1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
|
/* $Id: demuxmpeg.c,v 1.4 2004/10/19 23:11:36 titer Exp $
This file is part of the HandBrake source code.
Homepage: <http://handbrake.fr/>.
It may be used under the terms of the GNU General Public License. */
#include "hb.h"
/* Basic MPEG demuxer, only works with DVDs (2048 bytes packets) */
int hb_demux_ps( hb_buffer_t * buf_ps, hb_list_t * list_es, hb_psdemux_t* state )
{
hb_buffer_t * buf_es;
int pos = 0;
#define d (buf_ps->data)
/* pack_header */
if( d[pos] != 0 || d[pos+1] != 0 ||
d[pos+2] != 0x1 || d[pos+3] != 0xBA )
{
hb_log( "hb_demux_ps: not a PS packet (%02x%02x%02x%02x)",
d[pos], d[pos+1], d[pos+2], d[pos+3] );
return 0;
}
pos += 4; /* pack_start_code */
if ( state )
{
/*
* This section of code implements the timing model of
* the "Standard Target Decoder" (STD) of the MPEG2 standard
* (specified in ISO 13818-1 sections 2.4.2, 2.5.2 & Annex D).
* The STD removes and corrects for clock discontinuities so
* that the time stamps on the video, audio & other media
* streams can be used for cross-media synchronization. To do
* this the STD has its own timestamp value, the System Clock
* Reference or SCR, in the PACK header. Clock discontinuities
* are detected using the SCR & and the adjustment needed
* to correct post-discontinuity timestamps to be contiguous
* with pre-discontinuity timestamps is computed from pre- and
* post-discontinuity values of the SCR. Then this adjustment
* is applied to every media timestamp (PTS).
*
* ISO 13818-1 says there must be an SCR at least every 700ms
* (100ms for Transport Streams) so if the difference between
* this SCR & the previous is >700ms it's a discontinuity.
* If the difference is negative it's non-physical (time doesn't
* go backward) and must also be a discontinuity. When we find a
* discontinuity we adjust the scr_offset so that the SCR of the
* new packet lines up with that of the previous packet.
*/
/* extract the system clock reference (scr) */
int64_t scr = ((uint64_t)(d[pos] & 0x38) << 27) |
((uint64_t)(d[pos] & 0x03) << 28) |
((uint64_t)(d[pos+1]) << 20) |
((uint64_t)(d[pos+2] >> 3) << 15) |
((uint64_t)(d[pos+2] & 3) << 13) |
((uint64_t)(d[pos+3]) << 5) |
(d[pos+4] >> 3);
int64_t scr_delta = scr - state->last_scr;
if ( scr_delta > (90*700) || scr_delta < 0 )
{
++state->scr_changes;
state->scr_offset += scr_delta - 1;
}
state->last_scr = scr;
}
pos += 9; /* pack_header */
pos += 1 + ( d[pos] & 0x7 ); /* stuffing bytes */
/* system_header */
if( d[pos] == 0 && d[pos+1] == 0 &&
d[pos+2] == 0x1 && d[pos+3] == 0xBB )
{
int header_length;
pos += 4; /* system_header_start_code */
header_length = ( d[pos] << 8 ) + d[pos+1];
pos += 2 + header_length;
}
/* pes */
while( pos + 6 < buf_ps->size &&
d[pos] == 0 && d[pos+1] == 0 && d[pos+2] == 0x1 )
{
int id;
int pes_packet_length;
int pes_packet_end;
int pes_header_d_length;
int pes_header_end;
int has_pts;
int64_t pts = -1;
pos += 3; /* packet_start_code_prefix */
id = d[pos];
pos += 1;
pes_packet_length = ( d[pos] << 8 ) + d[pos+1];
pos += 2; /* pes_packet_length */
pes_packet_end = pos + pes_packet_length;
if( id != 0xE0 && id != 0xBD &&
( id & 0xC0 ) != 0xC0 )
{
/* Not interesting */
pos = pes_packet_end;
continue;
}
has_pts = ( ( d[pos+1] >> 6 ) & 0x2 ) ? 1 : 0;
pos += 2; /* Required headers */
pes_header_d_length = d[pos];
pos += 1;
pes_header_end = pos + pes_header_d_length;
if( has_pts )
{
pts = ( ( ( (uint64_t) d[pos] >> 1 ) & 0x7 ) << 30 ) +
( d[pos+1] << 22 ) +
( ( d[pos+2] >> 1 ) << 15 ) +
( d[pos+3] << 7 ) +
( d[pos+4] >> 1 );
}
pos = pes_header_end;
if( id == 0xBD )
{
id |= ( d[pos] << 8 );
if( ( id & 0xF0FF ) == 0x80BD ) /* A52 */
{
pos += 4;
}
else if( ( id & 0xE0FF ) == 0x20BD || /* SPU */
( id & 0xF0FF ) == 0xA0BD ) /* LPCM */
{
pos += 1;
}
}
/* Sanity check */
if( pos >= pes_packet_end )
{
pos = pes_packet_end;
continue;
}
/* Here we hit we ES payload */
buf_es = hb_buffer_init( pes_packet_end - pos );
buf_es->id = id;
buf_es->start = pts;
buf_es->stop = -1;
if (id == 0xE0) {
// Consume a chapter break, and apply it to the ES.
buf_es->new_chap = buf_ps->new_chap;
buf_ps->new_chap = 0;
}
memcpy( buf_es->data, d + pos, pes_packet_end - pos );
hb_list_add( list_es, buf_es );
pos = pes_packet_end;
}
#undef d
return 1;
}
|
