最简单的基于FFmpeg的直播系统开发移动端例子：IOS 视频解码器

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。

1.  
   /**
2.  
   * 最简单的基于FFmpeg的视频解码器-IOS
3.  
   * Simplest FFmpeg IOS Decoder
4.  
   *
5.  
   * 雷霄骅 Lei Xiaohua
6.  
   * leixiaohua1020@126.com
7.  
   * 中国传媒大学/数字电视技术
8.  
   * Communication University of China / Digital TV Technology
9.  
   * http://blog.csdn.net/leixiaohua1020
10.  
    *
11.  
    * 本程序是IOS平台下最简单的基于FFmpeg的视频解码器。
12.  
    * 它可以将输入的视频数据解码成YUV像素数据。
13.  
    *
14.  
    * This software is the simplest decoder based on FFmpeg in IOS.
15.  
    * It can decode video stream to raw YUV data.
16.  
    *
17.  
    */
18.  
     
19.  
    #import "ViewController.h"
20.  
    #include <libavcodec/avcodec.h>
21.  
    #include <libavformat/avformat.h>
22.  
    #include <libavutil/imgutils.h>
23.  
    #include <libswscale/swscale.h>
24.  
     
25.  
    @interface ViewController ()
26.  
     
27.  
    @end
28.  
     
29.  
    @implementation ViewController
30.  
     
31.  
    - (void)viewDidLoad {
32.  
    [super viewDidLoad];
33.  
    // Do any additional setup after loading the view, typically from a nib.
34.  
    }
35.  
     
36.  
    - (void)didReceiveMemoryWarning {
37.  
    [super didReceiveMemoryWarning];
38.  
    // Dispose of any resources that can be recreated.
39.  
    }
40.  
     
41.  
    - (IBAction)clickDecodeButton:(id)sender {
42.  
    AVFormatContext *pFormatCtx;
43.  
    int i, videoindex;
44.  
    AVCodecContext *pCodecCtx;
45.  
    AVCodec *pCodec;
46.  
    AVFrame *pFrame,*pFrameYUV;
47.  
    uint8_t *out_buffer;
48.  
    AVPacket *packet;
49.  
    int y_size;
50.  
    int ret, got_picture;
51.  
    struct SwsContext *img_convert_ctx;
52.  
    FILE *fp_yuv;
53.  
    int frame_cnt;
54.  
    clock_t time_start, time_finish;
55.  
    double time_duration = 0.0;
56.  
     
57.  
    char input_str_full[500]={0};
58.  
    char output_str_full[500]={0};
59.  
    char info[1000]={0};
60.  
     
61.  
    NSString *input_str= [NSString stringWithFormat:@"resource.bundle/%@",self.inputurl.text];
62.  
    NSString *output_str= [NSString stringWithFormat:@"resource.bundle/%@",self.outputurl.text];
63.  
     
64.  
    NSString *input_nsstr=[[[NSBundle mainBundle]resourcePath] stringByAppendingPathComponent:input_str];
65.  
    NSString *output_nsstr=[[[NSBundle mainBundle]resourcePath] stringByAppendingPathComponent:output_str];
66.  
     
67.  
    sprintf(input_str_full,"%s",[input_nsstr UTF8String]);
68.  
    sprintf(output_str_full,"%s",[output_nsstr UTF8String]);
69.  
     
70.  
    printf("Input Path:%s\n",input_str_full);
71.  
    printf("Output Path:%s\n",output_str_full);
72.  
     
73.  
    av_register_all();
74.  
    avformat_network_init();
75.  
    pFormatCtx = avformat_alloc_context();
76.  
     
77.  
    if(avformat_open_input(&pFormatCtx,input_str_full,NULL,NULL)!=0){
78.  
    printf("Couldn't open input stream.\n");
79.  
    return ;
80.  
    }
81.  
    if(avformat_find_stream_info(pFormatCtx,NULL)<0){
82.  
    printf("Couldn't find stream information.\n");
83.  
    return;
84.  
    }
85.  
    videoindex=-1;
86.  
    for(i=0; i<pFormatCtx->nb_streams; i++)
87.  
    if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){
88.  
    videoindex=i;
89.  
    break;
90.  
    }
91.  
    if(videoindex==-1){
92.  
    printf("Couldn't find a video stream.\n");
93.  
    return;
94.  
    }
95.  
    pCodecCtx=pFormatCtx->streams[videoindex]->codec;
96.  
    pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
97.  
    if(pCodec==NULL){
98.  
    printf("Couldn't find Codec.\n");
99.  
    return;
100.  
     }
101.  
     if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){
102.  
     printf("Couldn't open codec.\n");
103.  
     return;
104.  
     }
105.  
      
106.  
     pFrame=av_frame_alloc();
107.  
     pFrameYUV=av_frame_alloc();
108.  
     out_buffer=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height,1));
109.  
     av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize,out_buffer,
110.  
     AV_PIX_FMT_YUV420P,pCodecCtx->width, pCodecCtx->height,1);
111.  
     packet=(AVPacket *)av_malloc(sizeof(AVPacket));
112.  
      
113.  
     img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
114.  
     pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
115.  
      
116.  
      
117.  
     sprintf(info, "[Input ]%s\n", [input_str UTF8String]);
118.  
     sprintf(info, "%s[Output ]%s\n",info,[output_str UTF8String]);
119.  
     sprintf(info, "%s[Format ]%s\n",info, pFormatCtx->iformat->name);
120.  
     sprintf(info, "%s[Codec ]%s\n",info, pCodecCtx->codec->name);
121.  
     sprintf(info, "%s[Resolution]%dx%d\n",info, pCodecCtx->width,pCodecCtx->height);
122.  
      
123.  
      
124.  
     fp_yuv=fopen(output_str_full,"wb+");
125.  
     if(fp_yuv==NULL){
126.  
     printf("Cannot open output file.\n");
127.  
     return;
128.  
     }
129.  
      
130.  
     frame_cnt=0;
131.  
     time_start = clock();
132.  
      
133.  
     while(av_read_frame(pFormatCtx, packet)>=0){
134.  
     if(packet->stream_index==videoindex){
135.  
     ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
136.  
     if(ret < 0){
137.  
     printf("Decode Error.\n");
138.  
     return;
139.  
     }
140.  
     if(got_picture){
141.  
     sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
142.  
     pFrameYUV->data, pFrameYUV->linesize);
143.  
      
144.  
     y_size=pCodecCtx->width*pCodecCtx->height;
145.  
     fwrite(pFrameYUV->data[0],1,y_size,fp_yuv); //Y
146.  
     fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv); //U
147.  
     fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv); //V
148.  
     //Output info
149.  
     char pictype_str[10]={0};
150.  
     switch(pFrame->pict_type){
151.  
     case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break;
152.  
     case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break;
153.  
     case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break;
154.  
     default:sprintf(pictype_str,"Other");break;
155.  
     }
156.  
     printf("Frame Index: %5d. Type:%s\n",frame_cnt,pictype_str);
157.  
     frame_cnt++;
158.  
     }
159.  
     }
160.  
     av_free_packet(packet);
161.  
     }
162.  
     //flush decoder
163.  
     //FIX: Flush Frames remained in Codec
164.  
     while (1) {
165.  
     ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
166.  
     if (ret < 0)
167.  
     break;
168.  
     if (!got_picture)
169.  
     break;
170.  
     sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
171.  
     pFrameYUV->data, pFrameYUV->linesize);
172.  
     int y_size=pCodecCtx->width*pCodecCtx->height;
173.  
     fwrite(pFrameYUV->data[0],1,y_size,fp_yuv); //Y
174.  
     fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv); //U
175.  
     fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv); //V
176.  
     //Output info
177.  
     char pictype_str[10]={0};
178.  
     switch(pFrame->pict_type){
179.  
     case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break;
180.  
     case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break;
181.  
     case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break;
182.  
     default:sprintf(pictype_str,"Other");break;
183.  
     }
184.  
     printf("Frame Index: %5d. Type:%s\n",frame_cnt,pictype_str);
185.  
     frame_cnt++;
186.  
     }
187.  
     time_finish = clock();
188.  
     time_duration=(double)(time_finish - time_start);
189.  
      
190.  
     sprintf(info, "%s[Time ]%fus\n",info,time_duration);
191.  
     sprintf(info, "%s[Count ]%d\n",info,frame_cnt);
192.  
      
193.  
     sws_freeContext(img_convert_ctx);
194.  
      
195.  
     fclose(fp_yuv);
196.  
      
197.  
     av_frame_free(&pFrameYUV);
198.  
     av_frame_free(&pFrame);
199.  
     avcodec_close(pCodecCtx);
200.  
     avformat_close_input(&pFormatCtx);
201.  
      
202.  
     NSString * info_ns = [NSString stringWithFormat:@"%s", info];
203.  
     self.infomation.text=info_ns;
204.  
      
205.  
     }
206.  
      
207.  
      
208.  
     @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。

 

 

本文转载自网络，感谢原作者的分享，转载仅为分享干货知识，如有侵权欢迎联系作者进行删除处理。