[bmusb] / bmusb.h

#ifndef _BMUSB_H
#define _BMUSB_H

#include <stdint.h>
#include <atomic>
#include <condition_variable>
#include <deque>
#include <functional>
#include <mutex>
#include <string>
#include <thread>
#include <vector>

struct libusb_transfer;

// An interface for frame allocators; if you do not specify one
// (using set_video_frame_allocator), a default one that pre-allocates
// a freelist of eight frames using new[] will be used. Specifying
// your own can be useful if you have special demands for where you want the
// frame to end up and don't want to spend the extra copy to get it there, for
// instance GPU memory.
class FrameAllocator {
 public:
        struct Frame {
                uint8_t *data = nullptr;
                uint8_t *data2 = nullptr;  // Only if interleaved == true.
                size_t len = 0;  // Number of bytes we actually have.
                size_t size = 0;  // Number of bytes we have room for.
                size_t overflow = 0;
                void *userdata = nullptr;
                FrameAllocator *owner = nullptr;

                // If set to true, every other byte will go to data and to data2.
                // If so, <len> and <size> are still about the number of total bytes
                // so if size == 1024, there's 512 bytes in data and 512 in data2.
                bool interleaved = false;
        };

        virtual ~FrameAllocator();

        // Request a video frame. Note that this is called from the
        // USB thread, which runs with realtime priority and is
        // very sensitive to delays. Thus, you should not do anything
        // here that might sleep, including calling malloc().
        // (Taking a mutex is borderline.)
        //
        // The Frame object will be given to the frame callback,
        // which is responsible for releasing the video frame back
        // once it is usable for new frames (ie., it will no longer
        // be read from). You can use the "userdata" pointer for
        // whatever you want to identify this frame if you need to.
        //
        // Returning a Frame with data==nullptr is allowed;
        // if so, the frame in progress will be dropped.
        virtual Frame alloc_frame() = 0;

        virtual void release_frame(Frame frame) = 0;
};

typedef std::function<void(uint16_t timecode,
                           FrameAllocator::Frame video_frame, size_t video_offset, uint16_t video_format,
                           FrameAllocator::Frame audio_frame, size_t audio_offset, uint16_t audio_format)>
        frame_callback_t;

// The actual capturing class, representing capture from a single card.
class BMUSBCapture {
 public:
        BMUSBCapture(int card_index)
                : card_index(card_index)
        {
        }

        // Does not take ownership.
        void set_video_frame_allocator(FrameAllocator *allocator)
        {
                video_frame_allocator = allocator;
        }

        FrameAllocator *get_video_frame_allocator()
        {
                return video_frame_allocator;
        }

        // Does not take ownership.
        void set_audio_frame_allocator(FrameAllocator *allocator)
        {
                audio_frame_allocator = allocator;
        }

        FrameAllocator *get_audio_frame_allocator()
        {
                return audio_frame_allocator;
        }

        void set_frame_callback(frame_callback_t callback)
        {
                frame_callback = callback;
        }

        // Needs to be run before configure_card().
        void set_dequeue_thread_callbacks(std::function<void()> init, std::function<void()> cleanup)
        {
                dequeue_init_callback = init;
                dequeue_cleanup_callback = cleanup;
                has_dequeue_callbacks = true;
        }

        // Only valid after configure_card().
        std::string get_description() const {
                return description;
        }

        void configure_card();
        void start_bm_capture();
        void stop_dequeue_thread();

        static void start_bm_thread();
        static void stop_bm_thread();

 private:
        struct QueuedFrame {
                uint16_t timecode;
                uint16_t format;
                FrameAllocator::Frame frame;
        };

        void start_new_audio_block(const uint8_t *start);
        void start_new_frame(const uint8_t *start);

        void queue_frame(uint16_t format, uint16_t timecode, FrameAllocator::Frame frame, std::deque<QueuedFrame> *q);
        void dequeue_thread_func();

        static void usb_thread_func();
        static void cb_xfr(struct libusb_transfer *xfr);

        std::string description;

        FrameAllocator::Frame current_video_frame;
        FrameAllocator::Frame current_audio_frame;

        std::mutex queue_lock;
        std::condition_variable queues_not_empty;
        std::deque<QueuedFrame> pending_video_frames;
        std::deque<QueuedFrame> pending_audio_frames;

        FrameAllocator *video_frame_allocator = nullptr;
        FrameAllocator *audio_frame_allocator = nullptr;
        frame_callback_t frame_callback = nullptr;

        std::thread dequeue_thread;
        std::atomic<bool> dequeue_thread_should_quit;
        bool has_dequeue_callbacks = false;
        std::function<void()> dequeue_init_callback = nullptr;
        std::function<void()> dequeue_cleanup_callback = nullptr;

        int current_register = 0;

        static constexpr int NUM_BMUSB_REGISTERS = 60;
        uint8_t register_file[NUM_BMUSB_REGISTERS];

        int card_index;
        std::vector<libusb_transfer *> iso_xfrs;
        int assumed_frame_width = 1280;
};

// Get details for the given video format; returns false if detection was incomplete.
// Note: Frame rate is _frame_ rate, not field rate. So 1080i60 gets 30/1, _not_ 60/1.
// "second_field_start" is only valid for interlaced modes; it signifies
// how many lines from the very top of the frame there are before the second field
// starts (so it will always be >= height/2 + extra_lines_top).
bool decode_video_format(uint16_t video_format, unsigned *width, unsigned *height, unsigned *second_field_start,
                         unsigned *extra_lines_top, unsigned *extra_lines_bottom,
                         unsigned *frame_rate_nom, unsigned *frame_rate_den, bool *interlaced);

#endif