ffmpeg x264编译与使用介绍

问题1：
我用的是最新版本的ffmpeg和x264，刚刚编译出来，编译没有问题，但是在linux 环境使用ffmpeg的库时发现报错
error C3861: 'UINT64_C': identifier not found

解决方法在libavutil目录下的common.h里增加如下定义：

#ifndef INT64_C
#define INT64_C(c) (c ## LL)
#define UINT64_C(c) (c ## ULL)
#endif

问题2：链接基于ffmpeg的应用时报错：
/usr/local/lib/libavcodec.a(libx264.o): In function `X264_frame':
/home/qiuzhongming/disk2/source_pc/ffmpeg-0.6/libavcodec/libx264.c:105: undefined reference to `x264_encoder_encode'
/usr/local/lib/libavcodec.a(libx264.o): In function `X264_close':
/home/qiuzhongming/disk2/source_pc/ffmpeg-0.6/libavcodec/libx264.c:143: undefined reference to `x264_encoder_close'
/usr/local/lib/libavcodec.a(libx264.o): In function `X264_init':
/home/qiuzhongming/disk2/source_pc/ffmpeg-0.6/libavcodec/libx264.c:153: undefined reference to `x264_param_default'
/home/qiuzhongming/disk2/source_pc/ffmpeg-0.6/libavcodec/libx264.c:295: undefined reference to `x264_encoder_open_83'
/home/qiuzhongming/disk2/source_pc/ffmpeg-0.6/libavcodec/libx264.c:305: undefined reference to `x264_encoder_headers'
collect2: ld returned 1 exit status

解决方法是：编译时候没有带上x264库，带上就好了。

问题3：使用ffmpeg x264进行编码的时候，avcodec_open报错：
[libx264 @ 00021bb0]broken ffmpeg default settings detected
[libx264 @ 00021bb0]use an encoding preset (vpre)
解决方法：在 x264 的source file encoder/encoder.c 中找到该报错的地方
/* Detect default ffmpeg settings and terminate with an error. */
    {
        int score = 0;
        score += h->param.analyse.i_me_range == 0;
        score += h->param.rc.i_qp_step == 3;
        score += h->param.i_keyint_max == 12;
        score += h->param.rc.i_qp_min == 2;
        score += h->param.rc.i_qp_max == 31;
        score += h->param.rc.f_qcompress == 0.5;
        score += fabs(h->param.rc.f_ip_factor - 1.25) < 0.01;
        score += fabs(h->param.rc.f_pb_factor - 1.25) < 0.01;
        score += h->param.analyse.inter == 0 && h->param.analyse.i_subpel_refine == 8;
        if( score >= 5 )
        {
            x264_log( h, X264_LOG_ERROR, "broken ffmpeg default settings detected\n" );
            x264_log( h, X264_LOG_ERROR, "use an encoding preset (vpre)\n" );
            return -1;
        }
    }

We can see that if score >= 5,the function to open the codec will fail.
We must at least set 4 param of the AVCodecContext before open it.
在avcodec_open函数之间增加如下几个AVCodecContext 的初始化：
/*default settings for x264*/
        ctx->me_range = 16;
        ctx->max_qdiff = 4;
        ctx->qmin = 10;
        ctx->qmax = 51;
        ctx->qcompress = 0.6;

OK，解决。