mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-07-10 16:45:55 +00:00
a1cde30977
Original commit message from CVS: * docs/design/part-TODO.txt: * docs/design/part-segments.txt: * docs/design/part-streams.txt: Small updates.
69 lines
2 KiB
Plaintext
69 lines
2 KiB
Plaintext
Streams
|
|
-------
|
|
|
|
This document describes the objects that are passed from element to
|
|
element in the streaming thread.
|
|
|
|
|
|
Stream objects
|
|
--------------
|
|
|
|
The following objects are to be expected in the streaming thread:
|
|
|
|
- events
|
|
- NEW_SEGMENT (NS)
|
|
- EOS (EOS) *
|
|
- TAG (T)
|
|
- buffers (B) *
|
|
|
|
Objects marked with * need to be synchronised to the clock in sinks
|
|
and live sources.
|
|
|
|
|
|
Typical stream
|
|
--------------
|
|
|
|
A typical stream starts with a newsegment event that marks the
|
|
buffer timestamp range. After that buffers are send one after the
|
|
other. After the last buffer an EOS marks the end of the stream. No
|
|
more buffer are to be processed after the EOS event.
|
|
|
|
+--+ +-++-+ +-+ +---+
|
|
|NS| |B||B| ... |B| |EOS|
|
|
+--+ +-++-+ +-+ +---+
|
|
|
|
1) NEW_SEGMENT, rate, start/stop, time
|
|
- marks valid buffer timestamp range (start, stop)
|
|
- marks stream_time of buffers (time). This is the stream time of buffers
|
|
with a timestamp of NS.start.
|
|
- marks playback rate (rate). This is the required playback rate.
|
|
- marks applied rate (applied_rate). This is the already applied playback
|
|
rate. (See also part-trickmodes.txt)
|
|
|
|
2) N buffers
|
|
- displayable buffers are between start/stop of the NEW_SEGMENT. Buffers
|
|
outside the segment range should be dropped or clipped.
|
|
|
|
- running_time:
|
|
|
|
if (NS.rate > 0.0)
|
|
running_time = (B.timestamp - NS.start) / NS.abs_rate + NS.accum
|
|
else
|
|
running_time = (NS.stop - B.timestamp) / NS.abs_rate + NS.accum
|
|
|
|
* a monotonically increasing value that can be used to synchronize
|
|
against the clock (See also part-synchronisation.txt).
|
|
|
|
- stream_time:
|
|
|
|
stream_time = (B.timestamp - NS.start) * NS.abs_applied_rate + NS.time
|
|
|
|
* current position in stream between 0 and duration.
|
|
|
|
3) EOS
|
|
- marks the end of data, nothing is to be expected after EOS, elements
|
|
should refuse more data and return GST_FLOW_UNEXPECTED. A FLUSH_STOP
|
|
event clears the EOS state of an element.
|
|
|
|
|