[FFmpeg-devel,v11,09/14] avfilter/overlay_textsubs: Add overlay_textsubs and textsubs2video filters

Message ID MN2PR04MB59818187265DD5E31B7FC78DBAAA9@MN2PR04MB5981.namprd04.prod.outlook.com
State Superseded, archived
Headers
Series [FFmpeg-devel,v11,01/14] global: Prepare AVFrame for subtitle handling |

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Commit Message

Soft Works Sept. 30, 2021, 8:07 p.m. UTC
- overlay_textsubs {VS -> V)
  Overlay text subtitles onto a video stream.

- textsubs2video {S -> V)
  Converts text subtitles to video frames

Signed-off-by: softworkz <softworkz@hotmail.com>
---
 configure                         |   2 +
 doc/filters.texi                  |  69 ++++
 libavfilter/Makefile              |   2 +
 libavfilter/allfilters.c          |   2 +
 libavfilter/avfilter.c            |  18 +-
 libavfilter/vf_overlay_textsubs.c | 609 ++++++++++++++++++++++++++++++
 6 files changed, 697 insertions(+), 5 deletions(-)
 create mode 100644 libavfilter/vf_overlay_textsubs.c
  

Patch

diff --git a/configure b/configure
index d18bb73ed6..37fc4c20e7 100755
--- a/configure
+++ b/configure
@@ -3624,6 +3624,7 @@  openclsrc_filter_deps="opencl"
 overlay_opencl_filter_deps="opencl"
 overlay_qsv_filter_deps="libmfx"
 overlay_qsv_filter_select="qsvvpp"
+overlay_textsubs_filter_deps="avcodec libass"
 overlay_vulkan_filter_deps="vulkan_lib libglslang"
 owdenoise_filter_deps="gpl"
 pad_opencl_filter_deps="opencl"
@@ -3669,6 +3670,7 @@  superequalizer_filter_deps="avcodec"
 superequalizer_filter_select="rdft"
 surround_filter_deps="avcodec"
 surround_filter_select="rdft"
+textsub2video_filter_deps="avcodec libass"
 tinterlace_filter_deps="gpl"
 tinterlace_merge_test_deps="tinterlace_filter"
 tinterlace_pad_test_deps="tinterlace_filter"
diff --git a/doc/filters.texi b/doc/filters.texi
index 18b5273e6e..2f81df6489 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -25297,6 +25297,75 @@  The graphicsub2video is inserted automatically for compatibility with legacy com
 ffmpeg -i "https://streams.videolan.org/samples/sub/PGS/Girl_With_The_Dragon_Tattoo_2%3A23%3A56.mkv" -filter_complex "[0:0][0:1]overlay" output.mp4
 @end example
 @end itemize
+
+@section overlay_textsubs
+
+Overlay text subtitles onto a video stream.
+
+This filter supersedes the classic @ref{subtitles} filter opposed to which it does no longer require to open and access the source stream separately, which is often causing problems or doesn't even work for non-local or slow sources.
+
+Inputs:
+- 0: Video [YUV420P, YUV422P, YUV444P, ARGB, RGBA, ABGR, BGRA, RGB24, BGR24]
+- 1: Subtitles [text]
+
+Outputs:
+- 0: Video (same as input)
+
+It accepts the following parameters:
+
+@table @option
+
+@item alpha
+Process alpha channel, by default alpha channel is untouched.
+
+@item fonts_dir
+Set a directory path containing fonts that can be used by the filter.
+These fonts will be used in addition to whatever the font provider uses.
+
+@item force_style
+Override default style or script info parameters of the subtitles. It accepts a
+string containing ASS style format @code{KEY=VALUE} couples separated by ",".
+
+@end table
+
+@section textsub2video
+
+Converts text subtitles to video frames.
+
+For overlaying text subtitles onto video frames it is recommended to use the overlay_textsubs filter.
+The textsub2video is useful for for creating transparent text-frames when overlay is done via hw acceleration 
+
+Inputs:
+- 0: Subtitles [text]
+
+Outputs:
+- 0: Video [ARGB, RGBA, ABGR, BGRA]
+
+It accepts the following parameters:
+
+@table @option
+
+@item rate, r
+Set the framerate for updating overlay frames.
+Normally, overlay frames will only be updated each time when the subtitles to display are changing.
+In cases where subtitles include advanced features (like animation), this parameter determines the frequency by which the overlay frames should be updated.
+
+@item size, s
+Set the output frame size.
+Allows to override the size of output video frames.
+
+@item alpha
+Process alpha channel, by default alpha channel is untouched.
+
+@item fonts_dir
+Set a directory path containing fonts that can be used by the filter.
+These fonts will be used in addition to whatever the font provider uses.
+
+@item force_style
+Override default style or script info parameters of the subtitles. It accepts a
+string containing ASS style format @code{KEY=VALUE} couples separated by ",".
+
+@end table
 @c man end SUBTITLE FILTERS
 
 @chapter Multimedia Filters
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 01c3926bf8..584a97c9a3 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -366,6 +366,7 @@  OBJS-$(CONFIG_OVERLAY_OPENCL_FILTER)         += vf_overlay_opencl.o opencl.o \
                                                 opencl/overlay.o framesync.o
 OBJS-$(CONFIG_OVERLAY_QSV_FILTER)            += vf_overlay_qsv.o framesync.o
 OBJS-$(CONFIG_OVERLAY_GRAPHICSUBS_FILTER)    += vf_overlay_graphicsubs.o framesync.o
+OBJS-$(CONFIG_OVERLAY_TEXTSUBS_FILTER)       += vf_overlay_textsubs.o
 OBJS-$(CONFIG_OVERLAY_VULKAN_FILTER)         += vf_overlay_vulkan.o vulkan.o
 OBJS-$(CONFIG_OWDENOISE_FILTER)              += vf_owdenoise.o
 OBJS-$(CONFIG_PAD_FILTER)                    += vf_pad.o
@@ -454,6 +455,7 @@  OBJS-$(CONFIG_SWAPRECT_FILTER)               += vf_swaprect.o
 OBJS-$(CONFIG_SWAPUV_FILTER)                 += vf_swapuv.o
 OBJS-$(CONFIG_TBLEND_FILTER)                 += vf_blend.o framesync.o
 OBJS-$(CONFIG_TELECINE_FILTER)               += vf_telecine.o
+OBJS-$(CONFIG_TEXTSUB2VIDEO_FILTER)          += vf_overlay_textsubs.o
 OBJS-$(CONFIG_THISTOGRAM_FILTER)             += vf_histogram.o
 OBJS-$(CONFIG_THRESHOLD_FILTER)              += vf_threshold.o framesync.o
 OBJS-$(CONFIG_THUMBNAIL_FILTER)              += vf_thumbnail.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index c08145e274..8c3702aeea 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -347,6 +347,7 @@  extern const AVFilter ff_vf_overlay;
 extern const AVFilter ff_vf_overlay_opencl;
 extern const AVFilter ff_vf_overlay_qsv;
 extern const AVFilter ff_vf_overlay_graphicsubs;
+extern const AVFilter ff_vf_overlay_textsubs;
 extern const AVFilter ff_vf_overlay_vulkan;
 extern const AVFilter ff_vf_overlay_cuda;
 extern const AVFilter ff_vf_owdenoise;
@@ -527,6 +528,7 @@  extern const AVFilter ff_avf_showwaves;
 extern const AVFilter ff_avf_showwavespic;
 extern const AVFilter ff_vaf_spectrumsynth;
 extern const AVFilter ff_svf_graphicsub2video;
+extern const AVFilter ff_svf_textsub2video;
 
 /* multimedia sources */
 extern const AVFilter ff_avsrc_amovie;
diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index c567b7893b..639a54096b 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -464,7 +464,7 @@  static int64_t guess_status_pts(AVFilterContext *ctx, int status, AVRational lin
     return AV_NOPTS_VALUE;
 }
 
-static int ff_request_frame_to_filter(AVFilterLink *link)
+static int ff_request_frame_to_filter(AVFilterLink *link, int input_index)
 {
     int ret = -1;
 
@@ -473,8 +473,8 @@  static int ff_request_frame_to_filter(AVFilterLink *link)
     link->frame_blocked_in = 1;
     if (link->srcpad->request_frame)
         ret = link->srcpad->request_frame(link);
-    else if (link->src->inputs[0])
-        ret = ff_request_frame(link->src->inputs[0]);
+    else if (link->src->inputs[input_index])
+        ret = ff_request_frame(link->src->inputs[input_index]);
     if (ret < 0) {
         if (ret != AVERROR(EAGAIN) && ret != link->status_in)
             ff_avfilter_link_set_in_status(link, ret, guess_status_pts(link->src, ret, link->time_base));
@@ -1173,6 +1173,14 @@  static int forward_status_change(AVFilterContext *filter, AVFilterLink *in)
 {
     unsigned out = 0, progress = 0;
     int ret;
+    int input_index = 0;
+
+    for (int i = 0; i < in->dst->nb_inputs; i++) {
+        if (&in->dst->input_pads[i] == in->dstpad) {
+            input_index = i;
+            break;
+        }
+    }
 
     av_assert0(!in->status_out);
     if (!filter->nb_outputs) {
@@ -1182,7 +1190,7 @@  static int forward_status_change(AVFilterContext *filter, AVFilterLink *in)
     while (!in->status_out) {
         if (!filter->outputs[out]->status_in) {
             progress++;
-            ret = ff_request_frame_to_filter(filter->outputs[out]);
+            ret = ff_request_frame_to_filter(filter->outputs[out], input_index);
             if (ret < 0)
                 return ret;
         }
@@ -1219,7 +1227,7 @@  static int ff_filter_activate_default(AVFilterContext *filter)
     for (i = 0; i < filter->nb_outputs; i++) {
         if (filter->outputs[i]->frame_wanted_out &&
             !filter->outputs[i]->frame_blocked_in) {
-            return ff_request_frame_to_filter(filter->outputs[i]);
+            return ff_request_frame_to_filter(filter->outputs[i], 0);
         }
     }
     return FFERROR_NOT_READY;
diff --git a/libavfilter/vf_overlay_textsubs.c b/libavfilter/vf_overlay_textsubs.c
new file mode 100644
index 0000000000..ac99943d57
--- /dev/null
+++ b/libavfilter/vf_overlay_textsubs.c
@@ -0,0 +1,609 @@ 
+/*
+ * 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
+ * overlay text subtitles on top of a video frame
+ */
+
+#include <ass/ass.h>
+#include <libavutil/ass_internal.h>
+
+#include "drawutils.h"
+#include "filters.h"
+
+#include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"
+
+typedef struct TextSubsContext {
+    const AVClass *class;
+    ASS_Library   *library;
+    ASS_Renderer  *renderer;
+    ASS_Track     *track;
+
+    char *default_font_path;
+    char *fonts_dir;
+    char *fc_file;
+    double font_scale;
+    double font_size;
+    char *force_style;
+    char *language;
+    int margin;
+
+    int alpha;
+    FFDrawContext draw;
+
+    int got_header;
+    int out_w, out_h;
+    AVRational frame_rate;
+    AVFrame *last_frame;
+    int eof;
+} TextSubsContext;
+
+/* libass supports a log level ranging from 0 to 7 */
+static const int ass_libavfilter_log_level_map[] = {
+    AV_LOG_QUIET,               /* 0 */
+    AV_LOG_PANIC,               /* 1 */
+    AV_LOG_FATAL,               /* 2 */
+    AV_LOG_ERROR,               /* 3 */
+    AV_LOG_WARNING,             /* 4 */
+    AV_LOG_INFO,                /* 5 */
+    AV_LOG_VERBOSE,             /* 6 */
+    AV_LOG_DEBUG,               /* 7 */
+};
+
+static void ass_log(int ass_level, const char *fmt, va_list args, void *ctx)
+{
+    const int ass_level_clip = av_clip(ass_level, 0, FF_ARRAY_ELEMS(ass_libavfilter_log_level_map) - 1);
+    const int level = ass_libavfilter_log_level_map[ass_level_clip];
+
+    av_vlog(ctx, level, fmt, args);
+    av_log(ctx, level, "\n");
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    TextSubsContext *s = ctx->priv;
+
+    if (s->track)
+        ass_free_track(s->track);
+    if (s->renderer)
+        ass_renderer_done(s->renderer);
+    if (s->library)
+        ass_library_done(s->library);
+
+    s->track = NULL;
+    s->renderer = NULL;
+    s->library = NULL;
+
+    av_frame_free(&s->last_frame);
+}
+
+static int overlay_textsubs_query_formats(AVFilterContext *ctx)
+{
+    AVFilterFormats *formats;
+    AVFilterLink *inlink0 = ctx->inputs[0];
+    AVFilterLink *inlink1 = ctx->inputs[1];
+    AVFilterLink *outlink = ctx->outputs[0];
+    static const enum AVSubtitleType subtitle_fmts[] = { AV_SUBTITLE_FMT_ASS, AV_SUBTITLE_FMT_NONE };
+    int ret;
+
+    /* set input0 video formats */
+    formats = ff_draw_supported_pixel_formats(0);
+    if ((ret = ff_formats_ref(formats, &inlink0->outcfg.formats)) < 0)
+        return ret;
+
+    /* set input1 subtitle formats */
+    formats = ff_make_format_list(subtitle_fmts);
+    if ((ret = ff_formats_ref(formats, &inlink1->outcfg.formats)) < 0)
+        return ret;
+
+    /* set output0 video formats */
+    formats = ff_draw_supported_pixel_formats(0);
+    if ((ret = ff_formats_ref(formats, &outlink->incfg.formats)) < 0)
+        return ret;
+
+    return 0;
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+
+    outlink->w = ctx->inputs[0]->w;
+    outlink->h = ctx->inputs[0]->h;
+    outlink->time_base = ctx->inputs[0]->time_base;
+
+    return 0;
+}
+
+static int config_input_main(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx  = inlink->dst;
+    TextSubsContext *s = inlink->dst->priv;
+    int ret;
+
+    ret = ff_draw_init(&s->draw, inlink->format, s->alpha ? FF_DRAW_PROCESS_ALPHA : 0);
+    if (ret < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Could not initialize ff_draw.\n");
+        return ret;
+    }
+
+    ass_set_frame_size  (s->renderer, inlink->w, inlink->h);
+    ass_set_pixel_aspect(s->renderer, av_q2d(inlink->sample_aspect_ratio));
+
+    av_log(ctx, AV_LOG_VERBOSE, "Subtitle screen: %dx%d\n\n\n\n", inlink->w, inlink->h);
+
+    return 0;
+}
+
+/* libass stores an RGBA color in the format RRGGBBTT, where TT is the transparency level */
+#define AR(c)  ( (c)>>24)
+#define AG(c)  (((c)>>16)&0xFF)
+#define AB(c)  (((c)>>8) &0xFF)
+#define AA(c)  ((0xFF-(c)) &0xFF)
+
+static void overlay_ass_image(TextSubsContext *s, AVFrame *picref,
+                              const ASS_Image *image)
+{
+    for (; image; image = image->next) {
+        uint8_t rgba_color[] = {AR(image->color), AG(image->color), AB(image->color), AA(image->color)};
+        FFDrawColor color;
+        ff_draw_color(&s->draw, &color, rgba_color);
+        ff_blend_mask(&s->draw, &color,
+                      picref->data, picref->linesize,
+                      picref->width, picref->height,
+                      image->bitmap, image->stride, image->w, image->h,
+                      3, 0, image->dst_x, image->dst_y);
+    }
+}
+
+static void process_header(AVFilterContext *link, AVFrame *sub)
+{
+    TextSubsContext *s = link->priv;
+    ASS_Track *track = s->track;
+    ASS_Style *style;
+    int sid = 0;
+
+    if (!track)
+        return;
+
+    if (sub && sub->subtitle_header) {
+        char *subtitle_header = (char *)sub->subtitle_header->data;
+        ass_process_codec_private(s->track, subtitle_header, strlen(subtitle_header));
+    }
+    else {
+        char* subtitle_header = avpriv_ass_get_subtitle_header_default(0);
+        if (!subtitle_header)
+            return;
+
+        ass_process_codec_private(s->track, subtitle_header, strlen(subtitle_header));
+        av_free(subtitle_header);
+    }
+
+    if (s->language)
+        s->track->Language = strdup(s->language);
+
+    if (!s->track->event_format) {
+        s->track->event_format = strdup("ReadOrder, Layer, Style, Name, MarginL, MarginR, MarginV, Effect, Text");
+    }
+
+    if (s->track->n_styles == 0) {
+        sid = ass_alloc_style(track);
+        style = &s->track->styles[sid];
+        style->Name             = strdup("Default");
+        style->PrimaryColour    = 0xffffff00;
+        style->SecondaryColour  = 0x00ffff00;
+        style->OutlineColour    = 0x00000000;
+        style->BackColour       = 0x00000080;
+        style->Bold             = 200;
+        style->ScaleX           = 1.0;
+        style->ScaleY           = 1.0;
+        style->Spacing          = 0;
+        style->BorderStyle      = 1;
+        style->Outline          = 2;
+        style->Shadow           = 3;
+        style->Alignment        = 2;
+    }
+    else
+        style = &s->track->styles[sid];
+
+    style->FontSize         = s->font_size;
+    style->MarginL = style->MarginR = style->MarginV = s->margin;
+
+    track->default_style = sid;
+
+    s->got_header = 1;
+}
+
+static int filter_video_frame(AVFilterLink *inlink, AVFrame *frame)
+{
+    AVFilterContext *ctx = inlink->dst;
+    TextSubsContext *s = ctx->priv;
+    int detect_change = 0;
+
+    int64_t time_ms = frame->pts * av_q2d(inlink->time_base) * 1000;
+
+    ASS_Image *image = ass_render_frame(s->renderer, s->track, time_ms, &detect_change);
+
+    if (detect_change)
+        av_log(ctx, AV_LOG_DEBUG, "Change happened at time ms:%lld\n", time_ms);
+
+    overlay_ass_image(s, frame, image);
+
+    return ff_filter_frame(ctx->outputs[0], frame);
+}
+
+static int filter_subtitle_frame(AVFilterLink *inlink, AVFrame *sub)
+{
+    AVFilterContext *ctx = inlink->dst;
+    TextSubsContext *s = ctx->priv;
+
+    if (!s->got_header)
+        process_header(ctx, sub);
+
+    const int64_t start_time = av_rescale_q(sub->subtitle_pts, AV_TIME_BASE_Q, av_make_q(1, 1000));
+    const int64_t duration   = sub->subtitle_end_time;
+
+    for (unsigned i = 0; i < sub->num_subtitle_areas; i++) {
+        char *ass_line = sub->subtitle_areas[i]->ass;
+        if (!ass_line)
+            break;
+        ass_process_chunk(s->track, ass_line, strlen(ass_line), start_time, duration);
+    }
+
+    av_frame_free(&sub);
+    return 0;
+}
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    TextSubsContext *s = ctx->priv;
+
+    s->library = ass_library_init();
+
+    if (!s->library) {
+        av_log(ctx, AV_LOG_ERROR, "Could not initialize libass.\n");
+        return AVERROR(EINVAL);
+    }
+
+    ass_set_message_cb(s->library, ass_log, ctx);
+
+    /* Initialize fonts */
+    if (s->fonts_dir)
+        ass_set_fonts_dir(s->library, s->fonts_dir);
+
+    ass_set_extract_fonts(s->library, 1);
+
+    s->renderer = ass_renderer_init(s->library);
+    if (!s->renderer) {
+        av_log(ctx, AV_LOG_ERROR, "Could not initialize libass renderer.\n");
+        return AVERROR(EINVAL);
+    }
+
+    s->track = ass_new_track(s->library);
+    if (!s->track) {
+        av_log(ctx, AV_LOG_ERROR, "ass_new_track() failed!\n");
+        return AVERROR(EINVAL);
+    }
+
+    ass_set_fonts(s->renderer, s->default_font_path, NULL, 1, s->fc_file, 1);
+
+    if (s->force_style) {
+        char **list = NULL;
+        char *temp = NULL;
+        char *ptr = av_strtok(s->force_style, ",", &temp);
+        int i = 0;
+        while (ptr) {
+            av_dynarray_add(&list, &i, ptr);
+            if (!list) {
+                return AVERROR(ENOMEM);
+            }
+            ptr = av_strtok(NULL, ",", &temp);
+        }
+        av_dynarray_add(&list, &i, NULL);
+        if (!list) {
+            return AVERROR(ENOMEM);
+        }
+        ass_set_style_overrides(s->library, list);
+        av_free(list);
+    }
+
+    return 0;
+}
+
+static int textsub2video_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 input0 subtitle format */
+    formats = ff_make_format_list(subtitle_fmts);
+    if ((ret = ff_formats_ref(formats, &inlink->outcfg.formats)) < 0)
+        return ret;
+
+    /* set output0 video format */
+    formats = ff_draw_supported_pixel_formats(AV_PIX_FMT_FLAG_ALPHA);
+    if ((ret = ff_formats_ref(formats, &outlink->incfg.formats)) < 0)
+        return ret;
+
+    return 0;
+}
+
+static int textsub2video_config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    TextSubsContext *s = ctx->priv;
+
+    if (s->out_w <= 0 || s->out_h <= 0) {
+        s->out_w = inlink->w;
+        s->out_h = inlink->h;
+    }
+
+    return 0;
+}
+
+static int textsub2video_config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    TextSubsContext *s = ctx->priv;
+    int ret;
+
+    ret = ff_draw_init(&s->draw, outlink->format, FF_DRAW_PROCESS_ALPHA);
+    if (ret < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Could not initialize ff_draw.\n");
+        return ret;
+    }
+
+    if (s->out_w <= 0 || s->out_h <= 0) {
+        av_log(ctx, AV_LOG_ERROR, "No output image size set.\n");
+        return AVERROR(EINVAL);
+    }
+
+    ass_set_frame_size  (s->renderer, s->out_w, s->out_h);
+
+    outlink->w = s->out_w;
+    outlink->h = s->out_h;
+    outlink->sample_aspect_ratio = (AVRational){1,1};
+    outlink->frame_rate = s->frame_rate;
+
+    return 0;
+}
+
+static int textsub2video_filter_frame(AVFilterLink *inlink, AVFrame *sub)
+{
+    AVFilterContext *ctx = inlink->dst;
+    TextSubsContext *s = ctx->priv;
+
+    av_log(ctx, AV_LOG_VERBOSE, "textsub2video_filter_frame num_subtitle_rects: %d\n", sub->num_subtitle_areas);
+
+    if (!s->got_header)
+        process_header(ctx, sub);
+
+    const int64_t start_time = av_rescale_q(sub->subtitle_pts, AV_TIME_BASE_Q, av_make_q(1, 1000));
+    const int64_t duration   = sub->subtitle_end_time;
+
+    for (unsigned i = 0; i < sub->num_subtitle_areas; i++) {
+        char *ass_line = sub->subtitle_areas[i]->ass;
+        if (!ass_line)
+            break;
+        ass_process_chunk(s->track, ass_line, strlen(ass_line), start_time, duration);
+    }
+
+    av_frame_free(&sub);
+    return 0;
+}
+
+static int textsub2video_request_frame(AVFilterLink *outlink)
+{
+    TextSubsContext *s = outlink->src->priv;
+    const AVFilterLink *inlink = outlink->src->inputs[0];
+    int64_t last_pts = outlink->current_pts;
+    int64_t next_pts;
+    int i, detect_change = 0;
+    AVFrame *out;
+    ASS_Image *image;
+
+    if (last_pts == AV_NOPTS_VALUE)
+        last_pts = inlink->current_pts * av_q2d(inlink->time_base) / av_q2d(outlink->time_base);
+
+    next_pts = last_pts + (1.0 / av_q2d(outlink->frame_rate) / av_q2d(outlink->time_base));
+
+    int64_t time_ms = next_pts * av_q2d(outlink->time_base) * 1000;
+
+    image = ass_render_frame(s->renderer, s->track, time_ms, &detect_change);
+
+    if (detect_change)
+        av_log(outlink->src, AV_LOG_DEBUG, "Change happened at time ms:%lld\n", time_ms);
+    else if (s->last_frame) {
+        out = av_frame_clone(s->last_frame);
+        if (!out)
+            return AVERROR(ENOMEM);
+
+        out->pts = next_pts;
+        return ff_filter_frame(outlink, out);
+    }
+
+    out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+    if (!out)
+        return AVERROR(ENOMEM);
+
+    for (i = 2; i < AV_NUM_DATA_POINTERS; i++) {
+        if (out->buf[i] && i != 1)
+            memset(out->buf[i]->data, 0, out->buf[i]->size);
+    }
+
+    out->pts = next_pts;
+
+    if (image)
+        overlay_ass_image(s, out, image);
+
+    av_frame_free(&s->last_frame);
+
+    s->last_frame = av_frame_clone(out);
+
+    return ff_filter_frame(outlink, out);
+}
+
+static int activate(AVFilterContext *ctx)
+{
+    AVFilterLink *inlink = ctx->inputs[0];
+    AVFilterLink *outlink = ctx->outputs[0];
+    TextSubsContext *s = ctx->priv;
+    AVFrame *in;
+    int ret;
+
+    FF_FILTER_FORWARD_STATUS_BACK(outlink, inlink);
+
+    ret = ff_inlink_consume_frame(inlink, &in);
+    if (ret < 0)
+        return ret;
+    if (ret > 0)
+        return textsub2video_filter_frame(inlink, in);
+
+    if (ff_outlink_frame_wanted(outlink)) {
+        if (!s->eof && ff_outlink_get_status(ctx->inputs[0])) {
+            s->eof = 1;
+        }
+        if (!s->eof && ff_inlink_queued_frames(ctx->inputs[0]) == 0)
+            ff_inlink_request_frame(ctx->inputs[0]);
+        if (s->eof && ff_inlink_queued_frames(ctx->inputs[0]) <= 0) {
+            ff_outlink_set_status(outlink, AVERROR_EOF, AV_NOPTS_VALUE);
+        }
+        else {
+            return textsub2video_request_frame(outlink);
+        }
+
+        return 0;
+    }
+
+    return FFERROR_NOT_READY;
+}
+
+#define OFFSET(x) offsetof(TextSubsContext, x)
+#define FLAGS (AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_FILTERING_PARAM)
+
+static const AVOption overlay_textsubs_options[] = {
+    {"alpha",             "enable processing of alpha channel", OFFSET(alpha),           AV_OPT_TYPE_BOOL,   {.i64 = 0   }, 0,         1,        FLAGS},
+    {"font_scale",        "font scale factor",                OFFSET(font_scale),        AV_OPT_TYPE_DOUBLE, {.dbl = 1.0 }, 0.0,       100.0,    FLAGS},
+    {"font_size",         "default font size",                OFFSET(font_size),         AV_OPT_TYPE_DOUBLE, {.dbl = 18.0}, 0.0,       100.0,    FLAGS},
+    {"force_style",       "force subtitle style",             OFFSET(force_style),       AV_OPT_TYPE_STRING, {.str = NULL}, 0,         0,        FLAGS},
+    {"margin",            "default margin",                   OFFSET(margin),            AV_OPT_TYPE_INT,    {.i64 = 20  }, 0,         INT_MAX,  FLAGS},
+    {"default_font_path", "path to default font",             OFFSET(default_font_path), AV_OPT_TYPE_STRING, {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    {"fonts_dir",         "directory to scan for fonts",      OFFSET(fonts_dir),         AV_OPT_TYPE_STRING, {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    {"fontsdir",          "directory to scan for fonts",      OFFSET(fonts_dir),         AV_OPT_TYPE_STRING, {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    {"fontconfig_file",   "fontconfig file to load",          OFFSET(fc_file),           AV_OPT_TYPE_STRING, {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    {"language",          "default language",                 OFFSET(language),          AV_OPT_TYPE_STRING, {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    { NULL }
+};
+
+static const AVOption textsub2video_options[] = {
+    {"rate",              "set frame rate",                   OFFSET(frame_rate),        AV_OPT_TYPE_VIDEO_RATE, {.str="8"},   0,         INT_MAX,  FLAGS},
+    {"r",                 "set frame rate",                   OFFSET(frame_rate),        AV_OPT_TYPE_VIDEO_RATE, {.str="8"},   0,         INT_MAX,  FLAGS},
+    {"size",              "set video size",                   OFFSET(out_w),             AV_OPT_TYPE_IMAGE_SIZE, {.str = NULL}, 0,         0,        FLAGS},
+    {"s",                 "set video size",                   OFFSET(out_w),             AV_OPT_TYPE_IMAGE_SIZE, {.str = NULL}, 0,         0,        FLAGS},
+    {"font_scale",        "font scale factor",                OFFSET(font_scale),        AV_OPT_TYPE_DOUBLE,     {.dbl = 1.0 }, 0.0,       100.0,    FLAGS},
+    {"font_size",         "default font size",                OFFSET(font_size),         AV_OPT_TYPE_DOUBLE,     {.dbl = 18.0}, 0.0,       100.0,    FLAGS},
+    {"force_style",       "force subtitle style",             OFFSET(force_style),       AV_OPT_TYPE_STRING,     {.str = NULL}, 0,         0,        FLAGS},
+    {"margin",            "default margin",                   OFFSET(margin),            AV_OPT_TYPE_INT,        {.i64 = 20  }, 0,         INT_MAX,  FLAGS},
+    {"default_font_path", "path to default font",             OFFSET(default_font_path), AV_OPT_TYPE_STRING,     {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    {"fonts_dir",         "directory to scan for fonts",      OFFSET(fonts_dir),         AV_OPT_TYPE_STRING,     {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    {"fontsdir",          "directory to scan for fonts",      OFFSET(fonts_dir),         AV_OPT_TYPE_STRING,     {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    {"fontconfig_file",   "fontconfig file to load",          OFFSET(fc_file),           AV_OPT_TYPE_STRING,     {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    {"language",          "default language",                 OFFSET(language),          AV_OPT_TYPE_STRING,     {.str = NULL}, CHAR_MIN,  CHAR_MAX, FLAGS},
+    { NULL }
+};
+
+#if CONFIG_OVERLAY_TEXTSUBS_FILTER
+
+AVFILTER_DEFINE_CLASS(overlay_textsubs);
+
+static const AVFilterPad overlay_textsubs_inputs[] = {
+    {
+        .name         = "main",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = config_input_main,
+        .flags        = AVFILTERPAD_FLAG_NEEDS_WRITABLE,
+        .filter_frame = filter_video_frame,
+    },
+    {
+        .name         = "overlay",
+        .type         = AVMEDIA_TYPE_SUBTITLE,
+        .filter_frame = filter_subtitle_frame,
+    },
+};
+
+static const AVFilterPad overlay_textsubs_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .config_props  = config_output,
+    },
+};
+
+const AVFilter ff_vf_overlay_textsubs = {
+    .name          = "overlay_textsubs",
+    .description   = NULL_IF_CONFIG_SMALL("Overlay textual subtitles on top of the input."),
+    .init          = init,
+    .uninit        = uninit,
+    .priv_size     = sizeof(TextSubsContext),
+    .priv_class    = &overlay_textsubs_class,
+    .query_formats = overlay_textsubs_query_formats,
+    FILTER_INPUTS(overlay_textsubs_inputs),
+    FILTER_OUTPUTS(overlay_textsubs_outputs),
+};
+#endif
+
+#if CONFIG_TEXTSUB2VIDEO_FILTER
+
+AVFILTER_DEFINE_CLASS(textsub2video);
+
+static const AVFilterPad textsub2video_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_SUBTITLE,
+        .config_props = textsub2video_config_input,
+    },
+};
+
+static const AVFilterPad textsub2video_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .config_props  = textsub2video_config_output,
+    },
+};
+
+const AVFilter ff_svf_textsub2video = {
+    .name          = "textsub2video",
+    .description   = NULL_IF_CONFIG_SMALL("Convert textual subtitles to video frames"),
+    .init          = init,
+    .uninit        = uninit,
+    .query_formats = textsub2video_query_formats,
+    .priv_size     = sizeof(TextSubsContext),
+    .priv_class    = &textsub2video_class,
+    .activate      = activate,
+    FILTER_INPUTS(textsub2video_inputs),
+    FILTER_OUTPUTS(textsub2video_outputs),
+};
+#endif