GI.GstVideo.Objects.VideoDecoder

This base class is for video decoders turning encoded data into raw video frames.

The GstVideoDecoder base class and derived subclasses should cooperate as follows:

Configuration

• Initially, GstVideoDecoder calls start when the decoder element is activated, which allows the subclass to perform any global setup.

• GstVideoDecoder calls setFormat to inform the subclass of caps describing input video data that it is about to receive, including possibly configuration data. While unlikely, it might be called more than once, if changing input parameters require reconfiguration.
• Incoming data buffers are processed as needed, described in Data Processing below.
• GstVideoDecoder calls stop at end of all processing.

Data processing

• The base class gathers input data, and optionally allows subclass to parse this into subsequently manageable chunks, typically corresponding to and referred to as 'frames'.

• Each input frame is provided in turn to the subclass' handleFrame callback. The ownership of the frame is given to the handleFrame callback.
• If codec processing results in decoded data, the subclass should call gstVideoDecoderFinishFrame to have decoded data pushed. downstream. Otherwise, the subclass must call gstVideoDecoderDropFrame, to allow the base class to do timestamp and offset tracking, and possibly to requeue the frame for a later attempt in the case of reverse playback.

Shutdown phase

• The GstVideoDecoder class calls stop to inform the subclass that data parsing will be stopped.

Additional Notes

• Seeking/Flushing

• When the pipeline is seeked or otherwise flushed, the subclass is informed via a call to its reset callback, with the hard parameter set to true. This indicates the subclass should drop any internal data queues and timestamps and prepare for a fresh set of buffers to arrive for parsing and decoding.
• End Of Stream
• At end-of-stream, the subclass parse function may be called some final times with the at_eos parameter set to true, indicating that the element should not expect any more data to be arriving, and it should parse and remaining frames and call videoDecoderHaveFrame if possible.

The 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 provide information about the output caps, when they are known. This may be when the base class calls the subclass' setFormat function, though it might be during decoding, before calling gstVideoDecoderFinishFrame. This is done via gstVideoDecoderSetOutputState

The subclass is also responsible for providing (presentation) timestamps (likely based on corresponding input ones). If that is not applicable or possible, the base class provides limited framerate based interpolation.

Similarly, the base class provides some limited (legacy) seeking support if specifically requested by the subclass, as full-fledged support should rather be left to upstream demuxer, parser or alike. This simple approach caters for seeking and duration reporting using estimated input bitrates. To enable it, a subclass should call gstVideoDecoderSetEstimateRate to enable handling of incoming byte-streams.

The base class provides some support for reverse playback, in particular in case incoming data is not packetized or upstream does not provide fragments on keyframe boundaries. However, the subclass should then be prepared for the parsing and frame processing stage to occur separately (in normal forward processing, the latter immediately follows the former), The subclass also needs to ensure the parsing stage properly marks keyframes, unless it knows the upstream elements will do so properly for incoming data.

The bare minimum that a functional subclass needs to implement is:

• Provide pad templates
• Inform the base class of output caps via gstVideoDecoderSetOutputState
• Parse input data, if it is not considered packetized from upstream Data will be provided to parse which should invoke gstVideoDecoderAddToFrame and gstVideoDecoderHaveFrame to separate the data belonging to each video frame.
• Accept data in handleFrame and provide decoded results to gstVideoDecoderFinishFrame, or call gstVideoDecoderDropFrame.

Exported types

newtype VideoDecoder

Memory-managed wrapper type.

Constructors

VideoDecoder (ManagedPtr VideoDecoder)

Instances

Eq VideoDecoder

Defined in GI.GstVideo.Objects.VideoDecoder

Methods

(==) :: VideoDecoder -> VideoDecoder -> Bool

(/=) :: VideoDecoder -> VideoDecoder -> Bool

GObject VideoDecoder

Defined in GI.GstVideo.Objects.VideoDecoder

ManagedPtrNewtype VideoDecoder

Defined in GI.GstVideo.Objects.VideoDecoder

Methods

toManagedPtr :: VideoDecoder -> ManagedPtr VideoDecoder

TypedObject VideoDecoder

Defined in GI.GstVideo.Objects.VideoDecoder

Methods

glibType :: IO GType

HasParentTypes VideoDecoder

Defined in GI.GstVideo.Objects.VideoDecoder

IsGValue (Maybe VideoDecoder)

Convert VideoDecoder to and from GValue. See toGValue and fromGValue.

Defined in GI.GstVideo.Objects.VideoDecoder

Methods

gvalueGType_ :: IO GType

gvalueSet_ :: Ptr GValue -> Maybe VideoDecoder -> IO ()

gvalueGet_ :: Ptr GValue -> IO (Maybe VideoDecoder)

type ParentTypes VideoDecoder

Defined in GI.GstVideo.Objects.VideoDecoder

type ParentTypes VideoDecoder = '[Element, Object, Object]

class (GObject o, IsDescendantOf VideoDecoder o) => IsVideoDecoder o

Type class for types which can be safely cast to VideoDecoder, for instance with toVideoDecoder.

Instances

(GObject o, IsDescendantOf VideoDecoder o) => IsVideoDecoder o

Defined in GI.GstVideo.Objects.VideoDecoder

toVideoDecoder :: (MonadIO m, IsVideoDecoder o) => o -> m VideoDecoder

Cast to VideoDecoder, for types for which this is known to be safe. For general casts, use castTo.

Methods

Click to display all available methods, including inherited ones

Methods

abortState, addControlBinding, addPad, addPropertyDeepNotifyWatch, addPropertyNotifyWatch, addToFrame, allocateOutputBuffer, allocateOutputFrame, allocateOutputFrameWithParams, bindProperty, bindPropertyFull, callAsync, changeState, continueState, createAllPads, defaultError, dropFrame, finishFrame, forceFloating, foreachPad, foreachSinkPad, foreachSrcPad, freezeNotify, getv, hasActiveControlBindings, hasAncestor, hasAsAncestor, hasAsParent, haveFrame, isFloating, isLockedState, iteratePads, iterateSinkPads, iterateSrcPads, link, linkFiltered, linkPads, linkPadsFiltered, linkPadsFull, lostState, mergeTags, messageFull, messageFullWithDetails, negotiate, noMorePads, notify, notifyByPspec, postMessage, provideClock, proxyGetcaps, query, queryConvert, queryDuration, queryPosition, ref, refSink, releaseFrame, releaseRequestPad, removeControlBinding, removePad, removePropertyNotifyWatch, requestPad, runDispose, seek, seekSimple, sendEvent, stealData, stealQdata, suggestNextSync, syncStateWithParent, syncValues, thawNotify, unlink, unlinkPads, unparent, unref, watchClosure.

Getters

getAllocator, getBaseTime, getBufferPool, getBus, getClock, getCompatiblePad, getCompatiblePadTemplate, getContext, getContextUnlocked, getContexts, getControlBinding, getControlRate, getCurrentClockTime, getCurrentRunningTime, getData, getEstimateRate, getFactory, getFrame, getFrames, getGValueArray, getLatency, getMaxDecodeTime, getMaxErrors, getMetadata, getName, getNeedsFormat, getOldestFrame, getOutputState, getPacketized, getPadTemplate, getPadTemplateList, getParent, getPathString, getPendingFrameSize, getProperty, getQdata, getQosProportion, getRequestPad, getStartTime, getState, getStaticPad, getValue.

Setters

setBaseTime, setBus, setClock, setContext, setControlBindingDisabled, setControlBindingsDisabled, setControlRate, setData, setDataFull, setEstimateRate, setInterlacedOutputState, setLatency, setLockedState, setMaxErrors, setName, setNeedsFormat, setOutputState, setPacketized, setParent, setProperty, setStartTime, setState, setUseDefaultPadAcceptcaps.

addToFrame

videoDecoderAddToFrame

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> Int32

nBytes: the number of bytes to add

-> m ()

Removes next nBytes of input data and adds it to currently parsed frame.

allocateOutputBuffer

videoDecoderAllocateOutputBuffer

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m Buffer

Returns: allocated buffer, or NULL if no buffer could be allocated (e.g. when downstream is flushing or shutting down)

Helper function that allocates a buffer to hold a video frame for decoder's current VideoCodecState.

You should use videoDecoderAllocateOutputFrame instead of this function, if possible at all.

allocateOutputFrame

videoDecoderAllocateOutputFrame

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> VideoCodecFrame

frame: a VideoCodecFrame

-> m FlowReturn

Returns: FlowReturnOk if an output buffer could be allocated

Helper function that allocates a buffer to hold a video frame for decoder's current VideoCodecState. Subclass should already have configured video state and set src pad caps.

The buffer allocated here is owned by the frame and you should only keep references to the frame, not the buffer.

allocateOutputFrameWithParams

videoDecoderAllocateOutputFrameWithParams

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> VideoCodecFrame

frame: a VideoCodecFrame

-> BufferPoolAcquireParams

params: a BufferPoolAcquireParams

-> m FlowReturn

Returns: FlowReturnOk if an output buffer could be allocated

Same as gst_video_decoder_allocate_output_frame except it allows passing BufferPoolAcquireParams to the sub call gst_buffer_pool_acquire_buffer.

Since: 1.12

dropFrame

videoDecoderDropFrame

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

dec: a VideoDecoder

-> VideoCodecFrame

frame: the VideoCodecFrame to drop

-> m FlowReturn

Returns: a FlowReturn, usually GST_FLOW_OK.

Similar to videoDecoderFinishFrame, but drops frame in any case and posts a QoS message with the frame's details on the bus. In any case, the frame is considered finished and released.

finishFrame

videoDecoderFinishFrame

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> VideoCodecFrame

frame: a decoded VideoCodecFrame

-> m FlowReturn

Returns: a FlowReturn resulting from sending data downstream

frame should have a valid decoded data buffer, whose metadata fields are then appropriately set according to frame data and pushed downstream. If no output data is provided, frame is considered skipped. In any case, the frame is considered finished and released.

After calling this function the output buffer of the frame is to be considered read-only. This function will also change the metadata of the buffer.

getAllocator

videoDecoderGetAllocator

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m (Allocator, AllocationParams)

Lets VideoDecoder sub-classes to know the memory allocator used by the base class and its params.

Unref the allocator after use it.

getBufferPool

videoDecoderGetBufferPool

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m BufferPool

Returns: the instance of the BufferPool used by the decoder; free it after use it

No description available in the introspection data.

getEstimateRate

videoDecoderGetEstimateRate

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

dec: a VideoDecoder

-> m Int32

Returns: currently configured byte to time conversion setting

No description available in the introspection data.

getFrame

videoDecoderGetFrame

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> Int32

frameNumber: system_frame_number of a frame

-> m VideoCodecFrame

Returns: pending unfinished VideoCodecFrame identified by frameNumber.

Get a pending unfinished VideoCodecFrame

getFrames

videoDecoderGetFrames

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m [VideoCodecFrame]

Returns: pending unfinished VideoCodecFrame.

Get all pending unfinished VideoCodecFrame

getLatency

videoDecoderGetLatency

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m (Word64, Word64)

Query the configured decoder latency. Results will be returned via minLatency and maxLatency.

getMaxDecodeTime

videoDecoderGetMaxDecodeTime

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> VideoCodecFrame

frame: a VideoCodecFrame

-> m Int64

Returns: max decoding time.

Determines maximum possible decoding time for frame that will allow it to decode and arrive in time (as determined by QoS events). In particular, a negative result means decoding in time is no longer possible and should therefore occur as soon/skippy as possible.

getMaxErrors

videoDecoderGetMaxErrors

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

dec: a VideoDecoder

-> m Int32

Returns: currently configured decoder tolerated error count.

No description available in the introspection data.

getNeedsFormat

videoDecoderGetNeedsFormat

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

dec: a VideoDecoder

-> m Bool

Returns: True if required format handling is enabled.

Queries decoder required format handling.

Since: 1.4

getOldestFrame

videoDecoderGetOldestFrame

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m VideoCodecFrame

Returns: oldest pending unfinished VideoCodecFrame.

Get the oldest pending unfinished VideoCodecFrame

getOutputState

videoDecoderGetOutputState

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m VideoCodecState

Returns: VideoCodecState describing format of video data.

Get the VideoCodecState currently describing the output stream.

getPacketized

videoDecoderGetPacketized

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m Bool

Returns: TRUE if input data is considered packetized.

Queries whether input data is considered packetized or not by the base class.

getPendingFrameSize

videoDecoderGetPendingFrameSize

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m Word64

Returns: The number of bytes pending for the current frame

Returns the number of bytes previously added to the current frame by calling videoDecoderAddToFrame.

Since: 1.4

getQosProportion

videoDecoderGetQosProportion

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder current QoS proportion, or Nothing

-> m Double

Returns: The current QoS proportion.

No description available in the introspection data.

Since: 1.0.3

haveFrame

videoDecoderHaveFrame

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m FlowReturn

Returns: a FlowReturn

Gathers all data collected for currently parsed frame, gathers corresponding metadata and passes it along for further processing, i.e. handleFrame.

mergeTags

videoDecoderMergeTags

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> Maybe TagList

tags: a TagList to merge, or NULL to unset previously-set tags

-> TagMergeMode

mode: the TagMergeMode to use, usually GST_TAG_MERGE_REPLACE

-> m ()

Sets the audio decoder tags and how they should be merged with any upstream stream tags. This will override any tags previously-set with gst_audio_decoder_merge_tags().

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.

MT safe.

negotiate

videoDecoderNegotiate

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> m Bool

Returns: True if the negotiation succeeded, else False.

Negotiate with downstream elements to currently configured VideoCodecState. Unmark GST_PAD_FLAG_NEED_RECONFIGURE in any case. But mark it again if negotiate fails.

proxyGetcaps

videoDecoderProxyGetcaps

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> Maybe Caps

caps: initial caps

-> Maybe Caps

filter: filter caps

-> m Caps

Returns: a Caps owned by caller

Returns caps that express caps (or sink template caps if caps == NULL) restricted to resolution/format/... combinations supported by downstream elements.

Since: 1.6

releaseFrame

videoDecoderReleaseFrame

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

dec: a VideoDecoder

-> VideoCodecFrame

frame: the VideoCodecFrame to release

-> m ()

Similar to videoDecoderDropFrame, but simply releases frame without any processing other than removing it from list of pending frames, after which it is considered finished and released.

Since: 1.2.2

setEstimateRate

videoDecoderSetEstimateRate

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

dec: a VideoDecoder

-> Bool

enabled: whether to enable byte to time conversion

-> m ()

Allows baseclass to perform byte to time estimated conversion.

setInterlacedOutputState

videoDecoderSetInterlacedOutputState

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> VideoFormat

fmt: a VideoFormat

-> VideoInterlaceMode

interlaceMode: A VideoInterlaceMode

-> Word32

width: The width in pixels

-> Word32

height: The height in pixels

-> Maybe VideoCodecState

reference: An optional reference VideoCodecState

-> m VideoCodecState

Returns: the newly configured output state.

Same as gst_video_decoder_set_output_state() but also allows you to also set the interlacing mode.

Since: 1.16.

setLatency

videoDecoderSetLatency

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> Word64

minLatency: minimum latency

-> Word64

maxLatency: maximum latency

-> m ()

Lets VideoDecoder sub-classes tell the baseclass what the decoder latency is. Will also post a LATENCY message on the bus so the pipeline can reconfigure its global latency.

setMaxErrors

videoDecoderSetMaxErrors

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

dec: a VideoDecoder

-> Int32

num: max tolerated errors

-> m ()

Sets numbers of tolerated decoder errors, where a tolerated one is then only warned about, but more than tolerated will lead to fatal error. You can set -1 for never returning fatal errors. Default is set to GST_VIDEO_DECODER_MAX_ERRORS.

The '-1' option was added in 1.4

setNeedsFormat

videoDecoderSetNeedsFormat

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

dec: a VideoDecoder

-> Bool

enabled: new state

-> m ()

Configures decoder format needs. If enabled, subclass needs to be negotiated with format caps before it can process any data. It will then never be handed any data before it has been configured. Otherwise, it might be handed data without having been configured and is then expected being able to do so either by default or based on the input data.

Since: 1.4

setOutputState

videoDecoderSetOutputState

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> VideoFormat

fmt: a VideoFormat

-> Word32

width: The width in pixels

-> Word32

height: The height in pixels

-> Maybe VideoCodecState

reference: An optional reference VideoCodecState

-> m VideoCodecState

Returns: the newly configured output state.

Creates a new VideoCodecState with the specified fmt, width and height as the output state for the decoder. Any previously set output state on decoder will be replaced by the newly created one.

If the subclass wishes to copy over existing fields (like pixel aspec ratio, or framerate) from an existing VideoCodecState, it can be provided as a reference.

If the subclass wishes to override some fields from the output state (like pixel-aspect-ratio or framerate) it can do so on the returned VideoCodecState.

The new output state will only take effect (set on pads and buffers) starting from the next call to gst_video_decoder_finish_frame().

setPacketized

videoDecoderSetPacketized

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> Bool

packetized: whether the input data should be considered as packetized.

-> m ()

Allows baseclass to consider input data as packetized or not. If the input is packetized, then the parse method will not be called.

setUseDefaultPadAcceptcaps

videoDecoderSetUseDefaultPadAcceptcaps

Arguments

:: (HasCallStack, MonadIO m, IsVideoDecoder a)

=> a

decoder: a VideoDecoder

-> Bool

use: if the default pad accept-caps query handling should be used

-> m ()

Lets VideoDecoder sub-classes decide if they want the sink pad to use the default pad query handler to reply to accept-caps queries.

By setting this to true it is possible to further customize the default handler with GST_PAD_SET_ACCEPT_INTERSECT and GST_PAD_SET_ACCEPT_TEMPLATE

Since: 1.6

Properties

maxErrors

Maximum number of tolerated consecutive decode errors. See videoDecoderSetMaxErrors for more details.

Since: 1.18

constructVideoDecoderMaxErrors :: (IsVideoDecoder o, MonadIO m) => Int32 -> m (GValueConstruct o)

Construct a GValueConstruct with valid value for the “max-errors” property. This is rarely needed directly, but it is used by new.

getVideoDecoderMaxErrors :: (MonadIO m, IsVideoDecoder o) => o -> m Int32

Get the value of the “max-errors” property. When overloading is enabled, this is equivalent to

get videoDecoder #maxErrors

setVideoDecoderMaxErrors :: (MonadIO m, IsVideoDecoder o) => o -> Int32 -> m ()

Set the value of the “max-errors” property. When overloading is enabled, this is equivalent to

set videoDecoder [ #maxErrors := value ]

qos

If set to True the decoder will handle QoS events received from downstream elements. This includes dropping output frames which are detected as late using the metrics reported by those events.

Since: 1.18

constructVideoDecoderQos :: (IsVideoDecoder o, MonadIO m) => Bool -> m (GValueConstruct o)

Construct a GValueConstruct with valid value for the “qos” property. This is rarely needed directly, but it is used by new.

getVideoDecoderQos :: (MonadIO m, IsVideoDecoder o) => o -> m Bool

Get the value of the “qos” property. When overloading is enabled, this is equivalent to

get videoDecoder #qos

setVideoDecoderQos :: (MonadIO m, IsVideoDecoder o) => o -> Bool -> m ()

Set the value of the “qos” property. When overloading is enabled, this is equivalent to

set videoDecoder [ #qos := value ]