FFMPEG中的libswscale是做像素转换的,但是对于一些复杂的操作,比如添加水印等,这个库就不行了,这时候就要说一下另外一个AVFilter。AVFilter完全可以替代libswscale的所有功能,也许有一天,ffmpeg也会这样去做。AVFilter虽然学起来有点复杂,但是为了学好FFMPEG,为了涨工资,我忍了。(*^__^*) 嘻嘻……
概念:
做个directshow的同学,对于这一块应该很了解了。
1.AVFilterGraph:和dshow中的filtergraph功能基本上一样,管理filter的,可以看成filter的一个容器。
2.AVFilter:就是一个filter啦。但是为什么叫做filter,其实就是一个过滤器,目标资源通过该过滤器总该发生一点变化是吧。。。。。
3.AVFilterLink:代表两个filter的关联媒介。
4.AVFilterPad:代表一个filter的输入输出口,就跟dshow中的pin差不多。只有输入pad的叫做source,只有输出pad的叫做sink。
下面是官方提供的一个例子:
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- /*
- *modifier by tongli
- */
- #define _XOPEN_SOURCE 600
- #include <stdio.h>
- #include <windows.h>
- #include "snprintf.h"
- extern "C"
- {
- #include <libavcodec/avcodec.h>
- #include <libavformat/avformat.h>
- #include <libavfilter/avfiltergraph.h>
- #include <libavfilter/avcodec.h>
- #include <libavfilter/buffersink.h>
- #include <libavfilter/buffersrc.h>
- #include <libavutil/opt.h>
- }
- const char *filter_descr = "scale=78:24";
- static AVFormatContext *fmt_ctx;
- static AVCodecContext *dec_ctx;
- AVFilterContext *buffersink_ctx;
- AVFilterContext *buffersrc_ctx;
- AVFilterGraph *filter_graph;
- static int video_stream_index = -1;
- static int64_t last_pts = AV_NOPTS_VALUE;
- static int open_input_file(const char *filename)
- {
- int ret;
- AVCodec *dec;
- if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
- return ret;
- }
- if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
- return ret;
- }
- /* select the video stream */
- ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot find a video stream in the input file\n");
- return ret;
- }
- video_stream_index = ret;
- dec_ctx = fmt_ctx->streams[video_stream_index]->codec;
- av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
- /* init the video decoder */
- if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot open video decoder\n");
- return ret;
- }
- return 0;
- }
- static int init_filters(const char *filters_descr)
- {
- char args[512];
- int ret = 0;
- AVFilter *buffersrc = avfilter_get_by_name("buffer");
- AVFilter *buffersink = avfilter_get_by_name("buffersink");
- AVFilterInOut *outputs = avfilter_inout_alloc();
- AVFilterInOut *inputs = avfilter_inout_alloc();
- AVRational time_base = fmt_ctx->streams[video_stream_index]->time_base;
- enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
- filter_graph = avfilter_graph_alloc();
- if (!outputs || !inputs || !filter_graph) {
- ret = AVERROR(ENOMEM);
- goto end;
- }
- /* 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",
- dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
- time_base.num, time_base.den,
- dec_ctx->sample_aspect_ratio.num, 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");
- goto end;
- }
- /* buffer video sink: to terminate the filter chain. */
- 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");
- goto end;
- }
- 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");
- goto end;
- }
- /* 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;
- if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
- &inputs, &outputs, NULL)) < 0)
- goto end;
- if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
- goto end;
- end:
- avfilter_inout_free(&inputs);
- avfilter_inout_free(&outputs);
- return ret;
- }
- static void display_frame(const AVFrame *frame, AVRational time_base)
- {
- int x, y;
- uint8_t *p0, *p;
- int64_t delay;
- AVRational ar_base_q = { 1, AV_TIME_BASE };
- if (frame->pts != AV_NOPTS_VALUE) {
- if (last_pts != AV_NOPTS_VALUE) {
- /* sleep roughly the right amount of time;
- * usleep is in microseconds, just like AV_TIME_BASE. */
- delay = av_rescale_q(frame->pts - last_pts,
- time_base, ar_base_q);
- if (delay > 0 && delay < 1000000)
- //usleep(delay);
- Sleep(delay);
- }
- last_pts = frame->pts;
- }
- /* Trivial ASCII grayscale display. */
- p0 = frame->data[0];
- puts("\033c");
- for (y = 0; y < frame->height; y++) {
- p = p0;
- for (x = 0; x < frame->width; x++)
- putchar(" .-+#"[*(p++) / 52]);
- putchar('\n');
- p0 += frame->linesize[0];
- }
- fflush(stdout);
- }
- int main(int argc, char **argv)
- {
- int ret;
- AVPacket packet;
- AVFrame *frame = av_frame_alloc();
- AVFrame *filt_frame = av_frame_alloc();
- int got_frame;
- if (!frame || !filt_frame) {
- perror("Could not allocate frame");
- exit(1);
- }
- av_register_all();
- avfilter_register_all();
- if ((ret = open_input_file("style.ts")) < 0)
- goto end;
- if ((ret = init_filters(filter_descr)) < 0)
- goto end;
- /* read all packets */
- while (1) {
- if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
- break;
- if (packet.stream_index == video_stream_index) {
- got_frame = 0;
- ret = avcodec_decode_video2(dec_ctx, frame, &got_frame, &packet);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Error decoding video\n");
- break;
- }
- if (got_frame) {
- frame->pts = av_frame_get_best_effort_timestamp(frame);
- /* push the decoded frame into the filtergraph */
- if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, 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) {
- ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
- if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
- break;
- if (ret < 0)
- goto end;
- display_frame(filt_frame, buffersink_ctx->inputs[0]->time_base);
- av_frame_unref(filt_frame);
- }
- av_frame_unref(frame);
- }
- }
- av_free_packet(&packet);
- }
- end:
- avfilter_graph_free(&filter_graph);
- avcodec_close(dec_ctx);
- avformat_close_input(&fmt_ctx);
- av_frame_free(&frame);
- av_frame_free(&filt_frame);
- if (ret < 0 && ret != AVERROR_EOF) {
- fprintf(stderr, "Error occurred: %s\n"); //av_err2str(ret));
- exit(1);
- }
- exit(0);
- }
未完待续。。。。
时间: 2024-11-05 18:32:58