cs-iso14496 20240422

Facilities for ISO14496 files - the ISO Base Media File Format, the basis for several things including MP4 and MOV.

Facilities for ISO14496 files - the ISO Base Media File Format, the basis for several things including MP4 and MOV.

Latest release 20240422:

• Replace dropped UTF16NULField with BinaryUTF16NUL.
• Comment out unused CO64BoxBody.chunk_offsets, uses dropped (and not replaced) deferred_field.
• Drop FallbackBoxBody, we'll just use BoxBody when there's no box specific subclass.
• Replace pick_boxbody_class with BoxBody.for_box_type.
• Rename boxbody_type_from_klass to boxbody_type_from_class.
• Drop obsolete KNOWN_BOXBODY_CLASSES.
• MP4Command.cmd_info: print moov.udta.meta.ilst.cover in SIXEL format on a terminal.
• Rename parse_deref_path to get_deref_path like other lexical functions.
• ILSTBoxBody.getattr: fix lookup of long names.

ISO make the standard available here:

• available standards main page
• zip file download

Function add_body_subclass(superclass, box_type, section, desc)

Create and register a new BoxBody class that is simply a subclass of another. Return the new class.

Function add_generic_sample_boxbody(box_type, section, desc, struct_format_v0, sample_fields, struct_format_v1=None, has_inferred_entry_count=False)

Create and add a specific Time to Sample box - section 8.6.1.

Function add_time_to_sample_boxbody(box_type, section, desc)

Add a Time to Sample box - section 8.6.1.

Class Box(cs.binary.SimpleBinary)

Base class for all boxes - ISO14496 section 4.2.

This has the following fields:

• header: a BoxHeader
• body: a BoxBody instance, usually a specific subclass
• unparsed: any unconsumed bytes from the Box are stored as here

Property Box.BOX_TYPE: The default .BOX_TYPE is inferred from the class name.

Method Box.__getattr__(self, attr): If there is no direct attribute from SimpleBinary.__getattr__, have a look in the .header and .body.

Method Box.__iter__(self): Iterating over a Box iterates over its body. Typically that would be the .body.boxes but might be the samples if the body is a sample box, etc.

Method Box.ancestor(self, box_type): Return the closest ancestor box of type box_type.

Property Box.box_type: The Box header type.

Property Box.box_type_path: The type path to this Box.

Property Box.box_type_s: The Box header type as a string.

If the header type bytes decode as ASCII, return that, otherwise the header bytes' repr().

Method Box.dump(self, **kw): Dump this Box.

Method Box.gather_metadata(self): Walk the Box hierarchy looking for metadata. Yield (Box,TagSet) for each b'moov' or b'trak' Box.

Method Box.metatags(self): Return a TagSet containing metadata for this box.

Method Box.parse(bfr: cs.buffer.CornuCopyBuffer): Decode a Box from bfr and return it.

Method Box.parse_field(self, field_name, bfr: cs.buffer.CornuCopyBuffer, binary_cls): parse_field delegates to the Box body parse_field.

Property Box.parse_length: The length of the box as consumed from the buffer, computed as self.end_offset-self.offset.

Method Box.reparse_buffer(self): Context manager for continuing a parse from the unparsed field.

Pops the final unparsed field from the Box, yields a CornuCopyBuffer make from it, then pushes the unparsed field again with the remaining contents of the buffer.

Method Box.self_check(self): Sanity check this Box.

Method Box.transcribe(self): Transcribe the Box.

Before transcribing the data, we compute the total box_size from the lengths of the current header, body and unparsed components, then set the header length if that has changed. Since setting the header length can change its representation we compute the length again and abort if it isn't stable. Otherwise we proceeed with a regular transcription.

Property Box.unparsed_bs: The unparsed data as a single bytes instance.

Property Box.user_type: The header user_type.

Method Box.walk(self) -> Iterable[Tuple[ForwardRef('Box'), List[ForwardRef('Box')]]]: Walk this Box hierarchy.

Yields the starting box and its children as (self,subboxes) and then yields (subbox,subsubboxes) for each child in turn.

As with os.walk, the returned subboxes list may be modified in place to prune or reorder the subsequent walk.

Class BoxBody(cs.binary.SimpleBinary)

Abstract basis for all Box bodies.

Method BoxBody.__getattr__(self, attr): The following virtual attributes are defined:

• TYPEs: "boxes of type TYPE", an uppercased box type name with a training s; a list of all elements whose .box_type equals TYPE.lower().encode('ascii'). The elements are obtained by iterating over self which normally means iterating over the .boxes attribute.
• TYPE: "the box of type TYPE", an uppercased box type name; the sole element whose box type matches the type, obtained from .TYPEs[0] with a requirement that there is exactly one match.
• TYPE0: "the optional box of type TYPE", an uppercased box type name with a trailing 0; the sole element whose box type matches the type, obtained from .TYPEs[0] with a requirement that there is exactly zero or one match. If there are zero matches, return None. Otherwise return the matching box.

Method BoxBody.add_field(self, field_name, value): Add a field named field_name with the specified value to the box fields.

Method BoxBody.boxbody_type_from_class(): Compute the Box's 4 byte type field from the class name.

Method BoxBody.for_box_type(box_type: bytes): Return the BoxBody subclass suitable for the box_type.

Method BoxBody.parse(bfr: cs.buffer.CornuCopyBuffer): Create a new instance and gather the Box body fields from bfr.

Subclasses implement a parse_fields method to parse additional fields.

Method BoxBody.parse_boxes(self, bfr: cs.buffer.CornuCopyBuffer, **kw): Utility method to parse the remainder of the buffer as a sequence of Boxes.

Method BoxBody.parse_field(self, field_name, bfr: cs.buffer.CornuCopyBuffer, binary_cls): Parse an instance of binary_cls from bfr and store it as the attribute named field_name.

binary_cls may also be an int, in which case that many bytes are read from bfr.

Method BoxBody.parse_field_value(self, field_name, bfr: cs.buffer.CornuCopyBuffer, binary_cls): Parse a single value binary, store the value as field_name, store the instance as the field field_name+'__Binary' for transcription.

Note that this disassociaes the plain value attribute from what gets transcribed.

Method BoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Parse additional fields. This base class implementation consumes nothing.

Method BoxBody.transcribe(self): Transcribe the binary structure.

This default implementation transcribes the fields parsed with the parse_field method in the order parsed.

Method BoxBody.transcribe_fields(self): Transcribe the fields parsed with the parse_field method in the order parsed.

Class BoxHeader(cs.binary.BoxHeader)

An ISO14496 Box header packet.

Method BoxHeader.parse(bfr: cs.buffer.CornuCopyBuffer): Decode a box header from bfr.

Class BTRTBoxBody(BoxBody)

BitRateBoxBody - section 8.5.2.2.

Method BTRTBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the bufferSizeDB, maxBitrate and avgBitrate fields.

Class CO64BoxBody(FullBoxBody)

A 'c064' Chunk Offset box - section 8.7.5.

Method CO64BoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the entry_count and chunk_offsets fields.

Method CO64BoxBody.transcribe(self): Transcribe a CO64BoxBody.

Class ContainerBoxBody(BoxBody)

Common subclass of several things with .boxes.

Class CPRTBoxBody(FullBoxBody)

A 'cprt' Copyright box - section 8.10.2.

Property CPRTBoxBody.language: The language_field as the 3 character ISO 639-2/T language code.

Method CPRTBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the language and notice fields.

Class CSLGBoxBody(FullBoxBody)

A 'cslg' Composition to Decode box - section 8.6.1.4.

CSLGBoxBody.CSLGParamsLong

CSLGBoxBody.CSLGParamsQuad

Method CSLGBoxBody.__getattr__(self, attr): Present the params attributes at the top level.

Method CSLGBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the compositionToDTSShift, leastDecodeToDisplayDelta, greatestDecodeToDisplayDelta, compositionStartTimeandcompositionEndTime` fields.

Function decode_itunes_date_field(data) -> datetime.datetime

The iTunes 'Date' meta field: a year or an ISO timestamp.

Function deref_box(B, path)

Dereference a path with respect to this Box.

Class DREFBoxBody(FullBoxBody)

A 'dref' Data Reference box containing Data Entry boxes - section 8.7.2.1.

Method DREFBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the entry_count and boxes fields.

Function dump_box(B, indent='', fp=None, crop_length=170, indent_incr=None)

Recursively dump a Box.

Class ELNGBoxBody(FullBoxBody)

A ELNGBoxBody is a Extended Language Tag box - ISO14496 section 8.4.6.

Method ELNGBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the extended_language field.

Class ELSTBoxBody(FullBoxBody)

An 'elst' Edit List FullBoxBody - section 8.6.6.

ELSTBoxBody.V0EditEntry

ELSTBoxBody.V1EditEntry

Property ELSTBoxBody.entry_class: The class representing each entry.

Property ELSTBoxBody.entry_count: The number of entries.

Method ELSTBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Parse the fields of an ELSTBoxBody.

Method ELSTBoxBody.transcribe(self): Transcribe an ELSTBoxBody.

Class FREEBoxBody(BoxBody)

A 'free' or 'skip' box - ISO14496 section 8.1.2. Note the length and discard the data portion.

Method FREEBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer, end_offset=Ellipsis, **kw): Gather the padding field.

Class FTYPBoxBody(BoxBody)

An 'ftyp' File Type box - ISO14496 section 4.3. Decode the major_brand, minor_version and compatible_brands.

Property FTYPBoxBody.compatible_brands: The compatible brands as a list of 4 byte bytes instances.

Method FTYPBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer, **kw): Gather the major_brand, minor_version and brand_bs fields.

Class FullBoxBody(BoxBody)

A common extension of a basic BoxBody, with a version and flags field. ISO14496 section 4.2.

Property FullBoxBody.flags: The flags value, computed from the 3 flag bytes.

Function get_deref_path(path, offset=0)

Parse a path string from offset. Return the path components and the offset where the parse stopped.

Path components:

• identifier: an identifier represents a Box field or if such a field is not present, a the first subbox of this type
• [index]: the subbox with index index

Examples:

>>> get_deref_path('.abcd[5]')
(['abcd', 5], 8)

Class HDLRBoxBody(FullBoxBody)

A HDLRBoxBody is a Handler Reference box - ISO14496 section 8.4.3.

Property HDLRBoxBody.handler_type: The handler_type as an ASCII string, its usual form.

Method HDLRBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the handler_type_long and name fields.

Function ILSTAofBSchema(attribute_name)

Attribute name and type for ILST "A of B" schema.

Class ILSTBoxBody(ContainerBoxBody)

Apple iTunes Information List, container for iTunes metadata fields.

The basis of the format knowledge here comes from AtomicParsley's documentation here:

http://atomicparsley.sourceforge.net/mpeg-4files.html

and additional information from:

https://github.com/sergiomb2/libmp4v2/wiki/iTunesMetadata

Method ILSTBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): pylint: disable=attribute-defined-outside-init,too-many-locals pylint: disable=too-many-statements,too-many-branches

Function ILSTISOFormatSchema(attribute_name)

Attribute name and type for ILST ISO format schema.

Function ILSTRawSchema(attribute_name)

Attribute name and type for ILST raw schema.

Function ILSTTextSchema(attribute_name)

Attribute name and type for ILST text schema.

Function ILSTUInt32BESchema(attribute_name)

Attribute name and type for ILST UInt32BE schema.

Function ILSTUInt8Schema(attribute_name)

Attribute name and type for ILST UInt8BE schema.

Class itunes_media_type(builtins.tuple)

itunes_media_type(type, stik)

Property itunes_media_type.stik: Alias for field number 1

Property itunes_media_type.type: Alias for field number 0

Class itunes_store_country_code(builtins.tuple)

itunes_store_country_code(country_name, iso_3166_1_code, itunes_store_code)

Property itunes_store_country_code.country_name: Alias for field number 0

Property itunes_store_country_code.iso_3166_1_code: Alias for field number 1

Property itunes_store_country_code.itunes_store_code: Alias for field number 2

Function main(argv=None)

Command line mode.

Class MDATBoxBody(BoxBody)

A Media Data Box - ISO14496 section 8.1.1.

Method MDATBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather all data to the end of the field.

Method MDATBoxBody.transcribe(self): Transcribe the data. Raise an AssertionError if we skipped the data during the parse.

Method MDATBoxBody.transcribed_length(self): Return the transcription length even if we didn't keep the data.

Class MDHDBoxBody(FullBoxBody)

A MDHDBoxBody is a Media Header box - ISO14496 section 8.4.2.

Method MDHDBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the creation_time, modification_time, timescale, duration and language_short fields.

Class METABoxBody(FullBoxBody)

A 'meta' Meta BoxBody - section 8.11.1.

Method METABoxBody.__getattr__(self, attr): Present the ilst attributes if present.

Method METABoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the theHandler Box and gather the following Boxes as boxes.

Class MOOVBoxBody(ContainerBoxBody)

An 'moov' Movie box - ISO14496 section 8.2.1. Decode the contained boxes.

Class MP4Command(cs.cmdutils.BaseCommand)

Command line implementation.

Usage summary:

Usage: mp4 subcommand [...]
  Subcommands:
    autotag [-n] [-p prefix] [--prefix=prefix] paths...
      Tag paths based on embedded MP4 metadata.
      -n  No action.
      -p prefix, --prefix=prefix
          Set the prefix of added tags, default: 'mp4'
    deref boxspec paths...
      Dereference a Box specification against ISO14496 files.
    extract [-H] filename boxref output
      Extract the referenced Box from the specified filename into output.
      -H  Skip the Box header.
    help [-l] [subcommand-names...]
      Print help for subcommands.
      This outputs the full help for the named subcommands,
      or the short help for all subcommands if no names are specified.
      -l  Long help even if no subcommand-names provided.
    info [{-|filename}]...]
      Print informative report about each source.
    parse [{-|filename}...]
      Parse the named files (or stdin for "-").
    shell
      Run a command prompt via cmd.Cmd using this command's subcommands.
    tags [{-p,--prefix} prefix] path
      Report the tags of `path` based on embedded MP4 metadata.
    test [testnames...]
      Run self tests.

Method MP4Command.cmd_autotag(self, argv, fstags: Optional[cs.fstags.FSTags] = <function <lambda> at 0x108080040>): Usage: {cmd} [-n] [-p prefix] [--prefix=prefix] paths... Tag paths based on embedded MP4 metadata. -n No action. -p prefix, --prefix=prefix Set the prefix of added tags, default: 'mp4'

Method MP4Command.cmd_deref(self, argv): Usage: {cmd} boxspec paths... Dereference a Box specification against ISO14496 files.

Method MP4Command.cmd_extract(self, argv): Usage: {cmd} [-H] filename boxref output Extract the referenced Box from the specified filename into output. -H Skip the Box header.

Method MP4Command.cmd_info(self, argv): Usage: {cmd} [{{-|filename}}]...] Print informative report about each source.

Method MP4Command.cmd_parse(self, argv): Usage: {cmd} [{{-|filename}}...] Parse the named files (or stdin for "-").

Method MP4Command.cmd_tags(self, argv): Usage: {cmd} [{{-p,--prefix}} prefix] path Report the tags of path based on embedded MP4 metadata.

Method MP4Command.cmd_test(self, argv): Usage: {cmd} [testnames...] Run self tests.

Class MVHDBoxBody(FullBoxBody)

An 'mvhd' Movie Header box - ISO14496 section 8.2.2.

Class OverBox(cs.binary.BinaryListValues, HasBoxesMixin)

A fictitious Box encompassing all the Boxes in an input buffer.

Property OverBox.boxes: Alias .value as .boxes: the Boxes encompassed by this OverBox.

Method OverBox.dump(self, **kw): Dump this OverBox.

Property OverBox.length: The OverBox is as long as the subsidary Boxes.

Method OverBox.parse(bfr: cs.buffer.CornuCopyBuffer): Parse the OverBox.

Method OverBox.walk(self): Walk the Boxes in the OverBox.

This does not yield the OverBox itself, it isn't really a Box.

Function parse(o)

Return the OverBox from a source (str, int, bytes, file).

The leading o parameter may be one of:

• str: a filesystem file pathname
• int: a OS file descriptor
• bytes: a bytes object
• file: if not int or str the presumption is that this is a file-like object

Keyword arguments are as for OverBox.from_buffer.

Function parse_fields(bfr, copy_offsets=None, **kw)

Parse an ISO14496 stream from the CornuCopyBuffer bfr, yield top level OverBoxes.

Parameters:

• bfr: a CornuCopyBuffer provided the stream data, preferably seekable
• discard_data: whether to discard unparsed data, default False
• copy_offsets: callable to receive Box offsets

Function parse_tags(path, tag_prefix=None)

Parse the tags from path. Yield (box,tags) for each subbox with tags.

The optional tag_prefix parameter may be specified to prefix each tag name with a prefix. Other keyword arguments are passed to parse() (typical example: discard_data=True).

Class PDINBoxBody(FullBoxBody)

A 'pdin' Progressive Download Information box - ISO14496 section 8.1.3.

PDINBoxBody.PDInfo

Method PDINBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer, **kw): Gather the normal version information and then the (rate,initial_delay) pairs of the data section as the pdinfo field.

Function report(box, indent='', fp=None, indent_incr=None)

Report some human friendly information about a box.

Class SMHDBoxBody(FullBoxBody)

A 'smhd' Sound Media Headerbox - section 12.2.2.

Method SMHDBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the balance field.

Class STCOBoxBody(FullBoxBody)

A 'stco' Chunk Offset box - section 8.7.5.

Property STCOBoxBody.chunk_offsets: Parse the UInt32BE chunk offsets from stashed buffer.

Method STCOBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the entry_count and chunk_offsets fields.

Class STSCBoxBody(FullBoxBody)

'stsc' (Sample Table box - section 8.7.4.1.

STSCBoxBody.STSCEntry

Property STSCBoxBody.entries: A list of ints parsed from the STSCEntry list.

Method STSCBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the entry_count and entries fields.

Class STSZBoxBody(FullBoxBody)

A 'stsz' Sample Size box - section 8.7.3.2.

Property STSZBoxBody.entry_sizes: Parse the UInt32BE entry sizes from stashed buffer into a list of ints.

Method STSZBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the sample_size, sample_count, and entry_sizes fields.

Method STSZBoxBody.transcribe(self): Transcribe the STSZBoxBody.

Class STZ2BoxBody(FullBoxBody)

A 'stz2' Compact Sample Size box - section 8.7.3.3.

Method STZ2BoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the field_size, sample_count and entry_sizes fields.

Method STZ2BoxBody.transcribe(self): transcribe the STZ2BoxBody.

Class TimeStamp32(cs.binary.UInt32BE, TimeStampMixin)

The 32 bit form of an ISO14496 timestamp.

Class TimeStamp64(cs.binary.UInt64BE, TimeStampMixin)

The 64 bit form of an ISO14496 timestamp.

Class TimeStampMixin

Methods to assist with ISO14496 timestamps.

Property TimeStampMixin.datetime: This timestamp as an UTC datetime.

Property TimeStampMixin.unixtime: This timestamp as a UNIX time (seconds since 1 January 1970).

Class TKHDBoxBody(FullBoxBody)

A 'tkhd' Track Header box - ISO14496 section 8.2.2.

TKHDBoxBody.TKHDMatrix

Class TrackGroupTypeBoxBody(FullBoxBody)

A TrackGroupTypeBoxBody contains a track group id - ISO14496 section 8.3.3.2.

Method TrackGroupTypeBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the track_group_id field.

Class TrackReferenceTypeBoxBody(BoxBody)

A TrackReferenceTypeBoxBody contains references to other tracks - ISO14496 section 8.3.3.2.

Method TrackReferenceTypeBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the track_ids field.

Class TREFBoxBody(ContainerBoxBody)

Track Reference BoxBody, container for trackReferenceTypeBoxes - ISO14496 section 8.3.3.

Class TTSB_Sample(builtins.tuple)

TTSB_Sample(count, delta)

Property TTSB_Sample.count: Alias for field number 0

Property TTSB_Sample.delta: Alias for field number 1

Class URL_BoxBody(FullBoxBody)

An 'url ' Data Entry URL BoxBody - section 8.7.2.1.

Method URL_BoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the location field.

Class URN_BoxBody(FullBoxBody)

An 'urn ' Data Entry URL BoxBody - section 8.7.2.1.

Method URN_BoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the name and location fields.

Class UTF8or16Field(cs.binary.SimpleBinary)

An ISO14496 UTF8 or UTF16 encoded string.

Method UTF8or16Field.parse(bfr: cs.buffer.CornuCopyBuffer): Gather optional BOM and then UTF8 or UTF16 string.

Method UTF8or16Field.transcribe(self): Transcribe the field suitably encoded.

Class VMHDBoxBody(FullBoxBody)

A 'vmhd' Video Media Headerbox - section 12.1.2.

VMHDBoxBody.OpColor

Method VMHDBoxBody.parse_fields(self, bfr: cs.buffer.CornuCopyBuffer): Gather the graphicsmode and opcolor fields.

Release Log

Release 20240422:

• Replace dropped UTF16NULField with BinaryUTF16NUL.
• Comment out unused CO64BoxBody.chunk_offsets, uses dropped (and not replaced) deferred_field.
• Drop FallbackBoxBody, we'll just use BoxBody when there's no box specific subclass.
• Replace pick_boxbody_class with BoxBody.for_box_type.
• Rename boxbody_type_from_klass to boxbody_type_from_class.
• Drop obsolete KNOWN_BOXBODY_CLASSES.
• MP4Command.cmd_info: print moov.udta.meta.ilst.cover in SIXEL format on a terminal.
• Rename parse_deref_path to get_deref_path like other lexical functions.
• ILSTBoxBody.getattr: fix lookup of long names.

Release 20231129: Small updates and fixes.

Release 20230212:

• Drop cs.context.StackableState in favour of cs.threads.State.
• MP4Command.cmd_autotag: use @uses_fstags for the fstags parameter.

Release 20220606: Update obsolete use of Tag.with_prefix.

Release 20210306:

• Huge refactor of the Box classes to the new Binary* classes from cs.binary.
• mp4: new "tags" subcommand to print the tags parsed from a file.
• BoxHeader: fix the definition of MAX_BOX_SIZE_32.
• BoxBody: new parse_boxes utility method to part the remainder of a Box as subBoxes.
• MP4.cmd_parse: run the main parse in discard_data=True mode.
• METABoxBody.getattr: fix ILST typo.
• MP4Command: update for new cs.cmdutils.BaseCommand API.
• Many small fixes and tweaks.

Release 20200229:

• ILST: recognise @cpy as copyright, sfID as itunes_store_country_code.
• ILST: new SFID_ISO_3166_1_ALPHA_3_CODE and STIK_MEDIA_TYPES providing context data for various field values, as yet unused.
• Make various list fields of some boxes deferred because they are expensive to parse (uses new cs.binary deferred_field).
• add_generic_sample_boxbody: drop iter, causes dumb iterators to parse the samples.
• ILST: iTunes "Date" metadata seem to contain plain years or ISO8601 datestamps.
• mp4 autotag: add -n (no action) and -p,--prefix (set tag prefix, default 'mp4') options.
• mp4 autotag: use "mp4." as the tag prefix.

Release 20200130:

• Parsing of ILST boxes (iTunes metadata).
• Command line: new "info" subcommand reporting metadata, "autotag" applying metadata to fstags.
• Box tree walk, ancestor, iteration.
• Assorted cleanups and internal changes.

Release 20190220: parse_buffer yields instead of returns; some small bugfixes.

Release 20180810:

• parse_fd(): use a mmap to access the descriptor if a regular file and not discard_data;
• this lets us use the mmapped file as backing store for the data, a big win for the media sections.

Release 20180805: Initial PyPI release.