项目地址，求star
https://github.com/979451341/Audio-and-video-learning-materials/tree/master/FFmpeg(AVfilter%E8%BF%87%E6%BB%A4%EF%BC%89
1.AVfilter结构体成员
这个特效要靠AVfilter来实现，首先说一下说AVfilter这个结构体的成员
/ * *
*过滤器定义。这定义了一个过滤器包含的垫，以及所有的
*用于与筛选器交互的回调函数。
* /
typedef struct AVFilter {
/ * *
*过滤器名称。在过滤器中必须是非空且唯一的。
* /
const char *name;
/ * *
*描述滤波器。可能是空的。
*
你应该使用null_if_config_small()宏定义。
* /
const char *description;
/ * *
*输入清单，由零元终止。
*
*如果没有（静态）输入，则为null。过滤器实例
* avfilter_flag_dynamic_inputs集可能会有比现在更多的投入
*这份清单。
* /
const AVFilterPad *inputs;
/ * *
*输出清单，由零元终止。
*
*如果没有（静态）输出，则为null。过滤器实例
* avfilter_flag_dynamic_outputs集可能会有比现在更多的产出
*这份清单。
* /
const AVFilterPad *outputs;
/ * *
*一个私人数据的类，用于声明私人avoptions过滤器。
*此字段对于未声明任何选项的筛选器无效。
*
*如果该字段非空，则是筛选私有数据的第一个成员。
*必须是指针对avclass，这将由libavfilter通用
*这个类的代码。
* /
const AVClass *priv_class;
/ * *
*结合avfilter_flag_ *
* /
int flags;
2.AVfilter使用步骤
现在直接在代码上说这个AVfilter使用的步骤
因为使用滤镜，所以需要播放视频，就要解码，来段标准准备代码
// 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/pauseRecordDemo/video/2018-02-03-09-25-34.mp4";
//char *file_name = "/storage/emulated/0/video.avi";
av_register_all();
//注册所有AVFilter。
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;
开始滤镜的准备
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;
//为FilterGraph分配内存。
filter_graph = avfilter_graph_alloc();
//创建并向FilterGraph中添加一个Filter。
ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
args, NULL, filter_graph);
if (ret < 0) {
LOGD("Cannot create buffer source\n");
return ret;
}
buffersink_params = av_buffersink_params_alloc();
buffersink_params->pixel_fmts = pix_fmts;
//创建并向FilterGraph中添加一个Filter。
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;
}
给AVfilter的输入输出描述赋值
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;
配置和使用滤镜效果，改变u、v这个两个像素，使画面显示黑白
const char *filters_descr = "lutyuv='u=128:v=128'";
//将一串通过字符串描述的Graph添加到FilterGraph中。
if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
&inputs, &outputs, NULL)) < 0) {
LOGD("Cannot avfilter_graph_parse_ptr\n");
return ret;
}
//检查FilterGraph的配置。
if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0) {
LOGD("Cannot avfilter_graph_config\n");
return ret;
}
接下来就是渲染
// 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);
解码和释放资源,在解码的时候将解码的数据放入FilterGraph去显示
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);
//* 向FilterGraph中加入一个AVFrame。
if (av_buffersrc_add_frame(buffersrc_ctx, pFrame) < 0) {
LOGD("Could not av_buffersrc_add_frame");
break;
}
//从FilterGraph中取出一个AVFrame。
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);
这个想要真正掌握，需要将avfilter.c至少过个两个遍，因为这下面四个结构体还没有看看他们的内部成员
typedef struct AVFilterContext AVFilterContext;
typedef struct AVFilterLink AVFilterLink;
typedef struct AVFilterPad AVFilterPad;
typedef struct AVFilterFormats AVFilterFormats;