ffmpeg-音频编码

简单记录一下个人做语音聊天时使用的ffmpeg音频编码。

我们可以

1.使用ffmpeg将PCM编码得到想要的格式的数据输出到内存中，然后自己实现流媒体协议或者使用自己的RPC。

2.使用ffmpeg的avio_open直接推流,ffmpeg帮我们实现了http rtmp rtp 协议。

简单说下编码输出到内存的流程：

编码并推流的流程：

直接上代码

#ifndef _IEncode_H#define _IEncode_H#include "util.h"extern "C" {#include <libavcodec/avcodec.h>#include <libavformat/avformat.h>#include <libavutil/opt.h>};struct AudioParams {int sampleRate;int channels;enum AVSampleFormat fmt;long long bitRate;AVCodecID id;int64_t channel_layout;AudioParams() : sampleRate(-1), channels(-1), channel_layout(-1),fmt(AVSampleFormat::AV_SAMPLE_FMT_NONE), bitRate(-1),id(AVCodecID::AV_CODEC_ID_NONE){}AudioParams(const AudioParams& audioParams){*this = audioParams;}AudioParams& operator=(const AudioParams& audioParams){this->sampleRate = audioParams.sampleRate;this->channels = audioParams.channels;this->fmt = audioParams.fmt;this->bitRate = audioParams.bitRate;this->id = audioParams.id;this->channel_layout = audioParams.channel_layout;return *this;}};class IEncode{public:explicit IEncode();virtual int init() = 0;int inputData(uint8_t* data, size_t size);int getNextOutPacketData(bool &hasData);int getBufSize() const;AudioParams getAudioParams()const;virtual ~IEncode();protected:AudioParams audioParams;AVCodec* codec;AVCodecContext* ctx;AVFrame *frame;void *samples;int bufferSize;AVPacket avpkt;AVStream *out_stream;void setFrameParam(AVFrame *frame, AVCodecContext* ctx);virtual void release() = 0;virtual int writeFrame(AVPacket avpkt) = 0;};#endif // !_IEncode_H

#ifndef _IEncode_MEM_H#define _IEncode_MEM_H#include "IEncode.h"class IEncode_mem : public IEncode{public:typedef void(*writeOutDataFunc)(void *opaque, uint8_t *buf, int buf_size);public:explicit IEncode_mem();int init() override;void setAudioParams(const AudioParams& audioParams);void setWritePacketFuncCB(writeOutDataFunc func);void setOutputObj(void *outObj);~IEncode_mem();private:void* outObj;writeOutDataFunc writeData;int checkParams()const;int checkCodec(AVCodecID id)const;int checkSampleFmt(AVCodec *codec, enum AVSampleFormat sample_fmt)const;int writeFrame(AVPacket avpkt) override;void release() override;};#endif // !_IEncode_MEM_H

#ifndef _IEncode_URL_H#define _IEncode_URL_H#include "IEncode.h"#include <string>class IEncode_url : public IEncode{public:explicit IEncode_url();int init() override;void setUrl(const std::string& url);~IEncode_url();private:AVOutputFormat *ofmt;AVFormatContext *ofmtCtx;AVFormatContext *ifmtCtx;std::string url;int frameIndex;AVRational time_base1;private:void timeOffset(AVPacket& pkt);void close();void release() override;int writeFrame(AVPacket avpkt) override;};#endif // !_IEncode_URL_H

#include "IEncode.h"#include "error.h"#include "log.h"IEncode::IEncode() :codec(nullptr), ctx(nullptr),samples(nullptr), bufferSize(0),frame(nullptr), out_stream(nullptr){}IEncode::~IEncode(){codec = nullptr;ctx = nullptr;samples = nullptr;frame = nullptr;bufferSize = 0;}void IEncode::setFrameParam(AVFrame *frame, AVCodecContext* ctx){frame->nb_samples = ctx->frame_size;frame->format = ctx->sample_fmt;frame->channel_layout = ctx->channel_layout;}int IEncode::getBufSize() const{return bufferSize;}int IEncode::inputData(uint8_t* data, size_t size){if (data == nullptr)return Error::ERROR_INPUT_NULL_DATA;int got_output = 0;av_init_packet(&avpkt);avpkt.data = NULL;avpkt.size = 0;memcpy(samples, data, size);int ret = avcodec_encode_audio2(ctx, &avpkt, frame, &got_output);if (ret < 0){release();return Error::ERROR_ENCODEING_FRAME;}if (got_output){Error error = Error::ERROR_NONE;if (writeFrame(avpkt) < 0){error = Error::ERROR_WRITE_FRAME;}av_packet_unref(&avpkt);return error;}return Error::ERROR_NONE;}int IEncode::getNextOutPacketData(bool &hasData){int count = 0;hasData = false;int fog_frame = 0;int ret = avcodec_encode_audio2(ctx, &avpkt, nullptr, &fog_frame);if (ret < 0){release();hasData = false;return Error::ERROR_ENCODEING_FRAME;}if (fog_frame){Error error = Error::ERROR_NONE;hasData = true;if (writeFrame(avpkt) < 0) {error = Error::ERROR_WRITE_FRAME;}av_packet_unref(&avpkt);return error;}return Error::ERROR_NONE;}AudioParams IEncode::getAudioParams()const{return audioParams;}

#include "IEncode_mem.h"#include "error.h"#include "log.h"IEncode_mem::IEncode_mem():outObj(nullptr), writeData(nullptr){}IEncode_mem::~IEncode_mem(){release();}int IEncode_mem::init(){Error error = (Error)checkParams();if (Error::ERROR_NONE != error)return error;codec = avcodec_find_encoder(audioParams.id);if (!codec)return Error::ERROR_NO_CODEC_SUPPORT;ctx = avcodec_alloc_context3(codec);if (!ctx)return Error::ERROR_AVCODEC_CONTEXT;ctx->bit_rate = audioParams.bitRate;ctx->sample_fmt = audioParams.fmt;ctx->sample_rate = audioParams.sampleRate;ctx->channels = audioParams.channels;ctx->channel_layout = audioParams.channel_layout;if (avcodec_open2(ctx, codec, NULL) < 0)return Error::ERROR_OPEN_CODEC;frame = av_frame_alloc();if (!frame){avcodec_close(ctx);av_free(ctx);return Error::ERROR_FRAME_ALLOCATE;}setFrameParam(frame, ctx);bufferSize = av_samples_get_buffer_size(NULL,ctx->channels,ctx->frame_size,ctx->sample_fmt,0);if (bufferSize < 0){av_frame_free(&frame);avcodec_close(ctx);av_free(ctx);return Error::ERROR_CANT_GET_BUFF_SIZE;}samples = av_malloc(bufferSize);if (!samples){av_frame_free(&frame);avcodec_close(ctx);av_free(ctx);return Error::ERROR_ALLOCATE_SAMPLES_BUF;}int ret = avcodec_fill_audio_frame(frame, ctx->channels, ctx->sample_fmt,(const uint8_t*)samples, bufferSize, 0);if (ret < 0){release();return Error::ERROR_SETUP_FRAME;}return Error::ERROR_NONE;}int IEncode_mem::writeFrame(AVPacket avpkt){if (writeData)writeData(outObj, avpkt.data, avpkt.size);return 0;}void IEncode_mem::setWritePacketFuncCB(writeOutDataFunc func){this->writeData = func;}void IEncode_mem::setOutputObj(void *outObj){this->outObj = outObj;}void IEncode_mem::setAudioParams(const AudioParams& audioParams){this->audioParams = audioParams;}int IEncode_mem::checkParams() const{Error error = (Error)checkCodec(audioParams.id);if (Error::ERROR_NONE != error)return error;error = (Error)checkSampleFmt(avcodec_find_encoder(audioParams.id), audioParams.fmt);if (Error::ERROR_NONE != error)return error;return error;}int IEncode_mem::checkCodec(AVCodecID id)const{AVCodec *codec = avcodec_find_encoder(id);if (!codec){return Error::ERROR_NO_CODEC_SUPPORT;}return Error::ERROR_NONE;}int IEncode_mem::checkSampleFmt(AVCodec *codec, enum AVSampleFormat sample_fmt)const{const enum AVSampleFormat *p = codec->sample_fmts;while (*p != AV_SAMPLE_FMT_NONE){if (*p == sample_fmt)return Error::ERROR_NONE;p++;}return Error::ERROR_SAMPLEFMT;}void IEncode_mem::release(){if (samples)av_freep(&samples);if (frame)av_frame_free(&frame);if (ctx){avcodec_close(ctx);av_free(ctx);}}

#include "IEncode_url.h"#include "error.h"#include "log.h"IEncode_url::IEncode_url() :url(""),frameIndex(0),ofmt(nullptr), ofmtCtx(nullptr), ifmtCtx(nullptr){}IEncode_url::~IEncode_url(){close();frameIndex = 0;}int IEncode_url::init(){int ret = 0;ret = avformat_open_input(&ifmtCtx, url.c_str(), nullptr, nullptr);if (ret < 0){ifmtCtx = nullptr;return Error::ERROR_FORMAT_OPEN_INPUT;}if (0 > avformat_alloc_output_context2(&ofmtCtx, nullptr, nullptr, url.c_str())){release();return Error::ERROR_ENCODE_URL;}ofmt = ofmtCtx->oformat;AVStream *in_stream = nullptr;for (unsigned int i = 0; i < ifmtCtx->nb_streams; i++){in_stream = ifmtCtx->streams[i];audioParams.sampleRate = in_stream->codecpar->sample_rate;audioParams.bitRate = in_stream->codecpar->bit_rate;audioParams.fmt = AV_SAMPLE_FMT_FLTP;audioParams.id = in_stream->codecpar->codec_id;audioParams.channels = in_stream->codecpar->channels;time_base1 = in_stream->time_base;out_stream = avformat_new_stream(ofmtCtx, in_stream->codec->codec);if (!out_stream){release();return Error::ERROR_ALLOCATE_STREAM;}ret = avcodec_copy_context(out_stream->codec, in_stream->codec);if (ret < 0){release();return Error::ERROR_COPY_CONTEXT;}out_stream->codec->codec_tag = 0;if (ofmtCtx->oformat->flags & AVFMT_GLOBALHEADER)out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;}ctx = out_stream->codec;avformat_close_input(&ifmtCtx);if (!(ofmt->flags & AVFMT_NOFILE)){ret = avio_open(&ofmtCtx->pb, url.c_str(), AVIO_FLAG_WRITE);if (ret < 0){release();return Error::ERROR_AVIO_OPEN;}}avformat_write_header(ofmtCtx, nullptr);ctx->sample_fmt = AV_SAMPLE_FMT_FLTP;codec = avcodec_find_encoder((AVCodecID)audioParams.id);av_opt_set(ctx->priv_data, "tune", "zerolatency", 0);if (!codec){release();return Error::ERROR_NO_CODEC_SUPPORT;}if (avcodec_open2(ctx, codec, NULL) < 0){release();return Error::ERROR_OPEN_CODEC;}frame = av_frame_alloc();if (!frame){release();return Error::ERROR_FRAME_ALLOCATE;}setFrameParam(frame, ctx);bufferSize = av_samples_get_buffer_size(NULL,ctx->channels,ctx->frame_size,ctx->sample_fmt,0);if (bufferSize < 0){release();return Error::ERROR_CANT_GET_BUFF_SIZE;}samples = av_malloc(bufferSize);if (!samples){release();return Error::ERROR_ALLOCATE_SAMPLES_BUF;}ret = avcodec_fill_audio_frame(frame, ctx->channels, ctx->sample_fmt,(const uint8_t*)samples, bufferSize, 0);if (ret < 0){release();return Error::ERROR_SETUP_FRAME;}return Error::ERROR_NONE;}int IEncode_url::writeFrame(AVPacket avpkt){timeOffset(avpkt);return av_write_frame(ofmtCtx, &avpkt);}void IEncode_url::setUrl(const std::string& url){this->url = url;}void IEncode_url::timeOffset(AVPacket& avpkt){avpkt.pts = av_rescale_q((frameIndex++)*frame->nb_samples, AVRational{ 1, ctx->sample_rate }, ctx->time_base);avpkt.dts = avpkt.pts;avpkt.pos = -1;}void IEncode_url::close(){if (ofmtCtx){av_write_trailer(ofmtCtx);}release();}void IEncode_url::release(){if (ifmtCtx){avformat_close_input(&ifmtCtx);}if (ofmtCtx){avformat_close_input(&ofmtCtx);}if (samples){av_freep(&samples);}if (frame){av_frame_free(&frame);}}

这里我做了去掉延迟的处理：

av_opt_set(ctx->priv_data, "tune", "zerolatency", 0);