Segment

class Segment(**kwargs)

This helper structure holds the relevant values for tracking the region of interest in a media file, called a segment.

The structure can be used for two purposes:

performing seeks (handling seek events)

tracking playback regions (handling newsegment events)

The segment is usually configured by the application with a seek event which is propagated upstream and eventually handled by an element that performs the seek.

The configured segment is then propagated back downstream with a newsegment event. This information is then used to clip media to the segment boundaries.

A segment structure is initialized with init(), which takes a Format that will be used as the format of the segment values. The segment will be configured with a start value of 0 and a stop/duration of -1, which is undefined. The default rate and applied_rate is 1.0.

The public duration field contains the duration of the segment. When using the segment for seeking, the start and time members should normally be left to their default 0 value. The stop position is left to -1 unless explicitly configured to a different value after a seek event.

The current position in the segment should be set by changing the position member in the structure.

For elements that perform seeks, the current segment should be updated with the do_seek() and the values from the seek event. This method will update all the segment fields. The position field will contain the new playback position. If the start_type was different from GST_SEEK_TYPE_NONE, playback continues from the position position, possibly with updated flags or rate.

For elements that want to use Segment to track the playback region, update the segment fields with the information from the newsegment event. The clip() method can be used to check and clip the media data to the segment boundaries.

For elements that want to synchronize to the pipeline clock, to_running_time() can be used to convert a timestamp to a value that can be used to synchronize to the clock. This function takes into account the base as well as any rate or applied_rate conversions.

For elements that need to perform operations on media data in stream_time, to_stream_time() can be used to convert a timestamp and the segment info to stream time (which is always between 0 and the duration of the stream).

Constructors

class Segment

classmethod new() → Segment

Allocate a new Segment structure and initialize it using init().

Free-function: gst_segment_free

Methods

class Segment

clip(format: Format, start: int, stop: int) → tuple[bool, int, int]

Clip the given start and stop values to the segment boundaries given in segment. start and stop are compared and clipped to segment start and stop values.

If the function returns False, start and stop are known to fall outside of segment and clip_start and clip_stop are not updated.

When the function returns True, clip_start and clip_stop will be updated. If clip_start or clip_stop are different from start or stop respectively, the region fell partially in the segment.

Note that when stop is -1, clip_stop will be set to the end of the segment. Depending on the use case, this may or may not be what you want.

Parameters:

format – the format of the segment.
start – the start position in the segment
stop – the stop position in the segment

do_seek(rate: float, format: Format, flags: SeekFlags, start_type: SeekType, start: int, stop_type: SeekType, stop: int) → tuple[bool, bool]

Update the segment structure with the field values of a seek event (see new_seek()).

After calling this method, the segment field position and time will contain the requested new position in the segment. The new requested position in the segment depends on rate and start_type and stop_type.

For positive rate, the new position in the segment is the new segment start field when it was updated with a start_type different from GST_SEEK_TYPE_NONE. If no update was performed on segment start position (GST_SEEK_TYPE_NONE), start is ignored and segment position is unmodified.

For negative rate, the new position in the segment is the new segment stop field when it was updated with a stop_type different from GST_SEEK_TYPE_NONE. If no stop was previously configured in the segment, the duration of the segment will be used to update the stop position. If no update was performed on segment stop position (GST_SEEK_TYPE_NONE), stop is ignored and segment position is unmodified.

The applied rate of the segment will be set to 1.0 by default. If the caller can apply a rate change, it should update segment rate and applied_rate after calling this function.

update will be set to True if a seek should be performed to the segment position field. This field can be False if, for example, only the rate has been changed but not the playback position.

Parameters:

rate – the rate of the segment.
format – the format of the segment.
flags – the segment flags for the segment
start_type – the seek method
start – the seek start value
stop_type – the seek method
stop – the seek stop value

free() → None: Free the allocated segment segment.

init(format: Format) → None

The start/position fields are set to 0 and the stop/duration fields are set to -1 (unknown). The default rate of 1.0 and no flags are set.

Initialize segment to its default values.

Parameters:: format – the format of the segment.

is_equal(s1: Segment) → bool

Checks for two segments being equal. Equality here is defined as perfect equality, including floating point values.

Added in version 1.6.

Parameters:: s1 – a Segment structure.

offset_running_time(format: Format, offset: int) → bool

Adjust the values in segment so that offset is applied to all future running-time calculations.

Added in version 1.2.3.

Parameters:

format – the format of the segment.
offset – the offset to apply in the segment

position_from_running_time(format: Format, running_time: int) → int

Convert running_time into a position in the segment so that to_running_time() with that position returns running_time.

Added in version 1.8.

Parameters:

format – the format of the segment.
running_time – the running_time in the segment

position_from_running_time_full(format: Format, running_time: int) → tuple[int, int]

Translate running_time to the segment position using the currently configured segment. Compared to position_from_running_time() this function can return negative segment position.

This function is typically used by elements that need to synchronize buffers against the clock or each other.

running_time can be any value and the result of this function for values outside of the segment is extrapolated.

When 1 is returned, running_time resulted in a positive position returned in position.

When this function returns -1, the returned position was < 0, and the value in the position variable should be negated to get the real negative segment position.

Added in version 1.8.

Parameters:

format – the format of the segment.
running_time – the running-time

position_from_stream_time(format: Format, stream_time: int) → int

Convert stream_time into a position in the segment so that to_stream_time() with that position returns stream_time.

Added in version 1.8.

Parameters:

format – the format of the segment.
stream_time – the stream_time in the segment

position_from_stream_time_full(format: Format, stream_time: int) → tuple[int, int]

Translate stream_time to the segment position using the currently configured segment. Compared to position_from_stream_time() this function can return negative segment position.

This function is typically used by elements that need to synchronize buffers against the clock or each other.

stream_time can be any value and the result of this function for values outside of the segment is extrapolated.

When 1 is returned, stream_time resulted in a positive position returned in position.

When this function returns -1, the returned position should be negated to get the real negative segment position.

Added in version 1.8.

Parameters:

format – the format of the segment.
stream_time – the stream-time

set_running_time(format: Format, running_time: int) → bool

Adjust the start/stop and base values of segment such that the next valid buffer will be one with running_time.

Parameters:

format – the format of the segment.
running_time – the running_time in the segment

to_position(format: Format, running_time: int) → int

Convert running_time into a position in the segment so that to_running_time() with that position returns running_time.

Deprecated since version Unknown: Use position_from_running_time() instead.

Parameters:

format – the format of the segment.
running_time – the running_time in the segment

to_running_time(format: Format, position: int) → int

Translate position to the total running time using the currently configured segment. Position is a value between segment start and stop time.

This function is typically used by elements that need to synchronize to the global clock in a pipeline. The running time is a constantly increasing value starting from 0. When init() is called, this value will reset to 0.

This function returns -1 if the position is outside of segment start and stop.

Parameters:

format – the format of the segment.
position – the position in the segment

to_running_time_full(format: Format, position: int) → tuple[int, int]

Translate position to the total running time using the currently configured segment. Compared to to_running_time() this function can return negative running-time.

This function is typically used by elements that need to synchronize buffers against the clock or each other.

position can be any value and the result of this function for values outside of the segment is extrapolated.

When 1 is returned, position resulted in a positive running-time returned in running_time.

When this function returns -1, the returned running_time should be negated to get the real negative running time.

Added in version 1.6.

Parameters:

format – the format of the segment.
position – the position in the segment

to_stream_time(format: Format, position: int) → int

Translate position to stream time using the currently configured segment. The position value must be between segment start and stop value.

This function is typically used by elements that need to operate on the stream time of the buffers it receives, such as effect plugins. In those use cases, position is typically the buffer timestamp or clock time that one wants to convert to the stream time. The stream time is always between 0 and the total duration of the media stream.

Added in version 1.8.

Parameters:

format – the format of the segment.
position – the position in the segment

to_stream_time_full(format: Format, position: int) → tuple[int, int]

Translate position to the total stream time using the currently configured segment. Compared to to_stream_time() this function can return negative stream-time.

This function is typically used by elements that need to synchronize buffers against the clock or each other.

position can be any value and the result of this function for values outside of the segment is extrapolated.

When 1 is returned, position resulted in a positive stream-time returned in stream_time.

When this function returns -1, the returned stream_time should be negated to get the real negative stream time.

Added in version 1.8.

Parameters:

format – the format of the segment.
position – the position in the segment

Fields

class Segment

applied_rate: The applied rate is the rate that has been applied to the stream. The effective/resulting playback rate of a stream is rate * applied_rate. The applied rate can be set by source elements when a server is sending the stream with an already modified playback speed rate. Filter elements that modify the stream in a way that modifies the playback speed should also modify the applied rate. For example the videorate element when its videorate:rate property is set will set the applied rate of the segment it pushed downstream. Also scaletempo applies the input segment rate to the stream and outputs a segment with rate=1.0 and applied_rate=<inputsegment.rate>.

base: The running time (plus elapsed time, see offset) of the segment start (stop if rate < 0.0).

duration: The duration of the segment is the maximum absolute difference between Segment.start and Segment.stop if stop is not set, otherwise it should be the difference between those two values. This should be set by elements that know the overall stream duration (like demuxers) and will be used when seeking with GST_SEEK_TYPE_END.

flags: Flags for this segment

format: The unit used for all of the segment’s values.

offset: The offset expresses the elapsed time (in buffer timestamps) before a seek with its start (stop if rate < 0.0) seek type set to GST_SEEK_TYPE_NONE, the value is set to the position of the segment at the time of the seek.

position: The buffer timestamp position in the segment is supposed to be updated by elements such as sources, demuxers or parsers to track progress by setting it to the last pushed buffer’ end time (timestamp + Buffer.duration) for that specific segment. The position is used when reconfiguring the segment with gst_segment_do_seek when the seek is only updating the segment (see offset).

rate: The playback rate of the segment is set in response to a seek event and, without any seek, the value should be 1.0. This value is used by elements that synchronize buffer [running times](additional/design/synchronisation.md#running-time) on the clock (usually the sink elements), leading to consuming buffers faster (for a value > 1.0) or slower (for 0.0 < value < 1.0) than normal playback speed. The rate also defines the playback direction, meaning that when the value is lower than 0.0, the playback happens in reverse, and the stream-time is going backward. The rate value should never be 0.0.

start: The start time of the segment (in buffer timestamps) (PTS), that is the timestamp of the first buffer to output inside the segment (last one during reverse playback). For example decoders will clip out the buffers before the start time.

stop: The stop time of the segment (in buffer timestamps) (PTS), that is the timestamp of the last buffer to output inside the segment (first one during reverse playback). For example decoders will clip out buffers after the stop time.

time: The stream time of the segment start (stop if rate < 0.0).