Tracking - Revision history

Spomky: /* Tracking mapping into Ogg */

2011-08-09T11:03:45Z

Tracking mapping into Ogg

← Older revision		Revision as of 11:03, 9 August 2011
Line 95:		Line 95:
	The media mapping for Tracking into Ogg is as follows:		The media mapping for Tracking into Ogg is as follows:
	* The bos page contains a Tracking ident packet.		* The bos page contains a Tracking ident packet.
			* The next page contains all metadata each encoded in their own packet.
	* The content or data packets contain the "data" tags each encoded in their own packet and inserted at the accurate time.		* The content or data packets contain the "data" tags each encoded in their own packet and inserted at the accurate time.
	* The eos page contains a packet with an empty data tag.		* The eos page contains a packet with an empty data tag.
Line 114:		Line 115:
	\| ...		\| ...

	The Tracking<i>version</i> as described here is major=0 minor=1.		The Tracking<i>version</i> as described here is major=0 minor=1.

	=== The Tracking data packets ===		=== The Tracking data packets ===
Line 131:		Line 132:
	\| </data> \|		\| </data> \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


	== Development ==		== Development ==

Spomky: /* Tracking specification */

2011-08-09T10:47:56Z

Tracking specification

@@ Line 15: / Line 15: @@
 <?xml version="1.0"?>
 <track xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="track.xsd">
-	<data type="NMEA" position="0">
+	<metadata key="key1">value1</metadata>
 		$GPRMC,162254.00,A,3723.02837,N,12159.39853,W,0.820,188.36,110706,,,A*74
 		$GPVTG,188.36,T,,M,0.820,N,1.519,K,A*3F
@@ Line 27: / Line 29: @@
 		$GPZDA,162254.00,11,07,2006,00,00*63
 	</data>
-	<data type="NMEA" position="1">
+	<data position="1">
 		$GPRMC,162254.00,A,3723.02837,N,12159.39853,W,0.820,188.36,110706,,,A*74
 		$GPVTG,188.36,T,,M,0.820,N,1.519,K,A*3F
@@ Line 38: / Line 40: @@
 		$GPGLL,3723.02837,N,12159.39853,W,162254.00,A,A*7C
 		$GPZDA,162254.00,11,07,2006,00,00*63
 	</data>
 </track>
 </pre>
-The <b>data</b> elements have two required properties:
+The <b>track</b> element (root element) have no required property:
-* type: the type of data stored (only NMEA is supported yet)
+This root element contains metadata and data elements.
 * position: the position of the data in the video (in seconds)
 == Tracking mapping into Ogg ==

Spomky: Page creation. Please consider as a draft

2011-08-08T11:19:47Z

Page creation. Please consider as a draft

New page

'''Tracking''' is a timed text codec. It allows to localize a time-continuously sampled data file by providing geolocalisation from a GPS device. This geolocalisation is NMEA sentences and multimedia players have to parse them to extract informations (position, speed, orientation, satellites informations, ...).

Tracking is appropriate for use with all [[Ogg]] media formats. This description explains how to map Tracking into Ogg.

== Tracking specification ==

Before describing the actual data that goes into a logical Ogg bitstream, we need to understand what the stand-alone "codec" packets contains.

Tracking basically consists of data elements which contains NMEA sentences

An example Tracking file looks like this:

<pre>
<?xml version="1.0"?>
<track xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="track.xsd">
<data type="NMEA" position="0">
$GPRMC,162254.00,A,3723.02837,N,12159.39853,W,0.820,188.36,110706,,,A*74
$GPVTG,188.36,T,,M,0.820,N,1.519,K,A*3F
$GPGGA,162254.00,3723.02837,N,12159.39853,W,1,03,2.36,525.6,M,-25.6,M,,*65
$GPGSA,A,2,25,01,22,,,,,,,,,,2.56,2.36,1.00*02
$GPGSV,4,1,14,25,15,175,30,14,80,041,,19,38,259,14,01,52,223,18*76
$GPGSV,4,2,14,18,16,079,,11,19,312,,14,80,041,,21,04,135,25*7D
$GPGSV,4,3,14,15,27,134,18,03,25,222,,22,51,057,16,09,07,036,*79
$GPGSV,4,4,14,07,01,181,,15,25,135,*76
$GPGLL,3723.02837,N,12159.39853,W,162254.00,A,A*7C
$GPZDA,162254.00,11,07,2006,00,00*63
</data>
<data type="NMEA" position="1">
$GPRMC,162254.00,A,3723.02837,N,12159.39853,W,0.820,188.36,110706,,,A*74
$GPVTG,188.36,T,,M,0.820,N,1.519,K,A*3F
$GPGGA,162254.00,3723.02837,N,12159.39853,W,1,03,2.36,525.6,M,-25.6,M,,*65
$GPGSA,A,2,25,01,22,,,,,,,,,,2.56,2.36,1.00*02
$GPGSV,4,1,14,25,15,175,30,14,80,041,,19,38,259,14,01,52,223,18*76
$GPGSV,4,2,14,18,16,079,,11,19,312,,14,80,041,,21,04,135,25*7D
$GPGSV,4,3,14,15,27,134,18,03,25,222,,22,51,057,16,09,07,036,*79
$GPGSV,4,4,14,07,01,181,,15,25,135,*76
$GPGLL,3723.02837,N,12159.39853,W,162254.00,A,A*7C
$GPZDA,162254.00,11,07,2006,00,00*63
</data>
<data>
...
</data>
</track>
</pre>

The data elements have two required properties:
* type: the type of data stored (only NMEA is supported yet)
* position: the position of the data in the video (in seconds)

== Tracking mapping into Ogg ==

When Tracking is mapped into an Ogg logical bitstream it needs to be serialised first. XML is a hierarchical file format, so is not generally serialisable. However, Tracking has been designed to be serialised easily.

All of the Tracking bitstream information is text. As it gets encoded into a binary bitstream, an encoding format has to be specified. To simplify things, UTF-8 is defined as the mandatory encoding format for all data in a Tracking binary bitstream.

The media mapping for Tracking into Ogg is as follows:
* The bos page contains a Tracking ident packet.
* The content or data packets contain the "data" tags each encoded in their own packet and inserted at the accurate time.
* The eos page contains a packet with an empty data tag.

=== The Tracking ident header packet ===

The Tracking logical bitstream starts with an ident header which is encapsulated into the Tracking bos page. The ident header contains all information required to identify the Tracking bitstream and to set up a Tracking decoder. It has the following format:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1| Byte
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier 'TRCK\0\0\0\0' | 0-3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | 4-7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version major | Version minor | 8-11
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...

The Trackingversion as described here is major=0 minor=1.

=== The Tracking data packets ===

The data packets of the Tracking bitstream contain the Tracking data elements. Their position attributes however only exist for authoring purposes and are not copied into the bitstream (to avoid contradictory information), but are rather represented through the time mapping of the encapsulation format that interleaves Tracking data with data from other time-continuous bitstreams. Generally the time mapping is done through some timestamp representation and through the position in the stream.

A data tag is encoded with all tags (except for the position attribute) as a string printed into a clip packet. The data tag's position attribute tells the encapsulator at what time to insert the clip packet into the bitstream. It duration is one second.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1| Byte
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| <data ... | 0-
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| </data> |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

== Development ==

== External links ==

* NMEA sentences: [http://www.gpsinformation.org/dale/nmea.htm]

[[Category:Ogg Mappings]]