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jasker5183 2022-05-08 17:06:28 +00:00 • committed by Wim Taymans
parent 8afe5fe0f0
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doc/tutorial4.dox
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@ -1,4 +1,4 @@
/** \page page_tutorial4 Tutorial - Part 4: Playing a tone
/** \page page_tutorial4 Tutorial - Part 4: Playing A Tone
\ref page_tutorial3 | \ref page_tutorial "Index" | \ref page_tutorial5
@ -57,13 +57,12 @@ and `struct pw_core` automatically.
In the properties we need to give as much information about the stream as we
can so that the session manager can make good decisions about how and where
to route this stream. There are 3 important properties to configure:
to route this stream. There are three important properties to configure:
* `PW_KEY_MEDIA_TYPE` The media type, like Audio, Video, Midi
* `pw_KEY_MEDIA_CATEGORY` The category, like Playback, Capture, Duplex, Monitor
* `PW_KEY_MEDIA_ROLE` The media role, like Movie, Music, Camera, Screen,
Communication, Game, Notification, DSP,
Production, Accessibility, Test
- `PW_KEY_MEDIA_TYPE`: The media type; like Audio, Video, MIDI.
- `PW_KEY_MEDIA_CATEGORY`: The category; like Playback, Capture, Duplex, Monitor.
- `PW_KEY_MEDIA_ROLE`: The media role; like Movie, Music, Camera, Screen,
Communication, Game, Notification, DSP, Production, Accessibility, Test.
The properties are owned by the stream and freed when the stream is destroyed
later.
@ -122,15 +121,14 @@ Now we're ready to connect the stream and run the main loop:
To connect we specify that we have a `PW_DIRECTION_OUTPUT` stream. `PW_ID_ANY`
means that we are ok with connecting to any consumer. Next we set some flags:
* `PW_STREAM_FLAG_AUTOCONNECT` automatically connect this stream. This instructs
the session manager to link us to some consumer.
* `PW_STREAM_FLAG_MAP_BUFFERS` mmap the buffers for us so we can access the
memory. If you don't set these flags you have
either work with the fd or mmap yourself.
* `PW_STREAM_FLAG_RT_PROCESS` Run the process function in the realtime thread.
Only use this if the process function only
uses functions that are realtime safe, this means
no allocation or file access or any locking.
- `PW_STREAM_FLAG_AUTOCONNECT`: Automatically connect this stream. This instructs
the session manager to link us to some consumer.
- `PW_STREAM_FLAG_MAP_BUFFERS`: mmap the buffers for us so we can access the
memory. If you don't set these flags you have either work with the fd or mmap
yourself.
- `PW_STREAM_FLAG_RT_PROCESS`: Run the process function in the realtime thread.
Only use this if the process function only uses functions that are realtime
safe, this means no allocation or file access or any locking.
And last we pass the extra parameters for our stream. Here we only have the
allowed formats (`SPA_PARAM_EnumFormat`).
@ -140,11 +138,11 @@ Running the mainloop will then start processing and will result in our
The main program flow of the process function is:
* `pw_stream_dequeue_buffer()` to obtain a buffer to write into.
* Get pointers in buffer memory to write to
* write data into buffer
* adjust buffer with number of written bytes, offset, stride,
* `pw_stream_queue_buffer()` to queue the buffer for playback.
- `pw_stream_dequeue_buffer()` to obtain a buffer to write into.
- Get pointers in buffer memory to write to.
- Write data into buffer.
- Adjust buffer with number of written bytes, offset, stride.
- `pw_stream_queue_buffer()` to queue the buffer for playback.
\snippet tutorial4.c on_process