35 lines
1.7 KiB
Plaintext
35 lines
1.7 KiB
Plaintext
Windows Media works in an asynchronous manner.
|
|
The WM Decompressor (IWMReader) requires that you provide a class
|
|
deriving from IWMReader (and, optionally, IWMReaderAdvanced) to receive information
|
|
Each delivery of uncompressed media arrives in an OnSample method
|
|
Status messages arrive in an OnStatus method.
|
|
|
|
The main difficulty that arrives from this approach is that ALL messages funnel through
|
|
a single function. Audio data and Video data arrive in the same function.
|
|
Even worse, status messages for file opened, clock error, http buffering, and DRM requirements all arrive in the same function!
|
|
|
|
In order to handle this properly, a "chain of event handlers" class was developed (WMHandler)
|
|
Any object wishing to receive data or status messages can derive from the WMHandler. All unhandled
|
|
messages are automatically passed to the next handler in the chain. Messages that are handled can be
|
|
passed or not passed based on programming requirements.
|
|
|
|
The main object sets up the chain. The >> operator has been convienently defined to faciliate the chaining.
|
|
The left side of the >> line must be the source (WMCallback)
|
|
(e.g. callback >> clock >> drm >> video >> audio >> wait >> this;)
|
|
Handlers may create their own mini-chains (which will get added in-whole) using the WMHandler::Inject() method.
|
|
|
|
Threading
|
|
------
|
|
7 basic threads
|
|
|
|
1. Main (Windows) thread
|
|
2. Callback/OnStatus thread
|
|
3. Audio Decoder thread
|
|
4. Video Decoder thread
|
|
5. Audio buffering thread (ours)
|
|
6. Video buffering thread (ours)
|
|
7. Buffering-percent status thread (ours)
|
|
|
|
There might be additional threads (created in another module) calling in, for functions like getextendedfileinfo
|
|
|