Copyright | Will Thompson and Iñaki García Etxebarria |
---|---|
License | LGPL-2.1 |
Maintainer | Iñaki García Etxebarria |
Safe Haskell | Safe-Inferred |
Language | Haskell2010 |
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
callsBaseParseClass
::start
to inform subclass that data processing is about to start now.
BaseParse
class callsBaseParseClass
::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 callingbaseParseFinishFrame
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 withbaseParseSetMinFrameSize
. 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 internalAdapter
.
- A buffer of (at least) min_frame_size bytes is passed to subclass
with
BaseParseClass
::handle_frame
. Subclass checks the contents and can optionally returnGST_FLOW_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,BaseParseClass
::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, baseParseSetMinFrameSize
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 baseParseFinishFrame
.
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 BaseParseClass
::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 BaseParseClass
::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
BaseParseClass
::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
BaseParseClass
will handle both srcpad and sinkpad events. They will be passed to subclass ifBaseParseClass
::sink_event
orBaseParseClass
::src_event
implementations have been provided.
Shutdown phase
BaseParse
class callsBaseParseClass
::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' BaseParseClass
::set_sink_caps
function).
This base class uses FormatDefault
as a meaning of frames. So,
subclass conversion routine needs to know that conversion from
FormatTime
to FormatDefault
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
baseParseSetMinFrameSize
function. - Examine data chunks passed to subclass with
BaseParseClass
::handle_frame
and pass proper frame(s) tobaseParseFinishFrame
, and setting src pad caps and timestamps on frame. - Provide conversion functions
- Update the duration information with
baseParseSetDuration
- Optionally passthrough using
baseParseSetPassthrough
- Configure various baseparse parameters using
baseParseSetAverageBitrate
,baseParseSetSyncable
andbaseParseSetFrameRate
. - 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 providesBaseParse
with an estimated bitrate. A defaultBaseParseClass
::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.
Synopsis
- newtype BaseParse = BaseParse (ManagedPtr BaseParse)
- class (GObject o, IsDescendantOf BaseParse o) => IsBaseParse o
- toBaseParse :: (MonadIO m, IsBaseParse o) => o -> m BaseParse
- baseParseAddIndexEntry :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Word64 -> Word64 -> Bool -> Bool -> m Bool
- baseParseConvertDefault :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Format -> Int64 -> Format -> m (Bool, Int64)
- baseParseDrain :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> m ()
- baseParseFinishFrame :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> BaseParseFrame -> Int32 -> m FlowReturn
- baseParseMergeTags :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Maybe TagList -> TagMergeMode -> m ()
- baseParsePushFrame :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> BaseParseFrame -> m FlowReturn
- baseParseSetAverageBitrate :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Word32 -> m ()
- baseParseSetDuration :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Format -> Int64 -> Int32 -> m ()
- baseParseSetFrameRate :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Word32 -> Word32 -> Word32 -> Word32 -> m ()
- baseParseSetHasTimingInfo :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Bool -> m ()
- baseParseSetInferTs :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Bool -> m ()
- baseParseSetLatency :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Word64 -> Word64 -> m ()
- baseParseSetMinFrameSize :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Word32 -> m ()
- baseParseSetPassthrough :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Bool -> m ()
- baseParseSetPtsInterpolation :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Bool -> m ()
- baseParseSetSyncable :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Bool -> m ()
- baseParseSetTsAtOffset :: (HasCallStack, MonadIO m, IsBaseParse a) => a -> Word64 -> m ()
- constructBaseParseDisablePassthrough :: (IsBaseParse o, MonadIO m) => Bool -> m (GValueConstruct o)
- getBaseParseDisablePassthrough :: (MonadIO m, IsBaseParse o) => o -> m Bool
- setBaseParseDisablePassthrough :: (MonadIO m, IsBaseParse o) => o -> Bool -> m ()
Exported types
Memory-managed wrapper type.
Instances
Eq BaseParse Source # | |
GObject BaseParse Source # | |
Defined in GI.GstBase.Objects.BaseParse | |
ManagedPtrNewtype BaseParse Source # | |
Defined in GI.GstBase.Objects.BaseParse toManagedPtr :: BaseParse -> ManagedPtr BaseParse | |
TypedObject BaseParse Source # | |
Defined in GI.GstBase.Objects.BaseParse | |
HasParentTypes BaseParse Source # | |
Defined in GI.GstBase.Objects.BaseParse | |
IsGValue (Maybe BaseParse) Source # | Convert |
Defined in GI.GstBase.Objects.BaseParse gvalueGType_ :: IO GType gvalueSet_ :: Ptr GValue -> Maybe BaseParse -> IO () gvalueGet_ :: Ptr GValue -> IO (Maybe BaseParse) | |
type ParentTypes BaseParse Source # | |
Defined in GI.GstBase.Objects.BaseParse type ParentTypes BaseParse = '[Element, Object, Object] |
class (GObject o, IsDescendantOf BaseParse o) => IsBaseParse o Source #
Type class for types which can be safely cast to BaseParse
, for instance with toBaseParse
.
Instances
(GObject o, IsDescendantOf BaseParse o) => IsBaseParse o Source # | |
Defined in GI.GstBase.Objects.BaseParse |
toBaseParse :: (MonadIO m, IsBaseParse o) => o -> m BaseParse Source #
Methods
Click to display all available methods, including inherited ones
Methods
abortState, addControlBinding, addIndexEntry, addPad, addPropertyDeepNotifyWatch, addPropertyNotifyWatch, bindProperty, bindPropertyFull, callAsync, changeState, continueState, convertDefault, createAllPads, defaultError, drain, finishFrame, forceFloating, foreachPad, foreachSinkPad, foreachSrcPad, freezeNotify, getv, hasActiveControlBindings, hasAncestor, hasAsAncestor, hasAsParent, isFloating, isLockedState, iteratePads, iterateSinkPads, iterateSrcPads, link, linkFiltered, linkPads, linkPadsFiltered, linkPadsFull, lostState, mergeTags, messageFull, messageFullWithDetails, noMorePads, notify, notifyByPspec, postMessage, provideClock, pushFrame, query, queryConvert, queryDuration, queryPosition, ref, refSink, releaseRequestPad, removeControlBinding, removePad, removePropertyNotifyWatch, requestPad, requestPadSimple, runDispose, seek, seekSimple, sendEvent, stealData, stealQdata, suggestNextSync, syncStateWithParent, syncValues, thawNotify, unlink, unlinkPads, unparent, unref, watchClosure.
Getters
getBaseTime, getBus, getClock, getCompatiblePad, getCompatiblePadTemplate, getContext, getContextUnlocked, getContexts, getControlBinding, getControlRate, getCurrentClockTime, getCurrentRunningTime, getData, getFactory, getGValueArray, getMetadata, getName, getPadTemplate, getPadTemplateList, getParent, getPathString, getProperty, getQdata, getRequestPad, getStartTime, getState, getStaticPad, getValue.
Setters
setAverageBitrate, setBaseTime, setBus, setClock, setContext, setControlBindingDisabled, setControlBindingsDisabled, setControlRate, setData, setDataFull, setDuration, setFrameRate, setHasTimingInfo, setInferTs, setLatency, setLockedState, setMinFrameSize, setName, setParent, setPassthrough, setProperty, setPtsInterpolation, setStartTime, setState, setSyncable, setTsAtOffset.
addIndexEntry
baseParseAddIndexEntry Source #
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Word64 |
|
-> Word64 |
|
-> Bool |
|
-> Bool |
|
-> m Bool | Returns: |
Adds an entry to the index associating offset
to ts
. It is recommended
to only add keyframe entries. force
allows to bypass checks, such as
whether the stream is (upstream) seekable, another entry is already "close"
to the new entry, etc.
convertDefault
baseParseConvertDefault Source #
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Format |
|
-> Int64 |
|
-> Format |
|
-> m (Bool, Int64) | Returns: |
Default implementation of BaseParseClass
::convert
.
drain
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> m () |
Drains the adapter until it is empty. It decreases the min_frame_size to match the current adapter size and calls chain method until the adapter is emptied or chain returns with error.
Since: 1.12
finishFrame
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> BaseParseFrame |
|
-> Int32 |
|
-> m FlowReturn | Returns: a |
Collects parsed data and pushes this downstream. Source pad caps must be set when this is called.
If frame
's out_buffer is set, that will be used as subsequent frame data.
Otherwise, size
samples will be taken from the input and used for output,
and the output's metadata (timestamps etc) will be taken as (optionally)
set by the subclass on frame
's (input) buffer (which is otherwise
ignored for any but the above purpose/information).
Note that the latter buffer is invalidated by this call, whereas the
caller retains ownership of frame
.
mergeTags
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Maybe TagList |
|
-> TagMergeMode |
|
-> m () |
Sets the parser subclass's tags and how they should be merged with any
upstream stream tags. This will override any tags previously-set
with baseParseMergeTags
.
Note that this is provided for convenience, and the subclass is not required to use this and can still do tag handling on its own.
Since: 1.6
pushFrame
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> BaseParseFrame |
|
-> m FlowReturn | Returns: |
Pushes the frame's buffer downstream, sends any pending events and
does some timestamp and segment handling. Takes ownership of
frame's buffer, though caller retains ownership of frame
.
This must be called with sinkpad STREAM_LOCK held.
setAverageBitrate
baseParseSetAverageBitrate Source #
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Word32 |
|
-> m () |
Optionally sets the average bitrate detected in media (if non-zero), e.g. based on metadata, as it will be posted to the application.
By default, announced average bitrate is estimated. The average bitrate
is used to estimate the total duration of the stream and to estimate
a seek position, if there's no index and the format is syncable
(see baseParseSetSyncable
).
setDuration
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Format |
|
-> Int64 |
|
-> Int32 |
|
-> m () |
Sets the duration of the currently playing media. Subclass can use this
when it is able to determine duration and/or notices a change in the media
duration. Alternatively, if interval
is non-zero (default), then stream
duration is determined based on estimated bitrate, and updated every interval
frames.
setFrameRate
baseParseSetFrameRate Source #
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Word32 |
|
-> Word32 |
|
-> Word32 |
|
-> Word32 |
|
-> m () |
If frames per second is configured, parser can take care of buffer duration
and timestamping. When performing segment clipping, or seeking to a specific
location, a corresponding decoder might need an initial leadIn
and a
following leadOut
number of frames to ensure the desired segment is
entirely filled upon decoding.
setHasTimingInfo
baseParseSetHasTimingInfo Source #
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Bool |
|
-> m () |
Set if frames carry timing information which the subclass can (generally) parse and provide. In particular, intrinsic (rather than estimated) time can be obtained following a seek.
setInferTs
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Bool |
|
-> m () |
By default, the base class might try to infer PTS from DTS and vice versa. While this is generally correct for audio data, it may not be otherwise. Sub-classes implementing such formats should disable timestamp inferring.
setLatency
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Word64 |
|
-> Word64 |
|
-> m () |
Sets the minimum and maximum (which may likely be equal) latency introduced by the parsing process. If there is such a latency, which depends on the particular parsing of the format, it typically corresponds to 1 frame duration.
If the provided values changed from previously provided ones, this will also post a LATENCY message on the bus so the pipeline can reconfigure its global latency.
setMinFrameSize
baseParseSetMinFrameSize Source #
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Word32 |
|
-> m () |
Subclass can use this function to tell the base class that it needs to
be given buffers of at least minSize
bytes.
setPassthrough
baseParseSetPassthrough Source #
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Bool |
|
-> m () |
Set if the nature of the format or configuration does not allow (much)
parsing, and the parser should operate in passthrough mode (which only
applies when operating in push mode). That is, incoming buffers are
pushed through unmodified, i.e. no BaseParseClass
::handle_frame
will be invoked, but BaseParseClass
::pre_push_frame
will still be
invoked, so subclass can perform as much or as little is appropriate for
passthrough semantics in BaseParseClass
::pre_push_frame
.
setPtsInterpolation
baseParseSetPtsInterpolation Source #
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Bool |
|
-> m () |
By default, the base class will guess PTS timestamps using a simple interpolation (previous timestamp + duration), which is incorrect for data streams with reordering, where PTS can go backward. Sub-classes implementing such formats should disable PTS interpolation.
setSyncable
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Bool |
|
-> m () |
Set if frame starts can be identified. This is set by default and determines whether seeking based on bitrate averages is possible for a format/stream.
setTsAtOffset
baseParseSetTsAtOffset Source #
:: (HasCallStack, MonadIO m, IsBaseParse a) | |
=> a |
|
-> Word64 |
|
-> m () |
This function should only be called from a handleFrame
implementation.
BaseParse
creates initial timestamps for frames by using the last
timestamp seen in the stream before the frame starts. In certain
cases, the correct timestamps will occur in the stream after the
start of the frame, but before the start of the actual picture data.
This function can be used to set the timestamps based on the offset
into the frame data that the picture starts.
Since: 1.2
Properties
disablePassthrough
If set to True
, baseparse will unconditionally force parsing of the
incoming data. This can be required in the rare cases where the incoming
side-data (caps, pts, dts, ...) is not trusted by the user and wants to
force validation and parsing of the incoming data.
If set to False
, decision of whether to parse the data or not is up to
the implementation (standard behaviour).
constructBaseParseDisablePassthrough :: (IsBaseParse o, MonadIO m) => Bool -> m (GValueConstruct o) Source #
Construct a GValueConstruct
with valid value for the “disable-passthrough
” property. This is rarely needed directly, but it is used by new
.
getBaseParseDisablePassthrough :: (MonadIO m, IsBaseParse o) => o -> m Bool Source #
Get the value of the “disable-passthrough
” property.
When overloading is enabled, this is equivalent to
get
baseParse #disablePassthrough
setBaseParseDisablePassthrough :: (MonadIO m, IsBaseParse o) => o -> Bool -> m () Source #
Set the value of the “disable-passthrough
” property.
When overloading is enabled, this is equivalent to
set
baseParse [ #disablePassthrough:=
value ]