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io: add offset for clock times

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Add an offset to apply to the clock time before we can compare to the
segment values. This way we can keep the segment start independent of the
clock values and we only need to adjust the offset when paused. It's
like the base_time in GStreamer to calculate the running time.
This commit is contained in:
Wim Taymans 2019-08-28 10:28:06 +02:00
parent 2805713da3
commit 0a15e1f804
4 changed files with 31 additions and 19 deletions
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34
spa/include/spa/node/io.h
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@ -136,20 +136,20 @@ struct spa_io_segment_video {
};
/**
* A segment converts a raw clock time to a segment (stream) position.
* A segment converts a running time to a segment (stream) position.
*
* The segment position is valid when the current clock position is between
* The segment position is valid when the current running time is between
* start and start + duration. The position is then
* calculated as:
*
* (start - clock.position) * rate + position;
* (running time - start) * rate + position;
*
* Support for looping is done by specifying a non-zero duration. When the
* clock reaches start + duration, duration is added to start and the
* loop repeats.
* Support for looping is done by specifying the LOOPING flags with a
* non-zero duration. When the running time reaches start + duration,
* duration is added to start and the loop repeats.
*
* Care has to be taken when the clock.duration extends past the
* start + duration from the segment; the user should correctly
* Care has to be taken when the running time + clock.duration extends
* past the start + duration from the segment; the user should correctly
* wrap around and partially repeat the loop in the current cycle.
*
* Extra information can be placed in the segment by setting the valid flags
@ -162,15 +162,16 @@ struct spa_io_segment {
#define SPA_IO_SEGMENT_VALID_BAR (1<<1)
#define SPA_IO_SEGMENT_VALID_VIDEO (1<<2)
uint32_t valid; /**< indicates what fields are valid below */
uint64_t start; /**< position against clock position when this
uint64_t start; /**< value of running time when this
* info is active. Can be in the future for
* pending changes. It does not have to be in
* exact multiples of the clock duration. */
uint64_t duration; /**< duration when this info becomes invalid. If
* the duration is 0, this segment extends to the
* next segment. If the segment becomes invalid and
* the looping flag is set, the segment is repeats. */
uint64_t position; /**< The position when the clock == start. */
uint64_t duration; /**< duration when this info becomes invalid expressed
* in running time. If the duration is 0, this
* segment extends to the next segment. If the
* segment becomes invalid and the looping flag is
* set, the segment repeats. */
uint64_t position; /**< The position when the running time == start. */
double rate; /**< overal rate of the graph, can be negative for
* backwards time reporting. */
@ -202,6 +203,11 @@ enum spa_io_position_state {
struct spa_io_position {
struct spa_io_clock clock; /**< clock position of driver, always valid and
* read only */
int64_t offset; /**< an offset to subtract from the clock position
* to get a running time. This is the time that
* the state has been in the RUNNING state and the
* time that should be used to compare the segment
* start values against. */
uint32_t state; /**< one of enum spa_io_position_state */
uint32_t n_segments; /**< number of segments */