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
|
This documents the protocol used to pass data over fds between ipcpipelinesrc
and ipcpipelinesink.
The protocol is used in both directions. However, some combinations do
not make sense (eg, a buffer going from ipcpipelinesrc to ipcpipelinesink).
The protocol consists of an arbitrary number of variable sized chunks
with a type. Each chunk has a request ID which can be used to match a
request with its reply (ack / query result).
Each chunk consists of:
- a type (byte):
1: ack
2: query result
3: buffer
4: event
5: sink message event
6: query
7: state change
8: state lost
9: message
10: error/warning/info message
- a request ID, 4 bytes, little endian
- the payload size, 4 bytes, little endian
- N bytes payload
Depending on the type, the payload can contain:
- 1: ack
result: 4 bytes, little endian
interpreted as GstFlowReturn for buffers, boolean for events and
GstStateChangeReturn for state changes
- 2: query result
result boolean: 1 byte
query type: 4 bytes, little endian
returned query string representation, NUL terminated
- 3: buffer:
pts: 8 bytes, little endian
dts: 8 bytes, little endian
duration: 8 bytes, little endian
offset: 8 bytes, little endian
offset end: 8 bytes, little endian
flags: 8 bytes, little endian
buffer size: 4 bytes, little endian
data: contents of the buffer data, size specified in "buffer size"
number of GstMeta: 4 bytes, little endian
For each GstMeta:
bytes: 4 bytes, little endian
this is the number of bytes before the string representation
at the end of this block, including the 4 bytes of itself
flags: 4 bytes, little endian
length of the GstMetaInfo::api name: 4 bytes, little endian
GstMetaInfo::api name: string, NUL terminated
GstMetaInfo::size: 8 bytes, little endian
length of the string representation: 4 bytes, little endian
string representation, NUL terminated
- 4: event
event type: 4 bytes, little endian
sequence number: 4 bytes, little endian
direction: 1 byte
whether the event is going upstream (1) or downstream (0)
string representation, NUL terminated
- 5: sink message event
message type: 4 bytes, little endian
event sequence number: 4 bytes, little endian
message sequence number: 4 bytes, little endian
length: 4 bytes, little endian
event structure name: length bytes, NUL terminated
message structure string representation: remaining bytes, NUL terminated
- 6: query
query type: 4 bytes, little endian
direction: 1 byte
whether the query is going upstream (1) or downstream (0)
string representation, NUL terminated
- 7: state change
GstStateChange: 4 bytes, little endian
- 8: state lost
no payload
- 9: message
message type: 4 bytes, little endian
string representation, NUL terminated
- 10: error/warning/info message
message type (2 = error, 1 = warning, 0 = info): 1 byte
error domain string length: 4 bytes, little endian
string representation of the error domain, NUL terminated
error code: 4 bytes, little endian
length: 4 bytes, little endian
if zero: no error message
if non zero: As many bytes as this length: the error message, NUL terminated
length: 4 bytes, little endian
if zero: no extra message
if non zero: As many bytes as this length: the error extra debug message, NUL terminated
|
