gst.h

#ifndef pipeline_h
#define pipeline_h

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

typedef NS_ENUM(NSInteger, State) {
    playing,
    paused,
    null,
    ready,
};

@interface Context : NSObject

- (void)pushThreadDefault;
- (void)popThreadDefault;

@end

@interface Source : NSObject

- (void)setCallbackAsync;
- (void)attach:(Context *)context;

@end

@interface XObject : NSObject // FIXME

- (void)set:(NSString *)name to:(id)value;

@end

@interface Main: NSObject

- (id)initWithContext:(Context *)context;
- (void)run;

@end


// MARK: GStreamer


@interface Element : XObject

@property (readwrite) NSString *name;

- (BOOL)linkTo:(Element *)other; // FIXME error handling
- (BOOL)setState:(State)state; // FIXME error handling

@end

@interface StateChangeMessage: NSObject
    @property (readonly) State oldState;
    @property (readonly) State newState;
    @property (readonly) State pendingState;
@end

@interface ErrorMessage: NSObject
    @property (nonnull, readonly) NSError *error;
    @property (nonnull, readonly) NSString *debugInfo;
@end

@interface Message : NSObject

@property (nonnull, readonly) Element *source;

- (nullable StateChangeMessage *)parseStateChanged;
- (nullable ErrorMessage *)parseError;

@end

@interface Bus : XObject

- (Source *)createWatch;
- (void)onMessage:(NSString *)name callback:(void (^)(Bus *bus, Message *message))callbackBlock;

@end

@interface Pipeline : Element

@property (readonly) Bus *bus;

- (void)add:(Element *)element;
- (nullable Element *)getByInterface;

@end

@interface ElementFactory : NSObject

+ (nullable Element *)make:(NSString *)name;

@end

@interface VideoOverlay: Element

- (void)setWindowHandle:(UIView *)windowHandle;

@end

@interface GStreamer: NSObject

+ (nullable Pipeline *)parseLaunch:(NSString *)command error:(NSError **)error;

@end

NS_ASSUME_NONNULL_END

#endif /* pipeline_h */

GStreamerService.swift

import UIKit

protocol GStreamerDelegate {
    func onError()
    func onStateChange()
    func onInitialized()
}

class GStreamerService {
    let delegate: GStreamerDelegate
    let videoView: UIView
    var pipeline: Pipeline!

    init(delegate: GStreamerDelegate, videoView: UIView) {
        self.delegate = delegate
        self.videoView = videoView
    }

    func play() {
        pipeline.setState(.playing)
    }

    func pause() {
        pipeline.setState(.paused)
    }

    private func onError() {
        delegate.onError()
        pipeline.setState(.null)
    }

    private func onStateChange(message: Message) {
        if message.source == pipeline {
            delegate.onStateChange()
        }
    }

    func run() {
        DispatchQueue.global().async {
            let context = Context()
            context.pushThreadDefault()
            do {
                try self.pipeline = GStreamer.parseLaunch("avfvideosrc device-index=1 ! video/x-raw,width=352,height=288 ! tee name=t t. ! queue ! autovideosink t. ! queue ! vtenc_h264 bitrate=800 max-keyframe-interval-duration=2000000000 max-keyframe-interval=60 allow-frame-reordering=false realtime=true quality=0.5 ! flvmux streamable=1 ! rtmpsink location='rtmp://ec2-54-152-176-149.compute-1.amazonaws.com:1935/live/iphone live=1'")

                self.pipeline.setState(.ready)
                let videoSink = self.pipeline.getByInterface()!
                (videoSink as! VideoOverlay).setWindowHandle(self.videoView)
                let bus = self.pipeline.bus
                let source = bus.createWatch()
                source.setCallbackAsync()
                source.attach(context)
                bus.onMessage("error") { (bus, message) in
                    print("error", message.parseError()!)
                    self.pipeline.setState(.null)

                }
                bus.onMessage("state-changed") { (bus, message) in
                    if message.source == self.pipeline {
                        print(message.source.name, message.parseStateChanged()!)
                    }
                }

                let mainLoop = Main(context: context)
                self.delegate.onInitialized()
                mainLoop.run()
                context.popThreadDefault()
            } catch let error {
                print("error", error)
                
            }
        }
        
    }
}