播放mp3原始音频数据而不写入文件

#include <iostream>
#include <fstream>
#include <SDL2/SDL.h>
#include <SDL2/SDL_audio.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>

// 回调函数，用于向音频设备提供音频数据
void audio_callback(void* userdata, Uint8* stream, int len) {
    AVPacket packet;
    AVCodecContext* codec_ctx = (AVCodecContext*)userdata;
    int audio_size = 0;
    static uint8_t audio_buf[(AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) / 2];
    static unsigned int audio_buf_size = 0;
    static unsigned int audio_buf_index = 0;

    while (len > 0) {
        if (audio_buf_index >= audio_buf_size) {
            // 读取下一个音频帧
            if (av_read_frame(format_ctx, &packet) < 0) {
                break;
            }

            // 解码音频帧
            int ret = avcodec_send_packet(codec_ctx, &packet);
            if (ret < 0) {
                break;
            }

            while (ret >= 0) {
                ret = avcodec_receive_frame(codec_ctx, frame);
                if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
                    break;
                } else if (ret < 0) {
                    break;
                }

                // 将解码后的音频数据拷贝到缓冲区
                int data_size = av_samples_get_buffer_size(NULL, codec_ctx->channels, frame->nb_samples, codec_ctx->sample_fmt, 1);
                memcpy(audio_buf, frame->data[0], data_size);
                audio_buf_size = data_size;
                audio_buf_index = 0;
            }

            av_packet_unref(&packet);
        }

        // 将音频数据拷贝到音频设备的缓冲区
        int remaining = audio_buf_size - audio_buf_index;
        int to_copy = len > remaining ? remaining : len;
        memcpy(stream, audio_buf + audio_buf_index, to_copy);
        len -= to_copy;
        stream += to_copy;
        audio_buf_index += to_copy;
    }
}

int main() {
    // 初始化FFmpeg和SDL
    av_register_all();
    avformat_network_init();
    SDL_Init(SDL_INIT_AUDIO);

    // 打开mp3文件
    AVFormatContext* format_ctx = avformat_alloc_context();
    if (avformat_open_input(&format_ctx, "input.mp3", NULL, NULL) != 0) {
        std::cerr << "Failed to open input file" << std::endl;
        return -1;
    }

    // 查找音频流信息
    if (avformat_find_stream_info(format_ctx, NULL) < 0) {
        std::cerr << "Failed to find stream information" << std::endl;
        return -1;
    }

    // 查找音频解码器
    AVCodec* codec = NULL;
    int audio_stream_index = av_find_best_stream(format_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &codec, 0);
    if (audio_stream_index < 0) {
        std::cerr << "Failed to find audio stream" << std::endl;
        return -1;
    }

    // 创建音频解码器上下文
    AVCodecContext* codec_ctx = avcodec_alloc_context3(codec);
    if (avcodec_parameters_to_context(codec_ctx, format_ctx->streams[audio_stream_index]->codecpar) < 0) {
        std::cerr << "Failed to copy codec parameters to codec context" << std::endl;
        return -1;
    }

    // 打开音频解码器
    if (avcodec_open2(codec_ctx, codec, NULL) < 0) {
        std::cerr << "Failed to open audio codec" << std::endl;
        return -1;
    }

    // 创建音频设备参数
    SDL_AudioSpec wanted_spec, obtained_spec;
    wanted_spec.freq = codec_ctx->sample_rate;
    wanted_spec.format = AUDIO_S16SYS;
    wanted_spec.channels = codec_ctx->channels;
    wanted_spec.silence = 0;
    wanted_spec.samples = 1024;
    wanted_spec.callback = audio_callback;
    wanted_spec.userdata = codec_ctx;

    // 打开音频设备
    if (SDL_OpenAudio(&wanted_spec, &obtained_spec) < 0) {
        std::cerr << "Failed to open audio device" << std::endl;
        return -1;
    }

    // 开始播放音频
    SDL_PauseAudio(0);

    // 等待音频播放完成
    while (audio_buf_index < audio_buf_size) {
        SDL_Delay(100);
    }

    // 关闭音频设备
    SDL_CloseAudio();

    // 释放资源
    avcodec_free_context(&codec_ctx);
    avformat_close_input(&format_ctx);
    avformat_free_context(format_ctx);
    SDL_Quit();

    return 0;
}