On Mon, 2014-04-14 at 01:16 +0200, Lukasz Marek wrote: > Hi, > > I hope this is correct list for general questions about PulseAudio > development. I devel some stuff for FFmpeg project and I want to update > pulse output device. I have few questions: > > - Is this possible to detect that mute/volume for sink input has changed > without calling pa_context_get_sink_input_info periodically? > I saw some commits recently that seems to add this, but ubuntu still use > 4.0 for example, so probably not, but I still wanted to ask about it. You can get notifications about sink input changes with the subscription API: http://freedesktop.org/software/pulseaudio/doxygen/subscribe.html The API will tell you only that something changed (not necessarily volume/mute), so when you get a change event for a sink input that you are interested in, you then call pa_context_get_sink_input_info(). > - If not, would you judge pa_context_get_sink_input_info to be expensive > function? I think about calling it every time new data are written or > something. The function sends a packet to the server and the server sends a reply packet to the application. It's certainly much better to use the subscription API. > - Is it possible to write non-interleaved data? > For example, for stereo instead of > L R L R L R L R... samples > to write: > L L L L L .... R R R R R.... samples Not possible. > - pa_stream_write has parameter pa_free_cb_t to provide zero-copy. > Unfortunately it doesn't accept user data, in case of FFmpeg, the buffer > is inside AVBuffer, AVPacket, or AVFrame (AVBuffer technically). > Each of them contains a variable with a buffer that should be passed to > pa_stream_write, but free function should unref this structure, not > buffer itself. > It cannot be extracted without copying and this zero-copy is hard to reach. > My question is: do you think it is doable/acceptable to add other > function that would accept userdata for free callback? > I know there is pa_stream_begin_write, but this is not suitable neither. Yes, I think that would be acceptable. I wonder what would be a good name for the function. pa_stream_write_with_free_userdata? -- Tanu
