diff options
Diffstat (limited to 'libs/ardour/ardour/audio_backend.h')
-rw-r--r-- | libs/ardour/ardour/audio_backend.h | 102 |
1 files changed, 84 insertions, 18 deletions
diff --git a/libs/ardour/ardour/audio_backend.h b/libs/ardour/ardour/audio_backend.h index 0e39625e8c..387410685b 100644 --- a/libs/ardour/ardour/audio_backend.h +++ b/libs/ardour/ardour/audio_backend.h @@ -117,6 +117,17 @@ class AudioBackend : public PortEngine { * at any time. */ virtual std::vector<float> available_sample_rates (const std::string& device) const = 0; + + /* Returns the default sample rate that will be shown to the user when + * configuration options are first presented. If the derived class + * needs or wants to override this, it can. It also MUST override this + * if there is any chance that an SR of 44.1kHz is not in the list + * returned by available_sample_rates() + */ + virtual float default_sample_rate () const { + return 44100.0; + } + /** Returns a collection of uint32 identifying buffer sizes that are * potentially usable with the hardware identified by @param device. * Any of these values may be supplied in other calls to this backend @@ -126,6 +137,16 @@ class AudioBackend : public PortEngine { */ virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0; + /* Returns the default buffer size that will be shown to the user when + * configuration options are first presented. If the derived class + * needs or wants to override this, it can. It also MUST override this + * if there is any chance that a buffer size of 1024 is not in the list + * returned by available_buffer_sizes() + */ + virtual uint32_t default_buffer_size () const { + return 1024; + } + /** Returns the maximum number of input channels that are potentially * usable with the hardware identified by @param device. Any number from 1 * to the value returned may be supplied in other calls to this backend as @@ -239,8 +260,29 @@ class AudioBackend : public PortEngine { * app is undefined or cannot be launched. */ virtual void launch_control_app () = 0; - /* Basic state control */ + /* @return a vector of strings that describe the available + * MIDI options. + * + * These can be presented to the user to decide which + * MIDI drivers, options etc. can be used. The returned strings + * should be thought of as the key to a map of possible + * approaches to handling MIDI within the backend. Ensure that + * the strings will make sense to the user. + */ + virtual std::vector<std::string> enumerate_midi_options () const = 0; + + /* Request the use of the MIDI option named @param option, which + * should be one of the strings returned by enumerate_midi_options() + * + * @return zero if successful, non-zero otherwise + */ + virtual int set_midi_option (const std::string& option) = 0; + + virtual std::string midi_option () const = 0; + + /* State Control */ + /** Start using the device named in the most recent call * to set_device(), with the parameters set by various * the most recent calls to set_sample_rate() etc. etc. @@ -250,9 +292,30 @@ class AudioBackend : public PortEngine { * the AudioEngine referenced by @param engine. These calls will * occur in a thread created by and/or under the control of the backend. * + * @param for_latency_measurement if true, the device is being started + * to carry out latency measurements and the backend should this + * take care to return latency numbers that do not reflect + * any existing systemic latency settings. + * * Return zero if successful, negative values otherwise. - */ - virtual int start () = 0; + * + * + * + * + * Why is this non-virtual but ::_start() is virtual ? + * Virtual methods with default parameters create possible ambiguity + * because a derived class may implement the same method with a different + * type or value of default parameter. + * + * So we make this non-virtual method to avoid possible overrides of + * default parameters. See Scott Meyers or other books on C++ to understand + * this pattern, or possibly just this: + * + * http://stackoverflow.com/questions/12139786/good-pratice-default-arguments-for-pure-virtual-method + */ + int start (bool for_latency_measurement=false) { + return _start (for_latency_measurement); + } /** Stop using the device currently in use. * @@ -270,20 +333,6 @@ class AudioBackend : public PortEngine { */ virtual int stop () = 0; - /** Temporarily cease using the device named in the most recent call to set_parameters(). - * - * If the function is successfully called, no subsequent calls to the - * process_callback() of @param engine will be made after the function - * returns, until start() is called again. - * - * The backend will retain its existing parameter configuration after a successful - * return, and does NOT require any calls to set hardware parameters before it can be - * start()-ed again. - * - * Return zero if successful, 1 if the device is not in use, negative values on error - */ - virtual int pause () = 0; - /** While remaining connected to the device, and without changing its * configuration, start (or stop) calling the process_callback() of @param engine * without waiting for the device. Once process_callback() has returned, it @@ -312,7 +361,7 @@ class AudioBackend : public PortEngine { * Implementations can feel free to smooth the values returned over * time (e.g. high pass filtering, or its equivalent). */ - virtual float cpu_load() const = 0; + virtual float dsp_load() const = 0; /* Transport Control (JACK is the only audio API that currently offers the concept of shared transport control) @@ -421,8 +470,25 @@ class AudioBackend : public PortEngine { virtual void update_latencies () = 0; + /** Set @param speed and @param position to the current speed and position + * indicated by some transport sync signal. Return whether the current + * transport state is pending, or finalized. + * + * Derived classes only need implement this if they provide some way to + * sync to a transport sync signal (e.g. Sony 9 Pin) that is not + * handled by Ardour itself (LTC and MTC are both handled by Ardour). + * The canonical example is JACK Transport. + */ + virtual bool speed_and_position (double& speed, framepos_t& position) { + speed = 0.0; + position = 0; + return false; + } + protected: AudioEngine& engine; + + virtual int _start (bool for_latency_measurement) = 0; }; struct AudioBackendInfo { |