lavc/libaribcaption.c: add ARIB caption decoder using libaribcaption

This patch add another ARIB caption decoder using libaribcaption
external library.

Unlike libaribb24, it supports 3 types of subtitle outputs:
* text: plain text
* ass: ASS formatted text
* bitmap: bitmap image

Default subtitle type is ass as same as libaribb24.
Advantages compared with libaribb24 on ASS subtitle are:
* Subtitle positioning.
* Multi-rect subtitle: some captions are displayed at different
  position at a time.
* More stability and reproducibility.

To compile with this feature:
* libaribcaption external library has to be pre-installed.
  https://github.com/xqq/libaribcaption
* configure with `--enable-libaribcaption` option.

`--enable-libaribb24` and `--enable-libaribcaption` options are
not exclusive. If both enabled, libaribcaption precedes as
order listed in `libavcodec/allcodecs.c`.

Signed-off-by: rcombs <rcombs@rcombs.me>

Changelog

@@ -2,6 +2,7 @@ Entries are sorted chronologically from oldest to youngest within each release,
 releases are sorted from youngest to oldest.
 
 version <next>:
+- libaribcaption decoder
 
 version 6.0:
 - Radiance HDR image support

configure

@@ -218,6 +218,7 @@ External library support:
   --enable-lcms2           enable ICC profile support via LittleCMS 2 [no]
   --enable-libaom          enable AV1 video encoding/decoding via libaom [no]
   --enable-libaribb24      enable ARIB text and caption decoding via libaribb24 [no]
+  --enable-libaribcaption  enable ARIB text and caption decoding via libaribcaption [no]
   --enable-libass          enable libass subtitles rendering,
                            needed for subtitles and ass filter [no]
   --enable-libbluray       enable BluRay reading using libbluray [no]
@@ -1805,6 +1806,7 @@ EXTERNAL_LIBRARY_LIST="
     ladspa
     lcms2
     libaom
+    libaribcaption
     libass
     libbluray
     libbs2b
@@ -3331,6 +3333,7 @@ libaom_av1_decoder_deps="libaom"
 libaom_av1_encoder_deps="libaom"
 libaom_av1_encoder_select="extract_extradata_bsf"
 libaribb24_decoder_deps="libaribb24"
+libaribcaption_decoder_deps="libaribcaption"
 libcelt_decoder_deps="libcelt"
 libcodec2_decoder_deps="libcodec2"
 libcodec2_encoder_deps="libcodec2"
@@ -6569,6 +6572,7 @@ enabled libaom            && require_pkg_config libaom "aom >= 1.0.0" aom/aom_co
 enabled libaribb24        && { check_pkg_config libaribb24 "aribb24 > 1.0.3" "aribb24/aribb24.h" arib_instance_new ||
                                { enabled gpl && require_pkg_config libaribb24 aribb24 "aribb24/aribb24.h" arib_instance_new; } ||
                                die "ERROR: libaribb24 requires version higher than 1.0.3 or --enable-gpl."; }
+enabled libaribcaption    && require_pkg_config libaribcaption "libaribcaption >= 0.1.0" "aribcaption/aribcaption.h" aribcc_context_alloc
 enabled lv2               && require_pkg_config lv2 lilv-0 "lilv/lilv.h" lilv_world_new
 enabled libiec61883       && require libiec61883 libiec61883/iec61883.h iec61883_cmp_connect -lraw1394 -lavc1394 -lrom1394 -liec61883
 enabled libass            && require_pkg_config libass "libass >= 0.11.0" ass/ass.h ass_library_init

doc/decoders.texi

@@ -353,6 +353,156 @@ Enabled by default.
 
 @end table
 
+@section libaribcaption
+
+Yet another ARIB STD-B24 caption decoder using external @dfn{libaribcaption}
+library.
+
+Implements profiles A and C of the Japanse ARIB STD-B24 standard,
+Brazilian ABNT NBR 15606-1, and Philippines version of ISDB-T.
+
+Requires the presence of the libaribcaption headers and library
+(@url{https://github.com/xqq/libaribcaption}) during configuration.
+You need to explicitly configure the build with @code{--enable-libaribcaption}.
+If both @dfn{libaribb24} and @dfn{libaribcaption} are enabled, @dfn{libaribcaption}
+decoder precedes.
+
+@subsection libaribcaption Decoder Options
+
+@table @option
+
+@item -sub_type @var{subtitle_type}
+Specifies the format of the decoded subtitles.
+
+@table @samp
+@item bitmap
+Graphical image.
+@item ass
+ASS formatted text.
+@item text
+Simple text based output without formatting.
+@end table
+
+The default is @dfn{ass} as same as @dfn{libaribb24} decoder.
+Some present players (e.g., @dfn{mpv}) expect ASS format for ARIB caption.
+
+@item -caption_encoding @var{encoding_scheme}
+Specifies the encoding scheme of input subtitle text.
+
+@table @samp
+@item auto
+Automatically detect text encoding.
+@item jis
+8bit-char JIS encoding defined in ARIB STD B24.
+This encoding used in Japan for ISDB captions.
+@item utf8
+UTF-8 encoding defined in ARIB STD B24.
+This encoding is used in Philippines for ISDB-T captions.
+@item latin
+Latin character encoding defined in ABNT NBR 15606-1.
+This encoding is used in South America for SBTVD / ISDB-Tb captions.
+@end table
+
+The default is @dfn{ass} as same as @dfn{libaribb24} decoder.
+Some present players (e.g., @dfn{mpv}) expect ASS format for ARIB caption.
+
+@item -font @var{font_name[,font_name2,...]}
+Specify comma-separated list of font family names to be used for @dfn{bitmap}
+or @dfn{ass} type subtitle rendering.
+Only first font name is used for @dfn{ass} type subtitle.
+
+If not specified, use internaly defined default font family.
+
+@item -ass_single_rect @var{boolean}
+ARIB STD-B24 specifies that some captions may be displayed at different
+positions at a time (multi-rectangle subtitle).
+Since some players (e.g., old @dfn{mpv}) can't handle multiple ASS rectangles
+in a single AVSubtitle, or multiple ASS rectangles of indeterminate duration
+with the same start timestamp, this option can change the behavior so that
+all the texts are displayed in a single ASS rectangle.
+
+The default is @var{false}.
+
+If your player cannot handle AVSubtitles with multiple ASS rectangles properly,
+set this option to @var{true} or define @env{ASS_SINGLE_RECT=1} to change
+default behavior at compilation.
+
+@item -replace_fullwidth_ascii @var{boolean}
+Specify whether to replace MSZ (Middle Size, half width) fullwidth
+alphanumerics with halfwidth alphanumerics.
+
+The default is @var{true}.
+
+@item -force_outline_text @var{boolean}
+Specify whether always render outline text for all characters regardless of
+the indication by charactor style.
+
+The default is @var{false}.
+
+@item -outline_width @var{number} (0.0 - 3.0)
+Specify width for outline text, in dots (relative).
+
+The default is @var{1.5}.
+
+@item -ignore_background @var{boolean}
+Specify whether to ignore background color rendering.
+
+The default is @var{false}.
+
+@item -ignore_ruby @var{boolean}
+Specify whether to ignore rendering for ruby-like (furigana) characters.
+
+The default is @var{false}.
+
+@item -replace_drcs @var{boolean}
+Specify whether to render replaced DRCS characters as Unicode characters.
+
+The default is @var{true}.
+
+@item -canvas_size @var{image_size}
+Specify the resolution of the canvas to render subtitles to; usually, this
+should be frame size of input video.
+This only applies when @code{-subtitle_type} is set to @var{bitmap}.
+
+The libaribcaption decoder assumes input frame size for bitmap rendering as below:
+@enumerate
+@item
+PROFILE_A : 1440 x 1080 with SAR (PAR) 4:3
+@item
+PROFILE_C : 320 x 180 with SAR (PAR) 1:1
+@end enumerate
+
+If actual frame size of input video does not match above assumption,
+the rendered captions may be distorted.
+To make the captions undistorted, add @code{-canvas_size} option to specify
+actual input video size.
+
+Note that the @code{-canvas_size} option is not required for video with
+different size but same aspect ratio.
+In such cases, the caption will be stretched or shrunk to actual video size
+if @code{-canvas_size} option is not specified.
+If @code{-canvas_size} option is specified with different size,
+the caption will be stretched or shrunk as specified size with calculated SAR.
+
+@end table
+
+@subsection libaribcaption decoder usage examples
+
+Display MPEG-TS file with ARIB subtitle by @code{ffplay} tool:
+@example
+ffplay -sub_type bitmap MPEG.TS
+@end example
+
+Display MPEG-TS file with input frame size 1920x1080 by @code{ffplay} tool:
+@example
+ffplay -sub_type bitmap -canvas_size 1920x1080 MPEG.TS
+@end example
+
+Embed ARIB subtitle in transcoded video:
+@example
+ffmpeg -sub_type bitmap -i src.m2t -filter_complex "[0:v][0:s]overlay" -vcodec h264 dest.mp4
+@end example
+
 @section dvbsub
 
 @subsection Options

libavcodec/Makefile

@@ -1079,6 +1079,7 @@ OBJS-$(CONFIG_PCM_MULAW_AT_ENCODER)       += audiotoolboxenc.o
 OBJS-$(CONFIG_LIBAOM_AV1_DECODER)         += libaomdec.o libaom.o
 OBJS-$(CONFIG_LIBAOM_AV1_ENCODER)         += libaomenc.o libaom.o
 OBJS-$(CONFIG_LIBARIBB24_DECODER)         += libaribb24.o ass.o
+OBJS-$(CONFIG_LIBARIBCAPTION_DECODER)     += libaribcaption.o ass.o
 OBJS-$(CONFIG_LIBCELT_DECODER)            += libcelt_dec.o
 OBJS-$(CONFIG_LIBCODEC2_DECODER)          += libcodec2.o
 OBJS-$(CONFIG_LIBCODEC2_ENCODER)          += libcodec2.o

libavcodec/allcodecs.c

@@ -759,6 +759,8 @@ extern const FFCodec ff_pcm_mulaw_at_decoder;
 extern const FFCodec ff_qdmc_at_decoder;
 extern const FFCodec ff_qdm2_at_decoder;
 extern FFCodec ff_libaom_av1_encoder;
+/* preferred over libaribb24 */
+extern const FFCodec ff_libaribcaption_decoder;
 extern const FFCodec ff_libaribb24_decoder;
 extern const FFCodec ff_libcelt_decoder;
 extern const FFCodec ff_libcodec2_encoder;