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  • Flash Video

    Flash Video is a container file format used to deliver digital video content (e.g., TV shows, 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 video file formats known as Flash Video: FLV and F4V. The audio and video data within FLV files are encoded in the same manner as they are within SWF files. The F4V file format is based on the ISO base media file format and is starting with Flash Player 9 update 3. 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 used to be the de facto standard for web-based streaming video (over RTMP). Notable users of it include Hulu, VEVO, Yahoo! Video, metacafe, Reuters.com, and many other news providers.

    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. Authors of Flash Player strongly encourage use of the new standard file format F4V (ISO base media file format) because it overcomes functional limits with the FLV structure when streaming H.264 or AAC, which is one reason Adobe Systems is moving away from the older FLV file structure. Since 2002, the initial format is Flash Video and the file suffix is .flv with a MIME derived Internet media type of video/x-flv.

    The Flash Video FLV file format supports two versions of a so-called 'screenshare' (Screen video) codec which is an encoding format designed for screencasts. Both these formats are bitmap tile based, can be lossy by reducing color depths and are compressed using zlib. The second version is only playable in Flash Player 8 and newer. Audio in Flash Video files is usually encoded as MP3. However, audio in Flash Video FLV files recorded from the user's microphone use the proprietary Nellymoser Asao Codec. (Flash Player 10 released in 2008 also supports the open source Speex codec.) FLV files also support uncompressed audio or ADPCM format audio. Recent versions of Flash Player 9 support AAC (HE-AAC/AAC SBR, AAC Main Profile, and AAC-LC). Support for encoding Flash Video files is provided by an encoding tool included with Adobe's Flash Professional and Creative Suite products, On2's Flix encoding tools, Sorenson Squeeze, FFmpeg and other third party tools.

    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 a Adobe Flash Media Server.

    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.

    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.

    Flash Player 9 Update 3, released on 3 December 2007, also includes support for the new Flash Video file format F4V and H.264 video standard (also known as MPEG-4 part 10, or AVC) which is even more computationally demanding, but offers significantly better quality/bitrate ratio. Specifically, Flash Player now supports video compressed in H.264 (MPEG-4 Part 10), audio compressed using AAC (MPEG-4 Part 3), the F4V, MP4 (MPEG-4 Part 14), M4V, M4A, 3GP and MOV multimedia container formats, 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. 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.