What is FLV?
FLV stands for "Flash Live Video". It is a format designed for web video playback that offers high rates of compression and produces high quality video. Several products convert video files to FLV format, including our FLV Converter, Sorenson Squeeze, and the On2 (Wildform Flix).
Notable users of the FLV file include Google Video, Reuters.com and YouTube.
Most FLV converters use H.263, H.264 or On2 VP6 codecs to encode the video. The audio in FLV files is encoded in PCM, ADPCM, or MP3 format.
FLV Streaming - Progressive and Flash Comm Server:
There are two techniques used to stream an FLV file from a website, Progessive and Flash Comm Server. While this may confuse most end users, the 2 techniques depend on a few parameters that we will outline below.
Progressive Streaming - Introduced in Flash 7.0, this method is a low cost yet effective one for the user. An interface or video player in SWF (Flash File Format) is embedded in the HTML/JSP/PHP/ASP page. This video player contains the required code to playback a FLV file from a server location. Obviously the FLV file is externally placed. The video plays as the file is downloaded and the user doesn't have to wait until the whole file is downloaded.
Pros -
1. Easy to set-up and maintain
2. Consistent high quality playback at all connection speeds
3. No streaming servers required normally based on monthly fees
4. Limited technical support required
Cons -
1. The video needs to be downloaded completely before you can navigate to any particular part of it
2. As the file is downloaded, it will reside on the viewer's computer. Savvy users will be able to access their browser cache or temporary internet files to retrieve the video.
This is not necessarily harmful if you have no concerns about rights management for the video. But in case you want to protect your video, then this method of streaming is definitely not for you!
Flash Comm Server - Also known as Flash Media Server, this method is more professional way of serving streaming video on web. While in progressive download the file is downloaded to the viewer's machine and played back at the same time, in this method the file resides on the streaming server and is not downloaded while it is played. Apart from that there is no apparent difference between progressive download. The advantage of using Flash Comm Server are twofold. First, your media is protected from thieves. Secondly viewers can seek to any portion of the video to view that portion. This is particularly helpful if you have long hours of training material on your website.
Pros -
1. Ability to handle huge user load.
2. Immediate random access to different parts of a movie.
3. Video remains on server (cannot be saved by viewers).
Cons -
1. Not easy to setup for the average person.
2. Monthly Fees and much costly than progressive download.
Which should be your choice?
If you are looking for a low cost effective solution to put videos on your website and you have a low to moderate traffic then progressive download technique is your best option. If you have a pretty heavy user load BBC or CNN and you are concerned about your media rights then you definitely need a streaming server setup.
Top 5 reasons to choose FLV as your streaming video format:
1. FLV file sizes are small compared to others (almost 60% less). Thus they take up less space on a server.
2. FLV file plays directly in more browsers than Windows Media, Real Player or QuickTime.
3. FLV players can be completely customized for logos, brandings and embedded links matching your website or product.
4. FLV players can play files from a database like MySQL or MS SQL Server, and are easy to manage.
5. Flash Communications servers are easier to maintain than others, and are less prone to security threats.
What is Metadata?
Simple answer is, its data about data. For example a piece of paper contains data for 10 lines. Of these five lines are in bold and five lines are normal. Again total number of capital letters is twenty. So here is how a metadata for this paper will look like:
Total lines: 10
Bold: 5
Normal: 5
Capital letters: 20
Now if I paste the above information on top of the paper, it will be a metadata of the data contained on the paper. Simple.
FLV Metadata:
In this case, the information that composes an FLV file is the data, and the metadata is information about that video. The length of the video (duration), the number of frames per second that the video displays (frame rate), and the number of kilobytes of data transferred per second when the video plays (video and audio data rates, where applicable) are all examples of video metadata. Additionally the codec used to encode the video is also available.
Importance of FLV metadata:
Most FLV players read the metadata first to know the duration of the video file. After that it initializes or synchronizes the video file with its timeline or seekbar. If there is no metadata the seekbar will not progress with the video. Secondly for more intelligent FLV players that serve the video or rather buffer the video dynamically depending on the user?s internet speed the FLV players read the FLV video bitrate from the FLV metadata and then sets the buffer accordingly.
I'm working on a program which returns the metadata of FLV. I'll keep you posted once the program is ready to use.
FLV file size versus. FLV video quality:
Optimizing FLV conversion refers to the FLV file size versus FLV video quality. For web playback users wont be able to afford to huge sized files yet they have to ensure the video quality at the same time.
A common question of most users is how much reduction the file size will be when converted to FLV from other formats. In case of MPEG (MPEG-1 or MPEG-2) and raw AVI the file size reduces noticibly. However in case of compressed formats like WMV, ASF, MOV or divX, the file size does not reduce that much. In some rare cases it is found that the file size to have increased than the source. This happens due to the fact that these files are already in a compressed format and the file size that they have is already small. But yet a reduction can be achieved by tweaking the encoding settings a bit. For example if you want to convert a WMV that has a video window of 640 X 480 to FLV format you should use a lower video window size on the FLV converter like 400 X 300 or 320 X 240 (mostly used for website videos). This will reduce the file size a bit. But do not expect a huge reduction because technically that is not possible. Remember you will get the best results if your source file is MPEG or raw AVI.
Conversion Settings:
Best Source Video Formats: MPEG1 (files that have .mpg extention) and Raw AVI (files that have .avi extention). Note that some AVI file are DIVx AVI files and they are already compressed. Raw AVIs are generated mainly by DVCams, Webcams etc.
Optimum Video Window Size: 400 X 300 or 320 X 240 (normal) and 400 X 225 or 320 X 180 (wide screen)
Optimum Video Bitrate: 225Kbps or 350Kbps
Optimum Audio Bitrate: 48Kbps @ 22,500 Hz and Mono
If you are an expert you can always go for your own settings but this is a quick reference for all our users who wonder with the various settings of FLV Conversion.