gstreamer/gst/mpegtsdemux/payload_parsers.c

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/*
* payload_parsers.c
* Copyright (C) 2011 Janne Grunau
*
* Authors:
* Janne Grunau <janne.grunau@collabora.co.uk>
*
* 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.
*/
#include "payload_parsers.h"
#include <gst/base/gstbitreader.h>
#define PICTURE_START_CODE 0x00000100
#define GROUP_START_CODE 0x000001B8
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#define SLICE_NAL_UNIT_TYPE 0x01
#define SLICE_IDR_NAL_UNIT_TYPE 0x05
#define SEI_NAL_UNIT_TYPE 0x06
#define SEI_TYPE_RECOVERY_POINT 0x06
typedef struct Mpeg2PictureHeader
{
guint16 temporal_reference;
guint8 picture_coding_type;
guint16 vbv_delay;
/* picture_coding_type == 2 || picture_coding_type */
guint8 full_pel_forward_vector;
guint8 forward_f_code;
/* picture_coding_type == 3 */
guint8 full_pel_backward_vector;
guint8 backward_f_code;
} Mpeg2PictureHeader;
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/* shortened slice header */
typedef struct H264SliceHeader
{
guint32 first_mb_in_slice;
guint8 slice_type;
} H264SliceHeader;
static guint8 *
find_start_code (guint32 * start_code, guint8 * buffer, guint8 * buffer_end)
{
if (G_UNLIKELY (buffer == NULL) || G_UNLIKELY (buffer_end == NULL)
|| G_UNLIKELY (start_code == NULL))
return NULL;
while (buffer <= buffer_end) {
*start_code <<= 8;
*start_code |= *buffer++;
if ((*start_code & 0xffffff00) == 0x00000100)
return buffer;
}
return NULL;
}
static gboolean
parse_mpeg2_picture_header (Mpeg2PictureHeader * hdr, guint8 * buffer,
guint8 * buffer_end)
{
GstBitReader br = GST_BIT_READER_INIT (buffer, buffer_end - buffer);
if (gst_bit_reader_get_remaining (&br) < 40)
return FALSE;
hdr->temporal_reference = gst_bit_reader_get_bits_uint16_unchecked (&br, 10);
hdr->picture_coding_type = gst_bit_reader_get_bits_uint8_unchecked (&br, 3);
hdr->vbv_delay = gst_bit_reader_get_bits_uint16_unchecked (&br, 16);
if (hdr->picture_coding_type == 2 || hdr->picture_coding_type == 3) {
hdr->full_pel_forward_vector =
gst_bit_reader_get_bits_uint8_unchecked (&br, 1);
hdr->forward_f_code = gst_bit_reader_get_bits_uint8_unchecked (&br, 3);
}
if (hdr->picture_coding_type == 3) {
hdr->full_pel_backward_vector =
gst_bit_reader_get_bits_uint8_unchecked (&br, 1);
hdr->backward_f_code = gst_bit_reader_get_bits_uint8_unchecked (&br, 3);
}
return TRUE;
}
gboolean
gst_tsdemux_has_mpeg2_keyframe (guint32 * state,
MpegTSPacketizerPacket * packet, gboolean * need_more)
{
guint8 *data = packet->payload;
guint8 *data_end = packet->data_end;
GST_LOG ("state: 0x%08x", *state);
while (data <= data_end) {
data = find_start_code (state, data, data_end);
if (!data)
return FALSE;
GST_LOG ("found start code: 0x%08x", *state);
if (*state == GROUP_START_CODE) {
GST_DEBUG ("found group start code");
*state = 0xffffffff;
*need_more = FALSE;
return TRUE;
} else if (*state == PICTURE_START_CODE) {
Mpeg2PictureHeader hdr = { 0 };
gboolean success;
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success = parse_mpeg2_picture_header (&hdr, data, data_end);
GST_DEBUG ("found picture start code, %sparsed, picture coding type: %d",
success ? "" : "not ", hdr.picture_coding_type);
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*state = 0xffffffff;
*need_more = FALSE;
return success && hdr.picture_coding_type == 1;
}
}
return FALSE;
}
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/* variable length Exp-Golomb parsing according to H.264 spec 9.1*/
static gboolean
read_golomb (GstBitReader * br, guint32 * value)
{
guint8 b, leading_zeros = -1;
*value = 1;
for (b = 0; !b; leading_zeros++) {
if (!gst_bit_reader_get_bits_uint8 (br, &b, 1))
return FALSE;
*value *= 2;
}
*value = (*value >> 1) - 1;
if (leading_zeros > 0) {
guint32 tmp = 0;
if (!gst_bit_reader_get_bits_uint32 (br, &tmp, leading_zeros))
return FALSE;
*value += tmp;
}
return TRUE;
}
/* just parse the requirred bits of the slice header */
static gboolean
parse_h264_slice_header (H264SliceHeader * hdr, guint8 * buffer,
guint8 * buffer_end)
{
guint32 value;
GstBitReader br = GST_BIT_READER_INIT (buffer, buffer_end - buffer);
if (!read_golomb (&br, &value))
return FALSE;
hdr->first_mb_in_slice = value;
if (!read_golomb (&br, &value))
return FALSE;
hdr->slice_type = value;
return TRUE;
}
enum H264SliceTypes
{
h264_p_slice = 0,
h264_b_slice,
h264_i_slice,
h264_sp_slice,
h264_si_slice,
h264_p_slice_a,
h264_b_slice_a,
h264_i_slice_a,
h264_sp_slice_a,
h264_si_slice_a,
};
static gboolean
is_key_slice (guint8 slice_type)
{
switch (slice_type) {
case h264_i_slice:
case h264_si_slice:
case h264_i_slice_a:
case h264_si_slice_a:
return TRUE;
}
return FALSE;
}
gboolean
gst_tsdemux_has_h264_keyframe (guint32 * state, MpegTSPacketizerPacket * packet,
gboolean * need_more)
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{
guint8 *data = packet->payload;
guint8 *data_end = packet->data_end;
GST_LOG ("state: 0x%08x", *state);
while (data <= data_end) {
guint8 nal_unit_type;
guint8 *next_data = NULL;
data = find_start_code (state, data, data_end);
if (!data)
goto beach;
GST_LOG ("found start code: 0x%08x", *state);
/* determine length */
nal_unit_type = *state & 0x1f;
next_data = find_start_code (state, data, data_end);
if (nal_unit_type == SEI_NAL_UNIT_TYPE && !next_data) {
GST_WARNING ("NAL unit 0x%02x not completely in ts packet",
nal_unit_type);
goto beach;
}
next_data -= 4;
switch (nal_unit_type) {
case SLICE_IDR_NAL_UNIT_TYPE:
GST_DEBUG ("found SLICE_IDR NAL unit type");
*state = 0xffffffff;
*need_more = FALSE;
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return TRUE;
case SLICE_NAL_UNIT_TYPE:
{
H264SliceHeader hdr = { 0 };
gboolean success;
success = parse_h264_slice_header (&hdr, data, data_end);
GST_DEBUG ("found SLICE NAL unit type with slice type %d",
hdr.slice_type);
*state = 0xffffffff;
*need_more = FALSE;
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return success && is_key_slice (hdr.slice_type);
}
case SEI_NAL_UNIT_TYPE:
{
guint32 recovery_frame_count;
GstBitReader br = GST_BIT_READER_INIT (data, next_data - data);
break;
/* SEI message is at least 24 bit long */
while (gst_bit_reader_get_remaining (&br) >= 24) {
gint type = 0, size = 0;
guint8 tmp = 0;
do {
if (!gst_bit_reader_get_bits_uint8 (&br, &tmp, 8))
goto beach;
type += tmp;
} while (tmp == 255);
do {
if (!gst_bit_reader_get_bits_uint8 (&br, &tmp, 8))
goto beach;
size += tmp;
} while (tmp == 255);
GST_LOG ("found SEI msg type: %d, len: %d", type, size);
switch (type) {
case SEI_TYPE_RECOVERY_POINT:
if (!read_golomb (&br, &recovery_frame_count))
return FALSE;
gst_bit_reader_skip (&br, 1); /* exact_match */
gst_bit_reader_skip (&br, 1); /* broken_link_flag */
gst_bit_reader_skip (&br, 2); /* changing_slice_group_idc */
GST_DEBUG ("found SEI with recovery point message, "
"recovery_frame_count: %d", recovery_frame_count);
return TRUE;
default:
/* skip all other sei messages */
gst_bit_reader_skip (&br, size * 8);
}
}
}
data = next_data;
*state = 0xffffffff;
}
}
beach:
return FALSE;
}