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yjwx0017 authored 2024-04-29 21:26 . Add tutorial_4, refactor, using thread
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#include <SDL/SDL.h>
#include <SDL/SDL_thread.h>
#include <fstream>
#include <iostream>
#include <mutex>
#include <queue>
#include <thread>
extern "C" {
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavutil/imgutils.h>
#include <libswresample/swresample.h>
#include <libswscale/swscale.h>
}
#define MAX_AUDIO_FRAME_SIZE 192000
#define MAX_AUDIO_QUEUE_SIZE 250
#define MAX_VIDEO_QUEUE_SIZE 250
#define MAX_PICTURE_QUEUE_SIZE 1
class PacketQueue {
public:
int size() {
std::unique_lock<std::mutex> lock(m_mutex);
return (int)m_queue.size();
}
void notify_all() { m_cond.notify_all(); }
void push(AVPacket *pkt) {
std::unique_lock<std::mutex> lock(m_mutex);
m_queue.push(pkt);
lock.unlock();
m_cond.notify_all();
}
AVPacket *pop() {
AVPacket *pkt = nullptr;
std::unique_lock<std::mutex> lock(m_mutex);
if (m_queue.empty()) {
m_cond.wait(lock);
}
pkt = m_queue.front();
m_queue.pop();
return pkt;
}
private:
std::queue<AVPacket *> m_queue;
std::condition_variable m_cond;
std::mutex m_mutex;
};
struct VideoPicture {
SDL_Overlay *bmp = nullptr;
int width = 0;
int height = 0;
};
class PictureQueue {
public:
void notify_all() { m_cond.notify_all(); }
void push(const VideoPicture &vp) {
std::unique_lock<std::mutex> lock(m_mutex);
if (m_queue.size() >= MAX_PICTURE_QUEUE_SIZE) {
m_cond.wait(lock);
}
m_queue.push(vp);
}
VideoPicture pop() {
std::unique_lock<std::mutex> lock(m_mutex);
if (m_queue.empty()) {
return VideoPicture();
}
VideoPicture vp = m_queue.front();
m_queue.pop();
lock.unlock();
m_cond.notify_all();
return vp;
}
private:
std::queue<VideoPicture> m_queue;
std::condition_variable m_cond;
std::mutex m_mutex;
};
struct VideoState {
std::string filename;
bool quit = false;
AVFormatContext *format_ctx = nullptr;
int video_stream_index = -1;
int audio_stream_index = -1;
AVStream *audio_stream = nullptr;
AVCodecContext *audio_codec_ctx = nullptr;
PacketQueue audio_pkt_queue;
uint8_t audio_buf[MAX_AUDIO_FRAME_SIZE];
int audio_buf_size = 0;
int audio_buf_index = 0;
AVStream *video_stream = nullptr;
AVCodecContext *video_codec_ctx = nullptr;
PacketQueue video_pkt_queue;
SwsContext *sws_ctx = nullptr;
SwrContext *swr_ctx = nullptr;
PictureQueue picture_queue;
std::shared_ptr<std::thread> demux_thread; // 解复用线程
std::shared_ptr<std::thread> video_thread; // 视频解码线程
};
#define FF_REFRESH_EVENT (SDL_USEREVENT)
#define FF_QUIT_EVENT (SDL_USEREVENT + 1)
SDL_Surface *screen = nullptr;
std::mutex screen_mutex;
// 通过发送事件的方式让主线程更新视频画面
Uint32 sdl_refresh_timer_cb(Uint32 interval, void *param) {
SDL_Event event;
event.type = FF_REFRESH_EVENT;
event.user.data1 = param;
SDL_PushEvent(&event);
return 0;
}
void schedule_refresh(VideoState *is, int delay) {
SDL_AddTimer(delay, sdl_refresh_timer_cb, is);
}
// 将视频帧刷新到SDL窗口
void video_refresh_timer(void *userdata) {
VideoState *is = (VideoState *)userdata;
VideoPicture vp = is->picture_queue.pop();
if (is->video_stream) {
if (vp.bmp == nullptr) {
schedule_refresh(is, 1);
} else {
schedule_refresh(is, 10);
// 对于非方形像素 sample_aspect_ratio 的值不为1
SDL_Rect rect;
float aspect_ratio;
int w, h, x, y;
if (is->video_codec_ctx->sample_aspect_ratio.num == 0) {
aspect_ratio = 0;
} else {
aspect_ratio = (float)av_q2d(is->video_codec_ctx->sample_aspect_ratio) *
(float)is->video_codec_ctx->width /
(float)is->video_codec_ctx->height;
}
if (aspect_ratio <= 0.0) {
aspect_ratio = (float)is->video_codec_ctx->width /
(float)is->video_codec_ctx->height;
}
h = screen->h;
w = ((int)rint(h * aspect_ratio));
if (w > screen->w) {
w = screen->w;
h = ((int)rint(w / aspect_ratio));
}
x = (screen->w - w) / 2;
y = (screen->h - h) / 2;
rect.x = x;
rect.y = y;
rect.w = w;
rect.h = h;
std::unique_lock lock(screen_mutex);
SDL_DisplayYUVOverlay(vp.bmp, &rect);
}
} else {
schedule_refresh(is, 100);
}
if (vp.bmp) {
SDL_FreeYUVOverlay(vp.bmp);
}
}
int audio_decode_frame(VideoState *is, uint8_t *audioBuf, int bufSize) {
int dataSize(-1);
AVPacket *packet = is->audio_pkt_queue.pop();
if (packet == nullptr) {
return -1;
}
// packet 发送到解码器
avcodec_send_packet(is->audio_codec_ctx, packet);
// 获取解码后的帧,一个音频帧包含多个音频采样点
AVFrame *frame = av_frame_alloc();
while (avcodec_receive_frame(is->audio_codec_ctx, frame) == 0) {
// 音频重采样,将音频数据转换为所需的格式(采样频率、声道数、样本位数)
int out_nb_samples =
swr_convert(is->swr_ctx, &audioBuf, frame->nb_samples,
(const uint8_t **)frame->data, frame->nb_samples);
dataSize = av_samples_get_buffer_size(nullptr, 2, out_nb_samples,
AV_SAMPLE_FMT_S16, 1);
}
av_frame_free(&frame);
av_packet_free(&packet);
return dataSize;
}
void audio_callback(void *userdata, Uint8 *stream, int len) {
// 存放解码出音频数据
static uint8_t audioBuf[MAX_AUDIO_FRAME_SIZE];
static uint32_t audioBufSize = 0;
static uint32_t audioBufIndex = 0;
VideoState *is = (VideoState *)userdata;
AVCodecContext *codecCtx = is->audio_codec_ctx;
// 需要存放的字节数剩余
int lenRemain = len;
while (lenRemain > 0) {
if (audioBufIndex >= audioBufSize) {
// 解码出的音频数据为空(或已消耗完毕),则执行音频解码
int audioSize = audio_decode_frame(is, audioBuf, sizeof(audioBuf));
if (audioSize < 0) {
// 如果出错,填充数据 0,即无声音
audioBufSize = 1024;
std::memset(audioBuf, 0, audioBufSize);
} else {
audioBufSize = audioSize;
}
audioBufIndex = 0;
}
// 需要拷贝的音频数据大小
int cpSize = audioBufSize - audioBufIndex;
if (lenRemain < cpSize) {
cpSize = lenRemain;
}
// 拷贝数据,并更新缓冲区相关信息
std::memcpy(stream, (uint8_t *)audioBuf + audioBufIndex, cpSize);
audioBufIndex += cpSize;
stream += cpSize;
lenRemain -= cpSize;
}
}
// 视频解码线程
void video_thread(VideoState *is) {
AVFrame *frame = av_frame_alloc();
while (!is->quit) {
AVPacket *pkt = is->video_pkt_queue.pop();
if (pkt == nullptr) {
break;
}
// 解码视频帧
int ret = avcodec_send_packet(is->video_codec_ctx, pkt);
if (ret < 0) {
std::cout << "error: avcodec_send_packet() failed" << std::endl;
av_packet_free(&pkt);
goto fail;
}
ret = avcodec_receive_frame(is->video_codec_ctx, frame);
if (ret == 0) {
VideoPicture vp;
vp.width = is->video_codec_ctx->width;
vp.height = is->video_codec_ctx->height;
std::unique_lock lock(screen_mutex);
// YV12 SDL_Overlay
vp.bmp = SDL_CreateYUVOverlay(is->video_codec_ctx->width,
is->video_codec_ctx->height,
SDL_YV12_OVERLAY, screen);
lock.unlock();
SDL_LockYUVOverlay(vp.bmp);
// YV12 和 YUV420P 格式区别,UV分量顺序不同
// https://blog.csdn.net/dss875914213/article/details/120836765
AVFrame frameDst;
frameDst.data[0] = vp.bmp->pixels[0];
frameDst.data[1] = vp.bmp->pixels[2];
frameDst.data[2] = vp.bmp->pixels[1];
frameDst.linesize[0] = vp.bmp->pitches[0];
frameDst.linesize[1] = vp.bmp->pitches[2];
frameDst.linesize[2] = vp.bmp->pitches[1];
// 执行像素格式转换
sws_scale(is->sws_ctx, frame->data, frame->linesize, 0,
is->video_codec_ctx->height, frameDst.data, frameDst.linesize);
SDL_UnlockYUVOverlay(vp.bmp);
is->picture_queue.push(vp);
}
av_packet_free(&pkt);
}
fail:
SDL_Event event;
event.type = FF_QUIT_EVENT;
event.user.data1 = is;
SDL_PushEvent(&event);
av_frame_free(&frame);
}
bool stream_component_open(VideoState *is, int stream_index) {
if (stream_index < 0 || stream_index >= (int)is->format_ctx->nb_streams) {
return false;
}
// 获取解码器
const AVCodec *codec = avcodec_find_decoder(
is->format_ctx->streams[stream_index]->codecpar->codec_id);
if (!codec) {
std::cout << "error: Unsupported codec" << std::endl;
goto fail;
}
// 创建解码器上下文
AVCodecContext *codec_ctx = avcodec_alloc_context3(codec);
if (!codec_ctx) {
std::cout << "error: avcodec_alloc_context3() failed" << std::endl;
goto fail;
}
int ret = avcodec_parameters_to_context(
codec_ctx, is->format_ctx->streams[stream_index]->codecpar);
if (ret < 0) {
std::cout << "error: avcodec_parameters_to_context() failed" << std::endl;
goto fail;
}
ret = avcodec_open2(codec_ctx, codec, nullptr);
if (ret < 0) {
std::cout << "error: avcodec_open2() failed" << std::endl;
goto fail;
}
switch (codec_ctx->codec_type) {
case AVMEDIA_TYPE_AUDIO:
is->audio_stream = is->format_ctx->streams[stream_index];
is->audio_codec_ctx = codec_ctx;
AVChannelLayout outChLayout;
AVChannelLayout inChLayout;
av_channel_layout_default(&outChLayout, 2);
av_channel_layout_default(&inChLayout, codec_ctx->ch_layout.nb_channels);
// 创建音频重采样上下文
ret = swr_alloc_set_opts2(
&is->swr_ctx, &outChLayout, AV_SAMPLE_FMT_S16, codec_ctx->sample_rate,
&inChLayout, codec_ctx->sample_fmt, codec_ctx->sample_rate, 0, nullptr);
if (ret < 0) {
goto fail;
}
swr_init(is->swr_ctx);
SDL_AudioSpec wanted_spec, spec;
wanted_spec.freq = codec_ctx->sample_rate;
wanted_spec.format = AUDIO_S16SYS;
wanted_spec.channels = 2;
wanted_spec.silence = 0;
wanted_spec.samples = 1024;
wanted_spec.callback = audio_callback;
wanted_spec.userdata = is;
if (SDL_OpenAudio(&wanted_spec, &spec) < 0) {
std::cout << "error: SDL_OpenAudio() failed, " << SDL_GetError()
<< std::endl;
goto fail;
}
SDL_PauseAudio(0);
break;
case AVMEDIA_TYPE_VIDEO:
is->video_stream = is->format_ctx->streams[stream_index];
is->video_codec_ctx = codec_ctx;
is->video_thread = std::make_shared<std::thread>(video_thread, is);
is->sws_ctx =
sws_getContext(is->video_codec_ctx->width, is->video_codec_ctx->height,
is->video_codec_ctx->pix_fmt, is->video_codec_ctx->width,
is->video_codec_ctx->height, AV_PIX_FMT_YUV420P,
SWS_BILINEAR, NULL, NULL, NULL);
break;
default:
break;
}
return true;
fail:
avcodec_free_context(&codec_ctx);
return false;
}
void demux_thread(VideoState *is) {
// 打开文件
int ret = avformat_open_input(&is->format_ctx, is->filename.c_str(), nullptr,
nullptr);
if (ret < 0) {
std::cout << "error: avformat_open_input() failed" << std::endl;
goto fail;
}
ret = avformat_find_stream_info(is->format_ctx, nullptr);
if (ret < 0) {
std::cout << "error: avformat_find_stream_info() failed" << std::endl;
goto fail;
}
av_dump_format(is->format_ctx, 0, is->filename.c_str(), 0);
// 查找视频流、音频流
for (uint32_t i = 0; i < is->format_ctx->nb_streams; ++i) {
if (is->format_ctx->streams[i]->codecpar->codec_type ==
AVMEDIA_TYPE_VIDEO &&
is->video_stream_index < 0) {
is->video_stream_index = i;
} else if (is->format_ctx->streams[i]->codecpar->codec_type ==
AVMEDIA_TYPE_AUDIO &&
is->audio_stream_index < 0) {
is->audio_stream_index = i;
}
}
if (is->video_stream_index == -1) {
std::cout << "error: Didn't find a video stream";
goto fail;
}
if (is->audio_stream_index == -1) {
std::cout << "error: Didn't find a audio stream";
goto fail;
}
if (is->video_stream_index >= 0) {
if (!stream_component_open(is, is->video_stream_index)) {
std::cout << "error: video stream_component_open() failed";
goto fail;
}
}
if (is->audio_stream_index >= 0) {
if (!stream_component_open(is, is->audio_stream_index)) {
std::cout << "error: audio stream_component_open() failed";
goto fail;
}
}
AVPacket *packet = av_packet_alloc();
// 循环读取 packet 放到音视频对应的队列中
while (true) {
if (is->quit) {
break;
}
if (is->audio_pkt_queue.size() >= MAX_AUDIO_QUEUE_SIZE ||
is->video_pkt_queue.size() >= MAX_VIDEO_QUEUE_SIZE) {
SDL_Delay(10);
continue;
}
if (av_read_frame(is->format_ctx, packet) < 0) {
break;
}
if (packet->stream_index == is->video_stream_index) {
is->video_pkt_queue.push(av_packet_clone(packet));
} else if (packet->stream_index == is->audio_stream_index) {
is->audio_pkt_queue.push(av_packet_clone(packet));
}
av_packet_unref(packet);
}
fail:
SDL_Event event;
event.type = FF_QUIT_EVENT;
event.user.data1 = is;
SDL_PushEvent(&event);
av_packet_free(&packet);
}
// Spawning Threads
int main(int argc, char *argv[]) {
VideoState is;
// 取命令行参数获取文件名
std::string filename;
if (argc > 1) {
filename = argv[1];
} else {
filename = "C:/Users/zhou/Videos/bigbuckbunny.mp4";
}
// 初始化SDL
if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER) < 0) {
std::cout << "error: Could not initialize SDL - " << SDL_GetError()
<< std::endl;
goto fail;
}
// 创建 SDL_Surface
screen = SDL_SetVideoMode(800, 600, 0, 0);
if (!screen) {
std::cout << "error: SDL: could not set video mode" << std::endl;
goto fail;
}
is.filename = filename;
// 启动解复用线程
is.demux_thread = std::make_shared<std::thread>(demux_thread, &is);
schedule_refresh(&is, 40);
while (true) {
SDL_Event event;
SDL_WaitEvent(&event);
switch (event.type) {
case FF_QUIT_EVENT:
case SDL_QUIT:
is.quit = true;
break;
case FF_REFRESH_EVENT:
// 将视频帧刷新到SDL窗口
video_refresh_timer(event.user.data1);
break;
default:
break;
}
if (is.quit) {
break;
}
}
fail:
SDL_FreeSurface(screen);
SDL_Quit();
avcodec_free_context(&is.audio_codec_ctx);
avcodec_free_context(&is.video_codec_ctx);
sws_freeContext(is.sws_ctx);
swr_free(&is.swr_ctx);
avformat_free_context(is.format_ctx);
is.audio_pkt_queue.notify_all();
is.video_pkt_queue.notify_all();
is.picture_queue.notify_all();
is.video_thread->join();
is.demux_thread->join();
return 0;
}
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