VideoOutput Class Reference

Abstract class for video playback. This class is used to assemble a complete video frame in memory. A video frame is written via one or more write() calls, then finalized with flush() - implementations use flush() to know a frame is complete (there is no separate frame-size hint, unlike a length-prefixed chunk format). More...

#include <Video.h>

Inheritance diagram for VideoOutput:

Public Member Functions
virtual void	flush ()
virtual uint32_t	getWriteTimeMs () const
	Optional: returns the time (ms) spent in the last write() call.
virtual bool	hadOutput () const
virtual bool	isKeyFrame (const uint8_t *data, size_t len)
virtual void	setSkipRender (bool skip)
virtual size_t	write (const uint8_t *data, size_t len)=0

Detailed Description

Abstract class for video playback. This class is used to assemble a complete video frame in memory. A video frame is written via one or more write() calls, then finalized with flush() - implementations use flush() to know a frame is complete (there is no separate frame-size hint, unlike a length-prefixed chunk format).

Author

Phil Schatzmann

Copyright

GPLv3

Member Function Documentation

flush()

virtual void flush ( )

inlinevirtual

Finalizes the frame most recently written via one or more write() calls - see class comment. Default no-op for implementations that display/decode synchronously in write() instead.

Reimplemented in Muxer, H264DecoderESP32S3< Alloc >, MJPEGDecoder, MPGDecoder, MultiVideoDecoder, OutputOpenCV, PacedVideoOutput, and VideoFrameMeter.

getWriteTimeMs()

virtual uint32_t getWriteTimeMs ( ) const

inlinevirtual

Optional: returns the time (ms) spent in the last write() call.

Reimplemented in OutputTFT_eSPI, OutputTinyGPU, and OutputOpenCV.

hadOutput()

virtual bool hadOutput ( ) const

inlinevirtual

True if the most recent write()+flush() call actually produced a displayable picture - default true, matching every synchronous decoder (H264Decoder, MJPEGDecoder, ...), which always decodes and pushes pixels fully within that one call. Override this only if your decoder can legitimately accept/decode a frame's bytes without emitting a picture during that same call - e.g. MPGDecoder, whose B-picture display-order reordering can hold a just-decoded picture back and instead emit an earlier one (or nothing at all) from a given write(), see its own override. Used by PacedVideoOutput to avoid counting/timing a call that did no real rendering work as a rendered frame - without this, its outputFPS()/frameCountI()/ frameCountP()/avgFrameMs() would overcount for such a decoder.

Reimplemented in MPGDecoder.

isKeyFrame()

virtual bool isKeyFrame ( const uint8_t *  data, size_t  len  )

inlinevirtual

True if data (one complete encoded frame, as handed to write()) is a keyframe/sync-sample - self-contained, decodable without any earlier frame. Used e.g. by PacedVideoOutput to decide which frames are safe to drop, and whether it's safe to resume decoding after abandoning a backlog (see its own class comment). Default false: a plain VideoOutput doesn't know or care about codec structure - override this in a decoder for the bitstream format it actually parses (see H264Decoder/H264DecoderESP32S3's isH264KeyFrame()-based override, MPGDecoder's isMpeg1KeyFrame()- based one). Getting this right matters beyond bookkeeping: a target whose frames are never recognized as keyframes can leave a caller like PacedVideoOutput unable to ever resume after a resync.

Reimplemented in PacedVideoOutput, H264Decoder, H264DecoderESP32S3< Alloc >, MJPEGDecoder, MPGDecoder, and MultiVideoDecoder.

setSkipRender()

virtual void setSkipRender ( bool  skip )

inlinevirtual

Hint to skip the expensive part of displaying the next frame(s) (e.g. the panel refresh) while still accepting and fully processing write() calls - used to recover from falling behind the playback schedule without breaking a codec's decode state (e.g. H.264 inter-prediction reference chain, which requires every frame to still be decoded even if it's never shown). Default no-op: implementations that can't skip rendering cheaply just ignore it and always render.

Reimplemented in MultiVideoDecoder, OutputTinyGPU, PacedVideoOutput, and VideoFrameMeter.

write()

virtual size_t write ( const uint8_t *  data, size_t  len  )

pure virtual

Implemented in MuxerAVI, MuxerMP4, MuxerMPG, H264Decoder, H264DecoderESP32S3< Alloc >, MJPEGDecoder, MPGDecoder, MultiVideoDecoder, OutputOpenCV, OutputTFT_eSPI, OutputTinyGPU, PacedVideoOutput, and VideoFrameMeter.

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The documentation for this class was generated from the following file:

• src/AudioTools/Video/Video.h