// Audio File Properties
音频文件获取/设置属性调用的常量
@enum Audio File Properties
@abstract constants for AudioFile get/set property call
具体的参数
音频文件的格式 char *
@constant kAudioFilePropertyFileFormat
An AudioFileTypeID that identifies the format of the file
音频数据的格式 AudioStreamPacketDescription
@constant kAudioFilePropertyDataFormat
An AudioStreamBasicDescription describing the format of the audio data
支持的格式列表 编码格式list
@constant kAudioFilePropertyFormatList
In order to support formats such as AAC SBR where an encoded data stream can be decoded to
multiple destination formats, this property returns an array of AudioFormatListItems (see AudioFormat.h) of those formats.
The default behavior is to return the an AudioFormatListItem that has the same AudioStreamBasicDescription
that kAudioFilePropertyDataFormat returns.
是否可以优化 0/1
@constant kAudioFilePropertyIsOptimized
A UInt32 indicating whether an Audio File has been optimized.
Optimized means it is ready to start having sound data written to it.
A value of 0 indicates the file needs to be optimized.
A value of 1 indicates the file is currently optimized.
Magic Cookie文件头 char *
@constant kAudioFilePropertyMagicCookieData
A void * pointing to memory set up by the caller.
Some file types require that a magic cookie be provided before packets can be written
to the file, so this property should be set before calling
AudioFileWriteBytes()/AudioFileWritePackets() if a magic cookie exists.
文件长度 Uint64
@constant kAudioFilePropertyAudioDataByteCount
a UInt64 that indicates the number of bytes of audio data contained in the file
Packet的数目 Uint64
@constant kAudioFilePropertyAudioDataPacketCount
a UInt64 that indicates the number of packets of audio data contained in the file
最大的Packet大小 Uint32
@constant kAudioFilePropertyMaximumPacketSize
a UInt32 that indicates the maximum size of a packet for the data contained in the file
数据的偏移量 SInt64
@constant kAudioFilePropertyDataOffset
a SInt64 that indicates the byte offset in the file of the audio data.
声道结构 AudioFormatListItem
@constant kAudioFilePropertyChannelLayout
An AudioChannelLayout struct.
是否更新文件头信息 1/0
@constant kAudioFilePropertyDeferSizeUpdates
A UInt32. If 1, then updating the files sizes in the header is not done for every write,
but deferred until the file is read, optimized or closed. This is more efficient, but less safe
since, if the application crashes before the size is updated, the file may not be readable.
The default value is one, it doesn't update the header.
@constant kAudioFilePropertyDataFormatName
This is deprecated. Use kAudioFormatProperty_FormatName in AudioFormat.h instead.
音频中所有markers CFStringRef表示的Markers列表
@constant kAudioFilePropertyMarkerList
access the list of markers defined in the file. returns an AudioFileMarkerList.
The CFStringRefs in the returned structs must be released by the client.
(available in 10.2.4 and later)
音频中所有Region CFStringRef表示的Region列表
@constant kAudioFilePropertyRegionList
access the list of regions defined in the file. returns an Array of AudioFileRegions.
The CFStringRefs in the returned structs must be released by the client.
(available in 10.2.4 and later)
将包数转换成帧数 AudioFramePacketTranslation中mPacket做输入，mFrame做输出
@constant kAudioFilePropertyPacketToFrame
pass a AudioFramePacketTranslation with mPacket filled out and get mFrame back. mFrameOffsetInPacket is ignored.
将帧数转换成包数 AudioFramePacketTranslation中mFrame做输入，mFrameOffsetInPacket，mPacket做输出
@constant kAudioFilePropertyFrameToPacket
pass a AudioFramePacketTranslation with mFrame filled out and get mPacket and mFrameOffsetInPacket back.
@constant kAudioFilePropertyRestrictsRandomAccess
A UInt32 indicating whether an Audio File contains packets that cannot be used as random access points.
A value of 0 indicates that any packet can be used as a random access point, i.e. that a decoder can start decoding with any packet.
A value of 1 indicates that some packets cannot be used as random access points, i.e. that kAudioFilePropertyPacketToRollDistance must be employed in order to identify an appropriate initial packet for decoding.
@constant kAudioFilePropertyPacketToRollDistance
Pass an AudioPacketRollDistanceTranslation with mPacket filled out and get mRollDistance back.
The roll distance indicates the count of packets that must be decoded prior to the packet with the specified number in order to achieve the best practice for the decoding of that packet.
For file types for which a minimal roll distance is prohibitively expensive to determine per packet, the value returned may be derived from an upper bound for all packet roll distances.
If the value of kAudioFilePropertyRestrictsRandomAccess is 1, either kAudioFilePropertyPacketToRollDistance
or kAudioFilePropertyPacketToDependencyInfo must be used in order to identify an appropriate random access point.
If the value of kAudioFilePropertyRestrictsRandomAccess is 0, kAudioFilePropertyPacketToRollDistance can be used in
order to identify the best available random access point, which may be prior to the specified packet even if the specified
packet can be used as a random access point.
@constant kAudioFilePropertyPreviousIndependentPacket
@constant kAudioFilePropertyNextIndependentPacket
Pass an AudioIndependentPacketTranslation with mPacket filled out and get mIndependentlyDecodablePacket back.
A value of -1 means that no independent packet is present in the stream in the direction of interest. Otherwise,
for kAudioFilePropertyPreviousIndependentPacket, mIndependentlyDecodablePacket will be less than mPacket, and
for kAudioFilePropertyNextIndependentPacket, mIndependentlyDecodablePacket will be greater than mPacket.
@constant kAudioFilePropertyPacketToDependencyInfo
Pass an AudioPacketDependencyInfoTranslation with mPacket filled out and get mIsIndependentlyDecodable
and mPrerollPacketCount back.
A value of 0 for mIsIndependentlyDecodable indicates that the specified packet is not independently decodable.
A value of 1 for mIsIndependentlyDecodable indicates that the specified packet is independently decodable.
For independently decodable packets, mPrerollPacketCount indicates the count of packets that must be decoded
after the packet with the specified number in order to refresh the decoder.
If the value of kAudioFilePropertyRestrictsRandomAccess is 1, either kAudioFilePropertyPacketToRollDistance or
kAudioFilePropertyPacketToDependencyInfo must be used in order to identify an appropriate random access point.
将包数转换成字节数 AudioFramePacketTranslation中mPacket做输入，mByte做输出
@constant kAudioFilePropertyPacketToByte
pass an AudioBytePacketTranslation struct with mPacket filled out and get mByte back.
mByteOffsetInPacket is ignored. If the mByte value is an estimate then
kBytePacketTranslationFlag_IsEstimate will be set in the mFlags field.
将字节数转换成包数 AudioFramePacketTranslation中mByte做输入，mPacket和mByteOffsetInPacket做输出
@constant kAudioFilePropertyByteToPacket
pass an AudioBytePacketTranslation struct with mByte filled out and get mPacket and
mByteOffsetInPacket back. If the mPacket value is an estimate then
kBytePacketTranslationFlag_IsEstimate will be set in the mFlags field.
文件中的chunk编码格式 4字符编码格式数组
@constant kAudioFilePropertyChunkIDs
returns an array of OSType four char codes for each kind of chunk in the file.
字典表示的Info CFDictionary
@constant kAudioFilePropertyInfoDictionary
returns a CFDictionary filled with information about the data contained in the file.
See dictionary key constants already defined for info string types.
AudioFileComponents are free to add keys to the dictionaries that they return for this property...
caller is responsible for releasing the CFObject
设置PacketTableInfo PacketTableInfo
@constant kAudioFilePropertyPacketTableInfo
Gets or sets an AudioFilePacketTableInfo struct for the file types that support it.
When setting, the sum of mNumberValidFrames, mPrimingFrames and mRemainderFrames must be the same as the total
number of frames in all packets. If not you will get a kAudio_ParamError. The best way to ensure this is to get the value of
the property and make sure the sum of the three values you set has the same sum as the three values you got.
理论上的最大Packet大小 Uint64
@constant kAudioFilePropertyPacketSizeUpperBound
a UInt32 for the theoretical maximum packet size in the file (without actually scanning
the whole file to find the largest packet, as may happen with kAudioFilePropertyMaximumPacketSize).
@constant kAudioFilePropertyPacketRangeByteCountUpperBound
Pass an AudioPacketRangeByteCountTranslation with mPacket and mPacketCount filled out
and get mByteCountUpperBound back. The value of mByteCountUpperBound can be used to allocate a buffer
for use with AudioFileReadPacketData in order to accommodate the entire packet range.
May require scanning in order to obtain the requested information, but even if so, no scanning will occur
beyond the last packet in the specified range.
For file formats in which packets are directly accessible and stored both contiguously and byte-aligned,
the returned upper bound will be equal to the total size of the packets in the range. Otherwise the
upper bound may reflect per-packet storage overhead.
设置写保护区大小，单位为秒 Uint32
@constant kAudioFilePropertyReserveDuration
The value is a Float64 of the duration in seconds of data that is expected to be written.
Setting this property before any data has been written reserves space in the file header for a packet table
and/or other information so that it can appear before the audio data. Otherwise the packet table may get written at the
end of the file, preventing the file from being streamable.
估算的音频时长 ， 单位秒 Uint32
@constant kAudioFilePropertyEstimatedDuration
The value is a Float64 representing an estimated duration in seconds. If duration can be calculated without scanning the entire file,
or all the audio data packets have been scanned, the value will accurately reflect the duration of the audio data.
码率 Uint32
@constant kAudioFilePropertyBitRate
Returns the bit rate for the audio data as a UInt32. For some formats this will be approximate.
位深度 Uint32
@constant kAudioFilePropertySourceBitDepth
For encoded data this property returns the bit depth of the source as an SInt32, if known.
The bit depth is expressed as a negative number if the source was floating point, e.g. -32 for float, -64 for double.
专辑名 CFDataRef
@constant kAudioFilePropertyAlbumArtwork
returns a CFDataRef filled with the Album Art or NULL.
The caller is responsible for releasing a non-NULL CFDataRef.
In order to parse the contents of the data, CGImageSourceCreateWithData may be used.
@constant kAudioFilePropertyAudioTrackCount
a UInt32 that indicates the number of audio tracks contained in the file. (get property only)
@constant kAudioFilePropertyUseAudioTrack
a UInt32 that indicates the number of audio tracks contained in the file. (set property only)
@constant kAudioFilePropertyID3Tag
A void * pointing to memory set up by the caller to contain a fully formatted ID3 tag (get/set v2.2, v2.3, or v2.4, v1 get only).
The ID3 tag is not manipulated in anyway either for read or write.
When setting, this property must be called before calling AudioFileWritePackets.
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