ffmpeg playback with c++

player.cpp

#include "player.h"

using namespace std;

void data_callback(ma_device* pDevice, void* pOutput, const void* pInput, ma_uint32 frameCount) {
	AVAudioFifo* fifo = reinterpret_cast<AVAudioFifo*>(pDevice->pUserData);
	av_audio_fifo_read(fifo, &pOutput, frameCount);

	(void) pInput;
}

int main(int argc, char* argv[])
{
	if (argc < 2) {
		cerr << "没有文件" << endl;
		return -1;
	}

	// 打开文件
	cout << "打开文件" << endl;
	AVFormatContext* fmt_ctx{ nullptr };
	int ret = avformat_open_input(&fmt_ctx, argv[1], nullptr, nullptr);
	if (ret < 0) {
		cerr << "打不开文件" << endl;
		return -1;
	}

	cout << "找音视频流" << endl;
	ret = avformat_find_stream_info(fmt_ctx, nullptr);
	if (ret < 0) {
		cerr << "文件里没有音视频流" << endl;
		return -1;
	}

	cout << "文件里面有 " << fmt_ctx->nb_streams << " 条音视频流" << endl;

	cout << "找音轨" << endl;
	int index = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, nullptr, 0);
	if (index < 0) {
		cerr << "没有音轨" << endl;
		return -1;
	}

	AVStream* stream = fmt_ctx->streams[index];

	cout << "找对应的解码器" << endl;
	const AVCodec* decoder = avcodec_find_decoder(stream->codecpar->codec_id);
	if (!decoder) {
		cerr << "没有解码器" << endl;
		return -1;
	}

	cout << "创建解码器" << endl;
	AVCodecContext* codec_ctx{ avcodec_alloc_context3(decoder) };
	avcodec_parameters_to_context(codec_ctx, stream->codecpar);

	ret = avcodec_open2(codec_ctx, decoder, nullptr);
	if (ret < 0) {
		cerr << "解码器创建失败" << endl;
		return -1;
	}

	// 解码
	AVPacket* packet = av_packet_alloc();
	AVFrame* frame = av_frame_alloc();

	AVCodecParameters* codec_par = stream->codecpar;
	SwrContext* resampler{swr_alloc_set_opts(nullptr, codec_par->channel_layout, AV_SAMPLE_FMT_FLT,
		codec_par->sample_rate, codec_par->channel_layout, (AVSampleFormat) codec_par->format,
		codec_par->sample_rate, 0, nullptr)};

	AVAudioFifo* fifo = av_audio_fifo_alloc(AV_SAMPLE_FMT_FLT, codec_par->channels, 1);

	while (av_read_frame(fmt_ctx, packet) == 0) {
		if (packet->stream_index != stream->index) {
			continue;
		}
		cout << "将音频帧放进解码队列" << endl;
		ret = avcodec_send_packet(codec_ctx, packet);
		if (ret < 0) {
			if (ret != AVERROR(EAGAIN)) {
				cerr << "炸了" << endl;
			}
		}

		while ((ret = avcodec_receive_frame(codec_ctx, frame)) == 0) {
			cout << "从解码队列中取出解码结果" << endl;
			if (ret < 0) {
				if (ret == AVERROR(AVERROR_EOF)) {
					// 放完了
					break;
				}
				// 其他问题
				break;
			}

			cout << "重采样PCM转成所需要的格式" << endl;
			AVFrame* resampled_frame = av_frame_alloc();
			resampled_frame->sample_rate = frame->sample_rate;
			resampled_frame->channel_layout = frame->channel_layout;
			resampled_frame->channels = frame->channels;
			resampled_frame->format = AV_SAMPLE_FMT_FLT;

			ret = swr_convert_frame(resampler, resampled_frame, frame);

			cout << "写进FIFO队列" << endl;
			av_frame_unref(frame);
			av_audio_fifo_write(fifo, (void**)resampled_frame->data, resampled_frame->nb_samples);
			av_frame_free(&resampled_frame);
		}
	}

	// 播放
	ma_device_config deviceConfig;
	ma_device device;

	ma_backend backends[] = {
		ma_backend_wasapi
	};

	deviceConfig = ma_device_config_init(ma_device_type_playback);
	deviceConfig.playback.format = ma_format_f32;
	deviceConfig.playback.channels = codec_par->channels;
	deviceConfig.sampleRate = codec_par->sample_rate;
	deviceConfig.dataCallback = data_callback;
	deviceConfig.pUserData = fifo;

	cout << "释放FFMPEG内存" << endl;
	avformat_close_input(&fmt_ctx);
	av_frame_free(&frame);
	av_packet_free(&packet);
	avcodec_free_context(&codec_ctx);
	swr_free(&resampler);

	cout << "初始化音频设备" << endl;
	if (ma_device_init_ex(backends, sizeof(backends) / sizeof(backends[0]), NULL, &deviceConfig, &device) != MA_SUCCESS) {
		cerr << "无法初始化音频设备" << endl;
		return -1;
	}

	cout << "打开音频设备" << endl;
	if (ma_device_start(&device) != MA_SUCCESS) {
		cerr << "音频设备打开失败" << endl;
		ma_device_uninit(&device);
		return -1;
	}

	while (av_audio_fifo_size(fifo));
	
	cout << "释放FIFO队列内存" << endl;
	av_audio_fifo_free(fifo);
	cout << "关闭音频设备" << endl;
	ma_device_uninit(&device);

	getchar();

	return 0;
}

player.h

#pragma once

#include <iostream>

extern "C" {
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavutil/avutil.h>
#include <libavutil/audio_fifo.h>
#include <libswresample/swresample.h>
}

#define MINIAUDIO_IMPLEMENTATION
#include "miniaudio.h"