ffmpeg实战教程（八）Android平台下AVfilter 实现水印，滤镜等特效功能

上一篇我们实现了Android平台解码avi并用SurfaceView播放。
ffmpeg实战教程（七）Android CMake avi解码后SurfaceView显示

本篇我们在此基础上实现滤镜，水印等功能。

对ffmpeg不熟的客官看这里：ffmpeg源码简析（一）结构总览

先上两张效果图：
黑白：const char *filters_descr = “lutyuv=’u=128:v=128’”;

添加水印：const char *filters_descr = “movie=/storage/emulated/0/ws.jpg[wm];[in][wm]overlay=5:5[out]”;

在前面的几篇文章中我们已经学会了用ffmpeg对音视频进行编解码，下面我们就主要介绍一下libavfilter
ffmpeg的libavfilter是为音视频添加特效功能的。

libavfilter的关键函数如下所示：

avfilter_register_all()：注册所有AVFilter。
avfilter_graph_alloc()：为FilterGraph分配内存。
avfilter_graph_create_filter()：创建并向FilterGraph中添加一个Filter。
avfilter_graph_parse_ptr()：将一串通过字符串描述的Graph添加到FilterGraph中。
avfilter_graph_config()：检查FilterGraph的配置。
av_buffersrc_add_frame()：向FilterGraph中加入一个AVFrame。

av_buffersink_get_frame()：从FilterGraph中取出一个AVFrame。

今天我们的示例程序中提供了几种特效：

const char *filters_descr = "lutyuv='u=128:v=128'";
//const char *filters_descr = "hflip";
//const char *filters_descr = "hue='h=60:s=-3'";
//const char *filters_descr = "crop=2/3*in_w:2/3*in_h";
//const char *filters_descr = "drawbox=x=200:y=200:w=300:h=300:color=pink@0.5";
//const char *filters_descr = "movie=/storage/emulated/0/ws.jpg[wm];[in][wm]overlay=5:5[out]";
//const char *filters_descr="drawgrid=width=100:height=100:thickness=4:color=pink@0.9";

上面的黑白特效，和水印使用了下面的两个

const char *filters_descr = "lutyuv='u=128:v=128'";
//const char *filters_descr = "movie=/storage/emulated/0/ws.jpg[wm];[in][wm]overlay=5:5[out]";

更多的特效使用，请到官网学习，http://www.ffmpeg.org/ffmpeg-filters.html

下面看代码实现：

在我们的MainActivity中初始化了一个SurfaceView，并定义一个native函数用于把Surface传到底层（底层把处理过的数据交给Surface传给上层显示）

 SurfaceView surfaceView = (SurfaceView) findViewById(R.id.surface_view);
        surfaceHolder = surfaceView.getHolder();
        surfaceHolder.addCallback(this);

...
 public native int play(Object surface);

surfaceCreated（）函数中实现play函数。

  @Override
    public void surfaceCreated(SurfaceHolder holder) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                play(surfaceHolder.getSurface());
            }
        }).start();
    }

那么重点就是JNI层的play()函数做了什么？

首先我们在上一篇play()函数的基础上添加libavfilter各种特效需要的头文件

//added by ws for AVfilter start
#include <libavfilter/avfiltergraph.h>
#include <libavfilter/buffersrc.h>
#include <libavfilter/buffersink.h>
//added by ws for AVfilter end
};

然后我们声明初始化一些必要的结构体。

//added by ws for AVfilter start

const char *filters_descr = "lutyuv='u=128:v=128'";
//const char *filters_descr = "hflip";
//const char *filters_descr = "hue='h=60:s=-3'";
//const char *filters_descr = "crop=2/3*in_w:2/3*in_h";
//const char *filters_descr = "drawbox=x=200:y=200:w=300:h=300:color=pink@0.5";
//const char *filters_descr = "movie=/storage/emulated/0/ws.jpg[wm];[in][wm]overlay=5:5[out]";
//const char *filters_descr="drawgrid=width=100:height=100:thickness=4:color=pink@0.9";

AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;


//added by ws for AVfilter end

现在我们可以正式的初始化AVfilter 了，代码比较多，对着上面的AVfilter 关键函数看比较好

 //added by ws for AVfilter start----------init AVfilter--------------------------ws


    char args[512];
    int ret;
    AVFilter *buffersrc  = avfilter_get_by_name("buffer");
    AVFilter *buffersink = avfilter_get_by_name("buffersink");//新版的ffmpeg库必须为buffersink
    AVFilterInOut *outputs = avfilter_inout_alloc();
    AVFilterInOut *inputs  = avfilter_inout_alloc();
    enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };
    AVBufferSinkParams *buffersink_params;

    filter_graph = avfilter_graph_alloc();

    /* buffer video source: the decoded frames from the decoder will be inserted here. */
    snprintf(args, sizeof(args),
             "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
             pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
             pCodecCtx->time_base.num, pCodecCtx->time_base.den,
             pCodecCtx->sample_aspect_ratio.num, pCodecCtx->sample_aspect_ratio.den);

    ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
                                       args, NULL, filter_graph);
    if (ret < 0) {
        LOGD("Cannot create buffer source\n");
        return ret;
    }

    /* buffer video sink: to terminate the filter chain. */
    buffersink_params = av_buffersink_params_alloc();
    buffersink_params->pixel_fmts = pix_fmts;
    ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
                                       NULL, buffersink_params, filter_graph);
    av_free(buffersink_params);
    if (ret < 0) {
        LOGD("Cannot create buffer sink\n");
        return ret;
    }

    /* Endpoints for the filter graph. */
    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;

   // avfilter_link(buffersrc_ctx, 0, buffersink_ctx, 0);

    if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
                                        &inputs, &outputs, NULL)) < 0) {
        LOGD("Cannot avfilter_graph_parse_ptr\n");
        return ret;
    }

    if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0) {
        LOGD("Cannot avfilter_graph_config\n");
        return ret;
    }

    //added by ws for AVfilter end------------init AVfilter------------------------------ws

初始化完成后，
我们把解码器解码出来的帧进行加工改造。

               //added by ws for AVfilter start
                pFrame->pts = av_frame_get_best_effort_timestamp(pFrame);

                //* push the decoded frame into the filtergraph
                if (av_buffersrc_add_frame(buffersrc_ctx, pFrame) < 0) {
                    LOGD("Could not av_buffersrc_add_frame");
                    break;
                }

                ret = av_buffersink_get_frame(buffersink_ctx, pFrame);
                if (ret < 0) {
                    LOGD("Could not av_buffersink_get_frame");
                    break;
                }
                //added by ws for AVfilter end

改造后的帧就是已经加上特效了
记着最后释放内存：

avfilter_graph_free(&filter_graph); //added by ws for avfilter

到此我们今天的功能已经实现了。

建议大家结合着代码看，否则如盲人摸象
这一篇可能助你理解libavfilter：
libavfilter实践指南 ：http://blog.csdn.net/king1425/article/details/71215686

对于C和JNI不熟悉的客官看这里：
http://blog.csdn.net/King1425/article/category/6865816

下面我们再看几个效果图，然后上源码：

const char *filters_descr = "hue='h=60:s=-3'";

const char *filters_descr="drawgrid=width=100:height=100:thickness=4:color=pink@0.9";

const char *filters_descr = "drawbox=x=200:y=200:w=300:h=300:color=pink@0.5";

下面是JNI源码:

#include <jni.h>
#include <android/log.h>
#include <android/native_window.h>
#include <android/native_window_jni.h>
#include "native-lib.h"

extern "C" {
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"

//added by ws for AVfilter start
#include <libavfilter/avfiltergraph.h>
#include <libavfilter/buffersrc.h>
#include <libavfilter/buffersink.h>
//added by ws for AVfilter end
};


#define  LOG_TAG    "ffmpegandroidplayer"
#define  LOGD(...)  __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)

//added by ws for AVfilter start

const char *filters_descr = "lutyuv='u=128:v=128'";
//const char *filters_descr = "hflip";
//const char *filters_descr = "hue='h=60:s=-3'";
//const char *filters_descr = "crop=2/3*in_w:2/3*in_h";
//const char *filters_descr = "drawbox=x=200:y=200:w=300:h=300:color=pink@0.5";
//const char *filters_descr = "movie=/storage/emulated/0/ws.jpg[wm];[in][wm]overlay=5:5[out]";
//const char *filters_descr="drawgrid=width=100:height=100:thickness=4:color=pink@0.9";

AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;


//added by ws for AVfilter end


JNIEXPORT jint JNICALL
Java_com_ws_ffmpegandroidavfilter_MainActivity_play
        (JNIEnv *env, jclass clazz, jobject surface) {
    LOGD("play");

    // sd卡中的视频文件地址,可自行修改或者通过jni传入
    char *file_name = "/storage/emulated/0/ws2.mp4";
    //char *file_name = "/storage/emulated/0/video.avi";

    av_register_all();

    avfilter_register_all();//added by ws for AVfilter

    AVFormatContext *pFormatCtx = avformat_alloc_context();

    // Open video file
    if (avformat_open_input(&pFormatCtx, file_name, NULL, NULL) != 0) {

        LOGD("Couldn't open file:%s\n", file_name);
        return -1; // Couldn't open file
    }

    // Retrieve stream information
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        LOGD("Couldn't find stream information.");
        return -1;
    }

    // Find the first video stream
    int videoStream = -1, i;
    for (i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO
            && videoStream < 0) {
            videoStream = i;
        }
    }
    if (videoStream == -1) {
        LOGD("Didn't find a video stream.");
        return -1; // Didn't find a video stream
    }

    // Get a pointer to the codec context for the video stream
    AVCodecContext *pCodecCtx = pFormatCtx->streams[videoStream]->codec;

    //added by ws for AVfilter start----------init AVfilter--------------------------ws


    char args[512];
    int ret;
    AVFilter *buffersrc  = avfilter_get_by_name("buffer");
    AVFilter *buffersink = avfilter_get_by_name("buffersink");//新版的ffmpeg库必须为buffersink
    AVFilterInOut *outputs = avfilter_inout_alloc();
    AVFilterInOut *inputs  = avfilter_inout_alloc();
    enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };
    AVBufferSinkParams *buffersink_params;

    filter_graph = avfilter_graph_alloc();

    /* buffer video source: the decoded frames from the decoder will be inserted here. */
    snprintf(args, sizeof(args),
             "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
             pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
             pCodecCtx->time_base.num, pCodecCtx->time_base.den,
             pCodecCtx->sample_aspect_ratio.num, pCodecCtx->sample_aspect_ratio.den);

    ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
                                       args, NULL, filter_graph);
    if (ret < 0) {
        LOGD("Cannot create buffer source\n");
        return ret;
    }

    /* buffer video sink: to terminate the filter chain. */
    buffersink_params = av_buffersink_params_alloc();
    buffersink_params->pixel_fmts = pix_fmts;
    ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
                                       NULL, buffersink_params, filter_graph);
    av_free(buffersink_params);
    if (ret < 0) {
        LOGD("Cannot create buffer sink\n");
        return ret;
    }

    /* Endpoints for the filter graph. */
    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;

   // avfilter_link(buffersrc_ctx, 0, buffersink_ctx, 0);

    if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
                                        &inputs, &outputs, NULL)) < 0) {
        LOGD("Cannot avfilter_graph_parse_ptr\n");
        return ret;
    }

    if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0) {
        LOGD("Cannot avfilter_graph_config\n");
        return ret;
    }

    //added by ws for AVfilter start------------init AVfilter------------------------------ws

    // Find the decoder for the video stream
    AVCodec *pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if (pCodec == NULL) {
        LOGD("Codec not found.");
        return -1; // Codec not found
    }

    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        LOGD("Could not open codec.");
        return -1; // Could not open codec
    }

    // 获取native window
    ANativeWindow *nativeWindow = ANativeWindow_fromSurface(env, surface);

    // 获取视频宽高
    int videoWidth = pCodecCtx->width;
    int videoHeight = pCodecCtx->height;

    // 设置native window的buffer大小,可自动拉伸
    ANativeWindow_setBuffersGeometry(nativeWindow, videoWidth, videoHeight,
                                     WINDOW_FORMAT_RGBA_8888);
    ANativeWindow_Buffer windowBuffer;

    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        LOGD("Could not open codec.");
        return -1; // Could not open codec
    }

    // Allocate video frame
    AVFrame *pFrame = av_frame_alloc();

    // 用于渲染
    AVFrame *pFrameRGBA = av_frame_alloc();
    if (pFrameRGBA == NULL || pFrame == NULL) {
        LOGD("Could not allocate video frame.");
        return -1;
    }

    // Determine required buffer size and allocate buffer
    // buffer中数据就是用于渲染的,且格式为RGBA
    int numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGBA, pCodecCtx->width, pCodecCtx->height,
                                            1);
    uint8_t *buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
    av_image_fill_arrays(pFrameRGBA->data, pFrameRGBA->linesize, buffer, AV_PIX_FMT_RGBA,
                         pCodecCtx->width, pCodecCtx->height, 1);

    // 由于解码出来的帧格式不是RGBA的,在渲染之前需要进行格式转换
    struct SwsContext *sws_ctx = sws_getContext(pCodecCtx->width,
                                                pCodecCtx->height,
                                                pCodecCtx->pix_fmt,
                                                pCodecCtx->width,
                                                pCodecCtx->height,
                                                AV_PIX_FMT_RGBA,
                                                SWS_BILINEAR,
                                                NULL,
                                                NULL,
                                                NULL);

    int frameFinished;
    AVPacket packet;
    while (av_read_frame(pFormatCtx, &packet) >= 0) {
        // Is this a packet from the video stream?
        if (packet.stream_index == videoStream) {

            // Decode video frame
            avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);



            // 并不是decode一次就可解码出一帧
            if (frameFinished) {

                //added by ws for AVfilter start
                pFrame->pts = av_frame_get_best_effort_timestamp(pFrame);

                //* push the decoded frame into the filtergraph
                if (av_buffersrc_add_frame(buffersrc_ctx, pFrame) < 0) {
                    LOGD("Could not av_buffersrc_add_frame");
                    break;
                }

                ret = av_buffersink_get_frame(buffersink_ctx, pFrame);
                if (ret < 0) {
                    LOGD("Could not av_buffersink_get_frame");
                    break;
                }
                //added by ws for AVfilter end

                // lock native window buffer
                ANativeWindow_lock(nativeWindow, &windowBuffer, 0);

                // 格式转换
                sws_scale(sws_ctx, (uint8_t const *const *) pFrame->data,
                          pFrame->linesize, 0, pCodecCtx->height,
                          pFrameRGBA->data, pFrameRGBA->linesize);

                // 获取stride
                uint8_t *dst = (uint8_t *) windowBuffer.bits;
                int dstStride = windowBuffer.stride * 4;
                uint8_t *src = (pFrameRGBA->data[0]);
                int srcStride = pFrameRGBA->linesize[0];

                // 由于window的stride和帧的stride不同,因此需要逐行复制
                int h;
                for (h = 0; h < videoHeight; h++) {
                    memcpy(dst + h * dstStride, src + h * srcStride, srcStride);
                }

                ANativeWindow_unlockAndPost(nativeWindow);
            }

        }
        av_packet_unref(&packet);
    }

    av_free(buffer);
    av_free(pFrameRGBA);

    // Free the YUV frame
    av_free(pFrame);

    avfilter_graph_free(&filter_graph); //added by ws for avfilter
    // Close the codecs
    avcodec_close(pCodecCtx);

    // Close the video file
    avformat_close_input(&pFormatCtx);
    return 0;
}

native-lib.h

#include <jni.h>


#ifndef FFMPEGANDROID_NATIVE_LIB_H
#define FFMPEGANDROID_NATIVE_LIB_H
#ifdef __cplusplus
extern "C" {
#endif

JNIEXPORT jint JNICALL Java_com_ws_ffmpegandroidavfilter_MainActivity_play
        (JNIEnv *, jclass, jobject);

#ifdef __cplusplus
}
#endif
#endif

demo:https://github.com/WangShuo1143368701/FFmpegAndroid/tree/master/ffmpegandroidavfilter