H264::KeyframeSequencer Class Reference

#include <h264utils.h>

Detailed Description

Minimalist state machine class used to detect H.264 keyframes.

Theory of operation: A true H.264 keyframe is an IDR (instantaneous decoding refresh) slice.

You submit bytes to instances of this class, and it will tell you if you're synced on a NAL unit. More bytes and you get the type. Keep going and you'll be know when you're on keyframes.

As a bonus, if you submit stream offsets, it will track access unit offsets such that you can seek in a stream and please H.264 decoders.

This class only applies to the byte stream format as specified by ITU-T Rec. H.264 (03/2005) Annex B.

Definition at line 143 of file h264utils.h.


Public Member Functions
	KeyframeSequencer ()
bool	IsErrored (void) const
bool	HasStateChanged (void) const
void	Reset (void)
uint32_t	AddBytes (const uint8_t *bytes, const uint32_t byte_count, const int64_t stream_offset)
	This function more or less follows the method in ITU-T Rec.
uint8_t	LastSyncedType (void) const
	This function returns the NAL unit type of the last synced unit.
bool	IsOnFrame (void) const
bool	IsOnKeyframe (void) const
int64_t	KeyframeAUStreamOffset (void) const
Private Member Functions
void	KeyframePredicate (const uint8_t new_first_NAL_byte)
Private Attributes
bool	errored
bool	state_changed
uint32_t	sync_accumulator
int64_t	sync_stream_offset
uint8_t	first_NAL_byte
bool	saw_AU_delimiter
bool	saw_first_VCL_NAL_unit
bool	saw_sps
bool	did_evaluate_once
bool	keyframe
int64_t	keyframe_sync_stream_offset

Constructor & Destructor Documentation

H264::KeyframeSequencer::KeyframeSequencer ( )

Definition at line 50 of file h264utils.cpp.

Member Function Documentation

bool H264::KeyframeSequencer::IsErrored ( void ) const [inline]

Definition at line 148 of file h264utils.h.

bool H264::KeyframeSequencer::HasStateChanged ( void ) const [inline]

Definition at line 150 of file h264utils.h.

Referenced by DTVRecorder::FindH264Keyframes(), and AvFormatDecoder::H264PreProcessPkt().

void H264::KeyframeSequencer::Reset ( void )

Definition at line 55 of file h264utils.cpp.

Referenced by AvFormatDecoder::CloseContext(), KeyframeSequencer(), DTVRecorder::ResetForNewFile(), and AvFormatDecoder::ScanStreams().

uint32_t H264::KeyframeSequencer::AddBytes	(	const uint8_t *	bytes,
		const uint32_t	byte_count,
		const int64_t	stream_offset
	)

This function more or less follows the method in ITU-T Rec.

H.264 (03/2005) B.2. It returns the number of bytes it has consumed when the sequencer's state has changed or when there are no bytes left to process.

Definition at line 139 of file h264utils.cpp.

Referenced by DTVRecorder::FindH264Keyframes(), and AvFormatDecoder::H264PreProcessPkt().

uint8_t H264::KeyframeSequencer::LastSyncedType ( void ) const [inline]

This function returns the NAL unit type of the last synced unit.

Definition at line 165 of file h264utils.h.

Referenced by DTVRecorder::FindH264Keyframes().

bool H264::KeyframeSequencer::IsOnFrame ( void ) const

Definition at line 170 of file h264utils.cpp.

Referenced by DTVRecorder::FindH264Keyframes().

bool H264::KeyframeSequencer::IsOnKeyframe ( void ) const [inline]

Definition at line 169 of file h264utils.h.

Referenced by DTVRecorder::FindH264Keyframes(), and AvFormatDecoder::H264PreProcessPkt().