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
173
174
175
176
177
|
Quick-and-dirty documentation for libmpeg2 0.3.1
Kees Cook <mpeg2@outflux.net>
2003-04-25
Basic Usage Pseudocode
----------------------
if (you need a certain acceleration)
mpeg2_accel(desired_acceleration);
handle=mpeg2_init();
info=mpeg2_info(handle);
while (data_available) {
state=mpeg2_parse(handle);
switch (state) {
case -1:
read some data
mpeg2_buffer(handle,data_start,data_end);
break;
case STATE_SLICE:
case STATE_END:
display the frame described in "info"
break;
case STATE_INVALID:
abort
break;
}
}
mpeg2_close(handle);
Basic Usage Explained
---------------------
libmpeg2 uses an opaque pointer which is the active "handle" to the mpeg2
decoder. To get this handle (of type "mpeg2dec_t"), call "mpeg2_init()".
Data is loaded into the decoder with "mpeg2_buffer" whenever "mpeg2_parse"
is ready for more data (return state is -1). Pictures are available whenever
"mpeg2_parse"'s return state is STATE_SLICE or STATE_END.
This means the *previous* picture is available, right? In other
words, when STATE_SLICE is seen, that means that the *previous*
picture is all done. Same thing for STATE_END. So if you want to
see one frame at a time (without starting to fill the mpeg2 decoder
with more data not from that picture) we'd have to inject something
to make it report STATE_END?
Basic Function Reference
------------------------
mpeg2dec_t * mpeg2_init()
Initializes a memory space for mpeg2 decoding. This memory must
be freed with a call to "mpeg2_close" when finished.
Returns NULL on error (when system is out of memory)
- Doesn't check if chunk_buffer is NULL?
uint32_t mpeg2_accel(uint32_t accel)
Sets the CPU acceleration type to be used for all decoders for the
life of the program. YOU CAN SAFELY IGNORE THIS FUNCTION.
By default, a call to mpeg2_accel is not needed, since the best
available acceleration will be auto-detected. To override the
default, this function must be called before any calls to
"mpeg2_init". See mpeg2.h for a list of the available accelerations
(prefix "MPEG2_ACCEL_...").
After a call to mpeg2_init, mpeg2_accel can be called to find out
what the selected acceleration list is. Once the accelerations have
been selected (through explicitly requesting one, or through
auto-detection) the "accel" parameter will be ignored.
Returns selected acceleration list. If the requested acceleration
is not available, the function will auto-detect the best available
accelerations and return that instead.
- Cannot be undone! This should maybe be a part of
the mpeg2 structure somehow?
const mpeg2_info_t * mpeg2_info(mpeg2dec_t * handle)
Gets structure for the mpeg2 decoder's "mpeg2_info_t" structure.
This will let you do something (like display!) the decoded pictures
with the mpeg2_info_t structure members:
display_fbuf:
memory area containing the rendered picture information.
If this is NULL, no frame is available.
display_fbuf->buf:
YUV coded pixel data for the picture.
display_picture:
data structure describing the current picture.
see mpeg2.h for more details.
sequence:
data structure describing the entire current picture sequence:
width: picture width in pixels.
height: picture height in pixels.
see mpeg2.h for more details.
user_data:
handy place to attach things needed by your program. Must
be detached before calling "mpeg2_close".
there are more...check mpeg2.h
int mpeg2_parse(mpeg2dec_t * handle)
Parses available data and returns state of the decoder:
-1:
ready for more data. decoder has finished reading
the buffer sent with mpeg2_buffer.
STATE_SEQUENCE:
A sequence header has been found.
STATE_SEQUENCE_REPEATED:
A repeated sequence header has been found and processed.
STATE_GOP:
A GOP has been found.
STATE_PICTURE:
A picture header has been found.
STATE_PICTURE_2ND:
A second field picture header has been found.
STATE_SLICE_1ST:
First slice of a multi-field picture has been found.
STATE_SLICE:
Final slice (multi-field or not) of a picture has been found.
Good time to update the display.
STATE_END:
End of the stream? Good time to update the display.
STATE_INVALID:
Filled the internal buffers without finding any start codes.
Cannot continue: mpeg2_close must be called next.
void mpeg2_buffer(mpeg2dec_t * handle, uint8_t * start, uint8_t * end)
Makes data between "start" and "end" available for processing.
If a subsequent call to "mpeg2_parse" doesn't find anything useful
(returns -1) then this data will be copied into the mpeg2 decoder's
private data area. This process repeats until something useful is
found with mpeg2_parse (returns something other than -1), or the
buffer fills up.
void mpeg2_close(mpeg2dec_t * handle)
Cleans up the memory associated with the mpeg2 decoder handle.
- does not check for NULL frees! (via mpeg2_free)
Advanced Function Reference
---------------------------
mpeg2_convert
mpeg2_set_buf
mpeg2_custom_fbuf
mpeg2_init_fbuf
mpeg2_slice
|
