ffmpeg压缩yuv

        以前写过ffmpeg压缩YUV成h264的代码，现在发现压缩成其他格式的流程也是类似的（如h263,mpeg1,mepg2,mpeg4），代码如下：
/*
 * Video encoding example
 */
static void video_encode_example(const char *filename)
{
    AVCodec *codec;
    AVCodecContext *c= NULL;
    int i, out_size, size, x, y, outbuf_size;
    FILE *f;
    AVFrame *picture;
    uint8_t *outbuf, *picture_buf;

    printf("Video encoding\n");

    /* find the mpeg1 video encoder */
    codec = avcodec_find_encoder(CODEC_ID_MPEG1VIDEO);
    if (!codec) {
        fprintf(stderr, "codec not found\n");
        exit(1);
    }

    c= avcodec_alloc_context();
    picture= avcodec_alloc_frame();

    /* put sample parameters */
    c->bit_rate = 400000;                          //根据实际情况，400K码率，10的帧率，就会崩溃。
    /* resolution must be a multiple of two */
    c->width = 352;
    c->height = 288;
    /* frames per second */
    c->time_base= (AVRational){1,25};
    c->gop_size = 10; /* emit one intra frame every ten frames */
    c->max_b_frames=1;
    c->pix_fmt = PIX_FMT_YUV420P;

    /* open it */
    if (avcodec_open(c, codec) < 0) {
        fprintf(stderr, "could not open codec\n");
        exit(1);
    }

    f = fopen(filename, "wb");
    if (!f) {
        fprintf(stderr, "could not open %s\n", filename);
        exit(1);
    }

    /* alloc image and output buffer */
    outbuf_size = 100000;
    outbuf = malloc(outbuf_size);
    size = c->width * c->height;
    picture_buf = malloc((size * 3) / 2); /* size for YUV 420 */

    picture->data[0] = picture_buf;
    picture->data[1] = picture->data[0] + size;
    picture->data[2] = picture->data[1] + size / 4;
    picture->linesize[0] = c->width;
    picture->linesize[1] = c->width / 2;
    picture->linesize[2] = c->width / 2;

    /* encode 1 second of video */
    for(i=0;i<25;i++) {
        fflush(stdout);
        /* prepare a dummy image */
        /* Y */
        for(y=0;yheight;y++) {
            for(x=0;xwidth;x++) {
                picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
            }
        }

        /* Cb and Cr */
        for(y=0;yheight/2;y++) {
            for(x=0;xwidth/2;x++) {
                picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
                picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
            }
        }

        /* encode the image */
        out_size = avcodec_encode_video(c, outbuf, outbuf_size, picture);
        printf("encoding frame %3d (size=%5d)\n", i, out_size);
        fwrite(outbuf, 1, out_size, f);
    }

    /* get the delayed frames */
    for(; out_size; i++) {
        fflush(stdout);

        out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
        printf("write frame %3d (size=%5d)\n", i, out_size);
        fwrite(outbuf, 1, out_size, f);
    }

    /* add sequence end code to have a real mpeg file */
    outbuf[0] = 0x00;
    outbuf[1] = 0x00;
    outbuf[2] = 0x01;
    outbuf[3] = 0xb7;
    fwrite(outbuf, 1, 4, f);
    fclose(f);
    free(picture_buf);
    free(outbuf);

    avcodec_close(c);
    av_free(c);
    av_free(picture);
    printf("\n");
}

测试代码如下：

int main(int argc, char **argv)
{
    const char *filename;

    /* must be called before using avcodec lib */
    avcodec_init();

    /* register all the codecs */
    avcodec_register_all();

    video_encode_example("test.mpg"); //test.mpg为输出的文件名
    return 0;
}

问题：

c->time_base= (AVRational){1,25}; 这句编译出问题

解决方法：

c->time_base.time_base.den = 25;c->time_base.time_base.num = 1,AVCodecContext中的AVRational根据帧率来设定，如25帧，那么num = 1，den=25。