gstreamer/subprojects/gst-plugins-good/gst/isomp4/qtdemux-webvtt.c

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/* GStreamer
* Copyright (C) 2008 Thijs Vermeir <thijsvermeir@gmail.com>
* Copyright (C) 2011 David Schleef <ds@schleef.org>
* Copyright (C) 2021 Jan Schmidt <jan@centricular.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "qtdemux-webvtt.h"
#include <gst/base/gstbytereader.h>
#include "fourcc.h"
#include "qtdemux.h"
#include "qtatomparser.h"
#include <stdlib.h>
#include <string.h>
GST_DEBUG_CATEGORY_EXTERN (qtdemux_debug);
#define GST_CAT_DEFAULT qtdemux_debug
gboolean
qtdemux_webvtt_is_empty (GstQTDemux * demux, guint8 * data, gsize size)
{
GstByteReader br;
guint32 atom_size;
guint32 atom_type;
gst_byte_reader_init (&br, data, size);
if (gst_byte_reader_get_remaining (&br) < 8)
return FALSE;
if (!gst_byte_reader_get_uint32_be (&br, &atom_size) ||
!qt_atom_parser_get_fourcc (&br, &atom_type))
return FALSE;
if (atom_type == FOURCC_vtte)
return TRUE;
return FALSE;
}
struct WebvttCue
{
const guint8 *cue_id;
guint32 cue_id_len;
const guint8 *cue_time;
guint32 cue_time_len;
const guint8 *settings;
guint32 settings_len;
const guint8 *cue_text;
guint32 cue_text_len;
};
static void
webvtt_append_timestamp_to_string (GstClockTime timestamp, GString * str)
{
guint h, m, s, ms;
h = timestamp / (3600 * GST_SECOND);
timestamp -= h * 3600 * GST_SECOND;
m = timestamp / (60 * GST_SECOND);
timestamp -= m * 60 * GST_SECOND;
s = timestamp / GST_SECOND;
timestamp -= s * GST_SECOND;
ms = timestamp / GST_MSECOND;
g_string_append_printf (str, "%02d:%02d:%02d.%03d", h, m, s, ms);
}
static gboolean
webvtt_decode_vttc (GstQTDemux * qtdemux, GstByteReader * br,
GstClockTime start, GstClockTime duration, GString * s)
{
struct WebvttCue cue = { 0, };
gboolean have_data = FALSE;
while (gst_byte_reader_get_remaining (br) >= 8) {
guint32 atom_size;
guint32 atom_type;
guint next_pos;
if (!gst_byte_reader_get_uint32_be (br, &atom_size) ||
!qt_atom_parser_get_fourcc (br, &atom_type))
break;
if (gst_byte_reader_get_remaining (br) < atom_size - 8)
break;
next_pos = gst_byte_reader_get_pos (br) - 8 + atom_size;
GST_LOG_OBJECT (qtdemux, "WebVTT cue atom %" GST_FOURCC_FORMAT " len %u",
GST_FOURCC_ARGS (atom_type), atom_size);
switch (atom_type) {
case FOURCC_ctim:
if (!gst_byte_reader_get_data (br, atom_size - 8, &cue.cue_time))
return FALSE;
cue.cue_time_len = atom_size - 8;
break;
case FOURCC_iden:
if (!gst_byte_reader_get_data (br, atom_size - 8, &cue.cue_id))
return FALSE;
cue.cue_id_len = atom_size - 8;
break;
case FOURCC_sttg:
if (!gst_byte_reader_get_data (br, atom_size - 8, &cue.settings))
return FALSE;
cue.settings_len = atom_size - 8;
break;
case FOURCC_payl:
if (!gst_byte_reader_get_data (br, atom_size - 8, &cue.cue_text))
return FALSE;
cue.cue_text_len = atom_size - 8;
have_data = TRUE;
break;
}
if (!gst_byte_reader_set_pos (br, next_pos))
break;
}
if (have_data) {
if (cue.cue_id)
g_string_append_printf (s, "%.*s\n", cue.cue_id_len, cue.cue_id);
/* Write the cue time and optional settings */
webvtt_append_timestamp_to_string (start, s);
g_string_append_printf (s, " --> ");
webvtt_append_timestamp_to_string (start + duration, s);
if (cue.settings)
g_string_append_printf (s, " %.*s\n", cue.settings_len, cue.settings);
else
g_string_append (s, "\n");
g_string_append_printf (s, "%.*s\n\n", cue.cue_text_len, cue.cue_text);
}
return have_data;
}
GstBuffer *
qtdemux_webvtt_decode (GstQTDemux * qtdemux, GstClockTime start,
GstClockTime duration, guint8 * data, gsize size)
{
GstByteReader br;
GString *str = NULL;
GstBuffer *buf = NULL;
gst_byte_reader_init (&br, data, size);
while (gst_byte_reader_get_remaining (&br) >= 8) {
guint32 atom_size;
guint32 atom_type;
guint next_pos;
if (!gst_byte_reader_get_uint32_be (&br, &atom_size) ||
!qt_atom_parser_get_fourcc (&br, &atom_type))
break;
if (gst_byte_reader_get_remaining (&br) < atom_size - 8)
break;
next_pos = gst_byte_reader_get_pos (&br) - 8 + atom_size;
switch (atom_type) {
case FOURCC_vttc:
GST_LOG_OBJECT (qtdemux,
"WebVTT cue atom %" GST_FOURCC_FORMAT " len %u",
GST_FOURCC_ARGS (atom_type), atom_size);
if (str == NULL)
str = g_string_new (NULL);
if (!webvtt_decode_vttc (qtdemux, &br, start, duration, str))
break;
break;
case FOURCC_vtte:
/* The empty segment case should be handled separately using qtdemux_webvtt_is_empty().
* Ignore it during decode */
break;
case FOURCC_vtta:
/* extra attributes */
break;
default:
GST_DEBUG_OBJECT (qtdemux,
"Unknown WebVTT sample atom %" GST_FOURCC_FORMAT,
GST_FOURCC_ARGS (atom_type));
break;
}
if (!gst_byte_reader_set_pos (&br, next_pos))
break;
}
if (str) {
gsize webvtt_len = str->len;
gchar *webvtt_chunk = g_string_free (str, FALSE);
buf = gst_buffer_new_wrapped (webvtt_chunk, webvtt_len);
}
return buf;
}