1. 介绍

在提取音视频文件中音频的PCM数据时，使用avcodec_receive_frame()函数进行解码时，遇到了一些问题，代码在Visual Studio 2022中运行结果符合预期，但是在CLion中运行时，获取的AVFrame有错误，和VS中获得的结果不一样。

FFMpeg 5.1.2

2. 源码

1. Utils.h

#pragma once#define _CRT_SECURE_NO_WARNINGSextern "C" {
#include <libavutil/error.h>
}static char* wrap_av_err2str(int errnum) {static char str[256] = {0};return av_make_error_string(str, sizeof(str), errnum);
}

2. AudioDecoder2.h

#pragma onceextern "C"
{
#include "libavutil/log.h"
#include "libavutil/imgutils.h"
#include "libavutil/samplefmt.h"
#include "libavutil/timestamp.h"
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
};
#include "Utils.h"
#include <cinttypes>class AudioDecoder2
{
public:AudioDecoder2();AudioDecoder2(const char* src_filename, const char* dst_filename);~AudioDecoder2();int start();private:int ret;char src_filename[256];char dst_filename[256];FILE* dst_fd = NULL;AVFormatContext* ifmt_ctx = NULL;AVCodecContext* audio_dec_ctx = NULL;const AVCodec* audio_dec = NULL;AVStream* audio_stream = NULL;int audio_stream_index = -1;AVFrame* frame = NULL;AVPacket* packet = NULL;
};

3. AudioDecoder2.cpp

#include "AudioDecoder2.h"AudioDecoder2::AudioDecoder2(const char* src_filename, const char* dst_filename) {sscanf(src_filename, "%s", this->src_filename);sscanf(dst_filename, "%s", this->dst_filename);
}int AudioDecoder2::start() {// 设置日志输出级别av_log_set_level(AV_LOG_INFO);// 打开输入文件ret = avformat_open_input(&ifmt_ctx, src_filename, NULL, NULL);if (ret < 0){av_log(NULL, AV_LOG_ERROR, "Can't open source file:%s\n", wrap_av_err2str(ret));return -1;}// 读取一部分数据获得一些相关信息ret = avformat_find_stream_info(ifmt_ctx, NULL);if (ret < 0){av_log(NULL, AV_LOG_ERROR, "Failed to find stream information: %s\n", wrap_av_err2str(ret));return -1;}// 查找流audio_stream_index = -1;audio_stream_index = av_find_best_stream(ifmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, NULL, 0);if (audio_stream_index < 0){av_log(NULL, AV_LOG_DEBUG, "Failed to find the best audio stream!\n");return AVERROR(EINVAL);}// 获取流audio_stream = ifmt_ctx->streams[audio_stream_index];// 通过数据流查找对应的解码器audio_dec = avcodec_find_decoder(audio_stream->codecpar->codec_id);if (audio_dec == NULL){av_log(NULL, AV_LOG_ERROR, "Failed to find codec.\n");return AVERROR(EINVAL);}// 创建解码器上下文audio_dec_ctx = avcodec_alloc_context3(audio_dec);if (audio_dec_ctx == NULL){av_log(NULL, AV_LOG_ERROR, "Failed to allocate the codec context.\n");return AVERROR(ENOMEM);}// 从输入流中拷贝对应的参数到解码器中ret = avcodec_parameters_to_context(audio_dec_ctx, audio_stream->codecpar);if (ret < 0){av_log(NULL, AV_LOG_ERROR, "Failed to copy codec parameters to decoder context.\n");return ret;}// 打开解码器ret = avcodec_open2(audio_dec_ctx, audio_dec, NULL);if (ret < 0){av_log(NULL, AV_LOG_ERROR, "Failed to open codec.\n");return ret;}// 创建输出文件dst_fd = fopen(dst_filename, "wb");if (!dst_fd){av_log(NULL, AV_LOG_ERROR, "Could not open destination file %s\n", dst_filename);return -1;}// 分配帧frame = av_frame_alloc();if (frame == NULL){av_log(NULL, AV_LOG_ERROR, "Failed to allocate frame.\n");return AVERROR(ENOMEM);}// 分配数据包packet = av_packet_alloc();if (packet == NULL){av_log(NULL, AV_LOG_ERROR, "Failed to allocate packet.\n");return AVERROR(ENOMEM);}// 读取音频流的数据包，并解码while (av_read_frame(ifmt_ctx, packet) >= 0){if (packet->stream_index == audio_stream_index){ret = avcodec_send_packet(audio_dec_ctx, packet);if (ret < 0){av_log(NULL, AV_LOG_ERROR, "Failed to decode packet.\n");return ret;}// 对数据进行解码输出while (ret >= 0){ret = avcodec_receive_frame(audio_dec_ctx, frame);if (ret < 0){if (ret == AVERROR_EOF || ret == AVERROR(EAGAIN)){break;}else{break;}}if (ret == 0){// 将内容输出到文件av_log(NULL, AV_LOG_INFO, "pts:%10" PRId64"\t packet size:%d\n",packet->pts, packet->size);size_t unpadded_linesize = frame->nb_samples * av_get_bytes_per_sample((enum AVSampleFormat)frame->format);fwrite(frame->extended_data[0], 1, unpadded_linesize, dst_fd);}av_frame_unref(frame);}}av_packet_unref(packet);}// 刷新解码器while (true){if (!(audio_dec->capabilities & AV_CODEC_CAP_DELAY)){return 0;}ret = avcodec_send_packet(audio_dec_ctx, packet);if (ret < 0){//            av_log(NULL, AV_LOG_ERROR, "Failed to decode packet.\n");//            return ret;break;}// 对数据进行解码输出while (ret >= 0){ret = avcodec_receive_frame(audio_dec_ctx, frame);if (ret < 0){if (ret == AVERROR_EOF || ret == AVERROR(EAGAIN)){break;}}// 将内容输出到文件size_t unpadded_linesize = frame->nb_samples * av_get_bytes_per_sample((enum AVSampleFormat)frame->format);fwrite(frame->extended_data[0], 1, unpadded_linesize, dst_fd);av_frame_unref(frame);}av_packet_unref(packet);}// 释放资源avcodec_free_context(&audio_dec_ctx);avformat_close_input(&ifmt_ctx);if (dst_fd){fclose(dst_fd);}av_packet_free(&packet);av_frame_free(&frame);return 0;
}

4. main.cpp

#include <iostream>
#include "AudioDecoder2.h"
using namespace std;int main(int argc, char** argv)
{char src_filename[20] = "ball_10s.mp4";char audio_dst_filename[20] = "ball_10s.pcm";AudioDecoder2* audioDecoder2 = new AudioDecoder2(src_filename, audio_dst_filename);audioDecoder2->start();return 0;
}

3. 问题

1. Visual Studio 2022调试结果

2. CLion中调试结果