diff --git a/block_additional_mappings/smpte-st12-1-timecode.md b/block_additional_mappings/smpte-st12-1-timecode.md
index 54b44f05a..897f10a3b 100644
--- a/block_additional_mappings/smpte-st12-1-timecode.md
+++ b/block_additional_mappings/smpte-st12-1-timecode.md
@@ -1,6 +1,4 @@
-## SMPTE ST 12-1 Timecode
-
-### Timecode Description
+## SMPTE ST 12-1 Timecode Description
 
 SMPTE ST 12-1 timecode values can be stored in the `BlockMore` element to associate
 the content of a Matroska Block with a particular timecode value.
@@ -43,15 +41,3 @@ For example, a timecode value of "07:32:54;18" can be expressed as a 64-bit SMPT
 10000000 01100000 01100000 01010000
 00100000 00110000 01110000 00000000
 ```
-
-### BlockAddIDType
-
-The `BlockAddIDType` value reserved for timecode is "121".
-
-### BlockAddIDName
-
-The `BlockAddIDName` value reserved for timecode is "SMPTE ST 12-1 timecode".
-
-### BlockAddIDExtraData
-
-`BlockAddIDExtraData` is unused within this block additional mapping.
diff --git a/block_additional_mappings_intro.md b/block_additional_mappings_intro.md
index 336df6d6a..709850694 100644
--- a/block_additional_mappings_intro.md
+++ b/block_additional_mappings_intro.md
@@ -22,10 +22,10 @@ The following XML depicts the nested elements of a `BlockGroup` element with an
 ```
 
 When the `BlockAddID` is set a value greater than "1", then the contents of the
-`BlockAdditional` element are defined by the `BlockAdditionalMapping` element, within
+`BlockAdditional` element are defined by the `BlockAdditionMapping` element, within
 the associated `TrackEntry` element, where the `BlockAddID` element of `BlockAdditional` element
-equals the `BlockAddIDValue` of the associated `TrackEntry`'s `BlockAdditionalMapping` element.
-That `BlockAdditionalMapping` element identifies a particular `Block Additional Mapping` by the `BlockAddIDType`.
+equals the `BlockAddIDValue` of the associated `TrackEntry`'s `BlockAdditionMapping` element.
+That `BlockAdditionMapping` element identifies a particular `Block Additional Mapping` by the `BlockAddIDType`.
 
 The values of `BlockAddID` that are 2 of greater have no semantic meaning, but simply
 associate the `BlockMore` element with a `BlockAdditionMapping` of the associated `Track`.
@@ -41,12 +41,12 @@ The following XML depicts a use of a `Block Additional Mapping` to associate a t
       <TrackNumber>1</TrackNumber>
       <TrackUID>568001708</TrackUID>
       <TrackType>1</TrackType>
-      <BlockAdditionalMapping>
+      <BlockAdditionMapping>
         <BlockAddIDValue>2</BlockAddIDValue><!--arbitrary value
           used in BlockAddID-->
         <BlockAddIDName>timecode</BlockAddIDName>
         <BlockAddIDType>12</BlockAddIDType>
-      </BlockAdditionalMapping>
+      </BlockAdditionMapping>
       <CodecID>V_FFV1</CodecID>
       <Video>
         <PixelWidth>1920</PixelWidth>
@@ -61,7 +61,7 @@ The following XML depicts a use of a `Block Additional Mapping` to associate a t
       <BlockAdditions>
         <BlockMore>
           <BlockAddID>2</BlockAddID><!--arbitrary value from
-            BlockAdditionalMapping-->
+            BlockAdditionMapping-->
           <BlockAdditional>01:00:00:00</BlockAdditional>
         </BlockMore>
       </BlockAdditions>
diff --git a/codec_iana.md b/codec_iana.md
index 6a5c12e7d..5d27fca35 100644
--- a/codec_iana.md
+++ b/codec_iana.md
@@ -121,10 +121,10 @@ BlockAddIDType | BlockAddIDName            | Reference
 1 | Opaque data | This document, (#opaque-data)
 4 | ITU T.35 metadata | This document, (#itu-t-35-metadata)
 121 | SMPTE ST 12-1 timecode | This document, (#smpte-st-12-1-timecode)
-0x64766343 | Dolby Vision configuration dvcC | This document, (#dvcc)
 0x61766345 | Dolby Vision enhancement-layer AVC configuration | This document, (#avce)
+0x68766345 | Dolby Vision enhancement-layer HEVC configuration | This document, (#hvce)
+0x64766343 | Dolby Vision configuration dvcC | This document, (#dvcc)
 0x64767643 | Dolby Vision configuration dvvC | This document, (#dvvc)
 0x64767743 | Dolby Vision configuration dvwC | This document, (#dvwc)
-0x68766345 | Dolby Vision enhancement-layer HEVC configuration | This document, (#hvce)
 0x6D766343 | MVC configuration | This document, (#mvcc)
 Table: Initial Contents of "Matroska BlockAdditional Type IDs" Registry{#blockadd-id-registry-table}
diff --git a/codec_specs.md b/codec_specs.md
index d488d320d..825eccc0c 100644
--- a/codec_specs.md
+++ b/codec_specs.md
@@ -1124,15 +1124,39 @@ Description: Based on MPEG/VOB PCI packets.
 The frame contains a header consisting of the string "butonDVD" followed by the width and height
 in pixels (16-bit unsigned integer each) and 4 reserved bytes. The rest is a full PCI packet described in [@!DVD-Info.PCI].
 
-## Block Addition Mappings
 
-Registered `BlockAddIDType` are:
+
+# Block Addition Mappings
+
+This section describes the various types of `BlockAdditionMapping` that can be stored in Matroska.
+These help the player interpret the multiple `BlockAdditions` that can be added to each Matroska `BlockGroup`.
+More defails can be found in section (#block-additional-mapping).
+
+## Defining Block Addition Mappings
+
+Support for a Block Addition mapping is defined in Matroska with the following values.
+
+### Block Type Identifier
+
+Each `BlockAdditionMapping` supported in Matroska **MUST** have a unique `BlockAddIDType`.
+It **MUST** be defined for each Block Addition Mapping.
+
+### Block Type Name
+
+Each `BlockAdditionMapping` supported in Matroska **MAY** have a `BlockAddIDName`.
+The `BlockAddIDName` provides a readable label for the encoding.
+
+### Description
+
+An optional description for the encoding. This value is only intended for human consumption.
+
+## Initial Block Addition Mappings
 
 ### Use BlockAddIDValue
 
 Block type identifier: 0
 
-Block type name: Use BlockAddIDValue
+Block type name: "Use BlockAddIDValue"
 
 Description: This value indicates that the actual type is stored in `BlockAddIDValue` instead.
 This value is expected to be used when it is important to have a strong compatibility
@@ -1143,7 +1167,7 @@ with an unknown `BlockAddIDValue`, and **SHOULD NOT** be used if it is possible
 
 Block type identifier: 1
 
-Block type name: Opaque data
+Block type name: "Opaque data"
 
 Description: the `BlockAdditional` data is interpreted as opaque additional data passed to the codec
 with the Block data.
@@ -1153,13 +1177,21 @@ The usage of these `BlockAdditional` data is defined in the "Codec BlockAddition
 
 Block type identifier: 4
 
-Block type name: ITU T.35 metadata
+Block type name: "ITU T.35 metadata"
 
 Description: the `BlockAdditional` data is interpreted as ITU T.35 metadata, as defined by [@?ITU-T.35]
 terminal codes. `BlockAddIDValue` **MUST** be 4.
 
 HDR10+ dynamic metadata can be stored as ITU T.35 terminal codes as defined in Table 8 of [@?CTA.861-4].
 
+### SMPTE ST 12-1 Timecode
+
+Block type identifier: 121
+
+Block type name: "SMPTE ST 12-1 timecode"
+
+Description: the `BlockAdditional` data is defined in (#smpte-st-12-1-timecode-description).
+
 ### avcE
 
 Block type identifier: 0x61766345
@@ -1174,7 +1206,7 @@ be used if `CodecID` is not `V_MPEG4/ISO/AVC`.
 
 Block type identifier: 0x68766345
 
-Block type name: Dolby Vision enhancement-layer HEVC configuration
+Block type name: "Dolby Vision enhancement-layer HEVC configuration"
 
 Description: the `BlockAddIDExtraData` data is interpreted as the Dolby Vision enhancement-layer HEVC configuration as described in [@!DolbyVision-ISOBMFF].
 This extension **MUST NOT** be used if `CodecID` is not `V_MPEGH/ISO/HEVC`.
@@ -1183,7 +1215,7 @@ This extension **MUST NOT** be used if `CodecID` is not `V_MPEGH/ISO/HEVC`.
 
 Block type identifier: 0x64766343
 
-Block type name: Dolby Vision configuration dvcC
+Block type name: "Dolby Vision configuration dvcC"
 
 Description: the `BlockAddIDExtraData` data is interpreted as `DOVIDecoderConfigurationRecord` structure, as defined in [@!DolbyVision-ISOBMFF],
 for Dolby Vision profiles 0 to 7 included.
@@ -1192,7 +1224,7 @@ for Dolby Vision profiles 0 to 7 included.
 
 Block type identifier: 0x64767643
 
-Block type name: Dolby Vision configuration dvvC
+Block type name: "Dolby Vision configuration dvvC"
 
 Description: the `BlockAddIDExtraData` data is interpreted as `DOVIDecoderConfigurationRecord` structure, as defined in [@!DolbyVision-ISOBMFF],
 for Dolby Vision profiles 8 to 10 included and 20.
@@ -1201,7 +1233,7 @@ for Dolby Vision profiles 8 to 10 included and 20.
 
 Block type identifier: 0x64767743
 
-Block type name: Dolby Vision configuration dvwC
+Block type name: "Dolby Vision configuration dvwC"
 
 Description: the `BlockAddIDExtraData` data is interpreted as `DOVIDecoderConfigurationRecord` structure, as defined in [@!DolbyVision-ISOBMFF],
 for Dolby Vision profiles 11 to 19 included.
@@ -1210,7 +1242,7 @@ for Dolby Vision profiles 11 to 19 included.
 
 Block type identifier: 0x6D766343
 
-Block type name: MVC configuration
+Block type name: "MVC configuration"
 
 Description: the `BlockAddIDExtraData` data is interpreted as `MVCDecoderConfigurationRecord` structure, as defined in [@!ISO.14496-15].
 This extension **MUST NOT** be used if `CodecID` is not `V_MPEG4/ISO/AVC`.