SpoolFileSampleTableStore< T > Class Template Reference

Writes every entry to a caller-provided scratch file as it's appended, instead of keeping it in RAM - get() seeks that file and reads the entry back. Unlike SourceSeekSampleTableStore this needs no knowledge of (or seekability in) the original MP4 source - it works even when that source is a live, non-seekable stream, since it's writing its own local, sequential copy as data streams past. The tradeoff is disk I/O (both a write during parsing and a seek+read during playback) instead of a pure RAM cost. More...

#include <SampleTableStore.h>

Inheritance diagram for SpoolFileSampleTableStore< T >:

Public Member Functions
	SpoolFileSampleTableStore (SpoolStorage &spool)
void	append (T value) override
	Appends one entry - call in file order, once per table entry.
void	clear () override
	Resets to empty - call once per begin()/track.
T	get (size_t index) override
	Reads back entry 'index' - index must be < size().
virtual void	setNextEntryOffset (uint64_t fileOffset)
virtual void	setOnDiskEntrySize (size_t bytes)
size_t	size () override
	Number of entries appended so far.

Protected Attributes
size_t	entry_count = 0
SpoolStorage *	p_spool

Detailed Description

template<typename T>
class audio_tools::SpoolFileSampleTableStore< T >

Writes every entry to a caller-provided scratch file as it's appended, instead of keeping it in RAM - get() seeks that file and reads the entry back. Unlike SourceSeekSampleTableStore this needs no knowledge of (or seekability in) the original MP4 source - it works even when that source is a live, non-seekable stream, since it's writing its own local, sequential copy as data streams past. The tradeoff is disk I/O (both a write during parsing and a seek+read during playback) instead of a pure RAM cost.

Unlike SourceSeekSampleTableStore there's no endianness/on-disk-width concern here - this store's on-disk layout is its own private format (whatever bytes T's native in-memory representation happens to be), not MP4's, so a plain byte-for-byte round-trip is correct as long as the same host reads back what it wrote (true here - never persisted across runs).

Each instance needs its own dedicated SpoolStorage - see DemuxerMP4::setSpoolStorageFactory() for how one gets created per table per track.

Constructor & Destructor Documentation

SpoolFileSampleTableStore()

template<typename T >

SpoolFileSampleTableStore ( SpoolStorage &  spool )

inline

'spool' must be open for reading, writing and seeking, and empty/truncated at construction time.

Member Function Documentation

append()

template<typename T >

void append ( T  value )

inlineoverridevirtual

Appends one entry - call in file order, once per table entry.

Implements SampleTableStore< T >.

clear()

template<typename T >

void clear ( )

inlineoverridevirtual

Resets to empty - call once per begin()/track.

Implements SampleTableStore< T >.

get()

template<typename T >

T get ( size_t  index )

inlineoverridevirtual

Reads back entry 'index' - index must be < size().

Implements SampleTableStore< T >.

setNextEntryOffset()

template<typename T >

virtual void setNextEntryOffset ( uint64_t  fileOffset )

inlinevirtualinherited

Only meaningful for SourceSeekSampleTableStore: the absolute byte offset (from the start of the original MP4 file) of the entry about to be appended next. Default no-op - other implementations ignore it, so callers can always call this unconditionally before append() without needing to know which implementation is active.

Reimplemented in SourceSeekSampleTableStore< T >.

setOnDiskEntrySize()

template<typename T >

virtual void setOnDiskEntrySize ( size_t  bytes )

inlinevirtualinherited

Only meaningful for SourceSeekSampleTableStore, and only for tables whose on-disk width isn't a fixed sizeof(T) - see its comment. Default no-op.

Reimplemented in SourceSeekSampleTableStore< T >.

size()

template<typename T >

size_t size ( )

inlineoverridevirtual

Number of entries appended so far.

Implements SampleTableStore< T >.

Member Data Documentation

entry_count

template<typename T >

size_t entry_count = 0

protected

p_spool

template<typename T >

SpoolStorage* p_spool

protected

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

• src/AudioTools/AudioCodecs/SampleTableStore.h