[Paranoid_Android]

Hello. I'm writing a custom datasource for streaming from an InputStream but I've a doubt:
Which is the class responsible for giving the support for streaming?It depends on the DataSource or it depends on the Player?
Or better..I know that a player does not support streaming,for example,from an InputStream.I can't pass an InputStream while it isn't complete so I began to write my own DataSource that manages the reading from the stream..but;
it's enought to write a custom DataSource or it depends also on how the Player is implemented?And if it depends on the player..what have I to do?
Have I to write a custom Player too..that begins to play before the reading from the stream is completed??

Thanks!!

[axs]

The class which is extending DataSource is responsible for keeping media locator, content type and SourceStream(s). The class which is implementing SourceStream interface is responsible for data receiving (also known as protocol handling) through the provided InputStream(s). Actually, it is no matter how and through which mediums you read your data, as long as you can put it into the output buffer during the "read()" method invocation. And this is the main idea behind the DataSource: you take care about the data delivery mechanizm, and Player takes care about the use of your data (of course, if it supports your media's MIME type).

So, to create the Player, the Manager class uses your DataSource object 1) to define MIME type of the media, 2) connect to it and 3) get SourceStream(s) after successful connection. The Player uses SourceStream in a very simple way: it asks for the length of data, asks seek type and after all repeadetly calls "read()" method of the SourceStream object (in hope that you have prepeared data for it). Oh... and I forgot about the "tell()" method which tells your Player where it is now. This how things are working in the emulator-world. Now welcome to the real world.

Unfortunatelly not all Nokia mobile phones (should I say firmwares?) are able to correctly create Players from the DataSource objects. The reason is not just in your code, but in the way how Java VM is implemented. For example, on some Nokia phones the Player calls "read()" method of the SourceStream objects only once, and tries to put all the data into the memory during this single method invocation. This is not only makes a delay (imagine how long will take loading of 4Mb mp3 file into the memory by using mobile Java), but also will bring OutOfMemoryError at the final stage, when 2Mb heap memory will be finally filled out by the half of your 4Mb music file. It's just ugly, and it is not even close to the MMAPI specifications, where "read()" method returns chunks of data, and Player plays them immidiatelly. Firmware updates usually (and unfortunatelly) are not bringing any solutions to these problems. Such things stay the same for the other mobile vendors too :/

[brokendove]

I have got an article on custom datasource and streaming coming up on Java.net in the coming weeks. I will post here again when that is up.

Regards,
Vikram Goyal,
Pro MMAPI Book
http://www.mmapibook.com