Metadata
includes information about your video file, such as duration, width, height,
and frame rate. The metadata information that is added to your video
file depends on the software you use to encode the video file.
var nc:NetConnection = new NetConnection();
nc.connect(null);
var ns:NetStream = new NetStream(nc);
ns.client = this;
ns.play("video.flv");
var vid:Video = new Video();
vid.attachNetStream(ns);
addChild(vid);
function onMetaData(infoObject:Object):void
{
var key:String;
for (key in infoObject)
{
trace(key + ": " + infoObject[key]);
}
}
The previous code generates output like the following:
width: 320
audiodelay: 0.038
canSeekToEnd: true
height: 213
cuePoints: ,,
audiodatarate: 96
duration: 16.334
videodatarate: 400
framerate: 15
videocodecid: 4
audiocodecid: 2
If your video does not have audio, the audio-related
metadata information (such as
audiodatarate
) returns
undefined
because no audio information is added to the metadata during encoding.
In the previous code, the cue point information was not displaying.
To display the cue point metadata, you can use the following function
which recursively displays the items in an Object:
function traceObject(obj:Object, indent:uint = 0):void
{
var indentString:String = "";
var i:uint;
var prop:String;
var val:*;
for (i = 0; i < indent; i++)
{
indentString += "\t";
}
for (prop in obj)
{
val = obj[prop];
if (typeof(val) == "object")
{
trace(indentString + " " + prop + ": [Object]");
traceObject(val, indent + 1);
}
else
{
trace(indentString + " " + prop + ": " + val);
}
}
}
Using the previous code snippet to trace the
infoObject
parameter
in the
onMetaData()
method creates the following
output:
width: 320
audiodatarate: 96
audiocodecid: 2
videocodecid: 4
videodatarate: 400
canSeekToEnd: true
duration: 16.334
audiodelay: 0.038
height: 213
framerate: 15
cuePoints: [Object]
0: [Object]
parameters: [Object]
lights: beginning
name: point1
time: 0.418
type: navigation
1: [Object]
parameters: [Object]
lights: middle
name: point2
time: 7.748
type: navigation
2: [Object]
parameters: [Object]
lights: end
name: point3
time: 16.02
type: navigation
The following example displays the metadata for an MP4 video.
It assumes that there is a TextArea object called
metaDataOut
,
to which it writes the metadata.
package
{
import flash.net.NetConnection;
import flash.net.NetStream;
import flash.events.NetStatusEvent;
import flash.media.Video;
import flash.display.StageDisplayState;
import flash.display.Loader;
import flash.display.Sprite;
import flash.events.MouseEvent;
public class onMetaDataExample extends Sprite
{
var video:Video = new Video();
public function onMetaDataExample():void
{
var videoConnection:NetConnection = new NetConnection();
videoConnection.connect(null);
var videoStream:NetStream = new NetStream(videoConnection);
videoStream.client = this;
addChild(video);
video.x = 185;
video.y = 5;
video.attachNetStream(videoStream);
videoStream.play("video.mp4");
videoStream.addEventListener(NetStatusEvent.NET_STATUS, netStatusHandler);
}
public function onMetaData(infoObject:Object):void
{
for(var propName:String in infoObject)
{
metaDataOut.appendText(propName + "=" + infoObject[propName] + "\n");
}
}
private function netStatusHandler(event:NetStatusEvent):void
{
if(event.info.code == "NetStream.Play.Stop")
stage.displayState = StageDisplayState.NORMAL;
}
}
}
The
onMetaData()
function produced the following
output for this video:
moovposition=731965
height=352
avclevel=21
videocodecid=avc1
duration=2.36
width=704
videoframerate=25
avcprofile=88
trackinfo=[object Object]
Using the information object
The
following table shows the possible values for video metadata that
are passed to the
onMetaData()
callback function
in the Object that they receive:
|
Parameter
|
Description
|
|
aacaot
|
AAC audio object type; 0, 1, or 2 are supported.
|
|
avclevel
|
AVC IDC level number such as 10, 11, 20,
21, and so on.
|
|
avcprofile
|
AVC profile number such as 55, 77, 100,
and so on.
|
|
audiocodecid
|
A string that indicates the audio codec
(code/decode technique) that was used - for example “.Mp3” or “mp4a”
|
|
audiodatarate
|
A number that indicates the rate at which
audio was encoded, in kilobytes per second.
|
|
audiodelay
|
A number that indicates what time in the
FLV file "time 0" of the original FLV file exists. The video content
needs to be delayed by a small amount to properly synchronize the
audio.
|
|
canSeekToEnd
|
A Boolean value that is
true
if
the FLV file is encoded with a keyframe on the last frame, which
allows seeking to the end of a progressive -download video file.
It is
false
if the FLV file is not encoded with
a keyframe on the last frame.
|
|
cuePoints
|
An array of objects, one for each cue point
embedded in the FLV file. Value is undefined if the FLV file does
not contain any cue points. Each object has the following properties:
-
type
: a string that specifies the type of
cue point as either "navigation" or "event".
-
name
: a string that is the name of the cue
point.
-
time
: a number that is the time of the cue
point in seconds with a precision of three decimal places (milliseconds).
-
parameters
: an optional object that has
name-value pairs that are designated by the user when creating the
cue points.
|
|
duration
|
A number that specifies the duration of
the video file, in seconds.
|
|
framerate
|
A number that is the frame rate of the FLV
file.
|
|
height
|
A number that is the height of the FLV file,
in pixels.
|
|
seekpoints
|
An array that lists the available keyframes
as timestamps in milliseconds. Optional.
|
|
tags
|
An array of key-value pairs that represent
the information in the “ilst” atom, which is the equivalent of ID3
tags for MP4 files. iTunes uses these tags. Can be used to display
artwork, if available.
|
|
trackinfo
|
Object that provides information on all
the tracks in the MP4 file, including their sample description ID.
|
|
videocodecid
|
A string that is the codec version that
was used to encode the video. - for example, “avc1” or “VP6F”
|
|
videodatarate
|
A number that is the video data rate of
the FLV file.
|
|
videoframerate
|
Framerate of the MP4 video.
|
|
width
|
A number that is the width of the FLV file,
in pixels.
|
The following table shows the possible
values for the
videocodecid
parameter:
|
videocodecid
|
Codec name
|
|
2
|
Sorenson H.263
|
|
3
|
Screen video (SWF version 7 and later only)
|
|
4
|
VP6 (SWF version 8 and later only)
|
|
5
|
VP6 video with alpha channel (SWF version
8 and later only)
|
The following table shows the possible
values for the
audiocodecid
parameter:
|
audiocodecid
|
Codec Name
|
|
0
|
uncompressed
|
|
1
|
ADPCM
|
|
2
|
Mp3
|
|
4
|
Nellymoser @ 16 kHz mono
|
|
5
|
Nellymoser, 8kHz mono
|
|
6
|
Nellymoser
|
|
10
|
AAC
|
|
11
|
Speex
|
