When switching output cards, do it from the mixer thread.

[nageru] / mixer.h

#ifndef _MIXER_H
#define _MIXER_H 1

// The actual video mixer, running in its own separate background thread.

#include <assert.h>
#include <epoxy/gl.h>

#undef Success

#include <stdbool.h>
#include <stdint.h>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <cstddef>
#include <functional>
#include <map>
#include <memory>
#include <mutex>
#include <queue>
#include <string>
#include <thread>
#include <vector>

#include "audio_mixer.h"
#include "bmusb/bmusb.h"
#include "defs.h"
#include "httpd.h"
#include "input_state.h"
#include "libusb.h"
#include "pbo_frame_allocator.h"
#include "ref_counted_frame.h"
#include "ref_counted_gl_sync.h"
#include "theme.h"
#include "timebase.h"
#include "video_encoder.h"

class ALSAOutput;
class ChromaSubsampler;
class DeckLinkOutput;
class QSurface;
class QSurfaceFormat;

namespace movit {
class Effect;
class EffectChain;
class FlatInput;
class ResourcePool;
}  // namespace movit

// For any card that's not the master (where we pick out the frames as they
// come, as fast as we can process), there's going to be a queue. The question
// is when we should drop frames from that queue (apart from the obvious
// dropping if the 16-frame queue should become full), especially given that
// the frame rate could be lower or higher than the master (either subtly or
// dramatically). We have two (conflicting) demands:
//
//   1. We want to avoid starving the queue.
//   2. We don't want to add more delay than is needed.
//
// Our general strategy is to drop as many frames as we can (helping for #2)
// that we think is safe for #1 given jitter. To this end, we set a lower floor N,
// where we assume that if we have N frames in the queue, we're always safe from
// starvation. (Typically, N will be 0 or 1. It starts off at 0.) If we have
// more than N frames in the queue after reading out the one we need, we head-drop
// them to reduce the queue.
//
// N is reduced as follows: If the queue has had at least one spare frame for
// at least 50 (master) frames (ie., it's been too conservative for a second),
// we reduce N by 1 and reset the timers. TODO: Only do this if N ever actually
// touched the limit.
//
// Whenever the queue is starved (we needed a frame but there was none),
// and we've been at N since the last starvation, N was obviously too low,
// so we increment it. We will never set N above 5, though.
class QueueLengthPolicy {
public:
        QueueLengthPolicy() {}
        void reset(unsigned card_index) {
                this->card_index = card_index;
                safe_queue_length = 0;
                frames_with_at_least_one = 0;
                been_at_safe_point_since_last_starvation = false;
        }

        void update_policy(int queue_length);  // Give in -1 for starvation.
        unsigned get_safe_queue_length() const { return safe_queue_length; }

private:
        unsigned card_index;  // For debugging only.
        unsigned safe_queue_length = 0;  // Called N in the comments.
        unsigned frames_with_at_least_one = 0;
        bool been_at_safe_point_since_last_starvation = false;
};

class Mixer {
public:
        // The surface format is used for offscreen destinations for OpenGL contexts we need.
        Mixer(const QSurfaceFormat &format, unsigned num_cards);
        ~Mixer();
        void start();
        void quit();

        void transition_clicked(int transition_num);
        void channel_clicked(int preview_num);

        enum Output {
                OUTPUT_LIVE = 0,
                OUTPUT_PREVIEW,
                OUTPUT_INPUT0,  // 1, 2, 3, up to 15 follow numerically.
                NUM_OUTPUTS = 18
        };

        struct DisplayFrame {
                // The chain for rendering this frame. To render a display frame,
                // first wait for <ready_fence>, then call <setup_chain>
                // to wire up all the inputs, and then finally call
                // chain->render_to_screen() or similar.
                movit::EffectChain *chain;
                std::function<void()> setup_chain;

                // Asserted when all the inputs are ready; you cannot render the chain
                // before this.
                RefCountedGLsync ready_fence;

                // Holds on to all the input frames needed for this display frame,
                // so they are not released while still rendering.
                std::vector<RefCountedFrame> input_frames;

                // Textures that should be released back to the resource pool
                // when this frame disappears, if any.
                // TODO: Refcount these as well?
                std::vector<GLuint> temp_textures;
        };
        // Implicitly frees the previous one if there's a new frame available.
        bool get_display_frame(Output output, DisplayFrame *frame) {
                return output_channel[output].get_display_frame(frame);
        }

        typedef std::function<void()> new_frame_ready_callback_t;
        void set_frame_ready_callback(Output output, new_frame_ready_callback_t callback)
        {
                output_channel[output].set_frame_ready_callback(callback);
        }

        // TODO: Should this really be per-channel? Shouldn't it just be called for e.g. the live output?
        typedef std::function<void(const std::vector<std::string> &)> transition_names_updated_callback_t;
        void set_transition_names_updated_callback(Output output, transition_names_updated_callback_t callback)
        {
                output_channel[output].set_transition_names_updated_callback(callback);
        }

        typedef std::function<void(const std::string &)> name_updated_callback_t;
        void set_name_updated_callback(Output output, name_updated_callback_t callback)
        {
                output_channel[output].set_name_updated_callback(callback);
        }

        typedef std::function<void(const std::string &)> color_updated_callback_t;
        void set_color_updated_callback(Output output, color_updated_callback_t callback)
        {
                output_channel[output].set_color_updated_callback(callback);
        }

        std::vector<std::string> get_transition_names()
        {
                return theme->get_transition_names(pts());
        }

        unsigned get_num_channels() const
        {
                return theme->get_num_channels();
        }

        std::string get_channel_name(unsigned channel) const
        {
                return theme->get_channel_name(channel);
        }

        std::string get_channel_color(unsigned channel) const
        {
                return theme->get_channel_color(channel);
        }

        int get_channel_signal(unsigned channel) const
        {
                return theme->get_channel_signal(channel);
        }

        int map_signal(unsigned channel)
        {
                return theme->map_signal(channel);
        }

        unsigned get_master_clock() const
        {
                return master_clock_channel;
        }

        void set_master_clock(unsigned channel)
        {
                master_clock_channel = channel;
        }

        void set_signal_mapping(int signal, int card)
        {
                return theme->set_signal_mapping(signal, card);
        }

        bool get_supports_set_wb(unsigned channel) const
        {
                return theme->get_supports_set_wb(channel);
        }

        void set_wb(unsigned channel, double r, double g, double b) const
        {
                theme->set_wb(channel, r, g, b);
        }

        // Note: You can also get this through the global variable global_audio_mixer.
        AudioMixer *get_audio_mixer() { return &audio_mixer; }
        const AudioMixer *get_audio_mixer() const { return &audio_mixer; }

        void schedule_cut()
        {
                should_cut = true;
        }

        unsigned get_num_cards() const { return num_cards; }

        std::string get_card_description(unsigned card_index) const {
                assert(card_index < num_cards);
                return cards[card_index].capture->get_description();
        }

        // The difference between this and the previous function is that if a card
        // is used as the current output, get_card_description() will return the
        // fake card that's replacing it for input, whereas this function will return
        // the card's actual name.
        std::string get_output_card_description(unsigned card_index) const {
                assert(card_can_be_used_as_output(card_index));
                assert(card_index < num_cards);
                if (cards[card_index].parked_capture) {
                        return cards[card_index].parked_capture->get_description();
                } else {
                        return cards[card_index].capture->get_description();
                }
        }

        bool card_can_be_used_as_output(unsigned card_index) const {
                assert(card_index < num_cards);
                return cards[card_index].output != nullptr;
        }

        std::map<uint32_t, bmusb::VideoMode> get_available_video_modes(unsigned card_index) const {
                assert(card_index < num_cards);
                return cards[card_index].capture->get_available_video_modes();
        }

        uint32_t get_current_video_mode(unsigned card_index) const {
                assert(card_index < num_cards);
                return cards[card_index].capture->get_current_video_mode();
        }

        void set_video_mode(unsigned card_index, uint32_t mode) {
                assert(card_index < num_cards);
                cards[card_index].capture->set_video_mode(mode);
        }

        void start_mode_scanning(unsigned card_index);

        std::map<uint32_t, std::string> get_available_video_inputs(unsigned card_index) const {
                assert(card_index < num_cards);
                return cards[card_index].capture->get_available_video_inputs();
        }

        uint32_t get_current_video_input(unsigned card_index) const {
                assert(card_index < num_cards);
                return cards[card_index].capture->get_current_video_input();
        }

        void set_video_input(unsigned card_index, uint32_t input) {
                assert(card_index < num_cards);
                cards[card_index].capture->set_video_input(input);
        }

        std::map<uint32_t, std::string> get_available_audio_inputs(unsigned card_index) const {
                assert(card_index < num_cards);
                return cards[card_index].capture->get_available_audio_inputs();
        }

        uint32_t get_current_audio_input(unsigned card_index) const {
                assert(card_index < num_cards);
                return cards[card_index].capture->get_current_audio_input();
        }

        void set_audio_input(unsigned card_index, uint32_t input) {
                assert(card_index < num_cards);
                cards[card_index].capture->set_audio_input(input);
        }

        void change_x264_bitrate(unsigned rate_kbit) {
                video_encoder->change_x264_bitrate(rate_kbit);
        }

        int get_output_card_index() const {  // -1 = no output, just stream.
                return desired_output_card_index;
        }

        void set_output_card(int card_index) { // -1 = no output, just stream.
                desired_output_card_index = card_index;
        }

private:
        void configure_card(unsigned card_index, bmusb::CaptureInterface *capture, bool is_fake_capture, DeckLinkOutput *output);
        void set_output_card_internal(int card_index);  // Should only be called from the mixer thread.
        void bm_frame(unsigned card_index, uint16_t timecode,
                bmusb::FrameAllocator::Frame video_frame, size_t video_offset, bmusb::VideoFormat video_format,
                bmusb::FrameAllocator::Frame audio_frame, size_t audio_offset, bmusb::AudioFormat audio_format);
        void bm_hotplug_add(libusb_device *dev);
        void bm_hotplug_remove(unsigned card_index);
        void place_rectangle(movit::Effect *resample_effect, movit::Effect *padding_effect, float x0, float y0, float x1, float y1);
        void thread_func();
        void handle_hotplugged_cards();
        void schedule_audio_resampling_tasks(unsigned dropped_frames, int num_samples_per_frame, int length_per_frame);
        void render_one_frame(int64_t duration);
        void audio_thread_func();
        void release_display_frame(DisplayFrame *frame);
        double pts() { return double(pts_int) / TIMEBASE; }

        HTTPD httpd;
        unsigned num_cards;

        QSurface *mixer_surface, *h264_encoder_surface, *decklink_output_surface;
        std::unique_ptr<movit::ResourcePool> resource_pool;
        std::unique_ptr<Theme> theme;
        std::atomic<unsigned> audio_source_channel{0};
        std::atomic<int> master_clock_channel{0};  // Gets overridden by <output_card_index> if set.
        int output_card_index = -1;  // -1 for none.

        // The mechanics of changing the output card are so intricately connected
        // with the work the mixer thread is doing. Thus, we don't change it directly,
        // we just set this variable instead, which signals to the mixer thread that
        // it should do the change before the next frame. This simplifies locking
        // considerations immensely.
        std::atomic<int> desired_output_card_index{-1};

        std::unique_ptr<movit::EffectChain> display_chain;
        std::unique_ptr<ChromaSubsampler> chroma_subsampler;
        std::unique_ptr<VideoEncoder> video_encoder;

        // Effects part of <display_chain>. Owned by <display_chain>.
        movit::FlatInput *display_input;

        int64_t pts_int = 0;  // In TIMEBASE units.

        // Accumulated errors in number of 1/TIMEBASE audio samples. If OUTPUT_FREQUENCY divided by
        // frame rate is integer, will always stay zero.
        unsigned fractional_samples = 0;

        std::mutex card_mutex;
        bool has_bmusb_thread = false;
        struct CaptureCard {
                std::unique_ptr<bmusb::CaptureInterface> capture;
                bool is_fake_capture;
                std::unique_ptr<DeckLinkOutput> output;

                // If this card is used for output (ie., output_card_index points to it),
                // it cannot simultaneously be uesd for capture, so <capture> gets replaced
                // by a FakeCapture. However, since reconstructing the real capture object
                // with all its state can be annoying, it is not being deleted, just stopped
                // and moved here.
                std::unique_ptr<bmusb::CaptureInterface> parked_capture;

                std::unique_ptr<PBOFrameAllocator> frame_allocator;

                // Stuff for the OpenGL context (for texture uploading).
                QSurface *surface = nullptr;

                struct NewFrame {
                        RefCountedFrame frame;
                        int64_t length;  // In TIMEBASE units.
                        bool interlaced;
                        unsigned field;  // Which field (0 or 1) of the frame to use. Always 0 for progressive.
                        std::function<void()> upload_func;  // Needs to be called to actually upload the texture to OpenGL.
                        unsigned dropped_frames = 0;  // Number of dropped frames before this one.
                        std::chrono::steady_clock::time_point received_timestamp = std::chrono::steady_clock::time_point::min();
                };
                std::queue<NewFrame> new_frames;
                bool should_quit = false;
                std::condition_variable new_frames_changed;  // Set whenever new_frames (or should_quit) is changed.

                QueueLengthPolicy queue_length_policy;  // Refers to the "new_frames" queue.

                int last_timecode = -1;  // Unwrapped.
        };
        CaptureCard cards[MAX_VIDEO_CARDS];  // Protected by <card_mutex>.
        AudioMixer audio_mixer;  // Same as global_audio_mixer (see audio_mixer.h).
        bool input_card_is_master_clock(unsigned card_index, unsigned master_card_index) const;
        struct OutputFrameInfo {
                int dropped_frames;  // Since last frame.
                int num_samples;  // Audio samples needed for this output frame.
                int64_t frame_duration;  // In TIMEBASE units.
        };
        OutputFrameInfo get_one_frame_from_each_card(unsigned master_card_index, bool master_card_is_output, CaptureCard::NewFrame new_frames[MAX_VIDEO_CARDS], bool has_new_frame[MAX_VIDEO_CARDS]);

        InputState input_state;

        // Cards we have been noticed about being hotplugged, but haven't tried adding yet.
        // Protected by its own mutex.
        std::mutex hotplug_mutex;
        std::vector<libusb_device *> hotplugged_cards;

        class OutputChannel {
        public:
                ~OutputChannel();
                void output_frame(DisplayFrame frame);
                bool get_display_frame(DisplayFrame *frame);
                void set_frame_ready_callback(new_frame_ready_callback_t callback);
                void set_transition_names_updated_callback(transition_names_updated_callback_t callback);
                void set_name_updated_callback(name_updated_callback_t callback);
                void set_color_updated_callback(color_updated_callback_t callback);

        private:
                friend class Mixer;

                unsigned channel;
                Mixer *parent = nullptr;  // Not owned.
                std::mutex frame_mutex;
                DisplayFrame current_frame, ready_frame;  // protected by <frame_mutex>
                bool has_current_frame = false, has_ready_frame = false;  // protected by <frame_mutex>
                new_frame_ready_callback_t new_frame_ready_callback;
                transition_names_updated_callback_t transition_names_updated_callback;
                name_updated_callback_t name_updated_callback;
                color_updated_callback_t color_updated_callback;

                std::vector<std::string> last_transition_names;
                std::string last_name, last_color;
        };
        OutputChannel output_channel[NUM_OUTPUTS];

        std::thread mixer_thread;
        std::thread audio_thread;
        std::atomic<bool> should_quit{false};
        std::atomic<bool> should_cut{false};

        std::unique_ptr<ALSAOutput> alsa;

        struct AudioTask {
                int64_t pts_int;
                int num_samples;
                bool adjust_rate;
        };
        std::mutex audio_mutex;
        std::condition_variable audio_task_queue_changed;
        std::queue<AudioTask> audio_task_queue;  // Under audio_mutex.

        // For mode scanning.
        bool is_mode_scanning[MAX_VIDEO_CARDS]{ false };
        std::vector<uint32_t> mode_scanlist[MAX_VIDEO_CARDS];
        unsigned mode_scanlist_index[MAX_VIDEO_CARDS]{ 0 };
        std::chrono::steady_clock::time_point last_mode_scan_change[MAX_VIDEO_CARDS];
};

extern Mixer *global_mixer;
extern bool uses_mlock;

#endif  // !defined(_MIXER_H)