ffmpeg 最简单的水印功能

     ffmpeg中的filter功能不得不说真不错，类似于gstreamer，所有的filter（过滤器）都是相互连接对应的pad来完成数据流在其中的转换的，从src filter进，从sink filter出。相信玩过gstreamer的朋友一定能理解这种模式，如果不明白的朋友可以去gst官网了解下其方式，我本人认为这个比直接看filter来理解更容易。 
   好了，那水印的添加也是通过avfilter这个模块来做的，主要是通过movie和overlay这两个filter来处理，废话不多说，上代码，主要提供一个最简单的使用avfilter的教程。

   代码下载地址：

const char* filename = "E:\\C++Learning\\FFMPEG_SDL_WIN32_PLAYER_by_nick_avfilter\\FLV_STREAM\\4.flv";
const char* filters_descr = "[in]scale=1280:720[scale];movie=1.jpg[wm];[scale][wm]overlay=0:0[out]";
int main()
{
    FILE *fp_yuv=fopen("test.yuv","wb+");
    if(!fp_yuv)
        return 0;
    int ret = 0;
    av_register_all();
    avfilter_register_all();
    AVFormatContext *pFormat = NULL;
    avformat_open_input(&pFormat,filename,NULL,NULL);
    if(!pFormat)
        return 0;
    if (avformat_find_stream_info(pFormat, NULL) < 0)
    {
        printf("Could not find stream information\n");
    }
    av_dump_format(pFormat, 0, filename, 0);
    AVCodecContext *video_dec_ctx = pFormat->streams[0]->codec;
    AVStream *video_st = pFormat->streams[0];
    AVCodec *video_dec = avcodec_find_decoder(video_dec_ctx->codec_id);
    avcodec_open2(video_dec_ctx, video_dec,NULL);
    if(!video_dec_ctx || !video_dec || !video_st)
        return 0;
    uint8_t *video_dst_data[4] = {NULL};
    int video_dst_linesize[4];
    int video_dst_bufsize;
    ret = av_image_alloc(video_dst_data, video_dst_linesize,
        1280, 720,
        video_dec_ctx->pix_fmt, 1);
    video_dst_bufsize = ret;
    AVPacket *pkt=(AVPacket *)malloc(sizeof(AVPacket));
    av_init_packet(pkt);

    //filter
    AVFilter *buffersrc = avfilter_get_by_name("buffer");
    AVFilter *buffersink = avfilter_get_by_name("buffersink");
    AVFilterInOut *outputs = avfilter_inout_alloc();
    AVFilterInOut *inputs = avfilter_inout_alloc();

    enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };
    AVFilterContext *buffersink_ctx;
    AVFilterContext *buffersrc_ctx;
    AVFilterGraph *filter_graph;
    filter_graph = avfilter_graph_alloc();
    if (!outputs || !inputs || !filter_graph) {
        ret = AVERROR(ENOMEM);
        return 0;
    }
    char args[512] = {0};
    _snprintf(args, sizeof(args),
        "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
        video_dec_ctx->width, video_dec_ctx->height, video_dec_ctx->pix_fmt,
        video_dec_ctx->time_base.num, video_dec_ctx->time_base.den,
        video_dec_ctx->sample_aspect_ratio.num, video_dec_ctx->sample_aspect_ratio.den);

    ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
        args, NULL, filter_graph);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
        return 0;
    }
    ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
        NULL, NULL, filter_graph);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
        return 0;
    }

    ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,
        AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
        return 0;
    }
    outputs->name = av_strdup("in");
    outputs->filter_ctx = buffersrc_ctx;
    outputs->pad_idx = 0;
    outputs->next = NULL;

    inputs->name = av_strdup("out");
    inputs->filter_ctx = buffersink_ctx;
    inputs->pad_idx = 0;
    inputs->next = NULL;

    if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
        &inputs, &outputs, NULL)) < 0)
        return 0;

    if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
        return 0;

    int gotpicture = 0;

    while(1)
    {
        av_read_frame(pFormat,pkt);
        if(pkt->stream_index == 0)
        {
            AVFrame* pFrame = avcodec_alloc_frame();
            ret = avcodec_decode_video2(video_dec_ctx,pFrame,&gotpicture,pkt);
            if(ret<0)
                return 0;
            if(gotpicture)
            {
                if (av_buffersrc_add_frame_flags(buffersrc_ctx, pFrame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
                    av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
                    break;
                }

                /* pull filtered frames from the filtergraph */
                while (1) {
                    AVFrame* filt_frame = avcodec_alloc_frame();
                    ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
                    if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF || ret == AVERROR(EIO))
                        break;
                    if (ret < 0)
                        return 0;
                    //int y_size=filt_frame->width*filt_frame->height;
                    av_image_copy(video_dst_data, video_dst_linesize,
                        (const uint8_t **)(filt_frame->data), filt_frame->linesize,
                        PIX_FMT_YUV420P, filt_frame->width, filt_frame->height);
                    fwrite(video_dst_data[0], 1, video_dst_bufsize, fp_yuv);
                    avcodec_free_frame(&filt_frame);
                }
                avcodec_free_frame(&pFrame);
                fclose(fp_yuv);
                return 0;
            }
            else
            {

            }
            printf("video\n");
        }
        av_free_packet(pkt);

    }
    return 0;

}