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Fri, 24 Sep 2021 00:31:22 +0000 From: Soft Works To: "ffmpeg-devel@ffmpeg.org" Thread-Topic: [PATCH v9 13/13] avfilter/graphicsub2text: Add new graphicsub2text filter (OCR) Thread-Index: AQHXsNuAo9JOE9DiTkuvThP/PmKgUQ== Date: Fri, 24 Sep 2021 00:31:22 +0000 Message-ID: References: <5bc443d3efba607cef8020fdacce3fbec59514b7.1632443311.git.softworkz@hotmail.com> <74b7003baacf9847f879d785c002e4a78293f57c.1632443311.git.softworkz@hotmail.com> <2b7a471b8c1a6fe4ce2c4133710261ecafbbf13d.1632443311.git.softworkz@hotmail.com> <64913621bc7223946c513126a1abe0ea2001d6f5.1632443311.git.softworkz@hotmail.com> <20dacbb0f094ee36ce241dbe938b7722bb6957e9.1632443311.git.softworkz@hotmail.com> <0e284d1eeb32bd78ddbbc8766f9af27128399d40.1632443311.git.softworkz@hotmail.com> In-Reply-To: <0e284d1eeb32bd78ddbbc8766f9af27128399d40.1632443311.git.softworkz@hotmail.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-messagesentrepresentingtype: 1 x-tmn: [G9r7Sh6rnTc/pwT8pDYvWzsTr95AA4EC] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 6d8ea338-1f01-4a4c-e61b-08d97ef2a2e4 x-ms-traffictypediagnostic: MN2PR04MB5743: x-microsoft-antispam: BCL:0; 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It is fast but less accurate than LSTM. +@item 1, lstm +Newer OCR implementation based on ML models. Provides usually better results, requires more processing resources. +@item 2, both +Use a combination of both modes. +@end table + +@item tessdata_path +The path to a folder containing the language models to be used. + +@item language +The recognition language. It needs to match the first three characters of a language model file in the tessdata path. + +@end table + + +@subsection Examples + +@itemize +@item +Convert DVB graphic subtitles to ASS (text) subtitles + +Note: For this to work, you need to have the data file 'eng.traineddata' in a 'tessdata' subfolder (see above). +@example +ffmpeg ffmpeg -loglevel verbose -i "https://streams.videolan.org/streams/ts/video_subs_ttxt%2Bdvbsub.ts" -filter_complex "[0:13]graphicsub2text=ocr_mode=both" -c:s ass -y output.mkv +@end example +@end itemize + + @section graphicsub2video Renders graphic subtitles as video frames. diff --git a/libavfilter/Makefile b/libavfilter/Makefile index 39abf6d2a6..312b67982c 100644 --- a/libavfilter/Makefile +++ b/libavfilter/Makefile @@ -290,6 +290,7 @@ OBJS-$(CONFIG_FSPP_FILTER) += vf_fspp.o qp_table.o OBJS-$(CONFIG_GBLUR_FILTER) += vf_gblur.o OBJS-$(CONFIG_GEQ_FILTER) += vf_geq.o OBJS-$(CONFIG_GRADFUN_FILTER) += vf_gradfun.o +OBJS-$(CONFIG_GRAPHICSUB2TEXT_FILTER) += sf_graphicsub2text.o OBJS-$(CONFIG_GRAPHICSUB2VIDEO_FILTER) += vf_overlay_graphicsubs.o framesync.o OBJS-$(CONFIG_GRAPHMONITOR_FILTER) += f_graphmonitor.o OBJS-$(CONFIG_GRAYWORLD_FILTER) += vf_grayworld.o diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c index 802465fce2..f3437789bf 100644 --- a/libavfilter/allfilters.c +++ b/libavfilter/allfilters.c @@ -527,6 +527,7 @@ extern const AVFilter ff_avf_showwaves; extern const AVFilter ff_avf_showwavespic; extern const AVFilter ff_vaf_spectrumsynth; extern const AVFilter ff_sf_censor; +extern const AVFilter ff_sf_graphicsub2text; extern const AVFilter ff_sf_show_speaker; extern const AVFilter ff_sf_split_cc; extern const AVFilter ff_sf_stripstyles; diff --git a/libavfilter/sf_graphicsub2text.c b/libavfilter/sf_graphicsub2text.c new file mode 100644 index 0000000000..c644f5b46c --- /dev/null +++ b/libavfilter/sf_graphicsub2text.c @@ -0,0 +1,322 @@ +/* + * 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 + * subtitle filter to convert graphical subs to text subs via OCR + */ + +#include +#include + +#include "libavutil/opt.h" +#include "subtitles.h" + +typedef struct SubOcrContext { + const AVClass *class; + int w, h; + + TessBaseAPI *tapi; + TessOcrEngineMode ocr_mode; + char *tessdata_path; + char *language; + + int readorder_counter; + + AVFrame *pending_frame; +} SubOcrContext; + + +static int init(AVFilterContext *ctx) +{ + SubOcrContext *s = ctx->priv; + const char* tver = TessVersion(); + int ret; + + s->tapi = TessBaseAPICreate(); + + if (!s->tapi || !tver || !strlen(tver)) { + av_log(ctx, AV_LOG_ERROR, "Failed to access libtesseract\n"); + return AVERROR(ENOSYS); + } + + av_log(ctx, AV_LOG_VERBOSE, "Initializing libtesseract, version: %s\n", tver); + + ret = TessBaseAPIInit4(s->tapi, s->tessdata_path, s->language, s->ocr_mode, NULL, 0, NULL, NULL, 0, 1); + if (ret < 0 ) { + av_log(ctx, AV_LOG_ERROR, "Failed to initialize libtesseract. Error: %d\n", ret); + return AVERROR(ENOSYS); + } + + ret = TessBaseAPISetVariable(s->tapi, "tessedit_char_blacklist", "|"); + if (ret < 0 ) { + av_log(ctx, AV_LOG_ERROR, "Failed to set 'tessedit_char_blacklist'. Error: %d\n", ret); + return AVERROR(EINVAL); + } + + return 0; +} + +static void uninit(AVFilterContext *ctx) +{ + SubOcrContext *s = ctx->priv; + + if (s->tapi) { + TessBaseAPIEnd(s->tapi); + TessBaseAPIDelete(s->tapi); + } +} + +static int query_formats(AVFilterContext *ctx) +{ + AVFilterFormats *formats, *formats2; + AVFilterLink *inlink = ctx->inputs[0]; + AVFilterLink *outlink = ctx->outputs[0]; + static const enum AVSubtitleType in_fmts[] = { AV_SUBTITLE_FMT_BITMAP, AV_SUBTITLE_FMT_NONE }; + static const enum AVSubtitleType out_fmts[] = { AV_SUBTITLE_FMT_ASS, AV_SUBTITLE_FMT_NONE }; + int ret; + + /* set input format */ + formats = ff_make_format_list(in_fmts); + if ((ret = ff_formats_ref(formats, &inlink->outcfg.formats)) < 0) + return ret; + + /* set output format */ + formats2 = ff_make_format_list(out_fmts); + if ((ret = ff_formats_ref(formats2, &outlink->incfg.formats)) < 0) + return ret; + + return 0; +} + +static int config_input(AVFilterLink *inlink) +{ + AVFilterContext *ctx = inlink->dst; + SubOcrContext *s = ctx->priv; + + if (s->w <= 0 || s->h <= 0) { + s->w = inlink->w; + s->h = inlink->h; + } + return 0; +} + +static int config_output(AVFilterLink *outlink) +{ + const AVFilterContext *ctx = outlink->src; + SubOcrContext *s = ctx->priv; + + outlink->format = AV_SUBTITLE_FMT_ASS; + outlink->w = s->w; + outlink->h = s->h; + + return 0; +} + +static uint8_t* create_grayscale_image(AVFilterContext *ctx, AVSubtitleArea *area) +{ + uint8_t gray_pal[256]; + const size_t img_size = area->buf[0]->size; + const uint8_t* img = area->buf[0]->data; + uint8_t* gs_img = av_malloc(img_size); + + if (!gs_img) + return NULL; + + for (unsigned i = 0; i < 256; i++) { + const uint8_t *col = (uint8_t*)&area->pal[i]; + const int val = (int)col[3] * FFMAX3(col[0], col[1], col[2]); + gray_pal[i] = (uint8_t)(val >> 8); + } + + for (unsigned i = 0; i < img_size; i++) + gs_img[i] = 255 - gray_pal[img[i]]; + + return gs_img; +} + +static int convert_area(AVFilterContext *ctx, AVSubtitleArea *area) +{ + SubOcrContext *s = ctx->priv; + char *ocr_text = NULL; + int ret; + uint8_t *gs_img = create_grayscale_image(ctx, area); + + if (!gs_img) + return AVERROR(ENOMEM); + + TessBaseAPISetImage(s->tapi, gs_img, area->w, area->h, 1, area->linesize[0]); + TessBaseAPISetSourceResolution(s->tapi, 70); + + ret = TessBaseAPIRecognize(s->tapi, NULL); + if (ret == 0) + ocr_text = TessBaseAPIGetUTF8Text(s->tapi); + + if (!ocr_text) { + av_log(ctx, AV_LOG_WARNING, "OCR didn't return a text. ret=%d\n", ret); + area->ass = NULL; + } + else { + const size_t len = strlen(ocr_text); + + if (len > 0 && ocr_text[len - 1] == '\n') + ocr_text[len - 1] = 0; + + av_log(ctx, AV_LOG_VERBOSE, "OCR Result: %s\n", ocr_text); + + area->ass = av_strdup(ocr_text); + + TessDeleteText(ocr_text); + } + + av_freep(&gs_img); + av_buffer_unref(&area->buf[0]); + area->type = AV_SUBTITLE_FMT_ASS; + + return 0; +} + +static int filter_frame(AVFilterLink *inlink, AVFrame *frame) +{ + AVFilterContext *ctx = inlink->dst; + SubOcrContext *s = ctx->priv; + AVFilterLink *outlink = inlink->dst->outputs[0]; + int ret, frame_sent = 0; + + if (s->pending_frame) { + const uint64_t pts_diff = frame->subtitle_pts - s->pending_frame->subtitle_pts; + s->pending_frame->subtitle_end_time = (uint32_t)(pts_diff / 1000); + + ret = ff_filter_frame(outlink, s->pending_frame); + s->pending_frame = NULL; + if (ret < 0) + return ret; + + frame_sent = 1; + + if (frame->num_subtitle_areas == 0) { + // No need to forward this empty frame + av_frame_free(&frame); + return 0; + } + } + + ret = av_frame_make_writable(frame); + + if (ret < 0) { + av_frame_free(&frame); + return ret; + } + + frame->format = AV_SUBTITLE_FMT_ASS; + + av_log(ctx, AV_LOG_DEBUG, "filter_frame sub_pts: %"PRIu64", start_time: %d, end_time: %d, num_areas: %d\n", + frame->subtitle_pts, frame->subtitle_start_time, frame->subtitle_end_time, frame->num_subtitle_areas); + + if (frame->num_subtitle_areas > 1 && + frame->subtitle_areas[0]->y > frame->subtitle_areas[frame->num_subtitle_areas - 1]->y) { + + for (unsigned i = 0; i < frame->num_subtitle_areas / 2; i++) + FFSWAP(AVSubtitleArea*, frame->subtitle_areas[i], frame->subtitle_areas[frame->num_subtitle_areas - i - 1]); + } + + for (unsigned i = 0; i < frame->num_subtitle_areas; i++) { + AVSubtitleArea *area = frame->subtitle_areas[i]; + + ret = convert_area(ctx, area); + if (ret < 0) + return ret; + + if (area->ass && area->ass[0] != '\0') { + char *tmp = area->ass; + + if (i == 0) + area->ass = ff_ass_get_dialog(s->readorder_counter++, 0, "Default", NULL, tmp); + else + area->ass = av_asprintf("\\N%s", tmp); + + av_free(tmp); + } + } + + // When decoders can't determine the end time, they are setting it either to UINT32_NAX + // or 30s (dvbsub). + if (frame->num_subtitle_areas > 0 && frame->subtitle_end_time >= 30000) { + // Can't send it without end time, wait for the next frame to determine the end_display time + s->pending_frame = frame; + + if (frame_sent) + return 0; + + // To keep all going, send an empty frame instead + frame = ff_get_subtitles_buffer(outlink, AV_SUBTITLE_FMT_ASS); + if (!frame) + return AVERROR(ENOMEM); + + av_frame_copy_props(frame, s->pending_frame); + frame->subtitle_end_time = 1; + } + + return ff_filter_frame(outlink, frame); +} + +#define OFFSET(x) offsetof(SubOcrContext, x) +#define FLAGS (AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_FILTERING_PARAM) + +static const AVOption graphicsub2text_options[] = { + { "ocr_mode", "set ocr mode", OFFSET(ocr_mode), AV_OPT_TYPE_INT, {.i64=OEM_TESSERACT_ONLY}, OEM_TESSERACT_ONLY, 2, FLAGS, "ocr_mode" }, + { "tesseract", "classic tesseract ocr", 0, AV_OPT_TYPE_CONST, {.i64=OEM_TESSERACT_ONLY}, 0, 0, FLAGS, "ocr_mode" }, + { "lstm", "lstm (ML based)", 0, AV_OPT_TYPE_CONST, {.i64=OEM_LSTM_ONLY}, 0, 0, FLAGS, "ocr_mode" }, + { "both", "use both models combined", 0, AV_OPT_TYPE_CONST, {.i64=OEM_TESSERACT_LSTM_COMBINED}, 0, 0, FLAGS, "ocr_mode" }, + { "tessdata_path", "path to tesseract data", OFFSET(tessdata_path), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, FLAGS, NULL }, + { "language", "ocr language", OFFSET(language), AV_OPT_TYPE_STRING, {.str = "eng"}, 0, 0, FLAGS, NULL }, + { NULL }, +}; + +AVFILTER_DEFINE_CLASS(graphicsub2text); + +static const AVFilterPad inputs[] = { + { + .name = "default", + .type = AVMEDIA_TYPE_SUBTITLE, + .filter_frame = filter_frame, + .config_props = config_input, + }, +}; + +static const AVFilterPad outputs[] = { + { + .name = "default", + .type = AVMEDIA_TYPE_SUBTITLE, + .config_props = config_output, + }, +}; + +const AVFilter ff_sf_graphicsub2text = { + .name = "graphicsub2text", + .description = NULL_IF_CONFIG_SMALL("Convert graphical subtitles to text subtitles via OCR"), + .init = init, + .uninit = uninit, + .query_formats = query_formats, + .priv_size = sizeof(SubOcrContext), + .priv_class = &graphicsub2text_class, + FILTER_INPUTS(inputs), + FILTER_OUTPUTS(outputs), +};