Understanding video formats
Flash Player 9 and later, Adobe AIR 1.0 and
later
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In addition to the Adobe FLV video format,
Flash Player and Adobe AIR support video and audio encoded in H.264
and HE-AAC from within MPEG-4 standard file formats. These formats
stream high quality video at lower bit rates. Developers can leverage
industry standard tools, including Adobe Premiere Pro and Adobe After
Effects, to create and deliver compelling video content.
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Type
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Format
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Container
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Video
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H.264
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MPEG-4: MP4, M4V, F4V, 3GPP
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Video
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Sorenson Spark
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FLV file
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Video
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ON2 VP6
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FLV file
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Audio
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AAC+ / HE-AAC / AAC v1 / AAC v2
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MPEG-4:MP4, M4V, F4V, 3GPP
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Audio
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Mp3
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Mp3
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Audio
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Nellymoser
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FLV file
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Audio
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Speex
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FLV file
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Encoding video for mobile devices
AIR on Android can decode a wide range of H.264 videos.
However, only a small subset of H.264 videos is suited to have a
smooth playback on mobile phones. It is because many mobile phones
are constrained for processing power. Adobe Flash Player for mobile
can decode H.264 videos using in-built hardware acceleration. This
decoding assures better quality at lower power consumption.
H.264 standard supports several encoding techniques. Only high-end
devices smoothly play videos with complex profiles and levels. However,
a majority of devices can play video encoded in baseline profile.
On mobile devices, hardware acceleration is available for a subset
of these techniques. The profile and the level parameters define
this subset of encoding techniques and settings used by the encoder.
For developers, it translates into encoding the video in selected resolution
which plays well on most devices.
Though resolutions that benefit from hardware acceleration vary
from device to device, but most devices support the following standard
resolutions.
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Aspect ratio
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Recommended resolutions
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4:3
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640 × 480
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512 × 384
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480 × 360
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16:9
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640 × 360
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512 x 288
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480 × 272
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Note:
Flash Player supports every level and profile of the H.264
standard. Adhering to these recommendations ensures hardware acceleration
and better user experience on most devices. These recommendations
are not mandatory.
For a detailed discussion and encoding settings in Adobe Media
Encoder CS5, see
Recommendations for encoding H.264 video
for Flash Player 10.1 on mobile devices
.
Note:
On iOS, only video encoded with the Sorenson Spark and On2
VP6 codecs can be played back using the Video class. You can play
back H.264 encoded video in the device video player by launching
the URL to the video using the
flash.net.navigateToURL()
function.
You can also play back H.264 video using the <video> tag in
an html page displayed in a StageWebView object.
Flash Player and AIR compatibility with encoded video files
Flash Player
7 supports FLV files that are encoded with the Sorenson™ Spark™ video codec. Flash Player 8 supports FLV
files encoded with Sorenson Spark or On2 VP6 encoder in Flash Professional
8. The On2 VP6 video codec supports an alpha channel.
Flash Player 9.0.115.0 and later versions support files derived
from the standard MPEG-4 container format. These files include F4V,
MP4, M4A, MOV, MP4V, 3GP, and 3G2, if they contain H.264 video or
HE-AAC v2 encoded audio, or both. H.264 delivers higher quality
video at lower bit rates when compared to the same encoding profile
in Sorenson or On2. HE-AAC v2 is an extension of AAC, a standard
audio format defined in the MPEG-4 video standard. HE-AAC v2 uses spectral
band replication (SBR) and parametric stereo (PS) techniques to
increase coding efficiency at low bit rates.
The following table lists the supported codecs. It also shows
the corresponding SWF file format and the versions of Flash Player
and AIR that are required to play them:
|
Codec
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SWF file format version (earliest supported
publish version)
|
Flash Player and AIR (earliest version required
for playback)
|
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Sorenson Spark
|
6
|
Flash Player 6, Flash Lite 3
|
|
On2 VP6
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6
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Flash Player 8, Flash Lite 3.
Only
Flash Player 8 and later versions support publish and playback of
On2 VP6 video.
|
|
H.264 (MPEG-4 Part 10)
|
9
|
Flash Player 9 Update 3, AIR 1.0
|
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ADPCM
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6
|
Flash Player 6, Flash Lite 3
|
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Mp3
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6
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Flash Player 6, Flash Lite 3
|
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AAC (MPEG-4 Part 3)
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9
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Flash Player 9 Update 3, AIR 1.0
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Speex (audio)
|
10
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Flash Player 10, AIR 1.5
|
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Nellymoser
|
6
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Flash Player 6
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Understanding the Adobe F4V and FLV video file formats
Adobe provides the F4V and FLV video file formats for streaming
content to Flash Player and AIR. For a complete description of these
video file formats, see
www.adobe.com/go/video_file_format
.
The F4V video file format
Beginning with Flash Player Update 3 (9.0.115.0) and AIR 1.0,
Flash Player and AIR support the Adobe F4V video format, which is
based on the ISO MP4 format, Subsets of the format support different
features. Flash Player expects a valid F4V file to begin with one
of the following top-level boxes:
-
ftyp
The ftyp
box identifies the features that a program must support to play
a particular file format.
-
moov
The moov box is effectively the header of an F4V
file. It contains one or more other boxes that in turn contain other
boxes that define the structure of the F4V data. An F4V file must
contain one and only one moov box.
-
mdat
An mdat box contains the data payload for the
F4V file. An FV file contains only one mdat box. A moov box also
must be present in the file because the mdat box cannot be understood
on its own.
F4V files support multibyte integers in big-endian byte order,
in which the most significant byte occurs first, at the lowest address.
The FLV video file format
The Adobe FLV file format contains encoded
audio and video data for delivery by Flash Player. You can use an
encoder, such as Adobe Media Encoder or Sorenson™ Squeeze,
to convert a QuickTime or Windows Media video file to an FLV file.
Note:
You can create FLV files by importing video into Flash and
exporting it as an FLV file. You can use the FLV Export plug-in
to export FLV files from supported video-editing applications. To
load FLV files from a web server, register the filename extension
and MIME type with your web server. Check your web server documentation.
The MIME type for FLV files is
video/x-flv
. For
more information, see
About configuring FLV files for hosting on a server
.
For more information on FLV files, see
Advanced topics for video files
.
External vs embedded video
Using external video files provides certain capabilities that
are not available when you use imported video:
-
Longer video clips can be used in your application
without slowing down playback. External video files use cached memory,
which means that large files are stored in small pieces and accessed
dynamically. For this reason, external F4V and FLV files require
less memory than embedded video files.
-
An external video file can have a different frame rate than
the SWF file in which it plays. For example, you can set the SWF
file frame rate to 30 frames per second (fps) and the video frame
rate to 21 fps. This setting gives you better control of the video
than embedded video, to ensure smooth video playback. It also allows
you to play video files at different frame rates without the need to
alter existing SWF file content.
-
With external video files, playback of the SWF content is
not interrupted while the video file is loading. Imported video
files can sometimes interrupt document playback to perform certain
functions, such as accessing a CD-ROM drive. Video files can perform
functions independently of the SWF content, without interrupting
playback.
-
Captioning video content is easier with external FLV files
because you can access the video metadata using event handlers.
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