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stream: update the docs a little

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Give some more information about the delay field and how it can be
negative.
This commit is contained in:
Wim Taymans 2025-07-23 12:46:45 +02:00
parent d2a9141913
commit c54d3764b2
1 changed files with 18 additions and 12 deletions
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30
src/pipewire/stream.h
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@ -273,7 +273,7 @@ struct pw_buffer {
uint64_t time; /**< For capture streams, this field contains the
* cycle time in nanoseconds when this buffer was
* queued in the stream. It can be compared against
* the pw_time values or pw_stream_get_nsec()
* the \ref pw_time values or pw_stream_get_nsec()
* Since 1.0.5 */
};
@ -311,15 +311,20 @@ struct pw_stream_control {
*
* pw_time.delay contains the total delay that a signal will travel through the
* graph. This includes the delay caused by filters in the graph as well as delays
* caused by the hardware. The delay is usually quite stable and should only change when
* the topology, quantum or samplerate of the graph changes.
* caused by the hardware and extra delay offsets added to this. The delay is usually
* quite stable and should only change when the topology, quantum or samplerate of
* the graph changes.
*
* The delay requires the application to send the stream early relative to other synchronized
* streams in order to arrive at the edge of the graph in time. This is usually done by
* delaying the other streams with the given delay.
* The (positive) delay requires the application to send the stream early relative to other
* synchronized streams in order to arrive at the edge of the graph in time. This is usually
* done by delaying the other streams with the given delay.
*
* Note that the delay can be negative. A negative delay means that this stream should be
* delayed with the (positive) delay relative to other streams.
* A delay offset is sometimes added (by the user) to improve synchronization of the streams
* when the reported latency is incorrect in some way. This means that with a large enough
* negative offset, the delay can become negative as well. A negative delay in this context
* means that the user would like this stream to be delayed with the (positive) delay amount
* in order to synchronize it with other streams. Streams are in general not expected to be
* able to delay themselves and it is acceptable to clamp negative delays to 0.
*
* pw_time.queued and pw_time.buffered is expressed in the time domain of the stream,
* or the format that is used for the buffers of this stream.
@ -385,10 +390,11 @@ struct pw_time {
* the playback device or the time a sample traveled
* from the capture device. This delay includes the
* delay introduced by all filters on the path between
* the stream and the device. The delay is normally
* constant in a graph and can change when the topology
* of the graph or the quantum changes. This delay does
* not include the delay caused by queued buffers. */
* the stream and the device and extra delay offsets. The
* delay is normally constant in a graph and can change when
* the topology of the graph or the quantum changes. This delay
* does not include the delay caused by queued buffers.
* The delay can be negative, see \ref pw_time . */
uint64_t queued; /**< data queued in the stream, this is the sum
* of the size fields in the pw_buffer that are
* currently queued */