Sound Metadata

2019年10月14日

Metadata记录了音频文件的元数据信息，包括声音的类别、描述、制作发行机构或个人、制作发行时间、所属专辑等等。由于历史原因，目前有多种协议、规范被广泛应用于不同的DAW、元数据管理工具及媒体播放器。在制作发行音效库时应该尽量兼容这些规范以保证素材可被更多工具正确检索。

标准本身及兼容情况

Name	Format	Specification	Metadata apps	Editing apps
BWAV	Open	Fixed	Basehead, BWF Metaedit, Soundly, Soundminer, Wave Agent	Audition, Nuendo, Peak, Pro Tools, Pyramix, SaDiE, Sequoia, soundBlade, Sound Forge Pro, Wave Agent, WaveLab
iXML	Open	Fixed + extensible	Basehead, BWF Metaedit, Soundly, Soundminer, Wave Agent	Audition, Cubase (extended tags), Final Cut Pro, Nuendo (extended tags), Pro Tools (standard tags), WaveLab
XMP	Open	Fixed + extensible	Soundminer	Audition, Premiere Pro CC
Soundminer Metawrapper	Closed	Fixed + evolving	Soundminer	Pro Tools
ID3	Open	Fixed	Basehead, iTunes, Soundminer, MP3TAG, TagScanner, many others	Audacity, WaveLab
MP4	Open	Fixed + optional XMP	iTunes, MP3TAG, Soundminer, TagScanner, many others	WaveLab
Vorbis	Open	Fixed	foobar2000, MP3TAG, TagScanner
LIST-INFO	Open	Fixed	BWF Metaedit, Soundminer	Audition, Audacity, Sound Forge, WaveLab

Metadata格式解析

Riff and fmt chunk

微软 wav 格式的头部，包括编码方式、采样率、通道数、字节率、Bit深度等信息。

5249 4646  98f4 3a00  5741 5645  666d 7420  1000 0000  0100 0200  0077 0100  00ca 0800  0600         1800 
R I  F F   size       W A  V E   f m  t                pcm  chn   SR         Byte rate  Block Align  Bit Depth 

Bext chunk

Broadcast Wave Format (BWF) 是Microsoft WAV格式的扩展，最早由European Broadcasting Union（EBU）于1997年提出初版，在2001年和2003年两次修订，最终成为 ITU建议 ITU-R BS.1352-3。其中2001年的 version1 定义了的如今广泛使用的Broadcast Audio Extension（bext）块。作为音效库元数据应用时，主要用到 Description, Originator, OriginatorReference, OriginationDate, OriginationTime 5个字段。按照规范要求，这5个字段应按 ASCII 格式编码。但各大音效库制作厂商并没有严格遵循，导致部分音效库采用了 ASCII-ext，甚至是 utf-8 编码。

broadcast_audio_extension typedef struct {
  DWORD ckID; /* (broadcastextension)ckID=bext. */
  DWORD ckSize; /* size of extension chunk */
  BYTE ckData[ckSize]; /* data of the chunk */
}
typedef struct broadcast_audio_extension {
  CHAR Description[256]; /* ASCII : «Description of the sound sequence» */
  CHAR Originator[32]; /* ASCII : «Name of the originator» */
  CHAR OriginatorReference[32]; /* ASCII : «Reference of the originator» */
  CHAR OriginationDate[10]; /* ASCII : «yyyy:mm:dd» */ 
  CHAR OriginationTime[8]; /* ASCII : «hh:mm:ss» */
  DWORD TimeReferenceLow; /* First sample count since midnight, low word */
  DWORD TimeReferenceHigh; /* First sample count since midnight, high word */
  WORD Version; /* Version of the BWF; unsigned binary number */
  BYTE UMID_0 /* Binary byte 0 of SMPTE UMID */
  ....
  BYTE UMID_63 /* Binary byte 63 of SMPTE UMID */
  WORD LoudnessValue; /* WORD : «Integrated Loudness Value of the file in LUFS (multiplied by 100) » */
  WORD LoudnessRange; /* WORD : «Loudness Range of the file in LU (multiplied by 100) » */
  WORD MaxTruePeakLevel; /* WORD : «Maximum True Peak Level of the file expressed as dBTP (multiplied by 100) » */
  WORD MaxMomentaryLoudness; /* WORD : «Highest value of the Momentary Loudness Level of the file in LUFS (multiplied by 100) » */
  WORD MaxShortTermLoudness; /* WORD : «Highest value of the Short-Term Loudness Level of the file in LUFS (multiplied by 100) » */
  BYTE Reserved[180]; /* 180 bytes, reserved for future use, set to “NULL” */
  CHAR CodingHistory[]; /* ASCII : « History coding » */
} BROADCAST_EXT 

例如：

6265 7874  5c02 0000  5549 2053  4d41 4c4c  2048 4947  4820 5469  6e79 2061  6e64 2067  6c61 7373  7920 636c  6963 6b73  2e00
b e  x t   size 604   U I    S   M A  L L     H  I G   H    T i   n y    a   n d    g   l a  s s   y    c l   i c  k s   .

c2a9 2032  3031 3820 424f 4f4d 204c 6962 7261 7279 2041 6c6c 2052 6967 6874 7320 7777 772e 626f 6f6d 6c69 6272 6172 792e 636f 6d00
©      2   0 1  8    B O  OM     L  ib   ra   ry     A  ll     R  ig   ht   s    ww   w.   bo   om   li   br   ar   y.   co   m

iXML Chunk

iXML 作为 BWF 的实现，通过xml突破了bext字段长度和编码的限制，提升了扩展性。 DAW 及元数据管理工具（如 sound minner 等）也喜欢在写入元数据时加入自己的标签和格式。为了更好的兼容，往往需要塞入大量冗余的元数据，例如：

<?xml version="1.0" encoding="utf-8"?>
<BWFXML>
  <IXML_VERSION>1.61</IXML_VERSION>
  <STEINBERG>
    <ATTR_LIST>
      <ATTR><NAME>MediaLibrary</NAME><TYPE>string</TYPE><VALUE>Modern UI</VALUE></ATTR>
      <ATTR><NAME>MediaCategoryPost</NAME><TYPE>string</TYPE><VALUE>User Interface</VALUE></ATTR>
      <ATTR><NAME>MediaLibraryManufacturerName</NAME><TYPE>string</TYPE><VALUE>BOOM Library</VALUE></ATTR>
      <ATTR><NAME>MediaArtist</NAME><TYPE>string</TYPE><VALUE>BOOM Library</VALUE></ATTR>
      <ATTR><NAME>MediaComment</NAME><TYPE>string</TYPE><VALUE>UI SMALL HIGH Tiny and glassy clicks.</VALUE></ATTR>
      <ATTR><NAME>MusicalCategory</NAME><TYPE>string</TYPE><VALUE>User Interface</VALUE></ATTR>
      <ATTR><NAME>SmfSongName</NAME><TYPE>string</TYPE><VALUE>MUI SELECT DIGITAL Beep Tiny.wav</VALUE></ATTR>
    </ATTR_LIST>
  </STEINBERG>
  <BEXT>
    <BWF_DESCRIPTION>UI SMALL HIGH Tiny and glassy clicks.</BWF_DESCRIPTION>
    <BWF_ORIGINATOR>BOOM Library</BWF_ORIGINATOR>
    <BWF_ORIGINATION_DATE>2003-10-30</BWF_ORIGINATION_DATE>
    <BWF_ORIGINATION_TIME>03:27:17</BWF_ORIGINATION_TIME>
  </BEXT>
</BWFXML>

iXML 块也经常被数字录音机用作同期录音的元数据格式，比如俺的 MixPre-6。这时用到的字段类似如下这些：

<?xml version="1.0" encoding="UTF-8"?>
<BWFXML>
  <IXML_VERSION>1.52</IXML_VERSION>
  <PROJECT>ANewMovie</PROJECT>
  <SCENE>21</SCENE>
  <TAKE>33</TAKE>
  <TAPE>10</TAPE>
  <CIRCLED>TRUE</CIRCLED>
  <NO_GOOD>FALSE</NO_GOOD>
  <FALSE_START>FALSE</FALSE_START>
  <WILD_TRACK>FALSE</WILD_TRACK>
  <FILE_UID>MTIPMX17654200508051445053840001</FILE_UID>
  <SPEED>
    <NOTE>camera overcranked</NOTE>
    <MASTER_SPEED>24/1</MASTER_SPEED>
    <CURRENT_SPEED>48/1</CURRENT_SPEED>
    <TIMECODE_FLAG>NDF</TIMECODE_FLAG>
    <TIMECODE_RATE>24000/1001</TIMECODE_RATE>
    <FILE_SAMPLE_RATE>48000</FILE_SAMPLE_RATE>
    <AUDIO_BIT_DEPTH>24</AUDIO_BIT_DEPTH>
    <DIGITIZER_SAMPLE_RATE>48048</DIGITIZER_SAMPLE_RATE>
    <TIMESTAMP_SAMPLES_SINCE_MIDNIGHT_HI>0</TIMESTAMP_SAMPLES_SINCE_MIDNIGHT_HI>
    <TIMESTAMP_SAMPLES_SINCE_MIDNIGHT_LO>48048000</TIMESTAMP_SAMPLES_SINCE_MIDNIGHT_LO>
    <TIMESTAMP_SAMPLE_RATE>48000</TIMESTAMP_SAMPLE_RATE>
  </SPEED>
</BWFXML>

ID3v2 chunk

这个规范也是mp3文件最常使用的规范，有时也被作为wav文件的元数据格式使用。音频素材的 description 信息写入到 COMM (comment) 标签位置。链接：ID3各版本标签定义

4944 3320  0070 0000  4944 3303  00        00    0001 5f76  
I D  3     size       ID3  v2.3  Revision  flag  tag size   

5443 4f50 0000 001c 0000 0032 3031 3820 424f 4f4d 204c 6962 7261 7279 2d4d 6f64 6572 6e20 5549 
TCOP      size 28   flag ␀2018 BOOM Library-Modern UI

544f 414c 0000 0014 0000 0077 7777 2e62 6f6f 6d6c 6962 7261 7279 2e63 6f6d 
TOAL      size 20   flag ␀www.boomlibrary.com 

544f 5259 0000 0005 0000 0032 3031 38 
TORY      size  5   flag ␀2018

54 5045 3200 0000 0a00 0000 4d6f 6465 726e 2055 49
TPE2      size 10   flag ␀Modern UI 

54 5945 5200 0000 0500 0000 3230 3138 
TYER      size  5   flag ␀2018

544f 574e 0000 000a 0000 004d 6f64 6572 6e20 5549
TOWN      size 10   flag ␀Modern UI 

434f 4d4d 0000 002a 0000 0000 0000 0055 4920 534d 414c 4c20 4849 4748 2054 696e 7920 616e 6420 676c 6173 7379 2063 6c69 636b 732e
COMM      size 42   flag ␀␀␀UI SMALL HIGH Tiny and glassy clicks. 

5452 434b 0000 0002 0000 0030 
TRCK                     ␀0

5449 5432 0000 0021 0000 004d 5549 2053 454c 4543 5420 4449 4749 5441 4c20 4265 6570 2054 696e 792e 7761 76
TIT2                     ␀MUI SELECT DIGITAL Beep Tiny.wav 

54 5045 3100 0000 0d00 0000 424f 4f4d 204c 6962 7261 7279
TPE1                     ␀BOOM Library 

5449 5433 0000 0043 0000 0041 6c6c 2073 6f75 6e64 2065 6666 6563 7473 2061 7265 2063 6f70 7972 6967 6874 2042 4f4f 4d20 4c69 6272
6172 7920 2d20 616c 6c20 7269 6768 7473 2072 6573 6572 7665 64
TIT3                     ␀All sound effects are copyright BOOM Library - all rights reserved 

41 5049 4300 0067 9000 0000 696d 6167 652f 6a70 6567 ...
APIC      size 26512     ␀image/jpeg 

54 434f 4e00 0000 0f00 0000 5573 6572 2049 6e74 6572 6661 6365 
TCON      size 15        ␀User Interface

SMED Chunk（Soundminer Metawrapper）

这个是Soundminer自己的数据库格式

534d 4544 a429 0100   0001 299e e3fd 75fc ...
SMED      size 76196  data of SMED ...

LIST-INFO Chunk

1991年的老规范

4c49 5354 ec00 0000 494e 464f 4947 4e52 1000 0000 5573 6572 2049 6e74 6572 6661 6365 0000 4941 5254 0e00 0000 424f 4f4d 204c 6962
7261 7279 0000
LIST      size 236  INFO      IGNR                User Interface                          IART                BOOM Library 

4943 4d54 2600 0000 5549 2053 4d41 4c4c 2048 4947 4820 5469 6e79 2061 6e64 2067 6c61 7373 7920 636c 6963 6b73 2e00 
ICMT                UI SMALL HIGH Tiny and glassy clicks. 

4943 4f50 3200 0000 3230 3138 2042 4f4f 4d20 4c69 6272 6172 7920 284d 6f64 6572 6e20 5549 2920 7777 772e 626f 6f6d 6c69 6272 6172
792e 636f 6d00 
ICOP                2018 BOOM Library (Modern UI) www.boomlibrary.com 

494e 414d 2200 0000 4d55 4920 5345 4c45 4354 2044 4947 4954 414c 2042 6565 7020 5469 6e79 2e77 6176 0000 
INAM                MUI SELECT DIGITAL Beep Tiny.wav 

4953 4654 0c00 0000 536f 756e 646d 696e 6572 0000 
ISFT                Soundminer 

4943 5244 0c00 0000 3230 3138 2d30 372d 3035 0000
ICRD                2018-07-05 

_PMX (XMP) Chunk

Extensible Metadata Platform

<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>
<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="XMP Core 5.5.0">
  <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <rdf:Description rdf:about=""
        xmlns:xmp="http://ns.adobe.com/xap/1.0/"
        xmlns:dc="http://purl.org/dc/elements/1.1/"
        xmlns:xmpDM="http://ns.adobe.com/xmp/1.0/DynamicMedia/">
      <xmp:CreatorTool>Soundminer v4</xmp:CreatorTool>
      <xmp:MetadataDate>2018-07-17T15:06:01+02:00</xmp:MetadataDate>
      <xmp:ModifyDate>2018-07-17T15:06:01+02:00</xmp:ModifyDate>
      <xmp:rating>0.000000</xmp:rating>
      <dc:description>
        <rdf:Alt>
          <rdf:li xml:lang="x-default">UI SMALL HIGH Tiny and glassy clicks.</rdf:li>
          <rdf:li xml:lang="en-US">UI SMALL HIGH Tiny and glassy clicks.</rdf:li>
        </rdf:Alt>
      </dc:description>
      <dc:publisher>
        <rdf:Bag>
          <rdf:li/>
        </rdf:Bag>
      </dc:publisher>
      <dc:title>
        <rdf:Alt>
          <rdf:li xml:lang="x-default">MUI SELECT DIGITAL Beep Tiny.wav</rdf:li>
          <rdf:li xml:lang="en-US">MUI SELECT DIGITAL Beep Tiny.wav</rdf:li>
        </rdf:Alt>
      </dc:title>
      <xmpDM:comment/>
      <xmpDM:album/>
      <xmpDM:artist>BOOM Library</xmpDM:artist>
      <xmpDM:composer/>
      <xmpDM:genre>User Interface</xmpDM:genre>
      <xmpDM:instrument/>
      <xmpDM:key/>
    </rdf:Description>
  </rdf:RDF>
</x:xmpmeta>

Data chunk

Wav文件的编码数据

6461 7461  3246 3900  0000 
d a  t a   size       sample starts here！

Metadata App Comparison Table

Product Name	Price	Mac OS	Windows	Demo	Copy Protection	Embed	Batch Meta	Search Style	# of DBs	Play lists	Text DB Import	Text DB Export	Number of Fields	Custom Fields	BEXT Read	BEXT Write	ID3 Read	ID3 Write	iXML Read	iXML Write	Multi-chnl?	Adv Search	Transfer to DAW	In-App Edit or Process	Max Sampling Rate	SR Conv	ReWire	Plug-in Support
Soundminer Standard	$599.00	10.7-10.12		30 days	iLok, HASP	√		DB	∞	√	√	√	64*		√	√	√	√	√	√	√	√	DnD, Bin, Timeline		192 / 24	√	2-channel
Soundminer vPro	$899.00	10.7-10.12		30 days	iLok, HASP	√	√	DB	∞	√	√	√	64*		√	√	√	√	√	√	√	√	DnD, Bin, Timeline	√	192 / 24	√	6-channel	VST
Soundminer HD Basic	$199.00	10.5+	XP, Vista, 7, 10	30 days	iLok, HASP	Category, Description		DB	2	√	√	√	Selection from 64		√	√	√	√	√	√	√		Bin, DnD		48 / 24	√
Soundminer HD Plus	$399.00	10.5+	XP, Vista, 7, 10	30 days	iLok, HASP	√		DB	∞	√	√	√	Selection from 64		√	√	√	√	√	√	√		DnD, Bin, Timeline		192 / 24, 48 / 24 export	√
Basehead 4.x	$249.00	10.9 - 10.12	XP, Vista, 7, 8	√	USB, CMStick, iLok, Drive	1		DB	∞	√			Varies by Type		√	√	√	√	√	√	√	√	DnD		192 / 32, 48 / 24 export	√
Basehead 4.x Lite	$399.00	10.9 - 10.12	XP, Vista, 7, 8	√	USB, CMStick, iLok, Drive	1		DB	∞	√			Varies by Type		√	√	√	√	√	√	√	√	DnD, Bin, Timeline		192 / 32, 48 / 24 export	√		VST
Basehead 4.x Ultra	$549.00	10.9 - 10.12	XP, Vista, 7, 8	√	USB, CMStick, iLok, Drive	√	√	DB	∞	√			Varies by Type		√	√		√	√	√	√	√	DnD, Bin, Timeline	√	192 / 32	√	6-channel	VST
Soundly	Free, $14.95+	10.6.8+	XP+		Login	√	√	DB	1	√	√	√	2		√	√	√		√	√	√	√	DnD, Timeline		192 / 32	√	2-channel
Resonic Pro	€69.00		7, 8, 10	√	Serial Number			DB	√	√					√		√		√		√		DnD	√	192 / 32	√
Library Monkey	$129.00	10.4+		√	Serial Number		√	DB	∞	√	√	√	Varies by Type	30	√		√	√			√	√	Bin		192 / 32	√
Library Monkey Pro	$449.00	10.4+		√	Serial Number		√	DB	∞	√	√	√	Varies by Type	30	√		√	√			√	√	Bin, Timeline	√	192 / 32	√		AU, VST
AudioFinder	$69.95	10.4+		√	Serial Number			DB	1	√	√		?	20	?		√				?	√	Timeline	√	?	√		?
iTunes	Free	10.9+	7+			√	√	DB	1	√	√	√	Varies by Type				√	√				√	DnD		192 / 24	√
Metadigger	Free	?	?					DB	>1	√	√	√	1 (No embedding)		√		√								96 / 24
Aural Probe	Free		Vista, 7, 8					DB	1	√													DnD		?
Sample Librarian	€30.00		XP, Vista, 7	30 days	Serial Number			DB	1	√		√	2 (No embedding)								√	√	DnD		48 / 32
SampleSort	Free		Vista, 7, 8, 10					DB	1			√	(No embedding)								√	√	DnD		192 / 32
MetadataTouch Standard Edition	$40.00		Server 03, Server 08, XP SP3, Vista SP1, 7-10	14 days	Serial Number	√		Single File					Varies by Type		√	√	√	√	√	√
MetadataTouch Professional Edition	$60.00		Server 03, Server 08, XP SP3, Vista SP1, 7-10	14 days	Serial Number	√		Single File					Varies by Type		√	√	√	√	√	√
Remetacator	Free	10.3+			Serial Number	√	√	Single File					31		√	√			√	√					192 / 24
TwistedWave	$79.90	10.6+		30 days	Serial Number	√		Single File					30		√	√	√	√			√			√	192 / 32	√		AU, VST
Wave Agent	Free	10.4+	XP, Vista, 7			√		Single File				√	7		√	√			√	√	√				96 / 24	√
BWF-Widget	$49.95 - $99.00		2000, XP, 9		Serial Number	√	√	Single File			√	√			√	√			√	√
BWF MetaEdit	Free	10.6-10.9	XP, Vista, 7, 8			√		Single File				√	Varies by Type		√	√			√	√					96 / 24
Commenteer	$13.99	10.6.8+			Mac App Store	√	√	Single File			√	√	1
Snapper	$79.00	10.9.5+		100 days	Serial Number			Single File							√		√				√		DnD, Timeline		192	√
NOTES			* = extra software required										* = total fields, only some are modifiable												• = max tested

References

Sound FX Metadata Tech Specs: Demystified

Soundminer Metadata 101

An Introduction to Sound FX Metadata Apps 2 – Comparing Apps

The Quick-Start Guide to Adding Sound FX Library Metadata