一、简介
FFmpeg 是一个开源的多媒体处理框架，非常适用于处理音视频的录制、转换、流化和播放。
二、代码
示例代码使用工作线程读取rtsp视频流，自动重连，支持手动退出，解码并将二进制文件保存下来。
注意： 代码中仅展示了 YUV420P 格式，其他 NV12/NV21 等格式可相应修改。
1. rtsp_decoder.cpp
#include <iostream>
#include <atomic>
#include <thread>
#include <cstdio>
extern "C" {
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
#include <libavutil/error.h>
}
const char* rtsp_url = "rtsp://172.0.0.1:8554/video"; // 替换为目标url
std::atomic<bool> running{true};
std::atomic<int> frame_number{0};
bool connect_rtsp(AVFormatContext*& fmt_ctx, AVCodecContext*& codec_ctx, int& video_stream_idx) {
fmt_ctx = avformat_alloc_context();
if (!fmt_ctx) {
std::cerr << "Failed to allocate format context" << std::endl;
return false;
}
AVDictionary* opts = nullptr;
av_dict_set(&opts, "rtsp_transport", "tcp", 0); // 使用TCP连接
av_dict_set(&opts, "stimeout", "5000000", 0); // 5秒超时，网络差连接时间长也可以不设置超时
av_dict_set(&opts, "reconnect", "1", 0); // 开启自动重连
av_dict_set(&opts, "reconnect_at_eof", "1", 0); // EOF后重连
if (avformat_open_input(&fmt_ctx, rtsp_url, nullptr, &opts) != 0) {
std::cerr << "Failed to open input" << std::endl;
av_dict_free(&opts);
return false;
}
av_dict_free(&opts);
if (avformat_find_stream_info(fmt_ctx, nullptr) < 0) {
std::cerr << "Failed to find stream info" << std::endl;
avformat_close_input(&fmt_ctx);
return false;
}
video_stream_idx = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, nullptr, 0);
if (video_stream_idx < 0) {
std::cerr << "Failed to find video stream" << std::endl;
avformat_close_input(&fmt_ctx);
return false;
}
AVStream* video_stream = fmt_ctx->streams[video_stream_idx];
const AVCodec* decoder = avcodec_find_decoder(video_stream->codecpar->codec_id);
if (!decoder) {
std::cerr << "Failed to find decoder" << std::endl;
avformat_close_input(&fmt_ctx);
return false;
}
codec_ctx = avcodec_alloc_context3(decoder);
if (!codec_ctx) {
std::cerr << "Failed to allocate codec context" << std::endl;
avformat_close_input(&fmt_ctx);
return false;
}
if (avcodec_parameters_to_context(codec_ctx, video_stream->codecpar) < 0) {
std::cerr << "Failed to copy codec parameters" << std::endl;
avcodec_free_context(&codec_ctx);
avformat_close_input(&fmt_ctx);
return false;
}
if (avcodec_open2(codec_ctx, decoder, nullptr) < 0) {
std::cerr << "Failed to open codec" << std::endl;
avcodec_free_context(&codec_ctx);
avformat_close_input(&fmt_ctx);
return false;
}
return true;
}
void save_yuv_frame(AVFrame* frame) {
if (frame->format != AV_PIX_FMT_YUV420P) {
std::cerr << "Unsupported pixel format" << std::endl;
return;
}
char filename[256];
int current_frame = frame_number.fetch_add(1);
snprintf(filename, sizeof(filename), "frame_%05d.yuv", current_frame);
FILE* file = fopen(filename, "wb");
if (!file) {
std::cerr << "Failed to open file: " << filename << std::endl;
return;
}
// 写入Y分量
for (int i = 0; i < frame->height; i++) {
fwrite(frame->data[0] + i * frame->linesize[0], 1, frame->width, file);
}
// 写入U分量
for (int i = 0; i < frame->height/2; i++) {
fwrite(frame->data[1] + i * frame->linesize[1], 1, frame->width/2, file);
}
// 写入V分量
for (int i = 0; i < frame->height/2; i++) {
fwrite(frame->data[2] + i * frame->linesize[2], 1, frame->width/2, file);
}
fclose(file);
}
void worker_thread() {
avformat_network_init();
while (running) {
AVFormatContext* fmt_ctx = nullptr;
AVCodecContext* codec_ctx = nullptr;
int video_stream_idx = -1;
if (connect_rtsp(fmt_ctx, codec_ctx, video_stream_idx)) {
AVPacket* packet = av_packet_alloc();
AVFrame* frame = av_frame_alloc();
while (running) {
int ret = av_read_frame(fmt_ctx, packet);
if (ret < 0) {
if (ret == AVERROR(EAGAIN)) continue;
char err_buf[AV_ERROR_MAX_STRING_SIZE] = {0};
av_strerror(ret, err_buf, sizeof(err_buf));
std::cerr << "Error reading packet: " << err_buf << std::endl;
break;
}
if (packet->stream_index == video_stream_idx) {
ret = avcodec_send_packet(codec_ctx, packet);
if (ret < 0) {
char err_buf[AV_ERROR_MAX_STRING_SIZE] = {0};
av_strerror(ret, err_buf, sizeof(err_buf));
std::cerr << "Error sending packet: " << err_buf << std::endl;
av_packet_unref(packet);
break;
}
while (ret >= 0) {
ret = avcodec_receive_frame(codec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
break;
} else if (ret < 0) {
char err_buf[AV_ERROR_MAX_STRING_SIZE] = {0};
av_strerror(ret, err_buf, sizeof(err_buf));
std::cerr << "Error receiving frame: " << err_buf << std::endl;
break;
}
save_yuv_frame(frame);
}
}
av_packet_unref(packet);
}
av_packet_free(&packet);
av_frame_free(&frame);
avcodec_free_context(&codec_ctx);
avformat_close_input(&fmt_ctx);
}
if (running) {
std::cout << "Reconnecting in 5 seconds..." << std::endl;
std::this_thread::sleep_for(std::chrono::seconds(5));
}
}
avformat_network_deinit();
}
int main() {
std::thread worker(worker_thread);
std::cout << "Running... Enter 'q' to quit" << std::endl;
while (running) {
char cmd = std::cin.get();
if (cmd == 'q') {
running = false;
}
}
worker.join();
std::cout << "Stopped" << std::endl;
return 0;
}
2. CMakeLists.txt
cmake_minimum_required(VERSION 3.10)
project(FFmpegYUVDecoder)
set(CMAKE_CXX_STANDARD 11)
find_package(PkgConfig REQUIRED)
pkg_check_modules(AVCODEC REQUIRED libavcodec)
pkg_check_modules(AVFORMAT REQUIRED libavformat)
pkg_check_modules(AVUTIL REQUIRED libavutil)
add_executable(rtsp_decoder rtsp_decoder.cpp)
target_include_directories(yuv_decoder PRIVATE
${AVCODEC_INCLUDE_DIRS}
${AVFORMAT_INCLUDE_DIRS}
${AVUTIL_INCLUDE_DIRS}
)
target_link_libraries(yuv_decoder
${AVCODEC_LIBRARIES}
${AVFORMAT_LIBRARIES}
${AVUTIL_LIBRARIES}
pthread
)
依赖的库在安装 ffmpeg 后应该都有，用到的就 libavcodec，libavformat，libavutil三个。
3. 文件目录结构
|—— CMakeLists.txt
|—— rtsp_decoder.cpp
三、编译和运行
1. 安装 ffmpeg
如果还没有安装过，可以如下安装
# Ubuntu/Debian
sudo apt update && sudo apt install ffmpeg
# 查看版本号
ffmpeg -version
如果缺少某个库，可以执行
sudo apt install libavcodec-dev libavformat-dev libavutil-dev
2. 编译
mkdir build
cd build
cmake ..
make -j4
3. 运行
只有一个输入参数，及输入视频的文件路径，输出路径默认在当前路径。
./rtsp_decoder
4. 查看
可以使用 ffplay 命令查看保持的 yuv 数据是否正确。以 1920x1080 大小，yuv420p格式为例：
ffplay -video_size 1920x1080 -pixel_format yuv420p 00001.yuv