ASP.NET 下载微信录音AMR文件，使用FFmpeg实现AMR转换MP3示例源码

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WeChatAudioUtils
{
    public class Program
    {
        public static void Main(string[] args)
        {
            // Token
            string access_token = "";
            
            // 音频id
            string media_id = "";
            
            // 请求URL
            string reqURL = $"https://api.weixin.qq.com/cgi-bin/media/get?access_token={access_token}&media_id={media_id}";

            // 本地测试转换amr文件路径
            //string downPath = Path.GetFullPath("../../download/132532654780617863.amr");

            // 下载字节流文件
            string downPath = AudioUtils.DownByteFile(reqURL);

            // 判断：文件下载状态，downPath不为空，则为下载成功
            if (!string.IsNullOrWhiteSpace(downPath))
            {
                // AMR文件保存路径
                Console.WriteLine("AMR：" + downPath);

                // MP3保存文件路径
                string mp3Path = Path.GetFullPath("../../download/" + DateTime.Now.ToFileTime() + ".mp3");

                // 音频转MP3状态
                bool isConvert = AudioUtils.ConvertToMp3(downPath, mp3Path);

                // 判断：文件转换状态
                if (isConvert)
                {
                    // MP3保存文件路径
                    Console.WriteLine("MP3：" + mp3Path);
                }
                else
                {
                    Console.WriteLine("转换失败！");
                }
            }
            else
            {
                Console.WriteLine("下载失败！");
            }

            Console.ReadKey();
        }


    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.IO;
using System.Net;
using System.Diagnostics;

namespace WeChatAudioUtils
{
    public class AudioUtils
    {
        /// <summary>
        /// 下载字节流文件
        /// </summary>
        public static string DownByteFile(string reqURL)
        {
            //初始化WebClient对象
            WebClient webClient = new WebClient();

            //获取文件字节流
            byte[] respData = webClient.DownloadData(reqURL);

            //保存文件路径
            string savePath = Path.GetFullPath("../../download/" + DateTime.Now.ToFileTime() + ".amr");

            bool isDown = ConvertByteToFile(respData, savePath);
            if (isDown)
            {
                return savePath;
            }
            else
            {
                return "";
            }
        }

        /// <summary>
        /// 将字节流保存为文件
        /// </summary>
        /// <param name="readByte"></param>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static bool ConvertByteToFile(byte[] readByte, string fileName)
        {
            FileStream fileStream = null;
            try
            {
                fileStream = new FileStream(fileName, FileMode.OpenOrCreate);
                fileStream.Write(readByte, 0, readByte.Length);
            }
            catch
            {
                return false;
            }

            finally
            {
                if (fileStream != null)
                    fileStream.Close();
            }

            return true;

        }

        public static bool ConvertToMp3(string amrPath, string mp3Path)
        {
            string c = Path.GetFullPath("../../tools/ffmpeg/bin/") + @"ffmpeg.exe -i " + amrPath + " " + mp3Path;
            string output = "";
            RunCmd(c, out output);
            if (!string.IsNullOrEmpty(output))
            {
                if (File.Exists(mp3Path))
                    return true;
                else
                    return false;
            }
            else
                return false;
        }

        /// <summary>
        /// 执行Cmd命令
        /// </summary>
        private static void RunCmd(string cmd, out string output)
        {
            cmd = cmd.Trim().TrimEnd('&') + "&exit";
            using (Process p = new Process())
            {
                p.StartInfo.FileName = "cmd.exe";
                p.StartInfo.UseShellExecute = false;        //是否使用操作系统shell启动
                p.StartInfo.RedirectStandardInput = true;   //接受来自调用程序的输入信息
                p.StartInfo.RedirectStandardOutput = true;  //由调用程序获取输出信息
                p.StartInfo.RedirectStandardError = true;   //重定向标准错误输出
                p.StartInfo.CreateNoWindow = true;          //不显示程序窗口
                p.Start();//启动程序
                          //向cmd窗口写入命令
                p.StandardInput.WriteLine(cmd);
                p.StandardInput.AutoFlush = true;
                //获取cmd窗口的输出信息
                output = p.StandardOutput.ReadToEnd();
                p.WaitForExit();//等待程序执行完退出进程
                p.Close();
            }
        }
    }
}