使用FFmpeg库对视频进行编码

#import "avformat.h"
#import "timestamp.h"
#import "avcodec.h"
#import "opt.h"
#import "samplefmt.h"
#import "swscale.h"
#import "avutil.h"

static int encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt, FILE *out){
    int ret = -1;

    ret = avcodec_send_frame(ctx, frame);
    if(ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Failed to send frame to encoder!\n");
        goto _END;
    }

    while( ret >= 0){
        ret = avcodec_receive_packet(ctx, pkt);
        if(ret == AVERROR(EAGAIN) || ret == AVERROR_EOF){
            return 0;
        } else if( ret < 0) {
            return -1; //退出tkyc
        }

        fwrite(pkt->data, 1, pkt->size, out);
        av_packet_unref(pkt);
    }
_END:
    return 0;
}

- (IBAction)encodeVideoAction:(id)sender {
    
    // 处理好的文件存储路径
    NSString * dstpath = [NSString stringWithFormat:@"%@/Library/Caches/1-1.h264",NSHomeDirectory()];
    char  dstChar [ 1024 ];
    strcpy (dstChar ,( char  *)[dstpath  UTF8String]);

    //编码格式
    NSString * type = @"libx264";
    char  typeChar [ 1024 ];
    strcpy (typeChar ,( char  *)[type  UTF8String]);
    
    char * argv[2];
    argv[0] = dstChar;
    argv[1] = typeChar;
    
    NSLog(@"存储路径：%@", dstpath);
    
    encodeVideo(2, argv);
}

#pragma mark 视频编码
void encodeVideo(int argc, char* argv[]) {
    int ret = -1;

    FILE *f = NULL;

    char *dst = NULL;
    char *codecName = NULL;

    const AVCodec *codec = NULL;
    AVCodecContext *ctx = NULL;

    AVFrame *frame = NULL;
    AVPacket *pkt = NULL;

    av_log_set_level(AV_LOG_DEBUG);

    //1. 输入参数
    if(argc < 2){
        av_log(NULL, AV_LOG_ERROR, "arguments must be more than 2\n");
        goto _ERROR;
    }

    dst = argv[0];
    codecName = argv[1];

    //2. 查找编码器
    codec = avcodec_find_encoder_by_name(codecName);
    if(!codec){
        av_log(NULL, AV_LOG_ERROR, "don't find Codec: %s", codecName);
        goto _ERROR;
    }

    //3. 创建编码器上下文
    ctx = avcodec_alloc_context3(codec);
    if(!ctx){
        av_log(NULL, AV_LOG_ERROR, "NO MEMRORY\n");
        goto _ERROR;
    }

    //4. 设置编码器参数
    ctx->width = 640;
    ctx->height = 480;
    ctx->bit_rate = 500000;// 码率
    //时间基
    ctx->time_base = (AVRational){1, 25};
    //帧率
    ctx->framerate = (AVRational){25, 1};

    ctx->gop_size = 10;
    ctx->max_b_frames = 1;
    ctx->pix_fmt = AV_PIX_FMT_YUV420P;

    if(codec->id == AV_CODEC_ID_H264){
        av_opt_set(ctx->priv_data, "preset", "slow", 0);
    }

    //5. 编码器与编码器上下文绑定到一起
    ret = avcodec_open2(ctx, codec , NULL);
    if(ret < 0) {
        av_log(ctx, AV_LOG_ERROR, "Don't open codec: %s \n", av_err2str(ret));
        goto _ERROR;
    }

    //6. 创建输出文件
    f = fopen(dst, "wb");// w写内容,b二进制
    if(!f){
        av_log(NULL, AV_LOG_ERROR, "Don't open file:%s", dst);
        goto _ERROR;
    }

    //7. 创建AVFrame
    frame = av_frame_alloc();
    if(!frame){
        av_log(NULL, AV_LOG_ERROR, "NO MEMORY!\n");
        goto _ERROR;
    }
    frame->width = ctx->width;
    frame->height = ctx->height;
    frame->format = ctx->pix_fmt;

    ret = av_frame_get_buffer(frame, 0);
    if(ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Could not allocate the video frame \n");
        goto _ERROR;
    }

    //8. 创建AVPacket
    pkt = av_packet_alloc();
     if(!pkt){
        av_log(NULL, AV_LOG_ERROR, "NO MEMORY!\n");
        goto _ERROR;
    }

    //9. 生成视频内容
    for(int i=0; i<25; i++){
        ret = av_frame_make_writable(frame);
        if(ret < 0) {
            break;
        }

        //Y分量
        for(int y = 0; y < ctx->height; y++){
            for(int x=0; x < ctx->width; x++){
                frame->data[0][y*frame->linesize[0]+x] = x + y + i * 3;
            }
        }

        //UV分量
        for(int y=0; y< ctx->height/2; y++){
            for(int x=0; x < ctx->width/2; x++){
                frame->data[1][y * frame->linesize[1] + x ] = 128 + y + i * 2;
                frame->data[2][y * frame->linesize[2] + x ] = 64 + x + i * 5;
            }
        }

        frame->pts = i;

        //10. 编码
        ret = encode(ctx, frame, pkt, f);
        if(ret == -1){
            goto _ERROR;
        }
    }
    //10. 编码
    encode(ctx, NULL, pkt, f);
_ERROR:
    //ctx
    if(ctx){
        avcodec_free_context(&ctx);
    }

    //avframe
    if(frame){
        av_frame_free(&frame);
    }

    //avpacket
    if(pkt){
        av_packet_free(&pkt);
    }

    //dst
    if(f){
        fclose(f);
    }
}