What is streaming? |
Why does my playback get interrupted? |
What is buffering? |
What media types are there? |
Where can I get players for media files? |
What is a codec, and where can I get it? |
What are these mms:// and rtsp:// urls?
What is streaming?
A stream is a way of thinking about digital information for which there may be no ending point. The most conventional form of digital information is the file. Files always have a beginning and an end, but streams may or may not, and therefore software which uses streams must not require finding the end of the file in order to process it. Streams are usually delivered in packets which are self-contained, and usually allow seeking (i.e. fast forward) for further points in the streams. They are particularly important when dealing with large sizes of digital information, so most video and audio on the Internet is streamed.
Why does my playback get interrupted?
Interruptions can come from either the source's site throughput, or the throughput of your internet service provider (ISP). (Throughput here refers to the rate at which information can be transmitted). Even if you have a high-bandwidth internet connection, if the source from which you are downloading is slow, it will not reach you at the speed of your network. And even if the source has a high bandwith, if the source is high in demand and many people are accessing it at once, it will tend to slow down the speed of their network. However, most sites will place an upper limit on the amount of people who can access a source at once, and if this limit is placed at a level appropriate to the medium, this will allow the item to be accessed at a speed which won't cause slowdowns. And this will depend on the site - some sites will not have provided this fine-tuning.
However, there are other factors that create slowdowns. Cable access will slow down when more people are using it, and will cause your bandwith to contract; DSL is not as liable to this. Some service providers, though, may provide penalties for high-bandwith use, and subtract from your bandwidth if they deem you a problem (usually for excessively long periods of constant downloads). And the Internet in general can be subject to slowdowns - it is a highly connnected series of networks at which key nodes can be subject to denial-of-service attacks, hacker malfeasance, and general traffic fluctuations, etc. Like a freeway, if too many are trying use it, there are traffic jams.
And in some situations, your own computer could be the culprit. Malware such as viruses, worms, spambots, adware could cause slowdowns in general performance, and other problems with hard drives, memories, and other configurations can slow performance.
What is buffering?
Players that read streaming media must first process a certain amount of the stream (at least one packet) in order to display anything. The buffer is a word for computer memory that stores digital information that will later be processed. The computer memory can either be in the form of RAM or a partial temporary file that the media player constructs from the stream. Buffers in streaming media players usually will store a certain number of seconds of information, to avoid jerky on-off playback; if the media player runs at a certain rate, and there is some latency (i.e. intermittent interruptions or slower downloading) in the stream, the display process will run more smoothly if there is a fair amount of information in the buffer before the playing begins. Of course, if the rate at which the stream comes in is too slow, there will inevitably be some interruptions in the playback, but if there is a lot stored in the buffer, the periods of play before interruptions will be long enough to be intelligible.
What media types are there?
I won't go into all media types, only those which are common enough on the Internet.
MPEG (.mpeg, .mpg files) is a media type that is not proprietary in type and was created by a consortium, and is a streaming format.
AVI (.avi) is a media format originally created by Microsoft, but is not proprietary, and is very common on the web; AVI is generally not a streaming format, although there are some kind that do stream.
Microsoft has its own kinds of media, with the .asf and .wmv video formats and the .wmp audio format.
Real Networks has .ra and .rm video and audio files.
Apple (with QuickTime) has .mov, .qt, .3gp and .mp4 files.
Macromedia (with Flash/Shockwave) has its own format (.swf) that requires the Flash plugin to run, and also is used as a convenient way of delivering other media types (notably on YouTube).
Nullsoft Streaming Video (.nsv) and Shoutcast, IceCast (GNU GPL/Open Source version of Shoutcast), Live365, are all formats that are used for streaming audio and video.
The creation of MP3 compression (.mp3) created a revolution in audio formats that changed the music industry, as music files became easily accessible from the Internet. MP3 has proprietary encoders, but there are plenty of free encoders available, and there are no limits on MP3 playback.
.wmp files are proprietary audio files from Microsoft.
.ra and .rm are proprietary audio files from Real Networks.
Ogg Vorbis (.ogg) is a compression format that offers higher-quality than .mp3.
acc Plus (.aac, .mp3) is a variant on the .mp3 encoding scheme that offers much higher quality at smaller sizes than .mp3 files.
Where can I get players for media files?
Microsoft Media Player (official site)
Real Player (official site)
Quicktime Player (official site)
Macromedia Flash Plugin (official site)
Winamp Media Player - Winamp is a fast, flexible, high-fidelity music/video player for Windows. Winamp supports playback of many audio (MP3, OGG, AAC, WAV, MOD, XM, S3M, IT, MIDI, etc) and video types (AVI, ASF, MPEG, NSV), custom appearances called skins (supporting both classic Winamp 1.x/2.x skins and Winamp 3 freeform skins), audio visualization and audio effect plug-ins (including two industry dominating visualization plug-ins), an advanced media library, Internet radio and TV support, CD ripping, and CD burning.
VLC Media Player - VLC (initially VideoLAN Client) is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, mp3, ogg, ...) as well as DVDs, VCDs, and various streaming protocols. It can also be used as a server to stream video.
Real Alternative Player - Real Alternative will allow you to play RealMedia files without having to install RealPlayer/RealOne Player. Supported: RealAudio (.ra .rpm), RealMedia (.rm .ram .rmvb .rpx .smi .smil), RealText (.rt), ReadPix (.rp), RealMedia embedded in webpages.
Media Player Classic - A great all-in-one player based on the Windows Media Player 6.4. Supports most formats if you have the codecs installed like DivX, XviD, AVI, MOV, MPEG1/2, RM. Built-in MPEG2/SVCD/DVD codec. SVCD/CVD switchable subtitle support.
QuickTime Alternative - QuickTime Alternative will allow you to play QuickTime files (.mov, .qt, .3gp and other extensions) without having to install the official QuickTime Player. It also supports QuickTime content that is embedded in webpages.
MPlayer - MPlayer is a movie player for Linux (and runs on many other Unix systems, and non-x86 CPUs, like Windows, Mac...). It plays most DVD, VCD, MPEG, VOB, AVI, OGG/OGM, VIVO, ASF/WMA/WMV, QT/MOV/MP4, FLI, RM, NuppelVideo, YUV4MPEG, FILM, RoQ, PVA files. Mencoder is a converter that supports many input video formats.
What is a codec, and where can I get it?
A codec is a downloadable software encoder or decoder for a particular media format that is geared towards a specific computer platform. Codecs function much like plugins for browsers, and are used by players or authoring software to work with the specific media type. Most codecs that you will come across are decoders that are geared to presenting media content to players. Most media players have a list of websites that supply codecs and will go in search of them when a file is played that requires a particular codec; otherwise use a search engine to look for it. Free-Codecs.com also lists free versions of codecs and is generally up to date.
What are these mms:// and rtsp:// urls?
These signal to the browser and player that a certain media protocol is being used. RTSP is used for Real Networks, Apple, and Windows formats; MMS is used only for the Windows media format.