Class AudioDecoder

java.lang.Object
org.javagi.base.ProxyInstance
org.gnome.gobject.TypeInstance
org.gnome.gobject.GObject
org.gnome.gobject.InitiallyUnowned
org.freedesktop.gstreamer.gst.GstObject
org.freedesktop.gstreamer.gst.Element
org.freedesktop.gstreamer.audio.AudioDecoder
All Implemented Interfaces:
Proxy
Direct Known Subclasses:
AudioDecoder.AudioDecoder$Impl
@Generated("org.javagi.JavaGI") public abstract class AudioDecoder extends Element

This base class is for audio decoders turning encoded data into raw audio samples.

GstAudioDecoder and subclass should cooperate as follows.

Configuration

  • Initially, GstAudioDecoder calls start when the decoder element is activated, which allows subclass to perform any global setup. Base class (context) parameters can already be set according to subclass capabilities (or possibly upon receive more information in subsequent setFormat).
  • GstAudioDecoder calls setFormat to inform subclass of the format of input audio data that it is about to receive. While unlikely, it might be called more than once, if changing input parameters require reconfiguration.
  • GstAudioDecoder calls stop at end of all processing.

As of configuration stage, and throughout processing, GstAudioDecoder provides various (context) parameters, e.g. describing the format of output audio data (valid when output caps have been set) or current parsing state. Conversely, subclass can and should configure context to inform base class of its expectation w.r.t. buffer handling.

Data processing

* Base class gathers input data, and optionally allows subclass
  to parse this into subsequently manageable (as defined by subclass)
  chunks.  Such chunks are subsequently referred to as 'frames',
  though they may or may not correspond to 1 (or more) audio format frame.
* Input frame is provided to subclass' `handleFrame.`
* If codec processing results in decoded data, subclass should call
  `gstAudioDecoderFinishFrame` to have decoded data pushed
  downstream.
* Just prior to actually pushing a buffer downstream,
  it is passed to `prePush.`  Subclass should either use this callback
  to arrange for additional downstream pushing or otherwise ensure such
  custom pushing occurs after at least a method call has finished since
  setting src pad caps.
* During the parsing process GstAudioDecoderClass will handle both
  srcpad and sinkpad events. Sink events will be passed to subclass
  if `event` callback has been provided.

Shutdown phase

  • GstAudioDecoder class calls 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. This is typically when base class calls subclass' setFormat function, though it might be delayed until calling gstAudioDecoderFinishFrame.

In summary, above process should have subclass concentrating on codec data processing while leaving other matters to base class, such as most notably timestamp handling. While it may exert more control in this area (see e.g. prePush), it is very much not recommended.

In particular, base class will try to arrange for perfect output timestamps as much as possible while tracking upstream timestamps. To this end, if deviation between the next ideal expected perfect timestamp and upstream exceeds GstAudioDecoder:tolerance, then resync to upstream occurs (which would happen always if the tolerance mechanism is disabled).

In non-live pipelines, baseclass can also (configurably) arrange for output buffer aggregation which may help to redue large(r) numbers of small(er) buffers being pushed and processed downstream. Note that this feature is only available if the buffer layout is interleaved. For planar buffers, the decoder implementation is fully responsible for the output buffer size.

On the other hand, it should be noted that baseclass only provides limited seeking support (upon explicit subclass request), 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.

Things that subclass need to take care of:

  • Provide pad templates

  • Set source pad caps when appropriate

  • Set user-configurable properties to sane defaults for format and implementing codec at hand, and convey some subclass capabilities and expectations in context.

  • Accept data in handleFrame and provide encoded results to gstAudioDecoderFinishFrame. If it is prepared to perform PLC, it should also accept NULL data in handleFrame and provide for data for indicated duration.

  • Constructor Details

    • AudioDecoder

      public AudioDecoder(MemorySegment address)
      Create a AudioDecoder instance for the provided memory address.
      Parameters:
      address - the memory address of the native object

    • AudioDecoder

      public AudioDecoder()
      Create a new AudioDecoder.

  • Method Details

    • getType

      public static @Nullable Type getType()
      Get the GType of the AudioDecoder class.
      Returns:
      the GType

    • getMemoryLayout

      public static MemoryLayout getMemoryLayout()
      The memory layout of the native struct.
      Returns:
      the memory layout

    • asParent

      protected AudioDecoder asParent()
      Return this instance as if it were its parent type. Comparable to the Java super keyword, but ensures the parent typeclass is also used in native code.
      Overrides:
      asParent in class Element
      Returns:
      the instance as if it were its parent type

    • allocateOutputBuffer

      public Buffer allocateOutputBuffer(long size)
      Helper function that allocates a buffer to hold an audio frame for dec's current output format.
      Parameters:
      size - size of the buffer
      Returns:
      allocated buffer

    • finishFrame

      public FlowReturn finishFrame(@Nullable Buffer buf, int frames)

      Collects decoded data and pushes it downstream.

      buf may be NULL in which case the indicated number of frames are discarded and considered to have produced no output (e.g. lead-in or setup frames). Otherwise, source pad caps must be set when it is called with valid data in buf.

      Note that a frame received in GstAudioDecoderClass.handle_frame() may be invalidated by a call to this function.

      Parameters:
      buf - decoded data
      frames - number of decoded frames represented by decoded data
      Returns:
      a GstFlowReturn that should be escalated to caller (of caller)

    • finishSubframe

      public FlowReturn finishSubframe(@Nullable Buffer buf)

      Collects decoded data and pushes it downstream. This function may be called multiple times for a given input frame.

      buf may be NULL in which case it is assumed that the current input frame is finished. This is equivalent to calling gst_audio_decoder_finish_subframe() with a NULL buffer and frames=1 after having pushed out all decoded audio subframes using this function.

      When called with valid data in buf the source pad caps must have been set already.

      Note that a frame received in GstAudioDecoderClass.handle_frame() may be invalidated by a call to this function.

      Parameters:
      buf - decoded data
      Returns:
      a GstFlowReturn that should be escalated to caller (of caller)
      Since:
      1.16

    • getAllocator

      public void getAllocator(@Nullable Out<Allocator> allocator, @Nullable AllocationParams params)

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

      Unref the allocator after use it.

      Parameters:
      allocator - the GstAllocator used
      params - the GstAllocationParams of allocator

    • getAudioInfo

      public AudioInfo getAudioInfo()

    • getDelay

      public int getDelay()

    • getDrainable

      public boolean getDrainable()
      Queries decoder drain handling.
      Returns:

      TRUE if drainable handling is enabled.

      MT safe.

    • getEstimateRate

      public int getEstimateRate()

    • getLatency

      public void getLatency(@Nullable ClockTime min, @Nullable ClockTime max)
      Sets the variables pointed to by min and max to the currently configured latency.
      Parameters:
      min - a pointer to storage to hold minimum latency
      max - a pointer to storage to hold maximum latency

    • getMaxErrors

      public int getMaxErrors()

    • getMinLatency

      public ClockTime getMinLatency()
      Queries decoder's latency aggregation.
      Returns:

      aggregation latency.

      MT safe.

    • getNeedsFormat

      public boolean getNeedsFormat()
      Queries decoder required format handling.
      Returns:

      TRUE if required format handling is enabled.

      MT safe.

    • getParseState

      public void getParseState(@Nullable Out<Boolean> sync, @Nullable Out<Boolean> eos)
      Return current parsing (sync and eos) state.
      Parameters:
      sync - a pointer to a variable to hold the current sync state
      eos - a pointer to a variable to hold the current eos state

    • getPlc

      public boolean getPlc()
      Queries decoder packet loss concealment handling.
      Returns:

      TRUE if packet loss concealment is enabled.

      MT safe.

    • getPlcAware

      public int getPlcAware()

    • getTolerance

      public ClockTime getTolerance()
      Queries current audio jitter tolerance threshold.
      Returns:

      decoder audio jitter tolerance threshold.

      MT safe.

    • mergeTags

      public void mergeTags(@Nullable TagList tags, TagMergeMode mode)

      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.

      Parameters:
      tags - a GstTagList to merge, or NULL
      mode - the GstTagMergeMode to use, usually GST_TAG_MERGE_REPLACE

    • negotiate

      public boolean negotiate()
      Negotiate with downstream elements to currently configured GstAudioInfo. Unmark GST_PAD_FLAG_NEED_RECONFIGURE in any case. But mark it again if negotiate fails.
      Returns:
      true if the negotiation succeeded, else false.

    • proxyGetcaps

      public Caps proxyGetcaps(@Nullable Caps caps, @Nullable Caps filter)
      Returns caps that express caps (or sink template caps if caps == NULL) restricted to rate/channels/... combinations supported by downstream elements.
      Parameters:
      caps - initial caps
      filter - filter caps
      Returns:
      a GstCaps owned by caller
      Since:
      1.6

    • setAllocationCaps

      public void setAllocationCaps(@Nullable Caps allocationCaps)
      Sets a caps in allocation query which are different from the set pad's caps. Use this function before calling gst_audio_decoder_negotiate(). Setting to null the allocation query will use the caps from the pad.
      Parameters:
      allocationCaps - a GstCaps or null
      Since:
      1.10

    • setDrainable

      public void setDrainable(boolean enabled)

      Configures decoder drain handling. If drainable, subclass might be handed a NULL buffer to have it return any leftover decoded data. Otherwise, it is not considered so capable and will only ever be passed real data.

      MT safe.

      Parameters:
      enabled - new state

    • setEstimateRate

      public void setEstimateRate(boolean enabled)
      Allows baseclass to perform byte to time estimated conversion.
      Parameters:
      enabled - whether to enable byte to time conversion

    • setLatency

      public void setLatency(ClockTime min, ClockTime max)
      Sets decoder latency. 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.
      Parameters:
      min - minimum latency
      max - maximum latency

    • setMaxErrors

      public void setMaxErrors(int num)
      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_AUDIO_DECODER_MAX_ERRORS.
      Parameters:
      num - max tolerated errors

    • setMinLatency

      public void setMinLatency(ClockTime num)

      Sets decoder minimum aggregation latency.

      MT safe.

      Parameters:
      num - new minimum latency

    • setNeedsFormat

      public void setNeedsFormat(boolean enabled)

      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.

      MT safe.

      Parameters:
      enabled - new state

    • setOutputCaps

      public boolean setOutputCaps(Caps caps)
      Configure output caps on the srcpad of dec. Similar to gst_audio_decoder_set_output_format(), but allows subclasses to specify output caps that can't be expressed via GstAudioInfo e.g. caps that have caps features.
      Parameters:
      caps - (fixed) GstCaps
      Returns:
      true on success.
      Since:
      1.16

    • setOutputFormat

      public boolean setOutputFormat(AudioInfo info)
      Configure output info on the srcpad of dec.
      Parameters:
      info - GstAudioInfo
      Returns:
      true on success.

    • setPlc

      public void setPlc(boolean enabled)

      Enable or disable decoder packet loss concealment, provided subclass and codec are capable and allow handling plc.

      MT safe.

      Parameters:
      enabled - new state

    • setPlcAware

      public void setPlcAware(boolean plc)
      Indicates whether or not subclass handles packet loss concealment (plc).
      Parameters:
      plc - new plc state

    • setTolerance

      public void setTolerance(ClockTime tolerance)

      Configures decoder audio jitter tolerance threshold.

      MT safe.

      Parameters:
      tolerance - new tolerance

    • setUseDefaultPadAcceptcaps

      public void setUseDefaultPadAcceptcaps(boolean use)

      Lets GstAudioDecoder 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

      Parameters:
      use - if the default pad accept-caps query handling should be used
      Since:
      1.6

    • close

      protected boolean close()
      Optional. Called when the element changes to GST_STATE_NULL. Allows closing external resources.

    • decideAllocation

      protected boolean decideAllocation(Query query)
      Optional. Setup the allocation parameters for allocating output buffers. The passed in query contains the result of the downstream allocation query. Subclasses should chain up to the parent implementation to invoke the default handler.

    • flush

      protected void flush(boolean hard)
      Optional. Instructs subclass to clear any codec caches and discard any pending samples and not yet returned decoded data. hard indicates whether a FLUSH is being processed, or otherwise a DISCONT (or conceptually similar).

    • getcaps

      protected Caps getcaps(Caps filter)
      Optional. Allows for a custom sink getcaps implementation. If not implemented, default returns gst_audio_decoder_proxy_getcaps applied to sink template caps.

    • handleFrame

      protected FlowReturn handleFrame(Buffer buffer)
      Provides input data (or NULL to clear any remaining data) to subclass. Input data ref management is performed by base class, subclass should not care or intervene, and input data is only valid until next call to base class, most notably a call to gst_audio_decoder_finish_frame().

    • open

      protected boolean open()
      Optional. Called when the element changes to GST_STATE_READY. Allows opening external resources.

    • parse

      protected FlowReturn parse(Adapter adapter, Out<Integer> offset, Out<Integer> length)

    • prePush

      protected FlowReturn prePush(Buffer[] buffer)
      Optional. Called just prior to pushing (encoded data) buffer downstream. Subclass has full discretionary access to buffer, and a not OK flow return will abort downstream pushing.

    • proposeAllocation

      protected boolean proposeAllocation(Query query)
      Optional. Propose buffer allocation parameters for upstream elements. Subclasses should chain up to the parent implementation to invoke the default handler.

    • setFormat

      protected boolean setFormat(Caps caps)
      Notifies subclass of incoming data format (caps).

    • sinkEvent

      protected boolean sinkEvent(Event event)
      Optional. Event handler on the sink pad. Subclasses should chain up to the parent implementation to invoke the default handler.

    • sinkQuery

      protected boolean sinkQuery(Query query)
      Optional. Query handler on the sink pad. This function should return TRUE if the query could be performed. Subclasses should chain up to the parent implementation to invoke the default handler. Since: 1.6

    • srcEvent

      protected boolean srcEvent(Event event)
      Optional. Event handler on the src pad. Subclasses should chain up to the parent implementation to invoke the default handler.

    • srcQuery

      protected boolean srcQuery(Query query)
      Optional. Query handler on the source pad. This function should return TRUE if the query could be performed. Subclasses should chain up to the parent implementation to invoke the default handler. Since: 1.6

    • start

      protected boolean start()
      Optional. Called when the element starts processing. Allows opening external resources.

    • stop

      protected boolean stop()
      Optional. Called when the element stops processing. Allows closing external resources.

    • transformMeta

      protected boolean transformMeta(Buffer outbuf, Meta meta, Buffer inbuf)
      Optional. Transform the metadata on the input buffer to the output buffer. By default this method copies all meta without tags and meta with only the "audio" tag. subclasses can implement this method and return true if the metadata is to be copied. Since: 1.6