lavfi: add libass based subtitles renderer

Changelog

@@ -124,6 +124,7 @@ easier to use. The changes are:
 - compact and csv output in ffprobe
 - pan audio filter
 - IFF Amiga Continuous Bitmap (ACBM) decoder
+- ass filter
 
 
 version 0.8:

configure

@@ -168,6 +168,7 @@ External library support:
   --enable-frei0r          enable frei0r video filtering
   --enable-gnutls          enable gnutls [no]
   --enable-libaacplus      enable AAC+ encoding via libaacplus [no]
+  --enable-libass          enable libass subtitles rendering [no]
   --enable-libcelt         enable CELT decoding via libcelt [no]
   --enable-libopencore-amrnb enable AMR-NB de/encoding via libopencore-amrnb [no]
   --enable-libopencore-amrwb enable AMR-WB decoding via libopencore-amrwb [no]
@@ -1008,6 +1009,7 @@ CONFIG_LIST="
     hardcoded_tables
     huffman
     libaacplus
+    libass
     libcdio
     libcelt
     libdc1394
@@ -1613,6 +1615,7 @@ udp_protocol_deps="network"
 
 # filters
 amovie_filter_deps="avcodec avformat"
+ass_filter_deps="libass"
 blackframe_filter_deps="gpl"
 boxblur_filter_deps="gpl"
 cropdetect_filter_deps="gpl"
@@ -3057,6 +3060,7 @@ enabled avisynth   && require2 vfw32 "windows.h vfw.h" AVIFileInit -lavifil32
 enabled frei0r     && { check_header frei0r.h || die "ERROR: frei0r.h header not found"; }
 enabled gnutls     && require_pkg_config gnutls gnutls/gnutls.h gnutls_global_init
 enabled libaacplus && require  "libaacplus >= 2.0.0" aacplus.h aacplusEncOpen -laacplus
+enabled libass     && require_pkg_config libass ass/ass.h ass_library_init
 enabled libcelt    && require libcelt celt/celt.h celt_decode -lcelt0
 enabled libdc1394  && require_pkg_config libdc1394-2 dc1394/dc1394.h dc1394_new
 enabled libdirac   && require_pkg_config dirac                          \
@@ -3395,6 +3399,7 @@ echo "AVISynth enabled          ${avisynth-no}"
 echo "frei0r enabled            ${frei0r-no}"
 echo "gnutls enabled            ${gnutls-no}"
 echo "libaacplus enabled        ${libaacplus-no}"
+echo "libass enabled            ${libass-no}"
 echo "libcdio support           ${libcdio-no}"
 echo "libcelt enabled           ${libcelt-no}"
 echo "libdc1394 support         ${libdc1394-no}"

doc/filters.texi

@@ -574,6 +574,22 @@ build.
 
 Below is a description of the currently available video filters.
 
+@section ass
+
+Draw ASS (Advanced Substation Alpha) subtitles on top of input video
+using the libass library.
+
+To enable compilation of this filter you need to configure FFmpeg with
+@code{--enable-libass}.
+
+This filter accepts in input the name of the ass file to render.
+
+For example, to render the file @file{sub.ass} on top of the input
+video, use the command:
+@example
+ass=sub.ass
+@end example
+
 @section blackframe
 
 Detect frames that are (almost) completely black. Can be useful to

libavfilter/Makefile

@@ -40,6 +40,7 @@ OBJS-$(CONFIG_ANULLSRC_FILTER)               += asrc_anullsrc.o
 OBJS-$(CONFIG_ABUFFERSINK_FILTER)            += sink_buffer.o
 OBJS-$(CONFIG_ANULLSINK_FILTER)              += asink_anullsink.o
 
+OBJS-$(CONFIG_ASS_FILTER)                    += vf_ass.o
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
 OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o
 OBJS-$(CONFIG_COPY_FILTER)                   += vf_copy.o

libavfilter/allfilters.c

@@ -51,6 +51,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (ABUFFERSINK, abuffersink, asink);
     REGISTER_FILTER (ANULLSINK,   anullsink,   asink);
 
+    REGISTER_FILTER (ASS,         ass,  vf);
     REGISTER_FILTER (BLACKFRAME,  blackframe,  vf);
     REGISTER_FILTER (BOXBLUR,     boxblur,     vf);
     REGISTER_FILTER (COPY,        copy,        vf);

libavfilter/avfilter.h

@@ -29,8 +29,8 @@
 #include "libavutil/rational.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  2
-#define LIBAVFILTER_VERSION_MINOR 49
-#define LIBAVFILTER_VERSION_MICRO  1
+#define LIBAVFILTER_VERSION_MINOR 50
+#define LIBAVFILTER_VERSION_MICRO  0
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_ass.c

@@ -0,0 +1,242 @@
+/*
+ * Copyright (c) 2011 Baptiste Coudurier
+ * Copyright (c) 2011 Stefano Sabatini
+ *
+ * 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
+ * Libass subtitles burning filter.
+ *
+ * @see{http://www.matroska.org/technical/specs/subtitles/ssa.html}
+ */
+
+#include <ass/ass.h>
+
+#include "libavutil/avstring.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/pixdesc.h"
+#include "drawutils.h"
+#include "avfilter.h"
+
+typedef struct {
+    ASS_Library  *library;
+    ASS_Renderer *renderer;
+    ASS_Track    *track;
+    int hsub, vsub;
+    char *filename;
+    uint8_t rgba_map[4];
+    int     pix_step[4];       ///< steps per pixel for each plane of the main output
+} AssContext;
+
+/* libass supports a log level ranging from 0 to 7 */
+int ass_libav_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)
+{
+    int level = ass_libav_log_level_map[ass_level];
+
+    av_vlog(ctx, level, fmt, args);
+    av_log(ctx, level, "\n");
+}
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+    AssContext *ass = ctx->priv;
+
+    if (args)
+        ass->filename = av_get_token(&args, ":");
+    if (!ass->filename || !*ass->filename) {
+        av_log(ctx, AV_LOG_ERROR, "No filename provided!\n");
+        return AVERROR(EINVAL);
+    }
+
+    ass->library = ass_library_init();
+    if (!ass->library) {
+        av_log(ctx, AV_LOG_ERROR, "Could not initialize libass.\n");
+        return AVERROR(EINVAL);
+    }
+    ass_set_message_cb(ass->library, ass_log, ctx);
+
+    ass->renderer = ass_renderer_init(ass->library);
+    if (!ass->renderer) {
+        av_log(ctx, AV_LOG_ERROR, "Could not initialize libass renderer.\n");
+        return AVERROR(EINVAL);
+    }
+
+    ass->track = ass_read_file(ass->library, ass->filename, NULL);
+    if (!ass->track) {
+        av_log(ctx, AV_LOG_ERROR,
+               "Could not create a libass track when reading file '%s'\n",
+               ass->filename);
+        return AVERROR(EINVAL);
+    }
+
+    ass_set_fonts(ass->renderer, NULL, NULL, 1, NULL, 1);
+
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    AssContext *ass = ctx->priv;
+
+    av_freep(&ass->filename);
+    if (ass->track)
+        ass_free_track(ass->track);
+    if (ass->renderer)
+        ass_renderer_done(ass->renderer);
+    if (ass->library)
+        ass_library_done(ass->library);
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum PixelFormat pix_fmts[] = {
+        PIX_FMT_ARGB,  PIX_FMT_RGBA,
+        PIX_FMT_ABGR,  PIX_FMT_BGRA,
+        PIX_FMT_RGB24, PIX_FMT_BGR24,
+        PIX_FMT_NONE
+    };
+
+    avfilter_set_common_pixel_formats(ctx, avfilter_make_format_list(pix_fmts));
+
+    return 0;
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+    AssContext *ass = inlink->dst->priv;
+    const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[inlink->format];
+    double sar = inlink->sample_aspect_ratio.num ?
+        av_q2d(inlink->sample_aspect_ratio) : 1;
+    double dar = inlink->w / inlink->h * sar;
+
+    av_image_fill_max_pixsteps(ass->pix_step, NULL, pix_desc);
+    ff_fill_rgba_map(ass->rgba_map, inlink->format);
+
+    ass->hsub = pix_desc->log2_chroma_w;
+    ass->vsub = pix_desc->log2_chroma_h;
+
+    ass_set_frame_size  (ass->renderer, inlink->w, inlink->h);
+    ass_set_aspect_ratio(ass->renderer, dar, sar);
+
+    return 0;
+}
+
+static void null_draw_slice(AVFilterLink *link, int y, int h, int slice_dir) { }
+
+#define R 0
+#define G 1
+#define B 2
+#define A 3
+
+#define SET_PIXEL_RGB(picref, rgba_color, val, x, y, pixel_step, r_off, g_off, b_off) { \
+    p   = picref->data[0] + (x) * pixel_step + ((y) * picref->linesize[0]);             \
+    alpha = rgba_color[A] * (val) * 129;                                                \
+    *(p+r_off) = (alpha * rgba_color[R] + (255*255*129 - alpha) * *(p+r_off)) >> 23;    \
+    *(p+g_off) = (alpha * rgba_color[G] + (255*255*129 - alpha) * *(p+g_off)) >> 23;    \
+    *(p+b_off) = (alpha * rgba_color[B] + (255*255*129 - alpha) * *(p+b_off)) >> 23;    \
+}
+
+/* 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(AVFilterBufferRef *picref, const uint8_t *rgba_map, const int pix_step,
+                              const ASS_Image *image)
+{
+    int i, j;
+    int alpha;
+    uint8_t *p;
+    const int ro = rgba_map[R];
+    const int go = rgba_map[G];
+    const int bo = rgba_map[B];
+
+    for (; image; image = image->next) {
+        uint8_t rgba_color[] = {AR(image->color), AG(image->color), AB(image->color), AA(image->color)};
+        unsigned char *row = image->bitmap;
+
+        for (i = 0; i < image->h; i++) {
+            for (j = 0; j < image->w; j++) {
+                if (row[j]) {
+                    SET_PIXEL_RGB(picref, rgba_color, row[j], image->dst_x + j, image->dst_y + i, pix_step, ro, go, bo);
+                }
+            }
+            row += image->stride;
+        }
+    }
+}
+
+static void end_frame(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    AssContext *ass = ctx->priv;
+    AVFilterBufferRef *picref = inlink->cur_buf;
+    int detect_change = 0;
+    double time_ms = picref->pts * av_q2d(inlink->time_base) * 1000;
+    ASS_Image *image = ass_render_frame(ass->renderer, ass->track,
+                                        time_ms, &detect_change);
+
+    if (detect_change)
+        av_log(ctx, AV_LOG_DEBUG, "Change happened at time ms:%f\n", time_ms);
+
+    overlay_ass_image(picref, ass->rgba_map, ass->pix_step[0], image);
+
+    avfilter_draw_slice(outlink, 0, picref->video->h, 1);
+    avfilter_end_frame(outlink);
+}
+
+AVFilter avfilter_vf_ass = {
+    .name          = "ass",
+    .description   = NULL_IF_CONFIG_SMALL("Render subtitles onto input video using the libass library."),
+    .priv_size     = sizeof(AssContext),
+    .init          = init,
+    .uninit        = uninit,
+    .query_formats = query_formats,
+
+    .inputs = (const AVFilterPad[]) {
+        { .name             = "default",
+          .type             = AVMEDIA_TYPE_VIDEO,
+          .get_video_buffer = avfilter_null_get_video_buffer,
+          .start_frame      = avfilter_null_start_frame,
+          .draw_slice       = null_draw_slice,
+          .end_frame        = end_frame,
+          .config_props     = config_input,
+          .min_perms        = AV_PERM_WRITE | AV_PERM_READ,
+          .rej_perms        = AV_PERM_PRESERVE },
+        { .name = NULL}
+    },
+    .outputs = (const AVFilterPad[]) {
+        { .name             = "default",
+          .type             = AVMEDIA_TYPE_VIDEO, },
+        { .name = NULL}
+    },
+};