Flash Video

Source: Wikipedia, the free encyclopedia.
"FLV" redirects here. For other uses, see FLV (disambiguation).
"Flash movie" redirects here. For the film based on the DC Comics character, see The Flash (film).

Flash Video
FLV file Icon from Adobe Systems
Filename extension
.flv, .fla, .f4v, .f4a, .f4b, .f4p
Internet media type
video/x-flv, video/mp4, audio/mp4
Developed by
MPEG-4 Part 12
Open format?Yes
Free format?No

Flash Video is a

movies, etc.) over the Internet using Adobe Flash Player version 6 and newer. Flash Video content may also be embedded within SWF files. There are two different Flash Video file formats: FLV and F4V. The audio and video data within FLV files are encoded in the same way as SWF files. The F4V file format is based on the ISO base media file format, starting with Flash Player 9 update 3.[1][2] Both formats are supported in Adobe Flash Player and developed by Adobe Systems. FLV was originally developed by Macromedia
. In the early 2000s, Flash Video was the de facto standard for web-based
Yahoo! Video, metacafe, Reuters.com
, and many other news providers.

Flash Video FLV files usually contain material encoded with

Adobe Flash Media Server.[4]

History

The 2002 release of Flash Player 6 added support for video in the SWF file format. The 2003 release of Flash Player 7 added direct support for the FLV file format. Because of restrictions in the FLV file format, Adobe Systems created new file formats in 2007, based on the

MP4 format, which is why F4V is sometimes informally called "Flash MP4". Flash Player does not check the filename extension but instead examines the file to determine the format of the thing created.[5][6]

The new file formats are very different from the older FLV file format. For example, F4V does not support Screen video, Sorenson Spark, VP6 video compression formats and ADPCM, or Nellymoser audio compression formats.

Internet media type
of video/x-flv.

The Adobe-branded file suffix .f4v was extended from 2007 to support the

Internet media type
of audio/mp4.

SWF files published for Flash Player 6 and later versions are able to exchange audio, video, and data over

RTMP connections with the Adobe Flash Media Server. One way to feed data to Flash Media Server is from files in the FLV file format. Flash Player can play SWF files created for Flash Player 7 and later versions in FLV format directly (MIME type video/x-flv). Flash Player can also play the new F4V file format, beginning with SWF files created for Flash Player 9 Update 3.[1]

Support for audio and video compression formats in Flash Player and in Flash Video[1][7][8][9]
Flash Player version Released File format Video compression formats Audio compression formats
6 2002 SWF Sorenson Spark, Screen video MP3, ADPCM, Nellymoser
7 2003 SWF, FLV Sorenson Spark, Screen video MP3, ADPCM, Nellymoser
8 2005 SWF, FLV On2 VP6, Sorenson Spark, Screen video, Screen video 2 MP3, ADPCM, Nellymoser
9 2007 SWF, FLV On2 VP6, Sorenson Spark, Screen video, Screen video 2, H.264[*] MP3, ADPCM, Nellymoser, AAC
SWF, F4V, ISO base media file format H.264 AAC, MP3
10 2008 SWF, FLV On2 VP6, Sorenson Spark, Screen video, Screen video 2, H.264[*] MP3, ADPCM, Nellymoser, Speex, AAC
SWF, F4V, ISO base media file format H.264 AAC, MP3

  • Use of the H.264 compression format in the FLV file format has some limitations so authors of Flash Player strongly encourage use of the new standard F4V file format.[6]

Encoding

Commonly, Flash Video FLV files contain video

On2 TrueMotion VP6 video bit streams (FourCC VP6F or FLV4). On2 VP6 is the preferred video compression format for use with Flash Player 8 and higher.[7][11] On2 VP6 can provide a higher visual quality than Sorenson Spark, especially when using lower bit rates. On the other hand, it is computationally more complex and therefore will not run as well on certain older system configurations.[14][16]

The Flash Video FLV file format supports two versions of a so-called 'screenshare' (Screen video) codec which is an encoding format designed for

On2's Flix encoding tools, Sorenson Squeeze, FFmpeg
and other third-party tools.

Media type support

Supported media types in both the Flash Video and ISO base media file formats:[1]

  • Video
    • H.264
      (added to MP4 and FLV)
    • unofficial Google GPL FLV implementations for Android[18]
  • Audio

Supported media types in just the Flash Video file format:[1]

  • General video
    • RGB (supported by same type code SWF uses)
    • run-length (supported by same type code SWF uses)
    • Sorenson's H.263
      (native to Flash Video)
    • On2 TrueMotion VP6 with and without alpha channel (added to Flash Video)
  • Animated video are the zlib based Screen 1 and 2 (native to SWF).
  • General audio are PCM and ADPCM (native to SWF).
  • Vocal audio
    • Nellymoser's Asao @ 16 or 8 or 5 kHz (native to SWF)
    • a-law and μ-law (native to SWF)
    • Speex (added to FLV)
  • Timed text requires ActionScript specific commands for loading captioning, which is only supported by external text files in either JSON or W3C XML formats.

Supported media types in just the ISO base media file format:[1]

  • Animated video are QuickTime types for GIF, PNG and JPEG, which replace the Screen 1 and 2 encodings.
  • Timed text requires ActionScript specific commands for loading captions embedded as either EIA-608 or QuickTime mac based styled text with the 3GPP derived version that supports Unicode.

FLV converters

An FLV converter is a type of

video conversion
software that is used for turning videos from different formats into FLV. Below is a list of popular free video converters which support conversion to FLV.

  • SUPER
    (freeware)
  • Free Studio (freeware)
  • Freemake Video Converter (freeware)
  • Format Factory
    (freeware)
  • GPL
    -licensed free software)
  • GPL
    -licensed free software)
  • Any Video Converter (freeware and commercial)
  • GPL
    -licensed free software)
  • Easy 7-Zip (7z)-Via Extraction of Audios (MP3) and Videos (no audio)

These programs run under

Mac OS X and Linux
.

Flash Video Structure

Header

FLV files start with a standard header which is shown below:[19]

Field Data Type Default Details
Signature byte[3] "FLV" Always "FLV"
Version uint8 1 Only 0x01 is valid
Flags uint8 bitmask 0x05 Bitmask: 0x04 is audio, 0x01 is video (so 0x05 is audio+video)
Header Size uint32_be 9 Used to skip a newer expanded header

Packets

After the header, the file is split into packets called "FLV tags", which have 15-byte packet headers. The first four bytes denote the size of the previous packet/tag (including the header without the first field), and aid in seeking backward.

Field Data Type Default Details
Size of previous packet uint32_be 0 For first packet set to NULL
Packet Type uint8 18 For first packet set to AMF Metadata
Payload Size uint24_be varies Size of packet data only
Timestamp Lower uint24_be 0 For first packet set to NULL
Timestamp Upper uint8 0 Extension to create a uint32_be value
Stream ID uint24_be 0 For first stream of same type set to NULL
Payload Data freeform varies Data as defined by packet type

The Packet Type byte of a packet/tag header is based on the RTMP message ID byte with the AMF metadata value of 18 (0x12), video payload value of 9 (0x09) and audio payload value of 8 (0x08) being the only valid types used. The third bit indicates the payload is encrypted using the same mechanism as RTMP uses, however this is rarely used due to encrypted transports such as RTMP being used instead. The FLV packet encryption is generally inherited from a MP4 file that is stored on an

Adobe Flash Media Server
.

  • Packet types enumerated as 1 is a RTMP set packet size.
  • Packet types enumerated from 3 are RTMP bytes read report, RTMP ping, RTMP server bandwidth, RTMP client bandwidth.
  • Packet types enumerated from 8 are Audio payload, Video payload.
  • Packet types enumerated from 15 are RTMP flex stream send, RTMP flex shared object, RTMP flex message, AMF metadata, shared object, RTMP invoke.
  • Packet type enumerated as 24 is an encapsulated flash video.
FLV Tag Structure

Following that, there are three bytes for the Payload Size denoting length of the Payload Data, then four bytes for the Timestamp in milliseconds (with the last byte used to extend the first three bytes), the next 3 bytes for the Stream ID (incremented for multiple streams of the same type), and finally followed by the actual payload data. There is a direct relation between the fields encountered in an FLV Tag and those found in a

RTMP packet
, as for example the FLV Packet Type field uses the same numeric values as the RTMP Chunk Type field (ex. 0x08 for audio and 0x09 for video). FLV tags are thus converted into RTMP packets when the file is streamed through a Flash Media Server or equivalent RTMP Server.

The first packet encountered is usually a metadata packet which contains information such as:

  • "duration" - 64-bit IEEE floating point value in seconds
  • "width" and "height" – 64-bit IEEE floating point value in pixels
  • "framerate" – 64-bit IEEE floating point value in frames per second
  • "keyframes" – an array with the positions of
    p-frames
    , needed when random access is sought.
  • "|AdditionalHeader" - an array of required stream decoding informational pairs
    • "Encryption" - an array of required encryption informational pairs
    • "Metadata" - Base64 encoded string of a signed X.509 certificate containing the Adobe Access AES decryption key required

When streamed using an

Actionscript built player, the metadata
values above are passed as arguments on the onMetaData callback function. Audio packets have the first byte of the payload defining the decoding details with the first four bits for the encoding used and the last four bits for the parameters required to process the encoding. Video packets have this order reversed.

Video encodings enumerated from 0 are:

Id Video encoding
0 RGB
1 run-length
2
Sorenson's H.263
3 Screen 1
4 On2 TrueMotion VP6
5 VP6 with alpha
6 Screen 2
7 MP4
H.264
8 ITU H.263
9 MPEG-4 ASP.

Video processing parameters enumerated from 1 are:

Id Video processing parameters
1 key frame
2 non-key frame
3 H.263 disposable frame
4 generated key frame
5 one byte frame seeking instruction

MPEG-4 encodings such as H.264, MPEG-4 ASP and AAC add a one byte value with a NULL value indicating that the payload contains MPEG-4 configuration details. MPEG-4 video encodings also add three bytes for composition timestamp offset which is required for encodings that use B-frames.

Audio encodings enumerated from 0 are:

Id Audio encoding
0 native PCM
1 ADPCM
2 MPEG layer 3
3 PCM - little endian
4 Asao 16 kHz
5 Asao 8 kHz
6 Asao parameter rate
7 a-law
8 μ-law

Audio encodings enumerated from 10 are:

Id Audio encoding
10 MP4 AAC
11 Speex

Audio encodings enumerated from 14 are MPEG layer 3 8 kHz, Device specific such as MIDI.

Audio processing parameters with the first two bits for the sampling rate, next bit flags 16-bit sample size on with off indicating 8-bit sample size, and the final bit flags stereophonic channels on with off indicating monaural only. Sampling rates enumerated from 0 are 5.5 kHz, 11.025 kHz quarter, 22.05 kHz half, 44.1 kHz full.

Encrypted packets have an additional 31 or 24 byte header before the AES-CBC encrypted payload as follows:

Field Data Type Default Details
NumFilters uint8 1 always only 1
FilterName C string "Encryption" if only selected payloads are encrypted then is "SE"
Length uint24_be 16 or 17 initialization vector length
EncryptedAU uint8 bitmask 0x80 or 0x00 only if FilterName is "SE", then 0x80 mean encrypted payload
IV uint128 varies initialization vector for AES decryption
Content freeform varies encrypted payload
Padding freeform 0x10 encryption padding

FLV players

An FLV player is a type of media player that is used for playing Flash video from PC as well as from Internet websites. An FLV player can be used standalone, without the need of the Adobe Flash authoring or developmental tools. It can also be embedded in the website using Flash component or embeddable version of FLV player.

Main article: Adobe Flash Player

Adobe Flash Player is a multimedia and application player originally developed by

H.264
video content as well.

H.264

Flash Player 9 Update 3, released on 3 December 2007,

3GPP Timed Text specification (MPEG-4 Part 17) which is a standardized subtitle format and partial parsing support for the 'ilst' atom which is the ID3 equivalent iTunes uses to store metadata. MPEG-4 Part 2 video (e.g. created with DivX or Xvid) is not supported.[5] In an interview with BBC News, the main programmer of Flash Jonathan Gay said that the company had wanted to use H.264 when video support was originally added to Flash, but had been deterred by the patent licensing fees of around $5 million (£3.5 million) per year.[21]

Playback

Flash Player supports two distinct modes of video playback:

  • Hardware Accelerated Video : Flash Player supports hardware accelerated video playback since version 10.2, for
    FLV video formats. Such video is displayed above all Flash content, and takes advantage of video codec chipsets installed on the user's device. Developers must specifically use the "StageVideo" technology within Flash Player in order for hardware decoding to be enabled. Flash Player internally uses technologies such as DirectX Video Acceleration and OpenGL
    to do so.

Desktop-based

Main article: Comparison of video player software

Microsoft Windows, Mac OS X, Unix-based

Mac OS devices can play flash videos in QuickTime with the help of additional software (such as the open source Perian component.)

PDA-based and smartphone-based

Windows Mobile, Palm OS–based

The

Skyfire web browser application.) Apple iOS has never supported Flash. Android versions above 2.1 through 4.0 supported Flash; Adobe has discontinued Flash Player for Android.[23] On 29 June 2012, Adobe announced that, as they were discontinuing development of the mobile version of Flash, they would prevent the Flash player from installing from the Google Play Store on any Android devices that do not already have the Flash player installed, and that they would not be releasing a version of Flash certified for use with Android version 4.1, codenamed Jelly Bean.[24]

Delivery options

Flash Video files can be delivered in several different ways:

Flash video recording

It is possible to record online flash videos using

leeching
measures are used.

See also

References

  1. ^ a b c d e f g h Adobe Systems Incorporated (August 2010). "Adobe Flash Video File Format Specification, Version 10.1" (PDF). Adobe Systems Incorporated. Archived (PDF) from the original on 1 December 2021. {{cite journal}}: Cite journal requires |journal= (help)
  2. Google Knol. 7 December 2008. Archived from the original
    on 13 February 2009. Retrieved 3 August 2009.
  3. ^ "Flash H.264". MainConcept. Archived from the original on 18 November 2010. Retrieved 24 September 2010.
  4. ^ Adobe Flash Media Server
  5. ^ a b Kaourantin.net (20 August 2007). "What just happened to video on the web". Archived from the original on 6 January 2010. Retrieved 12 August 2009.
  6. ^ a b c d Kaourantin.net (31 October 2007) Tinic Uro New File Extensions and MIME Types Archived 6 July 2010 at the Wayback Machine, Retrieved on 2009-08-03
  7. ^ a b Adobe Flash CS4 Professional Documentation – Digital video and Flash, Retrieved on 2009-08-09
  8. ^ a b MultimediaWiki Nelly Moser, Retrieved on 2009-08-11
  9. ^ Adobe (3 December 2007) List of codecs supported by Adobe Flash Player, Retrieved on 2009-08-10
  10. ^ Benjamin Larsson (17 March 2009). "h263-svq3 optimizations". FFmpeg-devel (Mailing list). Archived from the original on 17 August 2009. Retrieved 9 August 2009.
  11. ^ a b "The quest for a new video codec in Flash 8". Kaourantin.net. 13 August 2005. Archived from the original on 6 February 2009. Retrieved 10 August 2009.
  12. ^ "Sorenson Spark". MultimediaWiki. Retrieved 3 November 2009.
  13. ^ Sorenson Media Difference Between Flash 6 and Flash 8 video Archived 25 August 2009 at the Wayback Machine, Retrieved on 2009-08-09
  14. ^ a b Adobe LiveDocs (2005) Flash 8 Documentation – About the On2 VP6 and Sorenson Spark video codecs Archived 11 February 2009 at the Wayback Machine, Retrieved on 2009-08-09
  15. ^ "Flash CS3 – Comparing the On2 VP6 and Sorenson Spark video codecs". Archived from the original on 14 February 2011. Retrieved 4 February 2011. To support better quality video at the same data rate, the On2 VP6 codec is noticeably slower to encode and requires more processor power on the client computer to decode and play back. For this reason, carefully consider the lowest common denominator of computer you intend your viewing audience to use when accessing your Flash Video content. If you anticipate a large user base that uses older computers, consider encoding your FLV files using the Sorenson Spark codec.
  16. ^ Adobe LiveDocs (2005) Flash 8 Documentation – Comparing the On2 VP6 and Sorenson Spark video codecs Archived 2 December 2008 at the Wayback Machine, Retrieved on 2009-08-09
  17. ^ AskMeFlash.com (10 May 2009) Speex vs Nellymoser Archived 15 April 2009 at the Wayback Machine, Retrieved on 2009-08-12
  18. ^ "Git.videolan.org Git - ffmpeg.git/Blob - libavformat/Flvdec.c". Archived from the original on 24 March 2017. Retrieved 17 December 2019.
  19. ^ Open Source Flash (2011) Flash Video (FLV) [online] Available from (link already dead): http://osflash.org/flv#flv_format
  20. ^ "Adobe Flash Player 9 Downloads". Adobe. 3 December 2007. Retrieved 31 January 2008.
  21. ^ Frewin, Jonathan (18 May 2010). "Flash creator wades into Apple debate". BBC News. Retrieved 1 June 2010.
  22. ^ Melanson, Mike (27 January 2010). "Solving Different Problems". Penguin.SWF. Retrieved 15 November 2014.
  23. ^ "An Update on Flash Player and Android". Adobe. Retrieved 31 March 2016.
  24. ^ Arthur, Charles (29 June 2012). "Flash Player for Android: Adobe calls time, declares it dead". The Guardian. Retrieved 30 June 2012.
  25. ^ "Rtmpd – Outside of the Box Thinking".
  26. ^ Apple iPads and iPhones finally get Flash video 9 September 2011. Retrieved 10 September 2011.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Flash_Video&oldid=1186647834"