFilter ff_avf_showwaves;
> extern const AVFilter ff_avf_showwavespic;
> extern const AVFilter ff_vaf_spectrumsynth;
> +extern const AVFilter ff_sf_textmod;
> extern const AVFilter ff_svf_graphicsub2video;
> extern const AVFilter ff_svf_textsub2video;
>
> diff --git a/libavfilter/sf_textmod.c b/libavfilter/sf_textmod.c
> new file mode 100644
> index 0000000000..7c23ded9ef
> --- /dev/null
> +++ b/libavfilter/sf_textmod.c
> @@ -0,0 +1,381 @@
> +/*
> + * 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 allows to modify subtitle text in several ways
> + */
> +
> +#include <libavcodec/ass.h>
> +
> +#include "libavutil/avassert.h"
> +#include "libavutil/avstring.h"
> +#include "libavutil/opt.h"
> +#include "avfilter.h"
> +#include "internal.h"
> +#include "libavcodec/avcodec.h"
> +#include "libavcodec/ass_split.h"
> +
> +static const char* leet_src =
> "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
> +static const char* leet_dst =
> "abcd3f6#1jklmn0pq257uvwxyzAB(D3F6#1JKLMN0PQ257UVWXYZ";
> +
> +enum TextModOperation {
> + OP_LEET,
> + OP_TO_UPPER,
> + OP_TO_LOWER,
> + OP_REPLACE_CHARS,
> + OP_REMOVE_CHARS,
> + OP_REPLACE_WORDS,
> + OP_REMOVE_WORDS,
> + NB_OPS,
> +};
> +
> +typedef struct TextModContext {
> + const AVClass *class;
> + enum AVSubtitleType format;
> + enum TextModOperation operation;
> + char *find;
> + char *replace;
> + char *separator;
> + char **find_list;
> + int nb_find_list;
> + char **replace_list;
> + int nb_replace_list;
> +} TextModContext;
> +
> +static char **split_string(char *source, int *nb_elems, char delim)
> +{
> + char **list = NULL;
> + char *temp = NULL;
> + char *ptr = av_strtok(source, &delim, &temp);
> +
> + while (ptr) {
> + av_dynarray_add(&list, nb_elems, ptr);
> + if (!list)
> + return NULL;
> +
> + ptr = av_strtok(NULL, &delim, &temp);
> + }
> +
> + av_dynarray_add(&list, nb_elems, NULL);
> +
> + return list;
> +}
> +
> +static int init(AVFilterContext *ctx)
> +{
> + TextModContext *s = ctx->priv;
> +
> + switch (s->operation) {
> + case OP_REPLACE_CHARS:
> + case OP_REMOVE_CHARS:
> + case OP_REPLACE_WORDS:
> + case OP_REMOVE_WORDS:
> + if (!s->find || !strlen(s->find)) {
> + av_log(ctx, AV_LOG_ERROR, "Selected mode requires the 'find'
> parameter to be specified");
> + return AVERROR(EINVAL);
> + }
> + break;
> + }
> +
> + switch (s->operation) {
> + case OP_REPLACE_CHARS:
> + case OP_REPLACE_WORDS:
> + if (!s->replace || !strlen(s->replace)) {
> + av_log(ctx, AV_LOG_ERROR, "Selected mode requires the 'replace'
> parameter to be specified");
> + return AVERROR(EINVAL);
> + }
> + break;
> + }
> +
> + if (s->operation == OP_REPLACE_CHARS && strlen(s->find) !=
> strlen(s->replace)) {
> + av_log(ctx, AV_LOG_ERROR, "Selected mode requires the 'find' and
> 'replace' parameters to have the same length");
> + return AVERROR(EINVAL);
> + }
> +
> + if (s->operation == OP_REPLACE_WORDS || s->operation == OP_REMOVE_WORDS)
> {
> + if (!s->separator || strlen(s->separator) != 1) {
> + av_log(ctx, AV_LOG_ERROR, "Selected mode requires a single
> separator char to be specified");
> + return AVERROR(EINVAL);
> + }
> +
> + s->find_list = split_string(s->find, &s->nb_find_list,
> *s->separator);
> + if (!s->find_list)
> + return AVERROR(ENOMEM);
> +
> + if (s->operation == OP_REPLACE_WORDS) {
> +
> + s->replace_list = split_string(s->replace, &s->nb_replace_list,
> *s->separator);
> + if (!s->replace_list)
> + return AVERROR(ENOMEM);
> +
> + if (s->nb_find_list != s->nb_replace_list) {
> + av_log(ctx, AV_LOG_ERROR, "The number of words in 'find' and
> 'replace' needs to be equal");
> + return AVERROR(EINVAL);
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> +static void uninit(AVFilterContext *ctx)
> +{
> + TextModContext *s = ctx->priv;
> + int i;
> +
> + for (i = 0; i < s->nb_find_list; i++) {
> + av_free(&s->find_list[i]);
This is completely wrong and will crash: You either want to do
av_freep(&s->find_list[i]) or av_free(s->find_list[i]) if these strings
were independently allocated; but looking at split_string() shows that
they are not, they are substrings of s->find. Similar for the loop below.
> + }
> + s->nb_find_list = 0;
> + av_freep(&s->find_list);
> +
> + for (i = 0; i < s->nb_replace_list; i++) {
> + av_free(&s->replace_list[i]);
> + }
> + s->nb_replace_list = 0;
> + av_freep(&s->replace_list);
> +}
> +
> +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 *process_text(TextModContext *s, char *text)
> +{
> + const char *char_src = s->find;
> + const char *char_dst = s->replace;
> + char *result = NULL;
> + int escape_level = 0, k = 0;
> +
> + switch (s->operation) {
> + case OP_LEET:
> + case OP_REPLACE_CHARS:
> +
> + if (s->operation == OP_LEET) {
> + char_src = leet_src;
> + char_dst = leet_dst;
> + }
> +
> + result = av_strdup(text);
> + if (!result)
> + return NULL;
> +
> + for (size_t n = 0; n < strlen(result); n++) {
> + if (result[n] == '{')
> + escape_level++;
> +
> + if (!escape_level) {
> + for (size_t t = 0; t < FF_ARRAY_ELEMS(char_src); t++) {
> + if (result[n] == char_src[t]) {
> + result[n] = char_dst[t];
> + break;
> + }
> + }
> + }
> +
> + if (result[n] == '}')
> + escape_level--;
> + }
> +
> + break;
> + case OP_TO_UPPER:
> + case OP_TO_LOWER:
> +
> + result = av_strdup(text);
> + if (!result)
> + return NULL;
> +
> + for (size_t n = 0; n < strlen(result); n++) {
> + if (result[n] == '{')
> + escape_level++;
> + if (!escape_level)
> + result[n] = s->operation == OP_TO_LOWER ?
> av_tolower(result[n]) : av_toupper(result[n]);
> + if (result[n] == '}')
> + escape_level--;
> + }
> +
> + break;
> + case OP_REMOVE_CHARS:
> +
> + result = av_strdup(text);
> + if (!result)
> + return NULL;
> +
> + for (size_t n = 0; n < strlen(result); n++) {
> + int skip_char = 0;
> +
> + if (result[n] == '{')
> + escape_level++;
> +
> + if (!escape_level) {
> + for (size_t t = 0; t < FF_ARRAY_ELEMS(char_src); t++) {
> + if (result[n] == char_src[t]) {
> + skip_char = 1;
> + break;
> + }
> + }
> + }
> +
> + if (!skip_char)
> + result[k++] = result[n];
> +
> + if (result[n] == '}')
> + escape_level--;
> + }
> +
> + result[k] = 0;
> +
> + break;
> + case OP_REPLACE_WORDS:
> + case OP_REMOVE_WORDS:
> +
> + result = av_strdup(text);
> + if (!result)
> + return NULL;
> +
> + for (int n = 0; n < s->nb_find_list; n++) {
> + char *tmp = result;
> + const char *replace = (s->operation == OP_REPLACE_WORDS) ?
> s->replace_list[n] : "";
> +
> + result = av_strireplace(result, s->find_list[n], replace);
> + if (!result)
> + return NULL;
> +
> + av_free(tmp);
> + }
> +
> + break;
> + }
> +
> + return result;
> +}
> +
> +static char *process_dialog(TextModContext *s, char *ass_line)
> +{
> + ASSDialog *dialog = ff_ass_split_dialog(NULL, ass_line);
> + char *result, *text;
> +
> + if (!dialog)
> + return NULL;
> +
> + text = process_text(s, dialog->text);
> + if (!text)
> + return NULL;
> +
> + result = ff_ass_get_dialog(dialog->readorder, dialog->layer,
> dialog->style, dialog->name, text);
> +
> + av_free(text);
> + ff_ass_free_dialog(&dialog);
> + return result;
> +}
> +
> +static int filter_frame(AVFilterLink *inlink, AVFrame *src_frame)
> +{
> + TextModContext *s = inlink->dst->priv;
> + AVFilterLink *outlink = inlink->dst->outputs[0];
> + int ret;
> + AVFrame *out;
> +
> + outlink->format = inlink->format;
> +
> + out = av_frame_clone(src_frame);
Why clone? You can just reuse src_frame as is.
> + if (!out)
> + return AVERROR(ENOMEM);
> +
> + for (unsigned i = 0; i < out->num_subtitle_rects; i++) {
> +
> + AVSubtitleRect *rect = out->subtitle_rects[i];
> +
> + if (rect->ass) {
Is there are actually a reason that num_subtitle_rects can't be taken at
face value? Your query_formats callback after all signals that only ass
subtitles are accepted.
> + char *tmp = rect->ass;
> + rect->ass = process_dialog(s, rect->ass);
You may not be the sole owner of this AVSubtitleRect; after all,
they are shared. Ergo you must not modify it. Is it possible that you
believed that av_frame_clone() would make the frame writable? It does
not. For non-subtitle frames, av_frame_make_writable() makes them
writable; but it does not for subtitles, because you made
av_frame_get_buffer2() a no-op for subtitles and so
av_frame_make_writable() will temporarily increment the refcount and
then decrement it again.
> + av_free(tmp);
> + if (!rect->ass)
> + return AVERROR(ENOMEM);
> + }
> + }
> +
> + av_frame_free(&src_frame);
> + return ff_filter_frame(outlink, out);
> +}
> +
> +#define OFFSET(x) offsetof(TextModContext, x)
> +#define FLAGS (AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_FILTERING_PARAM)
> +
> +static const AVOption textmod_options[] = {
> + { "mode", "set operation mode",
> OFFSET(operation), AV_OPT_TYPE_INT, {.i64=OP_LEET}, OP_LEET,
> NB_OPS-1, FLAGS, "mode" },
> + { "leet", "convert text to 'leet speak'", 0,
> AV_OPT_TYPE_CONST, {.i64=OP_LEET}, 0, 0, FLAGS,
> "mode" },
> + { "to_upper", "change to upper case", 0,
> AV_OPT_TYPE_CONST, {.i64=OP_TO_UPPER}, 0, 0, FLAGS,
> "mode" },
> + { "to_lower", "change to lower case", 0,
> AV_OPT_TYPE_CONST, {.i64=OP_TO_LOWER}, 0, 0, FLAGS,
> "mode" },
> + { "replace_chars", "replace characters", 0,
> AV_OPT_TYPE_CONST, {.i64=OP_REPLACE_CHARS}, 0, 0, FLAGS,
> "mode" },
> + { "remove_chars", "remove characters", 0,
> AV_OPT_TYPE_CONST, {.i64=OP_REMOVE_CHARS}, 0, 0, FLAGS,
> "mode" },
> + { "replace_words", "replace words", 0,
> AV_OPT_TYPE_CONST, {.i64=OP_REPLACE_WORDS}, 0, 0, FLAGS,
> "mode" },
> + { "remove_words", "remove words", 0,
> AV_OPT_TYPE_CONST, {.i64=OP_REMOVE_WORDS}, 0, 0, FLAGS,
> "mode" },
> + { "find", "chars/words to find or remove", OFFSET(find),
> AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, FLAGS,
> NULL },
> + { "replace", "chars/words to replace",
> OFFSET(replace), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0,
> FLAGS, NULL },
> + { "separator", "word separator (default: ',')",
> OFFSET(separator), AV_OPT_TYPE_STRING, {.str = ","}, 0, 0,
> FLAGS, NULL },
> + { NULL },
> +};
> +
> +AVFILTER_DEFINE_CLASS(textmod);
> +
> +static const AVFilterPad inputs[] = {
> + {
> + .name = "default",
> + .type = AVMEDIA_TYPE_SUBTITLE,
> + .filter_frame = filter_frame,
> + },
> +};
> +
> +static const AVFilterPad outputs[] = {
> + {
> + .name = "default",
> + .type = AVMEDIA_TYPE_SUBTITLE,
> + },
> +};
> +
> +const AVFilter ff_sf_textmod = {
> + .name = "textmod",
> + .description = NULL_IF_CONFIG_SMALL("Modify subtitle text in several
> ways"),
> + .init = init,
> + .uninit = uninit,
> + .query_formats = query_formats,
> + .priv_size = sizeof(TextModContext),
> + .priv_class = &textmod_class,
> + FILTER_INPUTS(inputs),
> + FILTER_OUTPUTS(outputs),
> +};
>
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