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820 lines
37 KiB
820 lines
37 KiB
2 years ago
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# iOS AVDemo（8）：视频编码，H.264 和 H.265 都支持
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iOS/Android 客户端开发同学如果想要开始学习音视频开发，最丝滑的方式是对[音视频基础概念知识](https://mp.weixin.qq.com/mp/appmsgalbum?__biz=MjM5MTkxOTQyMQ==&action=getalbum&album_id=2140155659944787969#wechat_redirect)有一定了解后，再借助 iOS/Android 平台的音视频能力上手去实践音视频的`采集 → 编码 → 封装 → 解封装 → 解码 → 渲染`过程，并借助[音视频工具](https://mp.weixin.qq.com/mp/appmsgalbum?__biz=MjM5MTkxOTQyMQ==&action=getalbum&album_id=2216997905264082945#wechat_redirect)来分析和理解对应的音视频数据。
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在[音视频工程示例](https://mp.weixin.qq.com/mp/appmsgalbum?__biz=MjM5MTkxOTQyMQ==&action=getalbum&album_id=2273301900659851268#wechat_redirect)这个栏目，我们将通过拆解`采集 → 编码 → 封装 → 解封装 → 解码 → 渲染`流程并实现 Demo 来向大家介绍如何在 iOS/Android 平台上手音视频开发。
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这里是第八篇：**iOS 视频编码 Demo**。这个 Demo 里包含以下内容：
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- 1）实现一个视频采集模块；
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- 2）实现一个视频编码模块，支持 H.264/H.265；
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- 3）串联视频采集和编码模块，将采集到的视频数据输入给编码模块进行编码，并存储为文件；
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- 4）详尽的代码注释，帮你理解代码逻辑和原理。
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想要了解视频编码，可以看看这几篇：
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- [《视频编码（1）：H.264（AVC）》](https://mp.weixin.qq.com/s?__biz=MjM5MTkxOTQyMQ==&mid=2257484471&idx=1&sn=421be18e5b591043f13996734c60780b&scene=21#wechat_redirect)
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- [《视频编码（2）：H.265（HEVC）》](https://mp.weixin.qq.com/s?__biz=MjM5MTkxOTQyMQ==&mid=2257484563&idx=1&sn=f08f9994ef7d8a6ee09491e870c6e843&scene=21#wechat_redirect)
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- [《视频编码（3）：H.266（VVC）》](https://mp.weixin.qq.com/s?__biz=MjM5MTkxOTQyMQ==&mid=2257484673&idx=1&sn=9a6f5e69d9af825b85210c023b85b81a&scene=21#wechat_redirect)
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## 1、视频采集模块
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在这个 Demo 中，视频采集模块 `KFVideoCapture` 的实现与 [《iOS 视频采集 Demo》](https://mp.weixin.qq.com/s?__biz=MjM5MTkxOTQyMQ==&mid=2257485011&idx=1&sn=8bb9cfa01deba9670e9999bd20892440&scene=21#wechat_redirect) 中一样，这里就不再重复介绍了，其接口如下：
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```
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KFVideoCapture.h
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#import <Foundation/Foundation.h>
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#import "KFVideoCaptureConfig.h"
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NS_ASSUME_NONNULL_BEGIN
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@interface KFVideoCapture : NSObject
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+ (instancetype)new NS_UNAVAILABLE;
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- (instancetype)init NS_UNAVAILABLE;
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- (instancetype)initWithConfig:(KFVideoCaptureConfig *)config;
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@property (nonatomic, strong, readonly) KFVideoCaptureConfig *config;
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@property (nonatomic, strong, readonly) AVCaptureVideoPreviewLayer *previewLayer; // 视频预览渲染 layer。
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@property (nonatomic, copy) void (^sampleBufferOutputCallBack)(CMSampleBufferRef sample); // 视频采集数据回调。
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@property (nonatomic, copy) void (^sessionErrorCallBack)(NSError *error); // 视频采集会话错误回调。
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@property (nonatomic, copy) void (^sessionInitSuccessCallBack)(void); // 视频采集会话初始化成功回调。
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- (void)startRunning; // 开始采集。
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- (void)stopRunning; // 停止采集。
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- (void)changeDevicePosition:(AVCaptureDevicePosition)position; // 切换摄像头。
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@end
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NS_ASSUME_NONNULL_END
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```
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## 2、视频编码模块
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在实现视频编码模块之前，我们先实现一个视频编码配置类 `KFVideoEncoderConfig`：
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```
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KFVideoEncoderConfig.h
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#import <Foundation/Foundation.h>
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#import <AVFoundation/AVFoundation.h>
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NS_ASSUME_NONNULL_BEGIN
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@interface KFVideoEncoderConfig : NSObject
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@property (nonatomic, assign) CGSize size; // 分辨率。
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@property (nonatomic, assign) NSInteger bitrate; // 码率。
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@property (nonatomic, assign) NSInteger fps; // 帧率。
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@property (nonatomic, assign) NSInteger gopSize; // GOP 帧数。
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@property (nonatomic, assign) BOOL openBFrame; // 编码是否使用 B 帧。
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@property (nonatomic, assign) CMVideoCodecType codecType; // 编码器类型。
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@property (nonatomic, assign) NSString *profile; // 编码 profile。
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@end
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NS_ASSUME_NONNULL_END
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KFVideoEncoderConfig.m
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#import "KFVideoEncoderConfig.h"
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#import <VideoToolBox/VideoToolBox.h>
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@implementation KFVideoEncoderConfig
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- (instancetype)init {
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self = [super init];
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if (self) {
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_size = CGSizeMake(1080, 1920);
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_bitrate = 5000 * 1024;
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_fps = 30;
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_gopSize = _fps * 5;
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_openBFrame = YES;
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BOOL supportHEVC = NO;
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if (@available(iOS 11.0, *)) {
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if (&VTIsHardwareDecodeSupported) {
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supportHEVC = VTIsHardwareDecodeSupported(kCMVideoCodecType_HEVC);
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}
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}
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_codecType = supportHEVC ? kCMVideoCodecType_HEVC : kCMVideoCodecType_H264;
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_profile = supportHEVC ? (__bridge NSString *) kVTProfileLevel_HEVC_Main_AutoLevel : AVVideoProfileLevelH264HighAutoLevel;
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}
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return self;
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}
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@end
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```
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这里实现了在设备支持 H.265 时，默认选择 H.265 编码。
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接下来，我们来实现一个视频编码模块 `KFVideoEncoder`，在这里输入采集后的数据，输出编码后的数据。
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```
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KFVideoEncoder.h
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#import <Foundation/Foundation.h>
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#import "KFVideoEncoderConfig.h"
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NS_ASSUME_NONNULL_BEGIN
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@interface KFVideoEncoder : NSObject
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+ (instancetype)new NS_UNAVAILABLE;
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- (instancetype)init NS_UNAVAILABLE;
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- (instancetype)initWithConfig:(KFVideoEncoderConfig*)config;
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@property (nonatomic, strong, readonly) KFVideoEncoderConfig *config; // 视频编码配置参数。
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@property (nonatomic, copy) void (^sampleBufferOutputCallBack)(CMSampleBufferRef sampleBuffer); // 视频编码数据回调。
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@property (nonatomic, copy) void (^errorCallBack)(NSError *error); // 视频编码错误回调。
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- (void)encodePixelBuffer:(CVPixelBufferRef)pixelBuffer ptsTime:(CMTime)timeStamp; // 编码。
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- (void)refresh; // 刷新重建编码器。
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- (void)flush; // 清空编码缓冲区。
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- (void)flushWithCompleteHandler:(void (^)(void))completeHandler; // 清空编码缓冲区并回调完成。
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@end
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NS_ASSUME_NONNULL_END
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```
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上面是 `KFVideoEncoder` 接口的设计，除了`初始化方法`，主要是有`获取视频编码配置`以及视频编码`数据回调`和`错误回调`的接口，另外就是`编码`、`刷新重建编码器`、`清空编码缓冲区`的接口。
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其中`编码`接口对应着视频编码模块输入，`数据回调`接口则对应着输出。可以看到这里输出参数我们依然用的是 **CMSampleBufferRef**[1] 这个数据结构。不过输入的参数换成了 **CVPixelBufferRef**[2] 这个数据结构。它是对 `CVPixelBuffer` 的一个引用。
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之前我们介绍过，`CMSampleBuffer` 中包含着零个或多个某一类型（audio、video、muxed 等）的采样数据。比如：
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- 要么是一个或多个媒体采样的 **CMBlockBuffer**[3]。其中可以封装：音频采集后、编码后、解码后的数据（如：PCM 数据、AAC 数据）；视频编码后的数据（如：H.264/H.265 数据）。
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- 要么是一个 **CVImageBuffer**[4]（也作 **CVPixelBuffer**[5]）。其中包含媒体流中 CMSampleBuffers 的格式描述、每个采样的宽高和时序信息、缓冲级别和采样级别的附属信息。缓冲级别的附属信息是指缓冲区整体的信息，比如播放速度、对后续缓冲数据的操作等。采样级别的附属信息是指单个采样的信息，比如视频帧的时间戳、是否关键帧等。其中可以封装：视频采集后、解码后等未经编码的数据（如：YCbCr 数据、RGBA 数据）。
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所以，因为是视频编码的接口，这里用 `CVPixelBufferRef` 也就是图一个方便，其实也可以用 `CMSampleBufferRef`，只要编码用 `CMSampleBufferGetImageBuffer(...)` 取出对应的 `CVPixelBufferRef` 即可。
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```
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KFVideoEncoder.m
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#import "KFVideoEncoder.h"
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#import <VideoToolBox/VideoToolBox.h>
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#import <UIKit/UIKit.h>
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#define KFEncoderRetrySessionMaxCount 5
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#define KFEncoderEncodeFrameFailedMaxCount 20
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@interface KFVideoEncoder ()
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@property (nonatomic, assign) VTCompressionSessionRef compressionSession;
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@property (nonatomic, strong, readwrite) KFVideoEncoderConfig *config; // 视频编码配置参数。
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@property (nonatomic, strong) dispatch_queue_t encoderQueue;
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@property (nonatomic, strong) dispatch_semaphore_t semaphore;
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@property (nonatomic, assign) BOOL needRefreshSession; // 是否需要刷新重建编码器。
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@property (nonatomic, assign) NSInteger retrySessionCount; // 刷新重建编码器的次数。
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@property (nonatomic, assign) NSInteger encodeFrameFailedCount; // 编码失败次数。
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@end
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@implementation KFVideoEncoder
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#pragma mark - LifeCycle
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- (instancetype)initWithConfig:(KFVideoEncoderConfig *)config {
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self = [super init];
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if (self) {
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_config = config;
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_encoderQueue = dispatch_queue_create("com.KeyFrameKit.videoEncoder", DISPATCH_QUEUE_SERIAL);
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_semaphore = dispatch_semaphore_create(1);
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[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didEnterBackground:) name:UIApplicationDidEnterBackgroundNotification object:nil];
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}
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return self;
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}
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- (void)dealloc {
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[[NSNotificationCenter defaultCenter] removeObserver:self];
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dispatch_semaphore_wait(_semaphore, DISPATCH_TIME_FOREVER);
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[self _releaseCompressionSession];
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dispatch_semaphore_signal(_semaphore);
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}
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#pragma mark - Public Method
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- (void)refresh {
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self.needRefreshSession = YES; // 标记位待刷新重建编码器。
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}
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- (void)flush {
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// 清空编码缓冲区。
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__weak typeof(self) weakSelf = self;
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dispatch_async(self.encoderQueue, ^{
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dispatch_semaphore_wait(weakSelf.semaphore, DISPATCH_TIME_FOREVER);
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[weakSelf _flush];
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dispatch_semaphore_signal(weakSelf.semaphore);
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});
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}
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- (void)flushWithCompleteHandler:(void (^)(void))completeHandler {
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// 清空编码缓冲区并回调完成。
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__weak typeof(self) weakSelf = self;
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dispatch_async(self.encoderQueue, ^{
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dispatch_semaphore_wait(weakSelf.semaphore, DISPATCH_TIME_FOREVER);
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[weakSelf _flush];
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dispatch_semaphore_signal(weakSelf.semaphore);
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if (completeHandler) {
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completeHandler();
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}
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});
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}
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- (void)encodePixelBuffer:(CVPixelBufferRef)pixelBuffer ptsTime:(CMTime)timeStamp {
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// 编码。
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if (!pixelBuffer || self.retrySessionCount >= KFEncoderRetrySessionMaxCount || self.encodeFrameFailedCount >= KFEncoderEncodeFrameFailedMaxCount) {
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return;
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}
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CFRetain(pixelBuffer);
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__weak typeof(self) weakSelf = self;
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dispatch_async(self.encoderQueue, ^{
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dispatch_semaphore_wait(weakSelf.semaphore, DISPATCH_TIME_FOREVER);
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OSStatus setupStatus = noErr;
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// 1、如果还没创建过编码器或者需要刷新重建编码器，就创建编码器。
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if (!weakSelf.compressionSession || weakSelf.needRefreshSession) {
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[weakSelf _releaseCompressionSession];
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setupStatus = [weakSelf _setupCompressionSession];
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// 支持重试，记录重试次数。
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weakSelf.retrySessionCount = setupStatus == noErr ? 0 : (weakSelf.retrySessionCount + 1);
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if (setupStatus != noErr) {
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[weakSelf _releaseCompressionSession];
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NSLog(@"KFVideoEncoder setupCompressionSession error:%d", setupStatus);
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} else {
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weakSelf.needRefreshSession = NO;
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}
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}
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// 重试超过 KFEncoderRetrySessionMaxCount 次仍然失败则认为创建失败，报错。
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if (!weakSelf.compressionSession) {
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CFRelease(pixelBuffer);
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dispatch_semaphore_signal(weakSelf.semaphore);
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if (weakSelf.retrySessionCount >= KFEncoderRetrySessionMaxCount && weakSelf.errorCallBack) {
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dispatch_async(dispatch_get_main_queue(), ^{
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weakSelf.errorCallBack([NSError errorWithDomain:NSStringFromClass([KFVideoEncoder class]) code:setupStatus userInfo:nil]);
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});
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}
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return;
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}
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// 2、对 pixelBuffer 进行编码。
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VTEncodeInfoFlags flags;
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OSStatus encodeStatus = VTCompressionSessionEncodeFrame(weakSelf.compressionSession, pixelBuffer, timeStamp, CMTimeMake(1, (int32_t) weakSelf.config.fps), NULL, NULL, &flags);
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if (encodeStatus == kVTInvalidSessionErr) {
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// 编码失败进行重建编码器重试。
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[weakSelf _releaseCompressionSession];
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setupStatus = [weakSelf _setupCompressionSession];
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weakSelf.retrySessionCount = setupStatus == noErr ? 0 : (weakSelf.retrySessionCount + 1);
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if (setupStatus == noErr) {
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encodeStatus = VTCompressionSessionEncodeFrame(weakSelf.compressionSession, pixelBuffer, timeStamp, CMTimeMake(1, (int32_t) weakSelf.config.fps), NULL, NULL, &flags);
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} else {
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[weakSelf _releaseCompressionSession];
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}
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NSLog(@"KFVideoEncoder kVTInvalidSessionErr");
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}
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// 记录编码失败次数。
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if (encodeStatus != noErr) {
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NSLog(@"KFVideoEncoder VTCompressionSessionEncodeFrame error:%d", encodeStatus);
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}
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|
|
weakSelf.encodeFrameFailedCount = encodeStatus == noErr ? 0 : (weakSelf.encodeFrameFailedCount + 1);
|
||
|
|
|
||
|
|
CFRelease(pixelBuffer);
|
||
|
|
dispatch_semaphore_signal(weakSelf.semaphore);
|
||
|
|
|
||
|
|
// 编码失败次数超过 KFEncoderEncodeFrameFailedMaxCount 次，报错。
|
||
|
|
if (weakSelf.encodeFrameFailedCount >= KFEncoderEncodeFrameFailedMaxCount && weakSelf.errorCallBack) {
|
||
|
|
dispatch_async(dispatch_get_main_queue(), ^{
|
||
|
|
weakSelf.errorCallBack([NSError errorWithDomain:NSStringFromClass([KFVideoEncoder class]) code:encodeStatus userInfo:nil]);
|
||
|
|
});
|
||
|
|
}
|
||
|
|
});
|
||
|
|
}
|
||
|
|
|
||
|
|
#pragma mark - Privte Method
|
||
|
|
- (OSStatus)_setupCompressionSession {
|
||
|
|
if (_compressionSession) {
|
||
|
|
return noErr;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 1、创建视频编码器实例。
|
||
|
|
// 这里要设置画面尺寸、编码器类型、编码数据回调。
|
||
|
|
OSStatus status = VTCompressionSessionCreate(NULL, _config.size.width, _config.size.height, _config.codecType, NULL, NULL, NULL, encoderOutputCallback, (__bridge void *) self, &_compressionSession);
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 2、设置编码器属性：实时编码。
|
||
|
|
VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_RealTime, (__bridge CFTypeRef) @(YES));
|
||
|
|
|
||
|
|
// 3、设置编码器属性：编码 profile。
|
||
|
|
status = VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_ProfileLevel, (__bridge CFStringRef) self.config.profile);
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 4、设置编码器属性：是否支持 B 帧。
|
||
|
|
status = VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_AllowFrameReordering, (__bridge CFTypeRef) @(self.config.openBFrame));
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (self.config.codecType == kCMVideoCodecType_H264) {
|
||
|
|
// 5、如果是 H.264 编码，设置编码器属性：熵编码类型为 CABAC，上下文自适应的二进制算术编码。
|
||
|
|
status = VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_H264EntropyMode, kVTH264EntropyMode_CABAC);
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// 6、设置编码器属性：画面填充模式。
|
||
|
|
NSDictionary *transferDic= @{
|
||
|
|
(__bridge NSString *) kVTPixelTransferPropertyKey_ScalingMode: (__bridge NSString *) kVTScalingMode_Letterbox,
|
||
|
|
};
|
||
|
|
status = VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_PixelTransferProperties, (__bridge CFTypeRef) (transferDic));
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 7、设置编码器属性：平均码率。
|
||
|
|
status = VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_AverageBitRate, (__bridge CFTypeRef) @(self.config.bitrate));
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 8、设置编码器属性：码率上限。
|
||
|
|
if (!self.config.openBFrame && self.config.codecType == kCMVideoCodecType_H264) {
|
||
|
|
NSArray *limit = @[@(self.config.bitrate * 1.5 / 8), @(1)];
|
||
|
|
status = VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_DataRateLimits, (__bridge CFArrayRef) limit);
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// 9、设置编码器属性：期望帧率。
|
||
|
|
status = VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_ExpectedFrameRate, (__bridge CFTypeRef) @(self.config.fps));
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 10、设置编码器属性：最大关键帧间隔帧数，也就是 GOP 帧数。
|
||
|
|
status = VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_MaxKeyFrameInterval, (__bridge CFTypeRef) @(self.config.gopSize));
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 11、设置编码器属性：最大关键帧间隔时长。
|
||
|
|
status = VTSessionSetProperty(_compressionSession, kVTCompressionPropertyKey_MaxKeyFrameIntervalDuration, (__bridge CFTypeRef)@(_config.gopSize / _config.fps));
|
||
|
|
if (status != noErr) {
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 12、预备编码。
|
||
|
|
status = VTCompressionSessionPrepareToEncodeFrames(_compressionSession);
|
||
|
|
return status;
|
||
|
|
}
|
||
|
|
|
||
|
|
- (void)_releaseCompressionSession {
|
||
|
|
if (_compressionSession) {
|
||
|
|
// 强制处理完所有待编码的帧。
|
||
|
|
VTCompressionSessionCompleteFrames(_compressionSession, kCMTimeInvalid);
|
||
|
|
// 销毁编码器。
|
||
|
|
VTCompressionSessionInvalidate(_compressionSession);
|
||
|
|
CFRelease(_compressionSession);
|
||
|
|
_compressionSession = NULL;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
- (void)_flush {
|
||
|
|
// 清空编码缓冲区。
|
||
|
|
if (_compressionSession) {
|
||
|
|
// 传入 kCMTimeInvalid 时，强制处理完所有待编码的帧，清空缓冲区。
|
||
|
|
VTCompressionSessionCompleteFrames(_compressionSession, kCMTimeInvalid);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
#pragma mark - NSNotification
|
||
|
|
- (void)didEnterBackground:(NSNotification *)notification {
|
||
|
|
self.needRefreshSession = YES; // 退后台回来后需要刷新重建编码器。
|
||
|
|
}
|
||
|
|
|
||
|
|
#pragma mark - EncoderOutputCallback
|
||
|
|
static void encoderOutputCallback(void * CM_NULLABLE outputCallbackRefCon,
|
||
|
|
void * CM_NULLABLE sourceFrameRefCon,
|
||
|
|
OSStatus status,
|
||
|
|
VTEncodeInfoFlags infoFlags,
|
||
|
|
CMSampleBufferRef sampleBuffer) {
|
||
|
|
if (!sampleBuffer) {
|
||
|
|
if (infoFlags & kVTEncodeInfo_FrameDropped) {
|
||
|
|
NSLog(@"VideoToolboxEncoder kVTEncodeInfo_FrameDropped");
|
||
|
|
}
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 向外层回调编码数据。
|
||
|
|
KFVideoEncoder *videoEncoder = (__bridge KFVideoEncoder *) outputCallbackRefCon;
|
||
|
|
if (videoEncoder && videoEncoder.sampleBufferOutputCallBack) {
|
||
|
|
videoEncoder.sampleBufferOutputCallBack(sampleBuffer);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
@end
|
||
|
|
```
|
||
|
|
|
||
|
|
上面是 `KFVideoEncoder` 的实现，从代码上可以看到主要有这几个部分：
|
||
|
|
|
||
|
|
- 1）创建视频编码实例。
|
||
|
|
|
||
|
|
- - 在 `-_setupCompressionSession` 方法中实现。
|
||
|
|
|
||
|
|
- 2）实现视频编码逻辑，并在编码实例的数据回调中接收编码后的数据，抛给对外数据回调接口。
|
||
|
|
|
||
|
|
- - 在 `-encodePixelBuffer:ptsTime:` 方法中实现。
|
||
|
|
- 回调在 `encoderOutputCallback` 中实现。
|
||
|
|
|
||
|
|
- 3）实现清空编码缓冲区功能。
|
||
|
|
|
||
|
|
- - 在 `-_flush` 方法中实现。
|
||
|
|
|
||
|
|
- 4）刷新重建编码器功能。
|
||
|
|
|
||
|
|
- - 在 `-refresh` 方法中标记需要刷新重建，在 `-encodePixelBuffer:ptsTime:` 方法检查标记并重建编码器实例。
|
||
|
|
|
||
|
|
- 5）捕捉视频编码过程中的错误，抛给对外错误回调接口。
|
||
|
|
|
||
|
|
- - 主要在 `-encodePixelBuffer:ptsTime:` 方法捕捉错误。
|
||
|
|
|
||
|
|
- 6）清理视频编码器实例。
|
||
|
|
|
||
|
|
- - 在 `-_releaseCompressionSession` 方法中实现。
|
||
|
|
|
||
|
|
更具体细节见上述代码及其注释。
|
||
|
|
|
||
|
|
## 3、采集视频数据进行 H.264/H.265 编码和存储
|
||
|
|
|
||
|
|
我们在一个 ViewController 中来实现视频采集及编码逻辑，并且示范了将 iOS 编码的 AVCC/HVCC 码流格式转换为 AnnexB 码流格式后再存储。
|
||
|
|
|
||
|
|
我们先来简单介绍一下这两种格式的区别：
|
||
|
|
|
||
|
|
AVCC/HVCC 码流格式类似：
|
||
|
|
|
||
|
|
```
|
||
|
|
[extradata]|[length][NALU]|[length][NALU]|...
|
||
|
|
```
|
||
|
|
|
||
|
|
- VPS、SPS、PPS 不用 NALU 来存储，而是存储在 `extradata` 中；
|
||
|
|
- 每个 NALU 前有个 `length` 字段表示这个 NALU 的长度（不包含 `length` 字段），`length` 字段通常是 4 字节。
|
||
|
|
|
||
|
|
AnnexB 码流格式：
|
||
|
|
|
||
|
|
```
|
||
|
|
[startcode][NALU]|[startcode][NALU]|...
|
||
|
|
```
|
||
|
|
|
||
|
|
需要注意的是：
|
||
|
|
|
||
|
|
- 每个 NALU 前要添加起始码：`0x00000001`；
|
||
|
|
- VPS、SPS、PPS 也都用这样的 NALU 来存储，一般在码流最前面。
|
||
|
|
|
||
|
|
iOS 的 VideoToolbox 编码和解码只支持 AVCC/HVCC 的码流格式。但是 Android 的 MediaCodec 只支持 AnnexB 的码流格式。
|
||
|
|
|
||
|
|
```
|
||
|
|
KFVideoEncoderViewController.m
|
||
|
|
#import "KFVideoEncoderViewController.h"
|
||
|
|
#import "KFVideoCapture.h"
|
||
|
|
#import "KFVideoEncoder.h"
|
||
|
|
|
||
|
|
@interface KFVideoPacketExtraData : NSObject
|
||
|
|
@property (nonatomic, strong) NSData *sps;
|
||
|
|
@property (nonatomic, strong) NSData *pps;
|
||
|
|
@property (nonatomic, strong) NSData *vps;
|
||
|
|
@end
|
||
|
|
|
||
|
|
@implementation KFVideoPacketExtraData
|
||
|
|
@end
|
||
|
|
|
||
|
|
|
||
|
|
@interface KFVideoEncoderViewController ()
|
||
|
|
@property (nonatomic, strong) KFVideoCaptureConfig *videoCaptureConfig;
|
||
|
|
@property (nonatomic, strong) KFVideoCapture *videoCapture;
|
||
|
|
@property (nonatomic, strong) KFVideoEncoderConfig *videoEncoderConfig;
|
||
|
|
@property (nonatomic, strong) KFVideoEncoder *videoEncoder;
|
||
|
|
@property (nonatomic, assign) BOOL isEncoding;
|
||
|
|
@property (nonatomic, strong) NSFileHandle *fileHandle;
|
||
|
|
@end
|
||
|
|
|
||
|
|
@implementation KFVideoEncoderViewController
|
||
|
|
#pragma mark - Property
|
||
|
|
- (KFVideoCaptureConfig *)videoCaptureConfig {
|
||
|
|
if (!_videoCaptureConfig) {
|
||
|
|
_videoCaptureConfig = [[KFVideoCaptureConfig alloc] init];
|
||
|
|
// 这里我们采集数据用于编码，颜色格式用了默认的：kCVPixelFormatType_420YpCbCr8BiPlanarFullRange。
|
||
|
|
}
|
||
|
|
return _videoCaptureConfig;
|
||
|
|
}
|
||
|
|
|
||
|
|
- (KFVideoCapture *)videoCapture {
|
||
|
|
if (!_videoCapture) {
|
||
|
|
_videoCapture = [[KFVideoCapture alloc] initWithConfig:self.videoCaptureConfig];
|
||
|
|
__weak typeof(self) weakSelf = self;
|
||
|
|
_videoCapture.sessionInitSuccessCallBack = ^() {
|
||
|
|
dispatch_async(dispatch_get_main_queue(), ^{
|
||
|
|
// 预览渲染。
|
||
|
|
[weakSelf.view.layer insertSublayer:weakSelf.videoCapture.previewLayer atIndex:0];
|
||
|
|
weakSelf.videoCapture.previewLayer.backgroundColor = [UIColor blackColor].CGColor;
|
||
|
|
weakSelf.videoCapture.previewLayer.frame = weakSelf.view.bounds;
|
||
|
|
});
|
||
|
|
};
|
||
|
|
_videoCapture.sampleBufferOutputCallBack = ^(CMSampleBufferRef sampleBuffer) {
|
||
|
|
if (weakSelf.isEncoding && sampleBuffer) {
|
||
|
|
// 编码。
|
||
|
|
[weakSelf.videoEncoder encodePixelBuffer:CMSampleBufferGetImageBuffer(sampleBuffer) ptsTime:CMSampleBufferGetPresentationTimeStamp(sampleBuffer)];
|
||
|
|
}
|
||
|
|
};
|
||
|
|
_videoCapture.sessionErrorCallBack = ^(NSError* error) {
|
||
|
|
NSLog(@"KFVideoCapture Error:%zi %@", error.code, error.localizedDescription);
|
||
|
|
};
|
||
|
|
}
|
||
|
|
|
||
|
|
return _videoCapture;
|
||
|
|
}
|
||
|
|
|
||
|
|
- (KFVideoEncoderConfig *)videoEncoderConfig {
|
||
|
|
if (!_videoEncoderConfig) {
|
||
|
|
_videoEncoderConfig = [[KFVideoEncoderConfig alloc] init];
|
||
|
|
}
|
||
|
|
|
||
|
|
return _videoEncoderConfig;
|
||
|
|
}
|
||
|
|
|
||
|
|
- (KFVideoEncoder *)videoEncoder {
|
||
|
|
if (!_videoEncoder) {
|
||
|
|
_videoEncoder = [[KFVideoEncoder alloc] initWithConfig:self.videoEncoderConfig];
|
||
|
|
__weak typeof(self) weakSelf = self;
|
||
|
|
_videoEncoder.sampleBufferOutputCallBack = ^(CMSampleBufferRef sampleBuffer) {
|
||
|
|
// 保存编码后的数据。
|
||
|
|
[weakSelf saveSampleBuffer:sampleBuffer];
|
||
|
|
};
|
||
|
|
}
|
||
|
|
return _videoEncoder;
|
||
|
|
}
|
||
|
|
|
||
|
|
- (NSFileHandle *)fileHandle {
|
||
|
|
if (!_fileHandle) {
|
||
|
|
NSString *fileName = @"test.h264";
|
||
|
|
if (self.videoEncoderConfig.codecType == kCMVideoCodecType_HEVC) {
|
||
|
|
fileName = @"test.h265";
|
||
|
|
}
|
||
|
|
NSString *videoPath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:fileName];
|
||
|
|
[[NSFileManager defaultManager] removeItemAtPath:videoPath error:nil];
|
||
|
|
[[NSFileManager defaultManager] createFileAtPath:videoPath contents:nil attributes:nil];
|
||
|
|
_fileHandle = [NSFileHandle fileHandleForWritingAtPath:videoPath];
|
||
|
|
}
|
||
|
|
|
||
|
|
return _fileHandle;
|
||
|
|
}
|
||
|
|
|
||
|
|
#pragma mark - Lifecycle
|
||
|
|
- (void)viewDidLoad {
|
||
|
|
[super viewDidLoad];
|
||
|
|
|
||
|
|
// Navigation item.
|
||
|
|
UIBarButtonItem *startBarButton = [[UIBarButtonItem alloc] initWithTitle:@"Start" style:UIBarButtonItemStylePlain target:self action:@selector(start)];
|
||
|
|
UIBarButtonItem *stopBarButton = [[UIBarButtonItem alloc] initWithTitle:@"Stop" style:UIBarButtonItemStylePlain target:self action:@selector(stop)];
|
||
|
|
UIBarButtonItem *cameraBarButton = [[UIBarButtonItem alloc] initWithTitle:@"Camera" style:UIBarButtonItemStylePlain target:self action:@selector(changeCamera)];
|
||
|
|
self.navigationItem.rightBarButtonItems = @[stopBarButton,startBarButton,cameraBarButton];
|
||
|
|
|
||
|
|
[self requestAccessForVideo];
|
||
|
|
|
||
|
|
UITapGestureRecognizer *doubleTapGesture = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(handleDoubleTap:)];
|
||
|
|
doubleTapGesture.numberOfTapsRequired = 2;
|
||
|
|
doubleTapGesture.numberOfTouchesRequired = 1;
|
||
|
|
[self.view addGestureRecognizer:doubleTapGesture];
|
||
|
|
}
|
||
|
|
|
||
|
|
- (void)viewWillLayoutSubviews {
|
||
|
|
[super viewWillLayoutSubviews];
|
||
|
|
self.videoCapture.previewLayer.frame = self.view.bounds;
|
||
|
|
}
|
||
|
|
|
||
|
|
- (void)dealloc {
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
#pragma mark - Action
|
||
|
|
- (void)start {
|
||
|
|
if (!self.isEncoding) {
|
||
|
|
self.isEncoding = YES;
|
||
|
|
[self.videoEncoder refresh];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
- (void)stop {
|
||
|
|
if (self.isEncoding) {
|
||
|
|
self.isEncoding = NO;
|
||
|
|
[self.videoEncoder flush];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
- (void)onCameraSwitchButtonClicked:(UIButton *)button {
|
||
|
|
[self.videoCapture changeDevicePosition:self.videoCapture.config.position == AVCaptureDevicePositionBack ? AVCaptureDevicePositionFront : AVCaptureDevicePositionBack];
|
||
|
|
}
|
||
|
|
|
||
|
|
- (void)changeCamera {
|
||
|
|
[self.videoCapture changeDevicePosition:self.videoCapture.config.position == AVCaptureDevicePositionBack ? AVCaptureDevicePositionFront : AVCaptureDevicePositionBack];
|
||
|
|
}
|
||
|
|
|
||
|
|
-(void)handleDoubleTap:(UIGestureRecognizer *)sender {
|
||
|
|
[self.videoCapture changeDevicePosition:self.videoCapture.config.position == AVCaptureDevicePositionBack ? AVCaptureDevicePositionFront : AVCaptureDevicePositionBack];
|
||
|
|
}
|
||
|
|
|
||
|
|
#pragma mark - Private Method
|
||
|
|
- (void)requestAccessForVideo{
|
||
|
|
__weak typeof(self) weakSelf = self;
|
||
|
|
AVAuthorizationStatus status = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
|
||
|
|
switch (status) {
|
||
|
|
case AVAuthorizationStatusNotDetermined: {
|
||
|
|
// 许可对话没有出现，发起授权许可。
|
||
|
|
[AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
|
||
|
|
if (granted) {
|
||
|
|
[weakSelf.videoCapture startRunning];
|
||
|
|
} else {
|
||
|
|
// 用户拒绝。
|
||
|
|
}
|
||
|
|
}];
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
case AVAuthorizationStatusAuthorized: {
|
||
|
|
// 已经开启授权，可继续。
|
||
|
|
[weakSelf.videoCapture startRunning];
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
default:
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
- (KFVideoPacketExtraData *)getPacketExtraData:(CMSampleBufferRef)sampleBuffer {
|
||
|
|
// 从 CMSampleBuffer 中获取 extra data。
|
||
|
|
if (!sampleBuffer) {
|
||
|
|
return nil;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 获取编码类型。
|
||
|
|
CMVideoCodecType codecType = CMVideoFormatDescriptionGetCodecType(CMSampleBufferGetFormatDescription(sampleBuffer));
|
||
|
|
|
||
|
|
KFVideoPacketExtraData *extraData = nil;
|
||
|
|
if (codecType == kCMVideoCodecType_H264) {
|
||
|
|
// 获取 H.264 的 extra data：sps、pps。
|
||
|
|
CMFormatDescriptionRef format = CMSampleBufferGetFormatDescription(sampleBuffer);
|
||
|
|
size_t sparameterSetSize, sparameterSetCount;
|
||
|
|
const uint8_t *sparameterSet;
|
||
|
|
OSStatus statusCode = CMVideoFormatDescriptionGetH264ParameterSetAtIndex(format, 0, &sparameterSet, &sparameterSetSize, &sparameterSetCount, 0);
|
||
|
|
if (statusCode == noErr) {
|
||
|
|
size_t pparameterSetSize, pparameterSetCount;
|
||
|
|
const uint8_t *pparameterSet;
|
||
|
|
OSStatus statusCode = CMVideoFormatDescriptionGetH264ParameterSetAtIndex(format, 1, &pparameterSet, &pparameterSetSize, &pparameterSetCount, 0);
|
||
|
|
if (statusCode == noErr) {
|
||
|
|
extraData = [[KFVideoPacketExtraData alloc] init];
|
||
|
|
extraData.sps = [NSData dataWithBytes:sparameterSet length:sparameterSetSize];
|
||
|
|
extraData.pps = [NSData dataWithBytes:pparameterSet length:pparameterSetSize];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
} else if (codecType == kCMVideoCodecType_HEVC) {
|
||
|
|
// 获取 H.265 的 extra data：vps、sps、pps。
|
||
|
|
CMFormatDescriptionRef format = CMSampleBufferGetFormatDescription(sampleBuffer);
|
||
|
|
size_t vparameterSetSize, vparameterSetCount;
|
||
|
|
const uint8_t *vparameterSet;
|
||
|
|
if (@available(iOS 11.0, *)) {
|
||
|
|
OSStatus statusCode = CMVideoFormatDescriptionGetHEVCParameterSetAtIndex(format, 0, &vparameterSet, &vparameterSetSize, &vparameterSetCount, 0);
|
||
|
|
if (statusCode == noErr) {
|
||
|
|
size_t sparameterSetSize, sparameterSetCount;
|
||
|
|
const uint8_t *sparameterSet;
|
||
|
|
OSStatus statusCode = CMVideoFormatDescriptionGetHEVCParameterSetAtIndex(format, 1, &sparameterSet, &sparameterSetSize, &sparameterSetCount, 0);
|
||
|
|
if (statusCode == noErr) {
|
||
|
|
size_t pparameterSetSize, pparameterSetCount;
|
||
|
|
const uint8_t *pparameterSet;
|
||
|
|
OSStatus statusCode = CMVideoFormatDescriptionGetHEVCParameterSetAtIndex(format, 2, &pparameterSet, &pparameterSetSize, &pparameterSetCount, 0);
|
||
|
|
if (statusCode == noErr) {
|
||
|
|
extraData = [[KFVideoPacketExtraData alloc] init];
|
||
|
|
extraData.vps = [NSData dataWithBytes:vparameterSet length:vparameterSetSize];
|
||
|
|
extraData.sps = [NSData dataWithBytes:sparameterSet length:sparameterSetSize];
|
||
|
|
extraData.pps = [NSData dataWithBytes:pparameterSet length:pparameterSetSize];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
// 其他编码格式。
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
return extraData;
|
||
|
|
}
|
||
|
|
|
||
|
|
- (BOOL)isKeyFrame:(CMSampleBufferRef)sampleBuffer {
|
||
|
|
CFArrayRef array = CMSampleBufferGetSampleAttachmentsArray(sampleBuffer, true);
|
||
|
|
if (!array) {
|
||
|
|
return NO;
|
||
|
|
}
|
||
|
|
|
||
|
|
CFDictionaryRef dic = (CFDictionaryRef)CFArrayGetValueAtIndex(array, 0);
|
||
|
|
if (!dic) {
|
||
|
|
return NO;
|
||
|
|
}
|
||
|
|
|
||
|
|
// 检测 sampleBuffer 是否是关键帧。
|
||
|
|
BOOL keyframe = !CFDictionaryContainsKey(dic, kCMSampleAttachmentKey_NotSync);
|
||
|
|
|
||
|
|
return keyframe;
|
||
|
|
}
|
||
|
|
|
||
|
|
- (void)saveSampleBuffer:(CMSampleBufferRef)sampleBuffer {
|
||
|
|
// 将编码数据存储为文件。
|
||
|
|
// iOS 的 VideoToolbox 编码和解码只支持 AVCC/HVCC 的码流格式。但是 Android 的 MediaCodec 只支持 AnnexB 的码流格式。这里我们做一下两种格式的转换示范，将 AVCC/HVCC 格式的码流转换为 AnnexB 再存储。
|
||
|
|
// 1、AVCC/HVCC 码流格式：[extradata]|[length][NALU]|[length][NALU]|...
|
||
|
|
// VPS、SPS、PPS 不用 NALU 来存储，而是存储在 extradata 中；每个 NALU 前有个 length 字段表示这个 NALU 的长度（不包含 length 字段），length 字段通常是 4 字节。
|
||
|
|
// 2、AnnexB 码流格式：[startcode][NALU]|[startcode][NALU]|...
|
||
|
|
// 每个 NAL 前要添加起始码：0x00000001；VPS、SPS、PPS 也都用这样的 NALU 来存储，一般在码流最前面。
|
||
|
|
if (sampleBuffer) {
|
||
|
|
NSMutableData *resultData = [NSMutableData new];
|
||
|
|
uint8_t nalPartition[] = {0x00, 0x00, 0x00, 0x01};
|
||
|
|
|
||
|
|
// 关键帧前添加 vps（H.265)、sps、pps。这里要注意顺序别乱了。
|
||
|
|
if ([self isKeyFrame:sampleBuffer]) {
|
||
|
|
KFVideoPacketExtraData *extraData = [self getPacketExtraData:sampleBuffer];
|
||
|
|
if (extraData.vps) {
|
||
|
|
[resultData appendBytes:nalPartition length:4];
|
||
|
|
[resultData appendData:extraData.vps];
|
||
|
|
}
|
||
|
|
[resultData appendBytes:nalPartition length:4];
|
||
|
|
[resultData appendData:extraData.sps];
|
||
|
|
[resultData appendBytes:nalPartition length:4];
|
||
|
|
[resultData appendData:extraData.pps];
|
||
|
|
}
|
||
|
|
|
||
|
|
// 获取编码数据。这里的数据是 AVCC/HVCC 格式的。
|
||
|
|
CMBlockBufferRef dataBuffer = CMSampleBufferGetDataBuffer(sampleBuffer);
|
||
|
|
size_t length, totalLength;
|
||
|
|
char *dataPointer;
|
||
|
|
OSStatus statusCodeRet = CMBlockBufferGetDataPointer(dataBuffer, 0, &length, &totalLength, &dataPointer);
|
||
|
|
if (statusCodeRet == noErr) {
|
||
|
|
size_t bufferOffset = 0;
|
||
|
|
static const int NALULengthHeaderLength = 4;
|
||
|
|
// 拷贝编码数据。
|
||
|
|
while (bufferOffset < totalLength - NALULengthHeaderLength) {
|
||
|
|
// 通过 length 字段获取当前这个 NALU 的长度。
|
||
|
|
uint32_t NALUnitLength = 0;
|
||
|
|
memcpy(&NALUnitLength, dataPointer + bufferOffset, NALULengthHeaderLength);
|
||
|
|
NALUnitLength = CFSwapInt32BigToHost(NALUnitLength);
|
||
|
|
|
||
|
|
// 拷贝 AnnexB 起始码字节。
|
||
|
|
[resultData appendData:[NSData dataWithBytes:nalPartition length:4]];
|
||
|
|
// 拷贝这个 NALU 的字节。
|
||
|
|
[resultData appendData:[NSData dataWithBytes:(dataPointer + bufferOffset + NALULengthHeaderLength) length:NALUnitLength]];
|
||
|
|
|
||
|
|
// 步进。
|
||
|
|
bufferOffset += NALULengthHeaderLength + NALUnitLength;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
[self.fileHandle writeData:resultData];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
@end
|
||
|
|
```
|
||
|
|
|
||
|
|
上面是 `KFVideoEncoderViewController` 的实现，主要分为以下几个部分：
|
||
|
|
|
||
|
|
- 1）在 `-videoCaptureConfig` 中初始化采集配置参数，在 `-videoEncoderConfig` 中初始化编码配置参数。
|
||
|
|
|
||
|
|
- - 这里需要注意的是，由于采集的数据后续用于编码，我们设置了采集的颜色空间格式为默认的 `kCVPixelFormatType_420YpCbCr8BiPlanarFullRange`。
|
||
|
|
- 编码参数配置这里，默认是在设备支持 H.265 时，选择 H.265 编码。
|
||
|
|
|
||
|
|
- 2）在 `-videoCapture` 中初始化采集器，并实现了采集会话初始化成功的回调、采集数据回调、采集错误回调。
|
||
|
|
|
||
|
|
- 3）在采集会话初始化成功的回调 `sessionInitSuccessCallBack` 中，对采集预览渲染视图层进行布局。
|
||
|
|
|
||
|
|
- 4）在采集数据回调 `sampleBufferOutputCallBack` 中，从 CMSampleBufferRef 中取出 CVPixelBufferRef 送给编码器编码。
|
||
|
|
|
||
|
|
- 5）在编码数据回调 `sampleBufferOutputCallBack` 中，调用 `-saveSampleBuffer:` 将编码数据存储为 H.264/H.265 文件。
|
||
|
|
|
||
|
|
- - 这里示范了将 AVCC/HVCC 格式的码流转换为 AnnexB 再存储的过程。
|
||
|
|
|
||
|
|
## 4、用工具播放 H.264/H.265 文件
|
||
|
|
|
||
|
|
完成视频采集和编码后，可以将 App Document 文件夹下面的 `test.h264` 或 `test.h265` 文件拷贝到电脑上，使用 `ffplay` 播放来验证一下视频采集是效果是否符合预期：
|
||
|
|
|
||
|
|
```
|
||
|
|
$ ffplay -i test.h264
|
||
|
|
$ ffplay -i test.h265
|
||
|
|
```
|
||
|
|
|
||
|
|
关于播放 H.264/H.265 文件的工具，可以参考[《FFmpeg 工具》第 2 节 ffplay 命令行工具](https://mp.weixin.qq.com/s?__biz=MjM5MTkxOTQyMQ==&mid=2257484831&idx=1&sn=6bab905a5040c46b971bab05f787788b&scene=21#wechat_redirect)和[《可视化音视频分析工具》第 2.1 节 StreamEye](https://mp.weixin.qq.com/s?__biz=MjM5MTkxOTQyMQ==&mid=2257484834&idx=1&sn=5dd9768bfc0d01ca1b036be8dd2f5fa1&scene=21#wechat_redirect)。
|
||
|
|
|
||
|
|
## 5、参考资料
|
||
|
|
|
||
|
|
[1]CMSampleBufferRef: *https://developer.apple.com/documentation/coremedia/cmsamplebufferref/*
|
||
|
|
|
||
|
|
[2]CVPixelBufferRef: *https://developer.apple.com/documentation/corevideo/cvpixelbufferref/*
|
||
|
|
|
||
|
|
[3]CMBlockBuffer: *https://developer.apple.com/documentation/coremedia/cmblockbuffer-u9i*
|
||
|
|
|
||
|
|
[4]CVImageBuffer: *https://developer.apple.com/documentation/corevideo/cvimagebuffer-q40*
|
||
|
|
|
||
|
|
[5]CVPixelBuffer: *https://developer.apple.com/documentation/corevideo/cvpixelbuffer-q2e*
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
原文链接：https://mp.weixin.qq.com/s/M2l-9_W8heu_NjSYKQLCRA
|
||
|
|
|