如何从目标C中未显示的视频生成视频缩略图

Question

对于objective中的iOS项目，我需要显示没有显示在屏幕上的rtsp视频流的缩略图(我不能截图)。我的视图显示一个视频流和其他流的三个缩略图(定期刷新)，这样用户就可以在它们之间切换。

那么，我如何生成这个缩略图呢？我使用MobileVLCKit显示我的主要视频流(我更愿意使用这个框架来生成我的缩略图.如果可能的话)。

我在论坛和谷歌的结果中发现了很多结果，但没有一个结果与我的情况相匹配:流+不显示视频。

谢谢你的帮忙!

编辑:

我也试过VLC的拇指钉，但没有成功：

VLCMedia *media = [VLCMedia mediaWithURL:[NSURL URLWithString:<Rtsp Url>]];
thumbnailer = [VLCMediaThumbnailer thumbnailerWithMedia:media andDelegate:self];

但我总是采用mediaThumbnailerDidTimeOut委托方法。

Answer 1

基本上，您需要做的就是使用VLCKit 'VLCMediaThumbnailer‘类并实现'VLCMediaThumbnailerDelegate’所需的两个函数。

下面是一个目标-C示例

@implementation DummyObject <VLCMediaThumbnailerDelegate>

- (void)workerMethod
{
    NSURL *url = [NSURL urlWithString:@""];
    VLCMedia *media = [VLCMedia mediaWithURL:url];

    VLCMediaThumbnailer *thumbnailer = [VLCMediaThumbnailer thumbnailerWithMedia:media delegate:self];

    CGSize thumbSize = CGSizeMake(800.,600.);
    thumbnailer.thumbnailWidth = thumbSize.width;
    thumbnailer.thumbnailHeight = thumbSize.height;

    [thumbnailer fetchThumbnail];
}

- (void)mediaThumbnailer:(VLCMediaThumbnailer *)mediaThumbnailer didFinishThumbnail:(CGImageRef)thumbnail
{
    if (thumbnail) {
        UIImage *thumbnailImage = [UIImage imageWithCGImage:thumbnail scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
        if (thumbnailImage) {
            // do something with the thumbnail
        }
    }
}

- (void)mediaThumbnailerDidTimeOut:(VLCMediaThumbnailer *)mediaThumbnailer
{
     // show error generating thumbnail
}

@end

目标-C代码的学分

这就是它在 SwiftUI中的样子。

func generateThumbnails()
{
    if mediaPlayer.media != nil
    {
        let vlcMediaThumbnailer: VLCMediaThumbnailer = VLCMediaThumbnailer(media: mediaPlayer.media, andDelegate: self)
        vlcMediaThumbnailer.thumbnailWidth = 440
        vlcMediaThumbnailer.thumbnailHeight = 225
        vlcMediaThumbnailer.snapshotPosition = 0.5 // get thumbs from the middle of the video

        vlcMediaThumbnailer.fetchThumbnail()
    }
}

func mediaThumbnailerDidTimeOut(_ mediaThumbnailer: VLCMediaThumbnailer!)
{
    print("failed generating thumbnail")
}

func mediaThumbnailer(_ mediaThumbnailer: VLCMediaThumbnailer!, didFinishThumbnail thumbnail: CGImage!)
{
    print("got another thumbnail - do something with it")
}

这是一个完整的工作演示 on tvOS 14.7和苹果电视在SwiftUI为缩略图在VLCKit

import SwiftUI
import AVFoundation

class VideoModel: ObservableObject
{
    @Published var thumbnails: [Image] = []
    var videoUrl: String = ""
    let thumbnailWidth: CGFloat = 400.0
    let thumbnailHeight: CGFloat = 225.0
}

struct VLCPlayerTestView: View
{
    @State var isPlayVideo: Bool = false
    
    let videoUrl: String = "https://upload.wikimedia.org/wikipedia/commons/transcoded/c/c0/Big_Buck_Bunny_4K.webm/Big_Buck_Bunny_4K.webm.480p.vp9.webm"
    var videoPlayer: VideoPlayer? = nil
    @ObservedObject var videoModel = VideoModel()
    
    init()
    {
        videoModel.videoUrl = videoUrl
        videoPlayer = VideoPlayer(videoModel: videoModel)
    }
    
    var body: some View
    {
        HStack(spacing: 20)
        {
            ForEach(0..<videoModel.thumbnails.count, id: \.self) { itemIndex in
                videoModel.thumbnails[itemIndex]
                    .resizable()
                    .aspectRatio(contentMode: .fill)
                    .frame(width: videoModel.thumbnailWidth, height: videoModel.thumbnailHeight, alignment: Alignment.center)
                    .focusable()
                    .onLongPressGesture(minimumDuration: 0.01) {
                        isPlayVideo = true
                    }
            }
        }
        .fullScreenCover(isPresented: $isPlayVideo)
        {
            videoPlayer
                .edgesIgnoringSafeArea(.all)
                .onAppear {
                    videoPlayer!.player.playVideo()
                }
                .onDisappear {
                    videoPlayer!.player.stopVideo()
                }
        }
    }
}

struct VideoPlayer: UIViewRepresentable
{
    var player: VLCPlayerView
    
    init(videoModel: VideoModel)
    {
        player = VLCPlayerView()
        player.videoModel = videoModel
        player.loadMedia()
        player.generateThumbnails()
    }

    func updateUIView(_ uiView: UIView, context: UIViewRepresentableContext<VideoPlayer>)
    {
    }

    func makeUIView(context: Context) -> UIView
    {
        return player
    }
}




class VLCPlayerView: UIView, VLCMediaPlayerDelegate, VLCMediaThumbnailerDelegate
{
    var videoModel: VideoModel?
    let mediaPlayer: VLCMediaPlayer = VLCMediaPlayer()

    override init(frame: CGRect)
    {
        super.init(frame: frame)
    }
    
    func loadMedia()
    {
        if !videoModel!.videoUrl.isEmpty
        {
            mediaPlayer.media = VLCMedia(url: URL(string: videoModel!.videoUrl)!)
            mediaPlayer.delegate = self
            mediaPlayer.drawable = self
            generateThumbnails()
        }
    }
    
    func playVideo()
    {
        if mediaPlayer.media != nil
        {
            mediaPlayer.play()
        }
    }
    
    func pauseVideo()
    {
        if mediaPlayer.media != nil && mediaPlayer.isPlaying
        {
            mediaPlayer.pause()
        }
    }
    
    func stopVideo()
    {
        if mediaPlayer.media != nil
        {
            mediaPlayer.stop()
        }
    }

    required init?(coder: NSCoder)
    {
      fatalError("init(coder:) has not been implemented")
    }

    override func layoutSubviews()
    {
      super.layoutSubviews()
    }
     
    func generateThumbnails()
    {
        if mediaPlayer.media != nil
        {
            let vlcMediaThumbnailer: VLCMediaThumbnailer = VLCMediaThumbnailer(media: mediaPlayer.media, andDelegate: self)
            vlcMediaThumbnailer.thumbnailWidth = videoModel!.thumbnailWidth
            vlcMediaThumbnailer.thumbnailHeight = videoModel!.thumbnailHeight
            vlcMediaThumbnailer.snapshotPosition = 0.5

            vlcMediaThumbnailer.fetchThumbnail()
        }
    }

    func mediaThumbnailerDidTimeOut(_ mediaThumbnailer: VLCMediaThumbnailer!)
    {
        print("failed generating thumbnail")
    }
    
    func mediaThumbnailer(_ mediaThumbnailer: VLCMediaThumbnailer!, didFinishThumbnail thumbnail: CGImage!)
    {
        print("got another thumbnail")
        if(thumbnail != nil)
        {
            let thumbnailUIImage = UIImage(cgImage: thumbnail)
            let image = Image(uiImage: thumbnailUIImage).renderingMode(.original)
            videoModel!.thumbnails.append(image)
        }
    }
}

结果：

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