Skip to content

Added support for carriage of ID3 tags in event message tracks. #50

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
jsaxton wants to merge 1 commit into
base: main
Choose a base branch
from
Open

Added support for carriage of ID3 tags in event message tracks. #50

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
54 changes: 48 additions & 6 deletions index.bs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4,12 +4,12 @@ Status: FD
Text Macro: SPECVERSION v1.0.0
Title: Carriage of ID3 Timed Metadata in the Common Media Application Format (CMAF)
URL: https://AOMediaCodec.github.io/id3-emsg
Shortname: id3-esmg
Shortname: id3-emsg
Editor: Krasimir Kolarov, [email protected];
Editor: John Simmons, [email protected]
Abstract: This specification defines how ID3 metadata can be carried as timed metadata in Common Media Application Format (CMAF) compatible fragmented MP4 streams using Event Message ('emsg') boxes.
Abstract: This specification defines how ID3 metadata can be carried as timed metadata in Common Media Application Format (CMAF) compatible fragmented MP4 streams using Event Message ('emsg') and Event Message Instance ('emib') boxes.
Date: 2020-03-12
Repository: AOMediaCodec/id3-esmg
Repository: AOMediaCodec/id3-emsg
Inline Github Issues: full
Boilerplate: property-index no, issues-index no, copyright yes
Markup Shorthands: css no
Expand Down Expand Up @@ -51,7 +51,14 @@ Markup Shorthands: css no
"title": "Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1: Media presentation description and segment formats",
"status": "Standard",
"publisher": "ISO"
}
},
"EMSG-TRACK": {
"href": "https://www.iso.org/standard/82529.html",
"id": "EMSG-TRACK",
"title": "Information technology - MPEG systems technologies - Part 18: Event message track format for the ISO base media file format",
"status": "Standard",
"publisher": "ISO"
}
}
</pre>

Expand All @@ -66,6 +73,8 @@ url: https://www.iso.org/standard/65274.html#; spec: DASH; type: dfn;
text: presentation_time_delta
text: presentation_time
text: id
url: https://www.iso.org/standard/82529.html#; spec: EMSG-TRACK; type: dfn;
text: emib
</pre>

# Introduction # {#introduction}
Expand All @@ -78,11 +87,13 @@ This specification describes how such ID3 metadata can be carried as timed metad

CMAF-compatible fragmented MP4 can also be used in DASH. The elements defined in this specification may also be used with DASH.

The specification also describes how ID3 metadata can be carried in a CMAF-compatible event message track as described in [[EMSG-TRACK]].

# Timed Metadata in a CMAF-compatible stream # {#timed-meta}

## Overview ## {#meta-overview}

Timed Metadata in a CMAF-compatible stream is signaled via one or more Event Message boxes (<code><a>emsg</a></code>) [[CMAF]] per segment.
Timed Metadata in a CMAF-compatible stream can be signaled via one or more Event Message boxes (<code><a>emsg</a></code>) [[CMAF]] per segment. Timed Metadata can also be signaled via an Event Message Instance Box (<code><a>emib</a></code>) as defined in [[EMSG-TRACK]].

Event messages with the scheme specified in this document will identify boxes that carry ID3v2 metadata [[ID3]].

Expand All @@ -94,7 +105,7 @@ One or more Event Message boxes (<code><a>emsg</a></code>) [[!CMAF]] can be incl

### Syntax ### {#emsg-syntax}

For convenience, the follow box definition is reproduced from [[DASH]], section 5.10.3.3.3.
For convenience, the following box definition is reproduced from [[DASH]], section 5.10.3.3.3.

```cpp
aligned(8) class DASHEventMessageBox extends FullBox('emsg', version, flags = 0)
Expand Down Expand Up @@ -134,6 +145,37 @@ The <a>presentation_time</a> must be within the time interval of the fragment.

The <a>id</a> field is not restricted in this version of the specification.

## ID3 Metadata in an Event Message Instance Box ## {#meta-emib}

### Introduction ### {#emib-intro}

In an event message track, one or more Event Message Instance Boxes (<code><a>emib</a></code>) can be included per segment.

### Syntax ### {#emib-syntax}

For convenience, the following box definition is reproduced from [[EMSG-TRACK]], section 6.1.2.

```cpp
aligned(8) class EventMessageInstanceBox extends FullBox('emib', version, flags = 0) {
unsigned int(32) reserved = 0;
signed int(64) presentation_time_delta;
unsigned int(32) event_duration;
unsigned int(32) id;
string scheme_id_uri;
string value;
unsigned int(8) message_data[];
}
```

### Semantics ### {#emib-semantics}

The <a>id</a>, <a>scheme_id_uri</a>, <a>value</a>, and <a>message_data</a> semantics are identical to the Event Message Box semantics.

The <a>presentation_time_delta</a> semantics defined in [[EMSG-TRACK]] remain unchanged.

In general, ID3 don't carry a duration and in those cases the <a>event_duration</a> field should be set to <code>0</code>.
If in a particular case, the ID3 message carries a duration, it should be reflected in the <a>event_duration</a> field.

## Signaling ## {#meta-signaling}

Files compliant to this specification should signal it using the brand <code><dfn>aid3</dfn></code> as part of the list compatible brands in the file type box.
Expand Down