IOS Gif图片压缩

February 22, 2024 in category, subcategory

IOS视频压缩

November 30, 2023 in category, subcategory

一. 首先说视频压缩的几个维度

宽高
码率
帧率
编码方式
GOP

二. 如果视频中有音轨，同时也可以压缩音轨

码率
采样率但是对音轨体积的压缩相对于视频整体体积来说意义不大

三. 参数讲解

宽高：就是视频或者图像的宽高，一般单位用像素表示
码率：单位时间（每秒）内传输数据长度
帧率：单位时间（每秒）内播放的画面数量
通常是h264、h265，x264，x265
GOP：两个关键帧的距离，关键帧中间有多少个非关键帧一般情况下短视频或者直播使用264编码即可，因为现在带宽都够，数据量大一些可以接受，264相对264压缩率会更高，但是转码过程中功耗相对较大，可以权衡利弊。 h和x的区别无非就是硬编码和软编码，硬编、解码就是使用硬件，一般是gpu去编码，厂家会自己去针对自己的gpu或者cpu去实现264和265的编码协议，所以硬编、解码一般功耗小，速度快。软编码、解码是软件厂商使用系统上层api去实现的265和264协议，所以一般无法做到效率很高，但是优势在于可以跨平台，无视硬件。

目前游戏直播，斗鱼，全民这些都使用265编码，因为一般观看者和主播很多都使用pc，性能够，而且支持动态切换分辨率（宽高）

手机端秀场直播一般采用264编码，视频尺寸大约在1000x2500这样，帧率在16-24之间，码率 20081024，可以设置为动态码率，适应手机性能和网络波动。码率影响的东西比较多，比如画面压缩程度，非关键帧的压缩程度

GOP：加入视频帧率是16帧，那么GOP一般设置为32，也就是两个关键帧就可以播放2s的视频，但同时也需要完全加载完两个关键帧才可以播放视频，如果是直播，那么用户和主播间的视频时差最小就是2s，这个根据业务尔定

四. 代码实现

方法声明
+ (void)compressWithVideoURL:(NSURL *)videoURL          // 视频数据源路径
                   outputURL:(NSURL *)outputURL         // 压缩后输出路径
                         fps:(NSInteger)fps             // 帧率
                     bitRate:(NSInteger)bitRate         // 码率
              dimensionScale:(CGFloat)dimensionScale
                  completion:(void(^)(BOOL success))completion;

// 创建视频asset
AVAsset *videoAsset = [AVAsset assetWithURL:videoURL];
NSError *readerError;
// asset读取器
AVAssetReader *reader = [AVAssetReader assetReaderWithAsset:videoAsset error:&readerError];
NSError *writerError;
// asset写入器
AVAssetWriter *writer = [AVAssetWriter assetWriterWithURL:outputURL fileType:AVFileTypeMPEG4 error:&writerError];

// 获取视频轨道
AVAssetTrack *videoTrack = [videoAsset tracksWithMediaType:AVMediaTypeVideo].firstObject;
AVAssetWriterInput *videoInput;
AVAssetReaderOutput *videoOutput;
    if (videoTrack) {
        NSDictionary *videoOutputSetting = @{
              (__bridge NSString *)kCVPixelBufferPixelFormatTypeKey:[NSNumber numberWithUnsignedInt:kCVPixelFormatType_422YpCbCr8]
            };
            
        videoOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:videoTrack outputSettings:videoOutputSetting];
        
        NSDictionary *videoCompressProperties = @{
            AVVideoAverageBitRateKey : @(bitRate),        // 码率
            AVVideoExpectedSourceFrameRateKey : @(fps),   // 帧率
            AVVideoProfileLevelKey : AVVideoProfileLevelH264HighAutoLevel
        };
        
        CGSize videoSize = [self sizeWithVideoURL:videoURL];
        CGFloat videoWidth = videoSize.width;
        CGFloat videoHeight = videoSize.height;
        NSDictionary *videoCompressSettings = @{
            AVVideoCodecKey : AVVideoCodecTypeH264,
            AVVideoWidthKey : @(videoWidth * dimensionScale),
            AVVideoHeightKey :@(videoHeight * dimensionScale),
            AVVideoCompressionPropertiesKey : videoCompressProperties,
            AVVideoScalingModeKey : AVVideoScalingModeResizeAspectFill
        };
        
        videoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoCompressSettings];
        videoInput.transform = videoTrack.preferredTransform;
        if ([reader canAddOutput:videoOutput]) {
            [reader addOutput:videoOutput];
        }
        
        if ([writer canAddInput:videoInput]) {
            [writer addInput:videoInput];
        }
    }

音频大致相同，省略。。。。

代码地址 https://github.com/Alienchang/VideoCompresser

Ffprobe的使用

June 20, 2023 in category, subcategory

图像分层

May 5, 2023 in category, subcategory

OpenCV识别人脸

February 28, 2023 in category, subcategory

IOS视频循环播放

December 17, 2022 in category, subcategory

一、AVPlayer监听播放结束，实现循环播放

添加播放器播放结束监听

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(playerItemDidPlayToEndTime:)
                                             name:AVPlayerItemDidPlayToEndTimeNotification
                                           object:nil];

在结束访法中seek视频到开始时间点

- (void)playerItemDidPlayToEndTime:(NSNotification *)notification {
    [self.player seekToTime:kCMTimeZero]
}

二、AVPlayerLooper循环播放

原生方法，可完全替代方法一

NSURL *url = nil;
AVPlayerItem *playerItem = [[AVPlayerItem alloc] initWithURL:url];
AVQueuePlayer *player = [AVQueuePlayer queuePlayerWithItems:@[playerItem]];
AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:player];
AVPlayerLooper *playerLooper = [AVPlayerLooper playerLooperWithPlayer:player templateItem:playerItem];
[player play];

三、MPMoviePlayerController实现循环播放

self.url = [NSURL fileURLWithPath:[[NSBundle mainBundle]pathForResource:@"new" ofType:@"mp4"]];
self.player = [[MPMoviePlayerController alloc] initWithContentURL:self.url];
[self.view addSubview:self.player.view];
self.player.shouldAutoplay = YES;
self.player.repeatMode = MPMovieRepeatModeOne;
[self.player.view setFrame:self.view.bounds];
self.player.scalingMode = MPMovieScalingModeAspectFill;
[self.player play];

四、ijkplayer循环播放

使用ijkPlayerDemo中的IJKFFMoviePlayerController做测试，IJKFFMoviePlayerController本身没有循环播放代码，需要手动添加一下。

先在IJKFFMoviePlayerController中添加loop属性，为bool类型，然后在.m文件421行添加相关代码 ijkmp_set_loop

- (void)play
{
    if (!_mediaPlayer)
        return;

    [self setScreenOn:_keepScreenOnWhilePlaying];

    [self startHudTimer];
    if (self.loop) {
        ijkmp_set_loop(_mediaPlayer, INT_MAX);
    } else {
        ijkmp_set_loop(_mediaPlayer, 1);
    }
    
    ijkmp_start(_mediaPlayer);
}

使用方法

self.videoPlayer = [[IJKFFMoviePlayerController alloc] initWithContentURL:[NSURL fileURLWithPath:path] withOptions:options];
self.videoPlayer.view.autoresizingMask = UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleHeight;
self.videoPlayer.view.frame = self.view.bounds;
self.videoPlayer.loop = YES;
self.videoPlayer.scalingMode = IJKMPMovieScalingModeAspectFill;
self.videoPlayer.shouldAutoplay = YES;
//        self.containView.autoresizesSubviews = YES;
[self.view addSubview:self.videoPlayer.view];
[self.videoPlayer prepareToPlay];
[self.videoPlayer play];

IOS视频采集以及预览

October 20, 2022 in category, subcategory

一、视频采集流程

1. 初始化采集会话 
2. 设置采集设备
3. 设置视频采集输入对象
4. 设置视频采集输出对象及参数
5. 开始采集
6. 采集回调数据处理

初始化采集会话

- (void)setupCaptureSession {
    self.captureSession = [AVCaptureSession new];
    [self.captureSession beginConfiguration];
    if ([self.captureSession canSetSessionPreset:AVCaptureSessionPreset1280x720]) {
        [self.captureSession setSessionPreset:AVCaptureSessionPreset1280x720];
    }
    [self.captureSession commitConfiguration];
}

设置采集设备

- (void)setupDevice {
    // 这里我们获取前置摄像头
    self.device = [self captureDeviceWithPosition:(AVCaptureDevicePositionFront)];
    // 一般直播16-18，电影24
    [self setFPS:16];
}

/// 获取采集设备
- (AVCaptureDevice *)captureDeviceWithPosition:(AVCaptureDevicePosition)position {
    AVCaptureDevice *deviceRet = nil;
    if (position != AVCaptureDevicePositionUnspecified) {
        NSArray<AVCaptureDeviceType> *deviceTypes = @[AVCaptureDeviceTypeBuiltInWideAngleCamera,    // 广角镜头
                                                      AVCaptureDeviceTypeBuiltInDualCamera];        // 正常情况下是主摄
        
        AVCaptureDeviceDiscoverySession *sessionDiscovery = [AVCaptureDeviceDiscoverySession discoverySessionWithDeviceTypes:deviceTypes mediaType:AVMediaTypeVideo position:AVCaptureDevicePositionFront];
        
        NSArray<AVCaptureDevice *> *devices = sessionDiscovery.devices;//当前可用的AVCaptureDevice集合
        for (AVCaptureDevice *device in devices) {
            if ([device position] == position) {
                deviceRet = device;
            }
        }
    }
    return deviceRet;
}

// 这是设备输出的fps
- (void)setFPS:(NSInteger)fps {
    if (fps > 0) {
        AVFrameRateRange *frameRateRange = self.device.activeFormat.videoSupportedFrameRateRanges.firstObject;
        if(!frameRateRange) {
            // 无法获取摄像头
            return;
        }

        if (fps >= frameRateRange.maxFrameRate) {
            fps = frameRateRange.maxFrameRate;
        } else if (fps <= frameRateRange.minFrameRate) {
            fps = frameRateRange.minFrameRate;
        }

        CMTime frameDuration = CMTimeMake(1 , (int)fps);
        [self.captureSession beginConfiguration];
        NSError *error = nil;
        if ([self.device lockForConfiguration:&error]) {
            self.device.activeVideoMaxFrameDuration = frameDuration;
            self.device.activeVideoMinFrameDuration = frameDuration;
            [self.device unlockForConfiguration];
        } else {
            // 设置失败
        }
        [self.captureSession commitConfiguration];
    }
}

设置视频采集输入对象

- (void)setupInput {
    NSError *error = nil;
    self.deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:self.device error:&error];
    [self.captureSession beginConfiguration];
    if ([self.captureSession canAddInput:self.deviceInput]) {
        [self.captureSession addInput:self.deviceInput];
    }
    [self.captureSession commitConfiguration];
}

设置视频采集输出对象及参数

- (void)setupOutput {
    self.deviceOutput = [AVCaptureVideoDataOutput new];
    // 输出下一帧时是否丢弃上一帧
    self.deviceOutput.alwaysDiscardsLateVideoFrames = YES;
    // 输出视频色彩空间为yuv420（也可以为RGB）
    self.deviceOutput.videoSettings = @{
        (id)kCVPixelBufferPixelFormatTypeKey : [NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange]
    };
    // 设置视频数据输出回调
    [self.deviceOutput setSampleBufferDelegate:self queue:self.bufferQueue];
    self.captureConnection = [self.deviceOutput connectionWithMediaType:AVMediaTypeVideo];
    
    // 设置输出图像方向
    if ([self.captureConnection isVideoOrientationSupported]) {
        [self.captureConnection setVideoOrientation:AVCaptureVideoOrientationPortrait];
    }
    
    // 设置是否镜像
    if ([self.captureConnection isVideoMirroringSupported]) {
        [self.captureConnection setVideoMirrored:YES];
    }
    
    [self.captureSession beginConfiguration];
    if ([self.captureSession canAddOutput:self.deviceOutput]) {
        [self.captureSession addOutput:self.deviceOutput];
    }
    [self.captureSession commitConfiguration];
}

开始采集

- (void)startCatpure {
    if (!(self.device && self.deviceInput && self.deviceOutput)) {
        return;
    }
    
    if (self.captureSession && ![self.captureSession isRunning]) {
        [self.captureSession startRunning];
    }
}

采集回调数据处理

#pragma mark -- AVCaptureVideoDataOutputSampleBufferDelegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    //获取每一帧图像信息
    CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)CMSampleBufferGetImageBuffer(sampleBuffer);
    NSLog(@"%@",pixelBuffer);
}

本文demo： https://github.com/Alienchang/TestiOSCapture

IOS Gif图片压缩

IOS视频压缩

一. 首先说视频压缩的几个维度

二. 如果视频中有音轨，同时也可以压缩音轨

三. 参数讲解

四. 代码实现

Ffprobe的使用

图像分层

OpenCV识别人脸

IOS视频循环播放

一、AVPlayer监听播放结束，实现循环播放

二、AVPlayerLooper循环播放

三、MPMoviePlayerController实现循环播放

四、ijkplayer循环播放

IOS视频采集以及预览

一、视频采集流程

初始化采集会话

设置采集设备

设置视频采集输入对象

设置视频采集输出对象及参数

开始采集

采集回调数据处理

刘畅