gstreamer/sys/ipcpipeline/protocol.txt

93 lines
3.4 KiB
Text
Raw Normal View History

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