公司项目中一部分文件放到了阿里云 OSS 上，其中有些音频文件是 amr 类型的，在后期使用的时候比较麻烦，所以需要转换成 mp3 的文件，方便以后使用。本来想使用 ffmpeg 处理，但由于文件都存放在阿里云 OSS 上，使用 ffmpeg 就需要把文件从远程下载下来，转码之后再重新传回阿里云上，还需要使用消息组件进行通知，而且转码对服务器的压力也会很大。不如直接使用阿里云的媒体转码服务来的快，阿里云只提供了 OSS 的 DotNet 类库，并没有提供 MTS 的，所以只能自己参考 API 和其他语言的类库来开发，还好 MTS 的 API 并不是很复杂，几次尝试之后就搞定了。
相关参数需要从阿里云的控制台获取。
阿里云媒体转码服务类：
///
/// 阿里云媒体转码服务助手类。
///
public class MediaTranscodeHelper
{
private static readonly Encoding ENCODE_TYPE = Encoding.UTF8;
private static readonly string ALGORITHM = "HmacSHA1";
private static readonly string HTTP_METHOD = "GET";
private static readonly string SEPARATOR = "&";
private static readonly string EQUAL = "=";
private static readonly string ISO8601_DATE_FORMAT = "yyyy-MM-dd'T'HH:mm:ss'Z'";
private static readonly string RegionId = "cn-beijing";
private static readonly string Version = "2014-06-18";
private static readonly string Action = "SubmitJobs";
private static readonly string Format = "JSON";
private static readonly string MtsDomain = "mts.cn-beijing.aliyuncs.com";
private static readonly int MaxRetryNumber = 3;
private static readonly bool AutoRetry = true;
private static readonly int TimeoutInMilliSeconds = 100000;
private static readonly string AccessKeyId = "you AccessKeyId";
private static readonly string AccessKeySecret = "you AccessKeySecret";
private static readonly string PipelineId = "you PipelineId";
///
/// 提交转码任务。
///
/// 输入文件。
/// 输出文件。
public static string SubmitTranscodeJob(string inputFile, string ossLocation)
{
string outputJob = string.Empty;
return outputJob;
}
///
/// 提交转码任务。
///
public async Task<(bool success, string response)> SubmitTranscodeJob()
{
string SignatureNonce = Guid.NewGuid().ToString();
var paramers = new Dictionary
{
{ "Action", Action },
{ "Version", "2014-06-18" },
{ "AccessKeyId", AccessKeyId },
{ "Timestamp", FormatIso8601Date(DateTime.Now) },
{ "SignatureMethod", "HMAC-SHA1" },
{ "SignatureVersion", "1.0" },
{ "SignatureNonce", SignatureNonce },
{ "Format", Format },
{ "PipelineId", PipelineId },
{ "Input", "{\"Bucket\":\"charlesbeijng\",\"Location\":\"oss-cn-beijing\",\"Object\":\"3.amr\"}" },
{ "OutputBucket", "charlesbeijng" },
{ "OutputLocation", "oss-cn-beijing" },
{ "Outputs", " [{\"OutputObject\":\"" + Guid.NewGuid().ToString() + ".mp3\",\"TemplateId\":\"1a94dc364cec44708f00367938a0122f\",\"Location\":\"oss-cn-beijing\",\"WaterMarks\":[{\"InputFile\":{\"Bucket\":\"charlesbeijng\",\"Location\":\"oss-cn-beijing\",\"Object\":\"1.png\"},\"WaterMarkTemplateId\":\"c473de87d0504f44be7ebdac1667ab13\"}]}]" }
};
try
{
string url = GetSignUrl(paramers, AccessKeySecret);
int retryTimes = 1;
var reply = await HttpGetAsync(url);
while (500 <= reply.StatusCode && AutoRetry && retryTimes < MaxRetryNumber)
{
url = GetSignUrl(paramers, AccessKeySecret);
reply = await HttpGetAsync(url);
retryTimes++;
}
if (!string.IsNullOrEmpty(reply.response))
{
var res = JsonConvert.DeserializeObject>(reply.response);
if (res != null && res.ContainsKey("Code") && "OK".Equals(res["Code"]))
{
return (true, reply.response);
}
}
return (false, reply.response);
}
catch (Exception ex)
{
return (false, response: ex.Message);
}
}
///
/// 同步请求。
///
///
///
/// 异步请求。
///
///
///
/// 把响应流转换为文本。
///
/// 响应流对象
/// 编码方式
/// 响应文本
private static string GetResponseAsString(HttpWebResponse rsp, Encoding encoding)
{
StringBuilder result = new StringBuilder();
Stream stream = null;
StreamReader reader = null;
try
{
// 以字符流的方式读取HTTP响应
stream = rsp.GetResponseStream();
//rsp.Close();
reader = new StreamReader(stream, encoding);
// 每次读取不大于256个字符，并写入字符串
char[] buffer = new char[256];
int readBytes = 0;
while ((readBytes = reader.Read(buffer, 0, buffer.Length)) > 0)
{
result.Append(buffer, 0, readBytes);
}
}
catch (WebException webEx)
{
if (webEx.Status == WebExceptionStatus.Timeout)
{
result = new StringBuilder();
}
}
finally
{
// 释放资源
if (reader != null) reader.Close();
if (stream != null) stream.Close();
if (rsp != null) rsp.Close();
}
return result.ToString();
}
///
/// 处理消息。
///
/// 消息内容。
public static void HandlingMessage(string message)
{
}
///
///
///
///
///
/// 签名
///
public static string SignString(string source, string accessSecret)
{
using (var algorithm = new HMACSHA1(Encoding.UTF8.GetBytes(accessSecret.ToCharArray())))
{
return Convert.ToBase64String(algorithm.ComputeHash(Encoding.UTF8.GetBytes(source.ToCharArray())));
}
}
private string GetSignUrl(Dictionary parameters, string accessSecret)
{
var imutableMap = new Dictionary(parameters)
{
//{ "Timestamp", FormatIso8601Date(DateTime.Now) },
//{ "SignatureMethod", "HMAC-SHA1" },
//{ "SignatureVersion", "1.0" },
//{ "SignatureNonce", Guid.NewGuid().ToString() },
//{ "Action", Action },
//{ "Version", Version },
//{ "Format", Format },
//{ "RegionId", RegionId }
};
IDictionary sortedDictionary = new SortedDictionary(imutableMap, StringComparer.Ordinal);
StringBuilder canonicalizedQueryString = new StringBuilder();
foreach (var p in sortedDictionary)
{
canonicalizedQueryString.Append("&")
.Append(PercentEncode(p.Key)).Append("=")
.Append(PercentEncode(p.Value));
}
StringBuilder stringToSign = new StringBuilder();
stringToSign.Append(HTTP_METHOD);
stringToSign.Append(SEPARATOR);
stringToSign.Append(PercentEncode("/"));
stringToSign.Append(SEPARATOR);
stringToSign.Append(PercentEncode(canonicalizedQueryString.ToString().Substring(1)));
string signature = SignString(stringToSign.ToString(), accessSecret + "&");
imutableMap.Add("Signature", signature);
return ComposeUrl(MtsDomain, imutableMap);
}
private static string ComposeUrl(string endpoint, Dictionary parameters)
{
StringBuilder urlBuilder = new StringBuilder("");
urlBuilder.Append("http://").Append(endpoint);
if (-1 == urlBuilder.ToString().IndexOf("?"))
{
urlBuilder.Append("/?");
}
string query = ConcatQueryString(parameters);
return urlBuilder.Append(query).ToString();
}
private static string ConcatQueryString(Dictionary parameters)
{
if (null == parameters)
{
return null;
}
StringBuilder sb = new StringBuilder();
foreach (var entry in parameters)
{
String key = entry.Key;
String val = entry.Value;
sb.Append(HttpUtility.UrlEncode(key, Encoding.UTF8));
if (val != null)
{
sb.Append("=").Append(HttpUtility.UrlEncode(val, Encoding.UTF8));
}
sb.Append("&");
}
int strIndex = sb.Length;
if (parameters.Count > 0)
sb.Remove(strIndex - 1, 1);
return sb.ToString();
}
public static string PercentEncode(string value)
{
StringBuilder stringBuilder = new StringBuilder();
string text = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.~";
byte[] bytes = Encoding.GetEncoding("UTF-8").GetBytes(value);
foreach (char c in bytes)
{
if (text.IndexOf(c) >= 0)
{
stringBuilder.Append(c);
}
else
{
stringBuilder.Append("%").Append(
string.Format(CultureInfo.InvariantCulture, "{0:X2}", (int)c));
}
}
return stringBuilder.ToString();
}
///
/// HMAC-SHA1加密算法
///
/// 密钥
/// 要加密的串
///
/// AES 算法加密(ECB模式) 将明文加密，加密后进行base64编码，返回密文
///
/// 明文
/// 密钥
/// 加密后base64编码的密文
public static string Encrypt(string EncryptStr, string Key)
{
try
{
//byte[] keyArray = Encoding.UTF8.GetBytes(Key);
byte[] keyArray = Convert.FromBase64String(Key);
byte[] toEncryptArray = Encoding.UTF8.GetBytes(EncryptStr);
RijndaelManaged rDel = new RijndaelManaged
{
Key = keyArray,
Mode = CipherMode.ECB,
Padding = PaddingMode.PKCS7
};
ICryptoTransform cTransform = rDel.CreateEncryptor();
byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
return Convert.ToBase64String(resultArray, 0, resultArray.Length);
}
catch (Exception)
{
return null;
}
}
public static string Decrypt(string toDecrypt, string key)
{
byte[] keyArray = Convert.FromBase64String(key); // 将 TestGenAESByteKey 类输出的字符串转为 byte 数组
byte[] toEncryptArray = Convert.FromBase64String(toDecrypt);
RijndaelManaged rDel = new RijndaelManaged
{
Key = keyArray,
Mode = CipherMode.ECB, // 必须设置为 ECB
Padding = PaddingMode.PKCS7 // 必须设置为 PKCS7
};
ICryptoTransform cTransform = rDel.CreateDecryptor();
byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
return Encoding.UTF8.GetString(resultArray);
}
private static string BuildCanonicalizedQueryString(Dictionary parameters)
{
// 对参数进行排序
List sortedKeys = new List(parameters.Keys);
sortedKeys.Sort();
StringBuilder temp = new StringBuilder();
foreach (var key in sortedKeys)
{
// 此处需要对 key 和 value 进行编码
string value = parameters[key];
temp.Append(SEPARATOR).Append(PercentEncode(key)).Append(EQUAL).Append(PercentEncode(value));
}
return temp.ToString().Substring(1);
}
private static string BuildRequestURL(string signature, Dictionary parameters)
{
// 生成请求 URL
StringBuilder temp = new StringBuilder("mts.cn-beijing.aliyuncs.com");
temp.Append(HttpUtility.UrlEncode("Signature", ENCODE_TYPE)).Append("=").Append(signature);
foreach (var item in parameters)
{
temp.Append("&").Append(PercentEncode(item.Key)).Append("=").Append(PercentEncode(item.Value));
}
return temp.ToString();
}
}
使用的时候直接调用 SubmitTranscodeJob 方法就可以了。