当前位置：首页 > news >正文

ff数据解析和解码

news 来源：原创 2025/6/13 14:55:52

ff数据

实现raii

#pragma once#include <concepts>
#include <functional>
#include <tuple>template <typename F, typename... Args>
requires requires(F f, Args... args) { std::invoke(f, args...); }
struct scope_guard {F f;std::tuple<Args...> values;template <typename Fn, typename... Ts>scope_guard(Fn &&func, Ts &&...args): f{std::forward<Fn>(func)}, values{std::forward<Ts>(args)...} {}~scope_guard() { std::apply(f, values); }scope_guard(const scope_guard &) = delete;scope_guard &operator=(const scope_guard &) = delete;
};template <typename F, typename... Args>
scope_guard(F &&, Args &&...)-> scope_guard<std::decay_t<F>, std::decay_t<Args>...>;

自定义日志

// 自定义日志回调函数，用于捕获FFmpeg警告static void log_callback(void* ptr, int level, const char* fmt, va_list vl) {if (level <= AV_LOG_WARNING) {char buffer[1024];vsnprintf(buffer, sizeof(buffer), fmt, vl);g_ffmpeg_warnings += std::string("[FFmpeg Warning] ") + buffer;// LOGI("FFmpeg Warning captured: %s", buffer);}}

检查合法性

    bool is_valid_image(const uint8_t *input, uint64_t len) {if (!g_log_callback_set) {av_log_set_callback(log_callback);g_log_callback_set = true;}g_ffmpeg_warnings.clear(); // 清空之前的警告信息// raiistatic auto free_avformat = [](AVFormatContext **p){if(*p) {if((*p)->pb) {av_free((*p)->pb->buffer);avio_context_free(&(*p)->pb);}avformat_free_context(*p);}};static auto free_avcodec = [](AVCodecContext *p){ p && (avcodec_free_context(&p), true); };static auto free_avframe = [](AVFrame *p){p && (av_frame_free(&p), true);};static auto free_avpacket = [](AVPacket *p){ p && (av_packet_free(&p), true); };static auto free_avio_ctx = [](AVIOContext *p){ p && (avio_context_free(&p), true); };static auto close_stream = [](AVFormatContext *p){ p && (avformat_close_input(&p), true); };auto fmt_ctx = avformat_alloc_context();scope_guard guard_fmt_ctx(free_avformat, &fmt_ctx);if (fmt_ctx == nullptr)return false;constexpr uint64_t avio_buf_len = 1024 * 1024ull;struct mem_input {const uint8_t *start{nullptr};const uint8_t *end{nullptr};const uint8_t *cur{nullptr};};static auto read = [](void *opaque, uint8_t *buf, int buf_size) -> int {auto &ctx = *reinterpret_cast<mem_input *>(opaque);auto residual = ctx.end - ctx.cur;auto sz = std::min<uint64_t>(residual, buf_size);if (sz > 0) {//   memcpy(buf, ctx.cur, sz);std::copy(ctx.cur, ctx.cur + sz, buf);ctx.cur += sz;}return sz == 0 ? AVERROR_EOF : sz;};static auto seek = [](void *opaque, int64_t offset, int whence) -> int64_t {auto &ctx = *reinterpret_cast<mem_input *>(opaque);auto len = ctx.end - ctx.start;int64_t ret = AVERROR_EOF;switch (whence) {case AVSEEK_SIZE:ret = static_cast<int64_t>(ctx.end - ctx.start);break;case SEEK_SET:if (offset >= 0) {if (offset >= len) {ret = AVERROR_EOF;} else {ctx.cur = ctx.start + offset;ret = 0;}}break;}return ret;};mem_input opaque{input, input + len, input};fmt_ctx->pb =avio_alloc_context(static_cast<uint8_t *>(av_malloc(avio_buf_len)),avio_buf_len, 0, &opaque, read, nullptr, seek);//   scope_guard guard_avio_ctx(free_avio_ctx, fmt_ctx->pb);// only videoif (avformat_open_input(&fmt_ctx, nullptr, nullptr, nullptr) < 0 ||avformat_find_stream_info(fmt_ctx, nullptr) < 0)return false;//int vid_idx = -1;for (int i = 0; i < fmt_ctx->nb_streams; ++i) {if (fmt_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {vid_idx = i;break;}}if (vid_idx < 0) {return false;}AVCodecContext *codec_ctx = nullptr;const auto codecpar = fmt_ctx->streams[vid_idx]->codecpar;auto codec = avcodec_find_decoder(codecpar->codec_id);if (codec != nullptr) {codec_ctx = avcodec_alloc_context3(codec);if (codec_ctx == nullptr)return false;if (avcodec_parameters_to_context(codec_ctx, codecpar) < 0)return false;if (avcodec_open2(codec_ctx, codec, nullptr) < 0)return false;}scope_guard guard_codec_ctx(free_avcodec, codec_ctx);int ret = 0;auto pkt = av_packet_alloc();scope_guard guard_pkt(free_avpacket, pkt);AVFrame *frame = av_frame_alloc();scope_guard guard_frame(free_avframe, frame);auto handle_packet = [](AVCodecContext *codec_ctx, AVFrame *frame,auto &&fn) -> void {int ret = 0;while (ret >= 0) {ret = avcodec_receive_frame(codec_ctx, frame);if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {av_frame_unref(frame);break;} else if (ret < 0) {av_frame_unref(frame);return;}fn(frame, codec_ctx->frame_number);av_frame_unref(frame);}};static auto pgm_save = [](unsigned char *buf, int wrap, int xsize, int ysize,const char *filename) {FILE *f;int i;f = fopen(filename, "wb");fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);for (i = 0; i < ysize; i++)fwrite(buf + i * wrap, 1, xsize, f);fclose(f);};static auto calc_entropy = [](cv::Mat mat) -> double {if (mat.channels() > 1) {cv::cvtColor(mat, mat, cv::COLOR_BGR2GRAY);}assert(mat.channels() == 1);cv::Mat grey = mat.clone();std::vector<cv::Mat> histChannels;cv::Mat hist;int histSize = 256;float range[] = {0, 256};const float *histRange = {range};cv::calcHist(&grey, 1, 0, cv::Mat(), hist, 1, &histSize, &histRange);hist /= (grey.rows * grey.cols);double entropy = 0.0;for (int i = 0; i < histSize; i++) {float p = hist.at<float>(i);if (p > 0) {entropy -= p * log(p);}}return entropy;};static auto calc_edge_ratio = [](cv::Mat mat) {assert(mat.channels() == 1);cv::Mat gray = mat.clone();cv::Canny(gray, gray, 50, 150);// cv::imwrite(std::string("D:/zzz/canny.png"), gray);return static_cast<double>(cv::countNonZero(gray)) /static_cast<double>(gray.rows * gray.cols);};static auto calc_std_dev = [](cv::Mat mat) -> double {assert(mat.channels() == 1);cv::Scalar mean, stddev;cv::meanStdDev(mat, mean, stddev);return stddev[0];};static auto sobel_edge = [](cv::Mat mat) -> cv::Mat {cv::Mat sobel_x, sobel_y;cv::Sobel(mat, sobel_x, CV_64F, 1, 0, 3);cv::Sobel(mat, sobel_y, CV_64F, 0, 1, 3);cv::Mat sobel_xy;cv::addWeighted(sobel_x, 0.5, sobel_y, 0.5, 0, sobel_xy);return sobel_xy;};static auto laplacian_edge = [](cv::Mat mat) -> cv::Mat {cv::Mat laplacian;cv::Laplacian(mat, laplacian, CV_64F, 3);return laplacian;};static auto calc_ratio = [](cv::Mat mat) -> double {cv::Mat out;cv::threshold(mat, out, 128.0, 255.0, cv::THRESH_BINARY);return static_cast<double>(cv::countNonZero(out)) /static_cast<double>(out.rows * out.cols);};static auto is_valid_image = [](cv::Mat mat) -> bool {auto entropy = calc_entropy(mat);auto edge_ratio = calc_edge_ratio(mat);auto std_dev = calc_std_dev(mat);return 0.5 <= entropy && entropy <= 7.5 && 0.009 <= edge_ratio &&edge_ratio <= 0.15 && 30.0 <= std_dev && std_dev <= 100.0;};bool flag = false;auto img_check_cb = [&](AVFrame *frame, int frame_num) {//  std::string filename = std::string("D:/zzz/") + std::to_string(frame_num) + ".pgm";//  pgm_save(frame->data[0], frame->linesize[0], frame->width, frame->height, filename.c_str());// // call opencv and decodecv::Mat mat(frame->height, frame->width, CV_8UC1, frame->data[0]);if (is_valid_image(mat)) {flag = true;return;}// auto sobel_xy = sobel_edge(mat);// auto laplacian = laplacian_edge(mat);// cv::imwrite(std::string("D:/zzz/sobel-") +// std::to_string(frame_num) + ".png", sobel_xy);// cv::imwrite(std::string("D:/zzz/laplacian-") +// std::to_string(frame_num) + ".png", laplacian); auto sobel_ratio// = calc_ratio(sobel_xy); auto laplacian_ratio =// calc_ratio(laplacian); std::cout << "sobel: " << sobel_ratio <<// "\n"; std::cout << "laplacian: " << laplacian_ratio << "\n";};while ((ret = av_read_frame(fmt_ctx, pkt)) >= 0) {if (pkt->stream_index != vid_idx) {av_packet_unref(pkt);continue;}int ret = avcodec_send_packet(codec_ctx, pkt);av_packet_unref(pkt);if (ret < 0) {break;}if (!g_ffmpeg_warnings.empty()) {LOGI("warn: %s", g_ffmpeg_warnings.c_str());}g_ffmpeg_warnings.clear();handle_packet(codec_ctx, frame, img_check_cb);av_frame_unref(frame);}ret = avcodec_send_packet(codec_ctx, nullptr);handle_packet(codec_ctx, frame, img_check_cb);av_frame_unref(frame);if (!g_ffmpeg_warnings.empty()) {LOGI("捕获到的FFmpeg警告信息: %s", g_ffmpeg_warnings.c_str());}return flag;}