How to play Internet streams
There are two main types of Internet stream:
Broadcasting streams
Sound files available on a web site
These streams cannot be loaded through the
LoadSound method: for this purpose you must use the
LoadInternetStream method which gives the possibility to pass a URL in place of a pathname. Let's see how to manage these different streams.
Broadcasting streams
Internet radio is a broadcasting service which transmits one or more sound streams via the Internet: for this kind of streams, the control will start buffering sound data and will fire the
DownloadBuffering event with its
nState parameter set to
STREAMING_BUFFERING.
Once there will be enough data to play, the control will fire the
StreamLoaded event allowing the container application to start the playback session through a call to the
PlaySound method. Immediately after starting playback, the control will fire again the
DownloadBuffering event with its
nState parameter set to
STREAMING_PLAYING: note that, during the playback session, the control will continue buffering data from the Internet: if for any reason, for example for a slow connection, the download should stall, the control will notify the container application firing again the
DownloadBuffering event with the
nState parameter set to
STREAMING_BUFFERING: when there will be again enough data to play, the control will automatically resume playback notifying the container application through the
DownloadBuffering event with the
nState parameter set to
STREAMING_PLAYING.
After a stall situation, the Internet stream provider could also close the connection: in this case the control will fire the
ServerClosed event.
During playback, the server will usually send information about the radio station and about the song in playback: the control has the capability to notify in real-time the availability of this information, usually called "tags", and to retrieve the various strings composing the same tag: for this purpose the control will fire the
MetaTagChanged event: at this point the container application will have the possibility to perform the following sequence of tasks:
instruct the control to retrieve the tag contents through a call to the ReadSoundInfo method
verify the effective availability of the tags and the number of strings composing the tag through a call to the IsTagAvailable method
retrieve each of the various strings composing the tag through a call to the GetTagString method.
Sound files available on a web site
Loading a sound file from a web site is very similar to loading a broadcast stream with the following differences:
The remote server will not send metadata so the control will never fire the MetaTagChanged event
Differently from streams, that can be created in real-time, sound files have a limited size: this means that, at a certain extent, the download of the file will be completed: the control will in this case fire a DownloadComplete method allowing the container application to gain access to tags like ID3V1 which, for MP3 files, are stored on the file's bottom.
A sample of access to Internet streams in Visual Basic 6 and Visual C++ 6 can be found inside the following sample installed with the product's setup package:
- InternetRadio
