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* audio/out: reduce amount of audio bufferingwm42014-03-101-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | Since the addition of the AO feed thread, 200ms of latency (MIN_BUFFER) was added to all push-based AOs. This is not so nice, because even AOs with relatively small buffering (e.g. ao_alsa on my system with ~170ms of buffer size), the additional latency becomes noticable when e.g. toggling mute with softvol. Fix this by trying to keep not only 200ms minimum buffer, but also 200ms maximum buffer. In other words, never buffer beyond 200ms in total. Do this by estimating the AO's buffer fill status using get_space and the initially known AO buffer size (the get_space return value on initialization, before any audio was played). We limit the maximum amount of data written to the soft buffer so that soft buffer size and audio buffer size equal to 200ms (MIN_BUFFER). To avoid weird problems with weird AOs, we buffer beyond MIN_BUFFER if the AO's get_space requests more data than that, and as long as the soft buffer is large enough. Note that this is just a hack to improve the latency. When the audio chain gains the ability to refilter data, this won't be needed anymore, and instead we can introduce some sort of buffer replacement function in order to update data in the soft buffer.
* audio/out: make draining a separate operationwm42014-03-091-1/+2
| | | | | | | | | | | | Until now, this was always conflated with uninit. This was ugly, and also many AOs emulated this manually (or just ignored it). Make draining an explicit operation, so AOs which support it can provide it, and for all others generic code will emulate it. For ao_wasapi, we keep it simple and basically disable the internal draining implementation (maybe it should be restored later). Tested on Linux only.
* audio/out: feed AOs from a separate threadwm42014-03-091-3/+56
| | | | | | | | | | | | | | | | | | This has 2 goals: - Ensure that AOs have always enough data, even if the device buffers are very small. - Reduce complexity in some AOs, which do their own buffering. One disadvantage is that performance is slightly reduced due to more copying. Implementation-wise, we don't change ao.c much, and instead "redirect" the driver's callback to an API wrapper in push.c. Additionally, we add code for dealing with AOs that have a pull API. These AOs usually do their own buffering (jack, coreaudio, portaudio), and adding a thread is basically a waste. The code in pull.c manages a ringbuffer, and allows callback-based AOs to read data directly.
* ao: remove opts fieldwm42014-03-091-1/+0
| | | | Apparently unused.
* audio/out: make ao struct opaquewm42014-03-091-0/+76
We want to move the AO to its own thread. There's no technical reason for making the ao struct opaque to do this. But it helps us sleep at night, because we can control access to shared state better.