gstreamer/gst/mpeg4videoparse/mpeg4parse.c

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2011-05-12 10:07:39 +00:00
/* GStreamer MPEG4-2 video Parser
* Copyright (C) <2008> Mindfruit B.V.
* @author Sjoerd Simons <sjoerd@luon.net>
* Copyright (C) <2007> Julien Moutte <julien@fluendo.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., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include "mpeg4parse.h"
#include <gst/base/gstbitreader.h>
GST_DEBUG_CATEGORY_EXTERN (mpeg4v_parse_debug);
#define GST_CAT_DEFAULT mpeg4v_parse_debug
#define GET_BITS(b, num, bits) G_STMT_START { \
if (!gst_bit_reader_get_bits_uint32(b, bits, num)) \
goto failed; \
GST_TRACE ("parsed %d bits: %d", num, *(bits)); \
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} G_STMT_END
#define MARKER_BIT(b) G_STMT_START { \
guint32 i; \
GET_BITS(b, 1, &i); \
if (i != 0x1) \
goto failed; \
} G_STMT_END
static inline gboolean
next_start_code (GstBitReader * b)
{
guint32 bits;
GET_BITS (b, 1, &bits);
if (bits != 0)
goto failed;
while (b->bit != 0) {
GET_BITS (b, 1, &bits);
if (bits != 0x1)
goto failed;
}
return TRUE;
failed:
return FALSE;
}
static inline gboolean
skip_user_data (GstBitReader * bs, guint32 * bits)
{
while (*bits == MPEG4_USER_DATA_STARTCODE_MARKER) {
guint32 b;
do {
GET_BITS (bs, 8, &b);
*bits = (*bits << 8) | b;
} while ((*bits >> 8) != MPEG4_START_MARKER);
}
return TRUE;
failed:
return FALSE;
}
static gint aspect_ratio_table[6][2] = {
{-1, -1}, {1, 1}, {12, 11}, {10, 11}, {16, 11}, {40, 33}
};
static gboolean
gst_mpeg4_params_parse_vo (MPEG4Params * params, GstBitReader * br)
{
guint32 bits;
guint16 time_increment_resolution = 0;
guint16 fixed_time_increment = 0;
gint aspect_ratio_width = -1, aspect_ratio_height = -1;
gint height = -1, width = -1;
/* expecting a video object startcode */
GET_BITS (br, 32, &bits);
if (bits > 0x11F)
goto failed;
/* expecting a video object layer startcode */
GET_BITS (br, 32, &bits);
if (bits < 0x120 || bits > 0x12F)
goto failed;
/* ignore random accessible vol and video object type indication */
GET_BITS (br, 9, &bits);
GET_BITS (br, 1, &bits);
if (bits) {
/* skip video object layer verid and priority */
GET_BITS (br, 7, &bits);
}
/* aspect ratio info */
GET_BITS (br, 4, &bits);
if (bits == 0)
goto failed;
/* check if aspect ratio info is extended par */
if (bits == 0xf) {
GET_BITS (br, 8, &bits);
aspect_ratio_width = bits;
GET_BITS (br, 8, &bits);
aspect_ratio_height = bits;
} else if (bits < 0x6) {
aspect_ratio_width = aspect_ratio_table[bits][0];
aspect_ratio_height = aspect_ratio_table[bits][1];
}
GST_DEBUG ("aspect ratio %d/%d", aspect_ratio_width, aspect_ratio_height);
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GET_BITS (br, 1, &bits);
if (bits) {
/* vol control parameters, skip chroma and low delay */
GET_BITS (br, 3, &bits);
GET_BITS (br, 1, &bits);
if (bits) {
/* skip vbv_parameters */
GET_BITS (br, 79, &bits);
}
}
/* layer shape */
GET_BITS (br, 2, &bits);
/* only support rectangular */
if (bits != 0)
goto failed;
MARKER_BIT (br);
GET_BITS (br, 16, &bits);
time_increment_resolution = bits;
MARKER_BIT (br);
GST_DEBUG ("time increment resolution %d", time_increment_resolution);
GET_BITS (br, 1, &bits);
if (bits) {
/* fixed time increment */
int n;
/* Length of the time increment is the minimal number of bits needed to
* represent time_increment_resolution */
for (n = 0; (time_increment_resolution >> n) != 0; n++);
GET_BITS (br, n, &bits);
fixed_time_increment = bits;
} else {
/* When fixed_vop_rate is not set we can't guess any framerate */
fixed_time_increment = 0;
}
GST_DEBUG ("fixed time increment %d", fixed_time_increment);
/* assuming rectangular shape */
MARKER_BIT (br);
GET_BITS (br, 13, &bits);
width = bits;
MARKER_BIT (br);
GET_BITS (br, 13, &bits);
height = bits;
MARKER_BIT (br);
GST_DEBUG ("width x height: %d x %d", width, height);
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/* so we got it all, report back */
params->width = width;
params->height = height;
params->time_increment_resolution = time_increment_resolution;
params->fixed_time_increment = fixed_time_increment;
params->aspect_ratio_width = aspect_ratio_width;
params->aspect_ratio_height = aspect_ratio_height;
return TRUE;
/* ERRORS */
failed:
{
GST_WARNING ("Failed to parse config data");
return FALSE;
}
}
static gboolean
gst_mpeg4_params_parse_vos (MPEG4Params * params, GstBitReader * br)
{
guint32 bits;
GET_BITS (br, 32, &bits);
if (bits != MPEG4_VOS_STARTCODE_MARKER)
goto failed;
GET_BITS (br, 8, &bits);
params->profile = bits;
/* invalid profile, warn but carry on */
if (params->profile == 0) {
GST_WARNING ("Invalid profile in VOS");
}
/* Expect Visual Object startcode */
GET_BITS (br, 32, &bits);
/* but skip optional user data */
if (!skip_user_data (br, &bits))
goto failed;
if (bits != MPEG4_VISUAL_OBJECT_STARTCODE_MARKER)
goto failed;
GET_BITS (br, 1, &bits);
if (bits == 0x1) {
/* Skip visual_object_verid and priority */
GET_BITS (br, 7, &bits);
}
GET_BITS (br, 4, &bits);
/* Only support video ID */
if (bits != 0x1)
goto failed;
/* video signal type */
GET_BITS (br, 1, &bits);
if (bits == 0x1) {
/* video signal type, ignore format and range */
GET_BITS (br, 4, &bits);
GET_BITS (br, 1, &bits);
if (bits == 0x1) {
/* ignore color description */
GET_BITS (br, 24, &bits);
}
}
if (!next_start_code (br))
goto failed;
/* skip optional user data */
GET_BITS (br, 32, &bits);
if (!skip_user_data (br, &bits))
goto failed;
/* rewind to start code */
gst_bit_reader_set_pos (br, gst_bit_reader_get_pos (br) - 32);
return gst_mpeg4_params_parse_vo (params, br);
/* ERRORS */
failed:
{
GST_WARNING ("Failed to parse config data");
return FALSE;
}
}
gboolean
gst_mpeg4_params_parse_config (MPEG4Params * params, const guint8 * data,
guint size)
{
GstBitReader br;
if (size < 4)
return FALSE;
gst_bit_reader_init (&br, data, size);
if (data[3] == MPEG4_VOS_STARTCODE)
return gst_mpeg4_params_parse_vos (params, &br);
else
return gst_mpeg4_params_parse_vo (params, &br);
}