FFmpeg过滤器框架分析-音频audio

最新推荐文章于 2024-12-18 23:00:21 发布

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最新推荐文章于 2024-12-18 23:00:21 发布

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#ffmpeg #音视频

音频过滤器框架同视频相似(可参考我的视频框架分析)，有一个小小不同是音频在出口过滤器abuffersink前还需要一个接收过滤器aformat。具体见代码。

下面是实例代码，输入2段音频，将音频混合起来。

AudioMixer.h文件

#pragma once
#include<map>
#include<mutex>
#include<cstdio>
#include<cstdint>
#include<string>
#include<memory>
#include<sstream>
#include<iostream>
#include<fstream>
extern "C" {
#include<libavcodec/avcodec.h>
#include<libavformat/avformat.h>
#include<libavfilter/avfilter.h>
#include<libavfilter/buffersink.h>
#include<libavfilter/buffersrc.h>
#include<libavutil/opt.h>
}

class AudioMixer
{
public:
	AudioMixer();
	virtual ~AudioMixer();

	int addAudioInput(uint32_t index, uint32_t samplerate, uint32_t channels,
		uint32_t bitsPerSample, AVSampleFormat format);

	int addAudioOutput(const uint32_t samplerate, const uint32_t channels,
		const uint32_t bitsPerSample, const AVSampleFormat format);

	int init(const char* duration = "longest");
	int exit();

	int addFrame(uint32_t index, uint8_t* inBuf, uint32_t size);
	int getFrame(uint8_t* outBuf, uint32_t maxOutBufSize);

private:

	struct AudioInfo
	{
		AudioInfo() {
			filterCtx = nullptr;
		}

		uint32_t samplerate;
		uint32_t channels;
		uint32_t bitsPerSample;
		AVSampleFormat format;
		std::string name;

		AVFilterContext* filterCtx;
	};

	bool initialized_ = false;
	std::mutex mutex_;
	std::map<uint32_t, AudioInfo> audio_input_info_;
	std::shared_ptr<AudioInfo> audio_out_info_;
	std::shared_ptr<AudioInfo> audio_mix_info_;
	std::shared_ptr<AudioInfo> audio_sink_info_;

	AVFilterGraph* filter_graph_ = nullptr;

};

AudioMixer.cpp文件

#include "AudioMixer.h"

AudioMixer::AudioMixer() :initialized_(false), filter_graph_(nullptr), audio_out_info_(nullptr)
{
    audio_mix_info_.reset(new AudioInfo);
    audio_mix_info_->name = "amix";

    audio_sink_info_.reset(new AudioInfo);
    audio_sink_info_->name = "sink";
}

AudioMixer::~AudioMixer()
{
    if (initialized_) {
        exit();
    }
}

int AudioMixer::addAudioInput(uint32_t index, uint32_t samplerate, uint32_t channels, 
    uint32_t bitsPerSample, AVSampleFormat format)
{
    std::lock_guard<std::mutex> locker(mutex_);

    if (initialized_) {
        return -1;
    }
    //判断是否存在当前输入
    if (audio_input_info_.find(index) != audio_input_info_.end()) {
        return -1;
    }
    //初始化输入，可以有多个输入流
    auto& filterInfo = audio_input_info_[index];
    filterInfo.samplerate = samplerate;
    filterInfo.channels = channels;
    filterInfo.bitsPerSample = bitsPerSample;
    filterInfo.format = format;
    filterInfo.name = std::string("input") + st