lavc: add raw text subtitles decoder.

1 files changed, 125 insertions, 0 deletions

diff --git a/libavcodec/textdec.c b/libavcodec/textdec.c
new file mode 100644
index 0000000..4b3a4ad
--- /dev/null
+++ b/libavcodec/textdec.c
@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2012 Clément Bœsch
+ *
+ * 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
+ * Raw subtitles decoder
+ */
+
+#include "avcodec.h"
+#include "ass.h"
+#include "libavutil/bprint.h"
+#include "libavutil/opt.h"
+
+typedef struct {
+    AVClass *class;
+    char *linebreaks;
+    int keep_ass_markup;
+} TextContext;
+
+#define OFFSET(x) offsetof(TextContext, x)
+#define SD AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_DECODING_PARAM
+static const AVOption options[] = {
+    { "linebreaks",      "Extra line breaks characters",    OFFSET(linebreaks),      AV_OPT_TYPE_STRING, {.str=NULL},    .flags=SD },
+    { "keep_ass_markup", "Set if ASS tags must be escaped", OFFSET(keep_ass_markup), AV_OPT_TYPE_INT,    {.i64=0}, 0, 1, .flags=SD },
+    { NULL }
+};
+
+static const AVClass text_decoder_class = {
+    .class_name = "text decoder",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+static int text_event_to_ass(const AVCodecContext *avctx, AVBPrint *buf,
+                             const char *p, const char *p_end)
+{
+    const TextContext *text = avctx->priv_data;
+
+    for (; p < p_end && *p; p++) {
+
+        /* forced custom line breaks, not accounted as "normal" EOL */
+        if (text->linebreaks && strchr(text->linebreaks, *p)) {
+            av_bprintf(buf, "\\N");
+
+        /* standard ASS escaping so random characters don't get mis-interpreted
+         * as ASS */
+        } else if (!text->keep_ass_markup && strchr("{}\\", *p)) {
+            av_bprintf(buf, "\\%c", *p);
+
+        /* some packets might end abruptly (no \0 at the end, like for example
+         * in some cases of demuxing from a classic video container), some
+         * might be terminated with \n or \r\n which we have to remove (for
+         * consistency with those who haven't), and we also have to deal with
+         * evil cases such as \r at the end of the buffer (and no \0 terminated
+         * character) */
+        } else if (p[0] == '\n') {
+            /* some stuff left so we can insert a line break */
+            if (p < p_end - 1)
+                av_bprintf(buf, "\\N");
+        } else if (p[0] == '\r' && p < p_end - 1 && p[1] == '\n') {
+            /* \r followed by a \n, we can skip it. We don't insert the \N yet
+             * because we don't know if it is followed by more text */
+            continue;
+
+        /* finally, a sane character */
+        } else {
+            av_bprint_chars(buf, *p, 1);
+        }
+    }
+    av_bprintf(buf, "\r\n");
+    return 0;
+}
+
+static int text_decode_frame(AVCodecContext *avctx, void *data,
+                             int *got_sub_ptr, AVPacket *avpkt)
+{
+    AVBPrint buf;
+    AVSubtitle *sub = data;
+    const char *ptr = avpkt->data;
+    const int ts_start     = av_rescale_q(avpkt->pts,      avctx->time_base, (AVRational){1,100});
+    const int ts_duration  = avpkt->duration != -1 ?
+                             av_rescale_q(avpkt->duration, avctx->time_base, (AVRational){1,100}) : -1;
+
+    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
+    if (ptr && avpkt->size > 0 && *ptr &&
+        !text_event_to_ass(avctx, &buf, ptr, ptr + avpkt->size)) {
+        if (!av_bprint_is_complete(&buf)) {
+            av_bprint_finalize(&buf, NULL);
+            return AVERROR(ENOMEM);
+        }
+        ff_ass_add_rect(sub, buf.str, ts_start, ts_duration, 0);
+    }
+    *got_sub_ptr = sub->num_rects > 0;
+    av_bprint_finalize(&buf, NULL);
+    return avpkt->size;
+}
+
+AVCodec ff_text_decoder = {
+    .name           = "text",
+    .priv_data_size = sizeof(TextContext),
+    .long_name      = NULL_IF_CONFIG_SMALL("Raw text subtitle"),
+    .type           = AVMEDIA_TYPE_SUBTITLE,
+    .id             = AV_CODEC_ID_TEXT,
+    .decode         = text_decode_frame,
+    .init           = ff_ass_subtitle_header_default,
+    .priv_class     = &text_decoder_class,
+};