Struct gstreamer_base::BaseParse

source · [−]

#[repr(transparent)]
pub struct BaseParse { /* private fields */ }

Expand description

This base class is for parser elements that process data and splits it into separate audio/video/whatever frames.

It provides for:

provides one sink pad and one source pad
handles state changes
can operate in pull mode or push mode
handles seeking in both modes
handles events (SEGMENT/EOS/FLUSH)
handles queries (POSITION/DURATION/SEEKING/FORMAT/CONVERT)
handles flushing

The purpose of this base class is to provide the basic functionality of a parser and share a lot of rather complex code.

Description of the parsing mechanism:

Set-up phase

BaseParse calls GstBaseParseClass::start to inform subclass that data processing is about to start now.
BaseParse class calls GstBaseParseClass::set_sink_caps to inform the subclass about incoming sinkpad caps. Subclass could already set the srcpad caps accordingly, but this might be delayed until calling BaseParseExtManual::finish_frame() with a non-queued frame.
At least at this point subclass needs to tell the BaseParse class how big data chunks it wants to receive (minimum frame size ). It can do this with BaseParseExt::set_min_frame_size().
BaseParse class sets up appropriate data passing mode (pull/push) and starts to process the data.

Parsing phase

BaseParse gathers at least min_frame_size bytes of data either by pulling it from upstream or collecting buffers in an internal Adapter.
A buffer of (at least) min_frame_size bytes is passed to subclass with GstBaseParseClass::handle_frame. Subclass checks the contents and can optionally return gst::FlowReturn::Ok along with an amount of data to be skipped to find a valid frame (which will result in a subsequent DISCONT). If, otherwise, the buffer does not hold a complete frame, GstBaseParseClass::handle_frame can merely return and will be called again when additional data is available. In push mode this amounts to an additional input buffer (thus minimal additional latency), in pull mode this amounts to some arbitrary reasonable buffer size increase.

Of course, BaseParseExt::set_min_frame_size() could also be used if a very specific known amount of additional data is required. If, however, the buffer holds a complete valid frame, it can pass the size of this frame to BaseParseExtManual::finish_frame().

If acting as a converter, it can also merely indicate consumed input data while simultaneously providing custom output data. Note that baseclass performs some processing (such as tracking overall consumed data rate versus duration) for each finished frame, but other state is only updated upon each call to GstBaseParseClass::handle_frame (such as tracking upstream input timestamp).

Subclass is also responsible for setting the buffer metadata (e.g. buffer timestamp and duration, or keyframe if applicable). (although the latter can also be done by BaseParse if it is appropriately configured, see below). Frame is provided with timestamp derived from upstream (as much as generally possible), duration obtained from configuration (see below), and offset if meaningful (in pull mode).

Note that GstBaseParseClass::handle_frame might receive any small amount of input data when leftover data is being drained (e.g. at EOS).

As part of finish frame processing, just prior to actually pushing the buffer in question, it is passed to GstBaseParseClass::pre_push_frame which gives subclass yet one last chance to examine buffer metadata, or to send some custom (tag) events, or to perform custom (segment) filtering.
During the parsing process GstBaseParseClass will handle both srcpad and sinkpad events. They will be passed to subclass if GstBaseParseClass::sink_event or GstBaseParseClass::src_event implementations have been provided.

Shutdown phase

BaseParse class calls GstBaseParseClass::stop to inform the subclass that data parsing will be stopped.

Subclass is responsible for providing pad template caps for source and sink pads. The pads need to be named “sink” and “src”. It also needs to set the fixed caps on srcpad, when the format is ensured (e.g. when base class calls subclass’ GstBaseParseClass::set_sink_caps function).

This base class uses gst::Format::Default as a meaning of frames. So, subclass conversion routine needs to know that conversion from gst::Format::Time to gst::Format::Default must return the frame number that can be found from the given byte position.

BaseParse uses subclasses conversion methods also for seeking (or otherwise uses its own default one, see also below).

Subclass start and stop functions will be called to inform the beginning and end of data processing.

Things that subclass need to take care of:

Provide pad templates
Fixate the source pad caps when appropriate
Inform base class how big data chunks should be retrieved. This is done with BaseParseExt::set_min_frame_size() function.
Examine data chunks passed to subclass with GstBaseParseClass::handle_frame and pass proper frame(s) to BaseParseExtManual::finish_frame(), and setting src pad caps and timestamps on frame.
Provide conversion functions
Update the duration information with BaseParseExtManual::set_duration()
Optionally passthrough using BaseParseExt::set_passthrough()
Configure various baseparse parameters using BaseParseExt::set_average_bitrate(), BaseParseExt::set_syncable() and BaseParseExtManual::set_frame_rate().
In particular, if subclass is unable to determine a duration, but parsing (or specs) yields a frames per seconds rate, then this can be provided to BaseParse to enable it to cater for buffer time metadata (which will be taken from upstream as much as possible). Internally keeping track of frame durations and respective sizes that have been pushed provides BaseParse with an estimated bitrate. A default GstBaseParseClass::convert (used if not overridden) will then use these rates to perform obvious conversions. These rates are also used to update (estimated) duration at regular frame intervals.

This is an Abstract Base Class, you cannot instantiate it.

Implements

BaseParseExt, gst::prelude::ElementExt, gst::prelude::ObjectExt, trait@glib::ObjectExt, BaseParseExtManual

Struct gstreamer_base::BaseParse

Implementations

impl BaseParse

pub const NONE: Option<&'static BaseParse>

Trait Implementations

impl Clone for BaseParse

fn clone(&self) -> Self

fn clone_from(&mut self, source: &Self)

impl Debug for BaseParse

fn fmt(&self, f: &mut Formatter<'_>) -> Result

impl Hash for BaseParse

fn hash<H>(&self, state: &mut H) where H: Hasher,

fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher,

impl<T: BaseParseImpl> IsSubclassable<T> for BaseParse

fn class_init(klass: &mut Class<Self>)

fn instance_init(instance: &mut InitializingObject<T>)

impl Ord for BaseParse

fn cmp(&self, other: &Self) -> Ordering

fn max(self, other: Self) -> Self

fn min(self, other: Self) -> Self

fn clamp(self, min: Self, max: Self) -> Self

impl ParentClassIs for BaseParse

type Parent = Element

impl<OT: ObjectType> PartialEq<OT> for BaseParse

fn eq(&self, other: &OT) -> bool

fn ne(&self, other: &Rhs) -> bool

impl<OT: ObjectType> PartialOrd<OT> for BaseParse

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

fn lt(&self, other: &Rhs) -> bool

fn le(&self, other: &Rhs) -> bool

fn gt(&self, other: &Rhs) -> bool

fn ge(&self, other: &Rhs) -> bool

impl StaticType for BaseParse

fn static_type() -> Type

impl Eq for BaseParse

impl IsA<Element> for BaseParse

impl IsA<Object> for BaseParse

impl Send for BaseParse

impl Sync for BaseParse

Auto Trait Implementations

impl RefUnwindSafe for BaseParse

impl Unpin for BaseParse

impl UnwindSafe for BaseParse

Blanket Implementations

impl<T> Any for T where T: 'static + ?Sized,

pub fn type_id(&self) -> TypeId

impl<T> Borrow<T> for T where T: ?Sized,

pub fn borrow(&self) -> &T

impl<T> BorrowMut<T> for T where T: ?Sized,

pub fn borrow_mut(&mut self) -> &mut T

impl<T> Cast for T where T: ObjectType,

fn upcast<T>(self) -> T where T: ObjectType, Self: IsA<T>,

fn upcast_ref<T>(&self) -> &T where T: ObjectType, Self: IsA<T>,

fn downcast<T>(self) -> Result<T, Self> where T: ObjectType, Self: CanDowncast<T>,

fn downcast_ref<T>(&self) -> Option<&T> where T: ObjectType, Self: CanDowncast<T>,

fn dynamic_cast<T>(self) -> Result<T, Self> where T: ObjectType,

fn dynamic_cast_ref<T>(&self) -> Option<&T> where T: ObjectType,

unsafe fn unsafe_cast<T>(self) -> T where T: ObjectType,

unsafe fn unsafe_cast_ref<T>(&self) -> &T where T: ObjectType,

impl<O> ElementExt for O where O: IsA<Element>,

pub fn abort_state(&self)

pub fn add_pad(&self, pad: &impl IsA<Pad>) -> Result<(), BoolError>

pub fn change_state( &self, transition: StateChange) -> Result<StateChangeSuccess, StateChangeError>

pub fn continue_state( &self, ret: impl Into<StateChangeReturn>) -> Result<StateChangeSuccess, StateChangeError>

pub fn create_all_pads(&self)

pub fn foreach_pad<P>(&self, func: P) -> bool where P: FnMut(&Element, &Pad) -> bool,

pub fn foreach_sink_pad<P>(&self, func: P) -> bool where P: FnMut(&Element, &Pad) -> bool,

pub fn foreach_src_pad<P>(&self, func: P) -> bool where P: FnMut(&Element, &Pad) -> bool,

pub fn base_time(&self) -> Option<ClockTime>

pub fn bus(&self) -> Option<Bus>

pub fn clock(&self) -> Option<Clock>

pub fn compatible_pad( &self, pad: &impl IsA<Pad>, caps: Option<&Caps>) -> Option<Pad>

pub fn compatible_pad_template( &self, compattempl: &PadTemplate) -> Option<PadTemplate>

pub fn context(&self, context_type: &str) -> Option<Context>

pub fn contexts(&self) -> Vec<Context, Global>ⓘNotable traits for Vec<u8, A>impl<A> Write for Vec<u8, A> where A: Allocator,

pub fn factory(&self) -> Option<ElementFactory>

pub fn start_time(&self) -> Option<ClockTime>

pub fn state( &self, timeout: impl Into<Option<ClockTime>>) -> (Result<StateChangeSuccess, StateChangeError>, State, State)

pub fn static_pad(&self, name: &str) -> Option<Pad>

pub fn is_locked_state(&self) -> bool

fn hash<H>(&self, state: &mut H) where
H: Hasher,

fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,

impl<T> Any for T where
T: 'static + ?Sized,

impl<T> Borrow<T> for T where
T: ?Sized,

impl<T> BorrowMut<T> for T where
T: ?Sized,

impl<T> Cast for T where
T: ObjectType,

fn upcast<T>(self) -> T where
T: ObjectType,
Self: IsA<T>,

fn upcast_ref<T>(&self) -> &T where
T: ObjectType,
Self: IsA<T>,

fn downcast<T>(self) -> Result<T, Self> where
T: ObjectType,
Self: CanDowncast<T>,

fn downcast_ref<T>(&self) -> Option<&T> where
T: ObjectType,
Self: CanDowncast<T>,

fn dynamic_cast<T>(self) -> Result<T, Self> where
T: ObjectType,

fn dynamic_cast_ref<T>(&self) -> Option<&T> where
T: ObjectType,

unsafe fn unsafe_cast<T>(self) -> T where
T: ObjectType,

unsafe fn unsafe_cast_ref<T>(&self) -> &T where
T: ObjectType,

impl<O> ElementExt for O where
O: IsA<Element>,

pub fn change_state(
&self,
transition: StateChange
) -> Result<StateChangeSuccess, StateChangeError>

pub fn continue_state(
&self,
ret: impl Into<StateChangeReturn>
) -> Result<StateChangeSuccess, StateChangeError>

pub fn foreach_pad<P>(&self, func: P) -> bool where
P: FnMut(&Element, &Pad) -> bool,

pub fn foreach_sink_pad<P>(&self, func: P) -> bool where
P: FnMut(&Element, &Pad) -> bool,

pub fn foreach_src_pad<P>(&self, func: P) -> bool where
P: FnMut(&Element, &Pad) -> bool,

pub fn compatible_pad(
&self,
pad: &impl IsA<Pad>,
caps: Option<&Caps>
) -> Option<Pad>

pub fn compatible_pad_template(
&self,
compattempl: &PadTemplate
) -> Option<PadTemplate>

pub fn contexts(&self) -> Vec<Context, Global>ⓘ
Notable traits for Vec<u8, A>
`impl<A> Write for Vec<u8, A> where A: Allocator,`

pub fn state(
&self,
timeout: impl Into<Option<ClockTime>>
) -> (Result<StateChangeSuccess, StateChangeError>, State, State )

pub fn link_filtered(
&self,
dest: &impl IsA<Element>,
filter: &Caps
) -> Result<(), BoolError>

pub fn link_pads(
&self,
srcpadname: Option<&str>,
dest: &impl IsA<Element>,
destpadname: Option<&str>
) -> Result<(), BoolError>

pub fn link_pads_filtered(
&self,
srcpadname: Option<&str>,
dest: &impl IsA<Element>,
destpadname: Option<&str>,
filter: &Caps
) -> Result<(), BoolError>

pub fn link_pads_full(
&self,
srcpadname: Option<&str>,
dest: &impl IsA<Element>,
destpadname: Option<&str>,
flags: PadLinkCheck
) -> Result<(), BoolError>

pub fn request_pad(
&self,
templ: &PadTemplate,
name: Option<&str>,
caps: Option<&Caps>
) -> Option<Pad>

pub fn set_clock(
&self,
clock: Option<&impl IsA<Clock>>
) -> Result<(), BoolError>

pub fn set_state(
&self,
state: State
) -> Result<StateChangeSuccess, StateChangeError>

pub fn unlink_pads(
&self,
srcpadname: &str,
dest: &impl IsA<Element>,
destpadname: &str
)

pub fn connect_no_more_pads<F>(&self, f: F) -> SignalHandlerId where
F: 'static + Fn(&O) + Send + Sync,

pub fn connect_pad_added<F>(&self, f: F) -> SignalHandlerId where
F: 'static + Fn(&O, &Pad) + Send + Sync,

pub fn connect_pad_removed<F>(&self, f: F) -> SignalHandlerId where
F: 'static + Fn(&O, &Pad) + Send + Sync,

impl<O> ElementExtManual for O where
O: IsA<Element>,

pub fn pad_template_list(&self) -> Vec<PadTemplate, Global>ⓘ
Notable traits for Vec<u8, A>
`impl<A> Write for Vec<u8, A> where A: Allocator,`

pub fn message_full<T>(
&self,
type_: ElementMessageType,
code: T,
message: Option<&str>,
debug: Option<&str>,
file: &str,
function: &str,
line: u32
) where
T: MessageErrorDomain,

pub fn message_full_with_details<T>(
&self,
type_: ElementMessageType,
code: T,
message: Option<&str>,
debug: Option<&str>,
file: &str,
function: &str,
line: u32,
structure: Structure
) where
T: MessageErrorDomain,

pub fn pads(&self) -> Vec<Pad, Global>ⓘ
Notable traits for Vec<u8, A>
`impl<A> Write for Vec<u8, A> where A: Allocator,`

pub fn sink_pads(&self) -> Vec<Pad, Global>ⓘ
Notable traits for Vec<u8, A>
`impl<A> Write for Vec<u8, A> where A: Allocator,`

pub fn src_pads(&self) -> Vec<Pad, Global>ⓘ
Notable traits for Vec<u8, A>
`impl<A> Write for Vec<u8, A> where A: Allocator,`

pub fn add_property_deep_notify_watch(
&self,
property_name: Option<&str>,
include_value: bool
) -> NotifyWatchId

pub fn add_property_notify_watch(
&self,
property_name: Option<&str>,
include_value: bool
) -> NotifyWatchId

pub fn query_convert<V, U>(&self, src_val: V) -> Option<U> where
V: Into<GenericFormattedValue>,
U: SpecificFormattedValue,

pub fn query_convert_generic<V>(
&self,
src_val: V,
dest_format: Format
) -> Option<GenericFormattedValue> where
V: Into<GenericFormattedValue>,

pub fn query_duration<T>(&self) -> Option<T> where
T: SpecificFormattedValueIntrinsic,

pub fn query_duration_generic(
&self,
format: Format
) -> Option<GenericFormattedValue>

pub fn query_position<T>(&self) -> Option<T> where
T: SpecificFormattedValueIntrinsic,

pub fn query_position_generic(
&self,
format: Format
) -> Option<GenericFormattedValue>