FFmpeg的使用

2016-12-08 本文已影响337人 ZHANG_GO

现状：现在视频直播非常的火，所以在视频直播开发中，使用的对视频进行遍解码的框架显得尤为重要了，其实，这种框架蛮多的，这次主要介绍一下FFmpeg视频播放器的集成和使用，FFmpeg是视频编解码的利器。

介绍：视频播放过程

首先简单介绍以下视频文件的相关知识。我们平时看到的视频文件有许多格式，比如 avi， mkv， rmvb， mov， mp4等等，这些被称为容器（Container），不同的容器格式规定了其中音视频数据的组织方式（也包括其他数据，比如字幕等）。容器中一般会封装有视频和音频轨，也称为视频流（stream）和音频流，播放视频文件的第一步就是根据视频文件的格式，解析（demux）出其中封装的视频流、音频流以及字幕（如果有的话），解析的数据读到包（packet）中，每个包里保存的是视频帧（frame）或音频帧，然后分别对视频帧和音频帧调用相应的解码器（decoder）进行解码，比如使用 H.264编码的视频和MP3编码的音频，会相应的调用H.264解码器和MP3解码器，解码之后得到的就是原始的图像(YUV or RGB)和声音(PCM)数据，然后根据同步好的时间将图像显示到屏幕上，将声音输出到声卡，最终就是我们看到的视频。

FFmpeg的API就是根据这个过程设计的，因此使用FFmpeg来处理视频文件的方法非常直观简单。下面就一步一步介绍从视频文件中解码出图片的过程。

属性：声明变量

AVFormatContext：保存需要读入的文件的格式信息，比如流的个数以及流数据等

AVCodecCotext：保存了相应流的详细编码信息，比如视频的宽、高，编码类型等。

pCodec：真正的编解码器，其中有编解码需要调用的函数

AVFrame：用于保存数据帧的数据结构，这里的两个帧分别是保存颜色转换前后的两帧图像

AVPacket：解析文件时会将音/视频帧读入到packet中

一本播放器原理:

通过ffmpeg对视频进行解码,解码出每一帧图片,然后根据一定时间播放每一帧图

二如何集成 ffmpeg

下载脚本ffmpeg脚本

根据上面链接的 README 进行编译

大致步骤：

1. 下载脚本：https://github.com/kewlbear/FFmpeg-iOS-build-script

2. 解压，找到文件 build-ffmpeg.sh

3. 进入终端，执行服本文件：./build-ffmpeg.sh, 由于本人没有事先安装Yasm，执行脚本文件会出错，提示Homebrew not found，Trying 头install.....如图：

根据提示,按下enter键进行安装并编译静态库FFmpeg，如下图：

这是编译后的静态库，截图如下：

集成到项目,新建工程,将编译好的静态库以及头文件导入工程(demo)

导入依赖库

设置头文件路径,路径一定要对,不然胡找不到头文件

我设置路径如下图：

先 command + B 编译一下,确保能编译成功

三开始编写代码

新建一个OC文件

////SJMoiveObject.h//SJLiveVideo////Created by king on 16/6/16.//Copyright © 2016年 king. All rights reserved.//#import"Common.h"#import#import"NSString+Extions.h"#include#include#include@interfaceSJMoiveObject : NSObject/*解码后的UIImage*/@property (nonatomic, strong,readonly) UIImage *currentImage;/*视频的frame高度*/@property (nonatomic, assign,readonly)intsourceWidth, sourceHeight;/*输出图像大小。默认设置为源大小。*/@property (nonatomic,assign)intoutputWidth, outputHeight;/*视频的长度，秒为单位*/@property (nonatomic, assign,readonly)doubleduration;/*视频的当前秒数*/@property (nonatomic, assign,readonly)doublecurrentTime;/*视频的帧率*/@property (nonatomic, assign,readonly)doublefps;/*视频路径。*/- (instancetype)initWithVideo:(NSString *)moviePath;/*切换资源*/- (void)replaceTheResources:(NSString *)moviePath;/*重拨*/- (void)redialPaly;/*从视频流中读取下一帧。返回假，如果没有帧读取（视频）。*/-(BOOL)stepFrame;/*寻求最近的关键帧在指定的时间*/- (void)seekTime:(double)seconds;@end开始实现API////SJMoiveObject.m//SJLiveVideo////Created by king on 16/6/16.//Copyright © 2016年 king. All rights reserved.//#import"SJMoiveObject.h"@interfaceSJMoiveObject ()

@property (nonatomic, copy) NSString*cruutenPath;@end@implementationSJMoiveObject

{

AVFormatContext*SJFormatCtx;

AVCodecContext*SJCodecCtx;

AVFrame*SJFrame;

AVStream*stream;

AVPacket packet;

AVPicture picture;intvideoStream;doublefps;

BOOL isReleaseResources;

}#pragmamark ------------------------------------#pragmamark 初始化- (instancetype)initWithVideo:(NSString *)moviePath {if(!(self=[super init]))returnnil;if([self initializeResources:[moviePath UTF8String]]) {

self.cruutenPath=[moviePath copy];returnself;

}else{returnnil;

}

}- (BOOL)initializeResources:(constchar*)filePath {

isReleaseResources=NO;

AVCodec*pCodec;//注册所有解码器avcodec_register_all();

av_register_all();

avformat_network_init();//打开视频文件if(avformat_open_input(&SJFormatCtx, filePath, NULL, NULL) !=0) {

SJLog(@"打开文件失败");gotoinitError;

}//检查数据流if(avformat_find_stream_info(SJFormatCtx, NULL) <0) {

SJLog(@"检查数据流失败");gotoinitError;

}//根据数据流,找到第一个视频流if((videoStream = av_find_best_stream(SJFormatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, &pCodec,0)) <0) {

SJLog(@"没有找到第一个视频流");gotoinitError;

}//获取视频流的编解码上下文的指针stream = SJFormatCtx->streams[videoStream];

SJCodecCtx= stream->codec;#ifDEBUG//打印视频流的详细信息av_dump_format(SJFormatCtx, videoStream, filePath,0);#endifif(stream->avg_frame_rate.den && stream->avg_frame_rate.num) {

fps= av_q2d(stream->avg_frame_rate);

}else{ fps =30; }//查找解码器pCodec = avcodec_find_decoder(SJCodecCtx->codec_id);if(pCodec ==NULL) {

SJLog(@"没有找到解码器");gotoinitError;

}//打开解码器if(avcodec_open2(SJCodecCtx, pCodec, NULL) <0) {

SJLog(@"打开解码器失败");gotoinitError;

}//分配视频帧SJFrame =av_frame_alloc();

_outputWidth= SJCodecCtx->width;

_outputHeight= SJCodecCtx->height;returnYES;

initError:returnNO;

}- (void)seekTime:(double)seconds {

AVRational timeBase= SJFormatCtx->streams[videoStream]->time_base;

int64_t targetFrame= (int64_t)((double)timeBase.den / timeBase.num *seconds);

avformat_seek_file(SJFormatCtx,

videoStream,0,

targetFrame,

AVSEEK_FLAG_FRAME);

avcodec_flush_buffers(SJCodecCtx);

}-(BOOL)stepFrame {intframeFinished =0;while(!frameFinished && av_read_frame(SJFormatCtx, &packet) >=0) {if(packet.stream_index ==videoStream) {

avcodec_decode_video2(SJCodecCtx,

SJFrame,&frameFinished,&packet);

}

}if(frameFinished ==0&& isReleaseResources ==NO) {

[self releaseResources];

}returnframeFinished !=0;

}- (void)replaceTheResources:(NSString *)moviePath {if(!isReleaseResources) {

[self releaseResources];

}

self.cruutenPath=[moviePath copy];

[self initializeResources:[moviePath UTF8String]];

}- (void)redialPaly {

[self initializeResources:[self.cruutenPath UTF8String]];

}#pragmamark ------------------------------------#pragmamark 重写属性访问方法-(void)setOutputWidth:(int)newValue {if(_outputWidth == newValue)return;

_outputWidth=newValue;

}-(void)setOutputHeight:(int)newValue {if(_outputHeight == newValue)return;

_outputHeight=newValue;

}-(UIImage *)currentImage {if(!SJFrame->data[0])returnnil;return[self imageFromAVPicture];

}-(double)duration {return(double)SJFormatCtx->duration /AV_TIME_BASE;

}- (double)currentTime {

AVRational timeBase= SJFormatCtx->streams[videoStream]->time_base;returnpacket.pts * (double)timeBase.num /timeBase.den;

}- (int)sourceWidth {returnSJCodecCtx->width;

}- (int)sourceHeight {returnSJCodecCtx->height;

}- (double)fps {returnfps;

}#pragmamark --------------------------#pragmamark - 内部方法- (UIImage *)imageFromAVPicture

{

avpicture_free(&picture);

avpicture_alloc(&picture, AV_PIX_FMT_RGB24, _outputWidth, _outputHeight);structSwsContext * imgConvertCtx = sws_getContext(SJFrame->width,

SJFrame->height,

AV_PIX_FMT_YUV420P,

_outputWidth,

_outputHeight,

AV_PIX_FMT_RGB24,

SWS_FAST_BILINEAR,

NULL,

NULL);if(imgConvertCtx == nil)returnnil;

sws_scale(imgConvertCtx,

SJFrame->data,

SJFrame->linesize,0,

SJFrame->height,

picture.data,

picture.linesize);

sws_freeContext(imgConvertCtx);

CGBitmapInfo bitmapInfo=kCGBitmapByteOrderDefault;

CFDataRef data=CFDataCreate(kCFAllocatorDefault,

picture.data[0],

picture.linesize[0] *_outputHeight);

CGDataProviderRef provider=CGDataProviderCreateWithCFData(data);

CGColorSpaceRef colorSpace=CGColorSpaceCreateDeviceRGB();

CGImageRef cgImage=CGImageCreate(_outputWidth,

_outputHeight,8,24,

picture.linesize[0],

colorSpace,

bitmapInfo,

provider,

NULL,

NO,

kCGRenderingIntentDefault);

UIImage*image =[UIImage imageWithCGImage:cgImage];

CGImageRelease(cgImage);

CGColorSpaceRelease(colorSpace);

CGDataProviderRelease(provider);

CFRelease(data);returnimage;

}#pragmamark --------------------------#pragmamark - 释放资源- (void)releaseResources {

SJLog(@"释放资源");

SJLogFunc

isReleaseResources=YES;//释放RGBavpicture_free(&picture);//释放frameav_packet_unref(&packet);//释放YUV frameav_free(SJFrame);//关闭解码器if(SJCodecCtx) avcodec_close(SJCodecCtx);//关闭文件if(SJFormatCtx) avformat_close_input(&SJFormatCtx);

avformat_network_deinit();

}@end

为了方便,在SB 拖一个 UIImageView 控件和按钮并连好线

////ViewController.m//SJLiveVideo////Created by king on 16/6/14.//Copyright © 2016年 king. All rights reserved.//#import"ViewController.h"#import"SJMoiveObject.h"#import#import"SJAudioObject.h"#import"SJAudioQueuPlay.h"#defineLERP(A,B,C) ((A)*(1.0-C)+(B)*C)@interfaceViewController ()

@property (weak, nonatomic) IBOutlet UIImageView*ImageView;

@property (weak, nonatomic) IBOutlet UILabel*fps;

@property (weak, nonatomic) IBOutlet UIButton*playBtn;

@property (weak, nonatomic) IBOutlet UIButton*TimerBtn;

@property (weak, nonatomic) IBOutlet UILabel*TimerLabel;

@property (nonatomic, strong) SJMoiveObject*video;

@property (nonatomic, strong) SJAudioObject*audio;

@property (nonatomic, strong) SJAudioQueuPlay*audioPlay;

@property (nonatomic, assign)floatlastFrameTime;@end@implementationViewController@synthesizeImageView, fps, playBtn, video;- (void)viewDidLoad {

[super viewDidLoad];

self.video= [[SJMoiveObject alloc] initWithVideo:[NSString bundlePath:@"Dalshabet.mp4"]];//self.video = [[SJMoiveObject alloc] initWithVideo:@"/Users/king/Desktop/Stellar.mp4"];//self.video = [[SJMoiveObject alloc] initWithVideo:@"/Users/king/Downloads/Worth it - Fifth Harmony ft.Kid Ink - May J Lee Choreography.mp4"];//self.video = [[SJMoiveObject alloc] initWithVideo:@"/Users/king/Downloads/4K.mp4"];//self.video = [[SJMoiveObject alloc] initWithVideo:@"http://wvideo.spriteapp.cn/video/2016/0328/56f8ec01d9bfe_wpd.mp4"];//video.outputWidth = 800;//video.outputHeight = 600;self.audio = [[SJAudioObject alloc] initWithVideo:@"/Users/king/Desktop/Stellar.mp4"];

NSLog(@"视频总时长>>>video duration: %f",video.duration);

NSLog(@"源尺寸>>>video size: %d x %d", video.sourceWidth, video.sourceHeight);

NSLog(@"输出尺寸>>>video size: %d x %d", video.outputWidth, video.outputHeight);////[self.audio seekTime:0.0];//SJLog(@"%f", [self.audio duration])//AVPacket *packet = [self.audio readPacket];//SJLog(@"%ld", [self.audio decode])inttns, thh, tmm, tss;

tns=video.duration;

thh= tns /3600;

tmm= (tns %3600) /60;

tss= tns %60;//NSLog(@"fps --> %.2f", video.fps);//// [ImageView setTransform:CGAffineTransformMakeRotation(M_PI)];//NSLog(@"%02d:%02d:%02d",thh,tmm,tss);}- (IBAction)PlayClick:(UIButton *)sender {

[playBtn setEnabled:NO];

_lastFrameTime= -1;//seek to 0.0 seconds[video seekTime:0.0];

[NSTimer scheduledTimerWithTimeInterval:1/video.fps

target:self

selector:@selector(displayNextFrame:)

userInfo:nil

repeats:YES];

}- (IBAction)TimerCilick:(id)sender {//NSLog(@"current time: %f s",video.currentTime);//[video seekTime:150.0];//[video replaceTheResources:@"/Users/king/Desktop/Stellar.mp4"];if(playBtn.enabled) {

[video redialPaly];

[self PlayClick:playBtn];

}

}-(void)displayNextFrame:(NSTimer *)timer {

NSTimeInterval startTime=[NSDate timeIntervalSinceReferenceDate];//self.TimerLabel.text = [NSString stringWithFormat:@"%f s",video.currentTime];self.TimerLabel.text =[self dealTime:video.currentTime];if(![video stepFrame]) {

[timer invalidate];

[playBtn setEnabled:YES];return;

}

ImageView.image=video.currentImage;floatframeTime =1.0/ ([NSDate timeIntervalSinceReferenceDate] -startTime);if(_lastFrameTime <0) {

_lastFrameTime=frameTime;

}else{

_lastFrameTime= LERP(frameTime, _lastFrameTime,0.8);

}

[fps setText:[NSString stringWithFormat:@"fps %.0f",_lastFrameTime]];

}- (NSString *)dealTime:(double)time {inttns, thh, tmm, tss;

tns=time;

thh= tns /3600;