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最簡單的基於FFmpeg的直播系統開發移動端例子：IOS 視頻解碼器

2020-09-04

本文記錄IOS平臺下基於FFmpeg的視頻解碼器。該示例C語言的源代碼來自於《最簡單的基於FFMPEG+SDL的視頻播放器》。相關的概念就不再重複記錄了。

源代碼
項目的目錄結構如圖所示。

C代碼位於ViewController.m文件中，內容如下所示。
/**

  • 最簡單的基於FFmpeg的視頻解碼器-IOS
  • Simplest FFmpeg IOS Decoder
    *
  • 雷霄驊 Lei Xiaohua
  • [email protected]
  • 中國傳媒大學/數字電視技術
  • Communication University of China / Digital TV Technology
  • http://blog.csdn.net/leixiaohua1020
    *
  • 本程序是IOS平臺下最簡單的基於FFmpeg的視頻解碼器。
  • 它可以將輸入的視頻數據解碼成YUV像素數據。
    *
  • This software is the simplest decoder based on FFmpeg in IOS.
  • It can decode video stream to raw YUV data.
    *

*/

import "ViewController.h"

include

include

include

include

@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:%sn",input_str_full);
    printf("Output Path:%sn",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; inb_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=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height,1));
    av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize,out_buffer,

                     AV_PIX_FMT_YUV420P,pCodecCtx->width, pCodecCtx->height,1);

    packet=(AVPacket *)av_malloc(sizeof(AVPacket));

    img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,

                                 pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);

    sprintf(info, "[Input ]%sn", [input_str UTF8String]);
    sprintf(info, "%s[Output ]%sn",info,[output_str UTF8String]);
    sprintf(info, "%s[Format ]%sn",info, pFormatCtx->iformat->name);
    sprintf(info, "%s[Codec ]%sn",info, pCodecCtx->codec->name);
    sprintf(info, "%s[Resolution]%dx%dn",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 ]%fusn",info,time_duration);
    sprintf(info, "%s[Count ]%dn",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

運行結果
App在手機上運行後的結果如下圖所示。單擊“Decode”，將會把位於resource.bundle中的“sintel.mov”文件解碼為“sintel.yuv”文件並存儲於相同的目錄下。

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