本文记录IOS平台下基于FFmpeg的视频解码器。该示例C语言的源代码来自于《最简单的基于FFMPEG+SDL的视频播放器》。相关的概念就不再重复记录了。

源代码

项目的目录结构如图所示。

C代码位于ViewController.m文件中，内容如下所示。

/**
 * 最简单的基于FFmpeg的视频解码器-IOS
 * Simplest FFmpeg IOS Decoder
 *
 * 雷霄骅 Lei Xiaohua
 * leixiaohua1020@126.com
 * 中国传媒大学/数字电视技术
 * Communication University of China / Digital TV Technology
 * http://blog.csdn.net/leixiaohua1020
 *
 * 本程序是IOS平台下最简单的基于FFmpeg的视频解码器。
 * 它可以将输入的视频数据解码成YUV像素数据。
 *
 * This software is the simplest decoder based on FFmpeg in IOS.
 * It can decode video stream to raw YUV data.
 *
 */

#import "ViewController.h"
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)clickDecodeButton:(id)sender {
    AVFormatContext	*pFormatCtx;
    int				i, videoindex;
    AVCodecContext	*pCodecCtx;
    AVCodec			*pCodec;
    AVFrame	*pFrame,*pFrameYUV;
    uint8_t *out_buffer;
    AVPacket *packet;
    int y_size;
    int ret, got_picture;
    struct SwsContext *img_convert_ctx;
    FILE *fp_yuv;
    int frame_cnt;
    clock_t time_start, time_finish;
    double  time_duration = 0.0;
    
    char input_str_full[500]={0};
    char output_str_full[500]={0};
    char info[1000]={0};
    
    NSString *input_str= [NSString stringWithFormat:@"resource.bundle/%@",self.inputurl.text];
    NSString *output_str= [NSString stringWithFormat:@"resource.bundle/%@",self.outputurl.text];
    
    NSString *input_nsstr=[[[NSBundle mainBundle]resourcePath] stringByAppendingPathComponent:input_str];
    NSString *output_nsstr=[[[NSBundle mainBundle]resourcePath] stringByAppendingPathComponent:output_str];
    
    sprintf(input_str_full,"%s",[input_nsstr UTF8String]);
    sprintf(output_str_full,"%s",[output_nsstr UTF8String]);
    
    printf("Input Path:%s\n",input_str_full);
    printf("Output Path:%s\n",output_str_full);
    
    av_register_all();
    avformat_network_init();
    pFormatCtx = avformat_alloc_context();
    
    if(avformat_open_input(&pFormatCtx,input_str_full,NULL,NULL)!=0){
        printf("Couldn't open input stream.\n");
        return ;
    }
    if(avformat_find_stream_info(pFormatCtx,NULL)<0){
        printf("Couldn't find stream information.\n");
        return;
    }
    videoindex=-1;
    for(i=0; i<pFormatCtx->nb_streams; i++)
        if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){
            videoindex=i;
            break;
        }
    if(videoindex==-1){
        printf("Couldn't find a video stream.\n");
        return;
    }
    pCodecCtx=pFormatCtx->streams[videoindex]->codec;
    pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
    if(pCodec==NULL){
        printf("Couldn't find Codec.\n");
        return;
    }
    if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){
        printf("Couldn't open codec.\n");
        return;
    }
    
    pFrame=av_frame_alloc();
    pFrameYUV=av_frame_alloc();
    out_buffer=(uint8_t *)av_malloc(avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height));
    avpicture_fill((AVPicture *)pFrameYUV, out_buffer, PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
    packet=(AVPacket *)av_malloc(sizeof(AVPacket));
    
    img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
                                     pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
    
    
    sprintf(info,   "[Input     ]%s\n", [input_str UTF8String]);
    sprintf(info, "%s[Output    ]%s\n",info,[output_str UTF8String]);
    sprintf(info, "%s[Format    ]%s\n",info, pFormatCtx->iformat->name);
    sprintf(info, "%s[Codec     ]%s\n",info, pCodecCtx->codec->name);
    sprintf(info, "%s[Resolution]%dx%d\n",info, pCodecCtx->width,pCodecCtx->height);
    
    
    fp_yuv=fopen(output_str_full,"wb+");
    if(fp_yuv==NULL){
        printf("Cannot open output file.\n");
        return;
    }
    
    frame_cnt=0;
    time_start = clock();
    
    while(av_read_frame(pFormatCtx, packet)>=0){
        if(packet->stream_index==videoindex){
            ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
            if(ret < 0){
                printf("Decode Error.\n");
                return;
            }
            if(got_picture){
                sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
                          pFrameYUV->data, pFrameYUV->linesize);
                
                y_size=pCodecCtx->width*pCodecCtx->height;
                fwrite(pFrameYUV->data[0],1,y_size,fp_yuv);    //Y
                fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv);  //U
                fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv);  //V
                //Output info
                char pictype_str[10]={0};
                switch(pFrame->pict_type){
                    case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break;
                    case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break;
                    case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break;
                    default:sprintf(pictype_str,"Other");break;
                }
                printf("Frame Index: %5d. Type:%s\n",frame_cnt,pictype_str);
                frame_cnt++;
            }
        }
        av_free_packet(packet);
    }
    //flush decoder
    //FIX: Flush Frames remained in Codec
    while (1) {
        ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
        if (ret < 0)
            break;
        if (!got_picture)
            break;
        sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
                  pFrameYUV->data, pFrameYUV->linesize);
        int y_size=pCodecCtx->width*pCodecCtx->height;
        fwrite(pFrameYUV->data[0],1,y_size,fp_yuv);    //Y
        fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv);  //U
        fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv);  //V
        //Output info
        char pictype_str[10]={0};
        switch(pFrame->pict_type){
            case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break;
            case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break;
            case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break;
            default:sprintf(pictype_str,"Other");break;
        }
        printf("Frame Index: %5d. Type:%s\n",frame_cnt,pictype_str);
        frame_cnt++;
    }
    time_finish = clock(); 
    time_duration=(double)(time_finish - time_start);
    
    sprintf(info, "%s[Time      ]%fus\n",info,time_duration);
    sprintf(info, "%s[Count     ]%d\n",info,frame_cnt);
    
    sws_freeContext(img_convert_ctx);
    
    fclose(fp_yuv);
    
    av_frame_free(&pFrameYUV);
    av_frame_free(&pFrame);
    avcodec_close(pCodecCtx);
    avformat_close_input(&pFormatCtx);
    
    NSString * info_ns = [NSString stringWithFormat:@"%s", info];
    self.infomation.text=info_ns;

}


@end

运行结果

App在手机上运行后的结果如下图所示。单击“Decode”，将会把位于resource.bundle中的“sintel.mov”文件解码为“sintel.yuv”文件并存储于相同的目录下。

生成的文件如下图所示。

下载

simplest ffmpeg mobile

项目主页

Github：https://github.com/leixiaohua1020/simplest_ffmpeg_mobile

开源中国：https://git.oschina.net/leixiaohua1020/simplest_ffmpeg_mobile

CSDN工程下载地址：http://download.csdn.net/detail/leixiaohua1020/8924391

本解决方案包含了使用FFmpeg在移动端处理多媒体的各种例子：

[Android]
simplest_android_player: 基于安卓接口的视频播放器
simplest_ffmpeg_android_helloworld: 安卓平台下基于FFmpeg的HelloWorld程序
simplest_ffmpeg_android_decoder: 安卓平台下最简单的基于FFmpeg的视频解码器
simplest_ffmpeg_android_decoder_onelib: 安卓平台下最简单的基于FFmpeg的视频解码器-单库版
simplest_ffmpeg_android_streamer: 安卓平台下最简单的基于FFmpeg的推流器
simplest_ffmpeg_android_transcoder: 安卓平台下移植的FFmpeg命令行工具
simplest_sdl_android_helloworld: 移植SDL到安卓平台的最简单程序
[IOS]
simplest_ios_player: 基于IOS接口的视频播放器
simplest_ffmpeg_ios_helloworld: IOS平台下基于FFmpeg的HelloWorld程序
simplest_ffmpeg_ios_decoder: IOS平台下最简单的基于FFmpeg的视频解码器
simplest_ffmpeg_ios_streamer: IOS平台下最简单的基于FFmpeg的推流器
simplest_ffmpeg_ios_transcoder: IOS平台下移植的ffmpeg.c命令行工具
simplest_sdl_ios_helloworld: 移植SDL到IOS平台的最简单程序