[FFmpeg-devel] [PATCH] avcodec/webvttenc: add webvtt encoder
ffmpeg at tmm1.net
ffmpeg at tmm1.net
Sun May 11 23:38:49 CEST 2014
From: Aman Gupta <ffmpeg at tmm1.net>
Mostly a copy of the srt encoder in libavcodec/srtenc.c.
The alignment and move callbacks are unimplemented, but the rest works well.
With this patch, ffmpeg can be used to convert subtitles into the .vtt format:
ffmpeg -i input.srt -c:s webvtt output.vtt
Signed-off-by: Aman Gupta <ffmpeg at tmm1.net>
---
Changelog | 1 +
libavcodec/Makefile | 1 +
libavcodec/allcodecs.c | 2 +-
libavcodec/webvttenc.c | 255 +++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 258 insertions(+), 1 deletion(-)
create mode 100644 libavcodec/webvttenc.c
diff --git a/Changelog b/Changelog
index 8d61c9d..611a2ad 100644
--- a/Changelog
+++ b/Changelog
@@ -22,6 +22,7 @@ version <next>:
- On2 AVC (Audio for Video) decoder
- support for decoding through DXVA2 in ffmpeg
- libbs2b-based stereo-to-binaural audio filter
+- WebVTT encoder
version 2.2:
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index d239924..fd5ae12 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -483,6 +483,7 @@ OBJS-$(CONFIG_WAVPACK_DECODER) += wavpack.o
OBJS-$(CONFIG_WAVPACK_ENCODER) += wavpackenc.o
OBJS-$(CONFIG_WEBP_DECODER) += vp8.o vp8dsp.o vp56rac.o
OBJS-$(CONFIG_WEBP_DECODER) += webp.o exif.o tiff_common.o
+OBJS-$(CONFIG_WEBVTT_ENCODER) += webvttenc.o
OBJS-$(CONFIG_WEBVTT_DECODER) += webvttdec.o
OBJS-$(CONFIG_WMALOSSLESS_DECODER) += wmalosslessdec.o wma_common.o
OBJS-$(CONFIG_WMAPRO_DECODER) += wmaprodec.o wma.o wma_common.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index a1cd44e..ce40308 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -493,7 +493,7 @@ void avcodec_register_all(void)
REGISTER_DECODER(SUBVIEWER1, subviewer1);
REGISTER_DECODER(TEXT, text);
REGISTER_DECODER(VPLAYER, vplayer);
- REGISTER_DECODER(WEBVTT, webvtt);
+ REGISTER_ENCDEC(WEBVTT, webvtt);
REGISTER_ENCDEC (XSUB, xsub);
/* external libraries */
diff --git a/libavcodec/webvttenc.c b/libavcodec/webvttenc.c
new file mode 100644
index 0000000..5099e78
--- /dev/null
+++ b/libavcodec/webvttenc.c
@@ -0,0 +1,255 @@
+/*
+ * WebVTT subtitle encoder
+ * Copyright (c) 2014 Aman Gupta <aman at tmm1.net>
+ *
+ * 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
+ */
+
+#include <stdarg.h>
+#include "avcodec.h"
+#include "libavutil/avstring.h"
+#include "libavutil/bprint.h"
+#include "ass_split.h"
+#include "ass.h"
+
+#define WEBVTT_STACK_SIZE 64
+typedef struct {
+ AVCodecContext *avctx;
+ ASSSplitContext *ass_ctx;
+ AVBPrint buffer;
+ unsigned timestamp_end;
+ int count;
+ char stack[WEBVTT_STACK_SIZE];
+ int stack_ptr;
+} WebVTTContext;
+
+#ifdef __GNUC__
+__attribute__ ((__format__ (__printf__, 2, 3)))
+#endif
+static void webvtt_print(WebVTTContext *s, const char *str, ...)
+{
+ va_list vargs;
+ va_start(vargs, str);
+ av_vbprintf(&s->buffer, str, vargs);
+ va_end(vargs);
+}
+
+static char webvtt_stack_push(WebVTTContext *s, char c)
+{
+ if (s->stack_ptr >= WEBVTT_STACK_SIZE)
+ return -1;
+ s->stack[s->stack_ptr++] = c;
+ return 0;
+}
+
+static char webvtt_stack_pop(WebVTTContext *s)
+{
+ if (s->stack_ptr <= 0)
+ return 0;
+ return s->stack[--s->stack_ptr];
+}
+
+static int webvtt_stack_find(WebVTTContext *s, const char c)
+{
+ int i;
+ for (i = s->stack_ptr-1; i >= 0; i--)
+ if (s->stack[i] == c)
+ break;
+ return i;
+}
+
+static void webvtt_close_tag(WebVTTContext *s, char tag)
+{
+ webvtt_print(s, "</%c%s>", tag, tag == 'f' ? "ont" : "");
+}
+
+static void webvtt_stack_push_pop(WebVTTContext *s, const char c, int close)
+{
+ if (close) {
+ int i = c ? webvtt_stack_find(s, c) : 0;
+ if (i < 0)
+ return;
+ while (s->stack_ptr != i)
+ webvtt_close_tag(s, webvtt_stack_pop(s));
+ } else if (webvtt_stack_push(s, c) < 0)
+ av_log(s->avctx, AV_LOG_ERROR, "tag stack overflow\n");
+}
+
+static void webvtt_style_apply(WebVTTContext *s, const char *style)
+{
+ ASSStyle *st = ff_ass_style_get(s->ass_ctx, style);
+ if (st) {
+ int c = st->primary_color & 0xFFFFFF;
+ if (st->font_name && strcmp(st->font_name, ASS_DEFAULT_FONT) ||
+ st->font_size != ASS_DEFAULT_FONT_SIZE ||
+ c != ASS_DEFAULT_COLOR) {
+ webvtt_print(s, "<font");
+ if (st->font_name && strcmp(st->font_name, ASS_DEFAULT_FONT))
+ webvtt_print(s, " face=\"%s\"", st->font_name);
+ if (st->font_size != ASS_DEFAULT_FONT_SIZE)
+ webvtt_print(s, " size=\"%d\"", st->font_size);
+ if (c != ASS_DEFAULT_COLOR)
+ webvtt_print(s, " color=\"#%06x\"",
+ (c & 0xFF0000) >> 16 | c & 0xFF00 | (c & 0xFF) << 16);
+ webvtt_print(s, ">");
+ webvtt_stack_push(s, 'f');
+ }
+ if (st->bold != ASS_DEFAULT_BOLD) {
+ webvtt_print(s, "<b>");
+ webvtt_stack_push(s, 'b');
+ }
+ if (st->italic != ASS_DEFAULT_ITALIC) {
+ webvtt_print(s, "<i>");
+ webvtt_stack_push(s, 'i');
+ }
+ if (st->underline != ASS_DEFAULT_UNDERLINE) {
+ webvtt_print(s, "<u>");
+ webvtt_stack_push(s, 'u');
+ }
+ }
+}
+
+static void webvtt_text_cb(void *priv, const char *text, int len)
+{
+ WebVTTContext *s = priv;
+ av_bprint_append_data(&s->buffer, text, len);
+}
+
+static void webvtt_new_line_cb(void *priv, int forced)
+{
+ webvtt_print(priv, "\r\n");
+}
+
+static void webvtt_style_cb(void *priv, char style, int close)
+{
+ webvtt_stack_push_pop(priv, style, close);
+ if (!close)
+ webvtt_print(priv, "<%c>", style);
+}
+
+static void webvtt_color_cb(void *priv, unsigned int color, unsigned int color_id)
+{
+ if (color_id > 1)
+ return;
+ webvtt_stack_push_pop(priv, 'f', color == 0xFFFFFFFF);
+ if (color != 0xFFFFFFFF)
+ webvtt_print(priv, "<font color=\"#%06x\">",
+ (color & 0xFF0000) >> 16 | color & 0xFF00 | (color & 0xFF) << 16);
+}
+
+static void webvtt_font_name_cb(void *priv, const char *name)
+{
+ webvtt_stack_push_pop(priv, 'f', !name);
+ if (name)
+ webvtt_print(priv, "<font face=\"%s\">", name);
+}
+
+static void webvtt_font_size_cb(void *priv, int size)
+{
+ webvtt_stack_push_pop(priv, 'f', size < 0);
+ if (size >= 0)
+ webvtt_print(priv, "<font size=\"%d\">", size);
+}
+
+static void webvtt_cancel_overrides_cb(void *priv, const char *style)
+{
+ webvtt_stack_push_pop(priv, 0, 1);
+ webvtt_style_apply(priv, style);
+}
+
+static void webvtt_end_cb(void *priv)
+{
+ webvtt_stack_push_pop(priv, 0, 1);
+}
+
+static const ASSCodesCallbacks webvtt_callbacks = {
+ .text = webvtt_text_cb,
+ .new_line = webvtt_new_line_cb,
+ .style = webvtt_style_cb,
+ .color = webvtt_color_cb,
+ .font_name = webvtt_font_name_cb,
+ .font_size = webvtt_font_size_cb,
+ .alignment = NULL,
+ .cancel_overrides = webvtt_cancel_overrides_cb,
+ .move = NULL,
+ .end = webvtt_end_cb,
+};
+
+static int webvtt_encode_frame(AVCodecContext *avctx,
+ unsigned char *buf, int bufsize, const AVSubtitle *sub)
+{
+ WebVTTContext *s = avctx->priv_data;
+ ASSDialog *dialog;
+ int i, num;
+
+ av_bprint_clear(&s->buffer);
+
+ for (i=0; i<sub->num_rects; i++) {
+
+ if (sub->rects[i]->type != SUBTITLE_ASS) {
+ av_log(avctx, AV_LOG_ERROR, "Only SUBTITLE_ASS type supported.\n");
+ return AVERROR(ENOSYS);
+ }
+
+ dialog = ff_ass_split_dialog(s->ass_ctx, sub->rects[i]->ass, 0, &num);
+ for (; dialog && num--; dialog++) {
+ webvtt_style_apply(s, dialog->style);
+ ff_ass_split_override_codes(&webvtt_callbacks, s, dialog->text);
+ }
+ }
+
+ if (!av_bprint_is_complete(&s->buffer))
+ return AVERROR(ENOMEM);
+ if (!s->buffer.len)
+ return 0;
+
+ if (s->buffer.len > bufsize) {
+ av_log(avctx, AV_LOG_ERROR, "Buffer too small for ASS event.\n");
+ return -1;
+ }
+ memcpy(buf, s->buffer.str, s->buffer.len);
+
+ return s->buffer.len;
+}
+
+static int webvtt_encode_close(AVCodecContext *avctx)
+{
+ WebVTTContext *s = avctx->priv_data;
+ ff_ass_split_free(s->ass_ctx);
+ av_bprint_finalize(&s->buffer, NULL);
+ return 0;
+}
+
+static av_cold int webvtt_encode_init(AVCodecContext *avctx)
+{
+ WebVTTContext *s = avctx->priv_data;
+ s->avctx = avctx;
+ s->ass_ctx = ff_ass_split(avctx->subtitle_header);
+ av_bprint_init(&s->buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
+ return s->ass_ctx ? 0 : AVERROR_INVALIDDATA;
+}
+
+AVCodec ff_webvtt_encoder = {
+ .name = "webvtt",
+ .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
+ .type = AVMEDIA_TYPE_SUBTITLE,
+ .id = AV_CODEC_ID_WEBVTT,
+ .priv_data_size = sizeof(WebVTTContext),
+ .init = webvtt_encode_init,
+ .encode_sub = webvtt_encode_frame,
+ .close = webvtt_encode_close,
+};
--
1.9.1
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