拼接音频

现有AMR的语音音频n段，要求在HTML5浏览器上播放，并且是在输出流时即进行拼接，不需在浏览器用脚本进行分段播放。根据 AMR文件格式分析 可知，拼接时需要将从第2段开始的amr字节流中去掉前6个字节"#!AMR "。以下两个例子分别是指定Content-Length和使用chunked方式输出，其中chunked方式在移动设备浏览器中不可用。

chunked输出方式：

 public class AudioHandler : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            //参数验证
            string voiceUrl = Path.GetFileNameWithoutExtension(context.Request.Url.LocalPath);
            if (string.IsNullOrEmpty(voiceUrl))
            {
                context.Response.StatusCode = 404;
                context.Response.End();
                return;
            }

            //获取音频地址
            IAudioContract audio = AudioManager.Create();
            GetAudioUrlsArgs args = new GetAudioUrlsArgs(){ VoiceUrl = voiceUrl};
            var result = audio.GetAudioUrls(args);
            if (result == null && result.Status != ExecuteStatus.OK && result.Data == null && 
                result.Data.AddressList == null && result.Data.AddressList.Count <= 0)
            {
                context.Response.StatusCode = 404;
                context.Response.End();
                return;
            }

            //输出配置
            context.Response.ContentType = "audio/amr";
            context.Response.BufferOutput = false;

            //输出音频, 移动设置不支持chunked
            List<string> filePaths = result.Data.AddressList;
            int count = filePaths.Count;
            for (int i = 0; i < count; i++)
            {
                OutputChunkedAudio(context, filePaths[i], (i == 0) ? true : false);
            }
            context.Response.Flush();

        }

        public bool IsReusable
        {
            get { return false; }
        }

        private void OutputChunkedAudio(HttpContext context, string filePath, bool first)
        {
            bool deleted = first ? true : false;

            Stream outputStream = context.Response.OutputStream;
            using (var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read))
            {
                byte[] buffer = new byte[6];
                while (true)
                {
                    int count = fileStream.Read(buffer, 0, 6);
                    if (count == 0)
                    {
                        return;
                    }
                    if (!deleted)
                    {
                        deleted = true;
                        continue;
                    }

                    //context.Response.Write(Encoding.UTF8.GetString(buffer));
                    outputStream.Write(buffer, 0, count);
                }

            }
        }

    }

指定Content-Length的方式：

 public class AudioHandler : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            //参数验证
            string voiceUrl = Path.GetFileNameWithoutExtension(context.Request.Url.LocalPath);
            if (string.IsNullOrEmpty(voiceUrl))
            {
                context.Response.StatusCode = 404;
                context.Response.End();
                return;
            }

            //获取音频地址
            IAudioContract audio = AudioManager.Create();
            GetAudioUrlsArgs args = new GetAudioUrlsArgs(){ VoiceUrl = voiceUrl};
            var result = audio.GetAudioUrls(args);
            if (result == null && result.Status != ExecuteStatus.OK && result.Data == null && 
                result.Data.AddressList == null && result.Data.AddressList.Count <= 0)
            {
                context.Response.StatusCode = 404;
                context.Response.End();
                return;
            }

            //输出配置
            context.Response.ContentType = "audio/amr";
            context.Response.BufferOutput = false;

            //输出音频
            List<byte> data = new List<byte>();
            List<string> filePaths = result.Data.AddressList;
            int count = filePaths.Count;
            for (int i = 0; i < count; i++)
            {
                LoadFullAudio(filePaths[i], (i == 0) ? true : false, ref data);
            }
            context.Response.AppendHeader("Content-Length", data.Count.ToString());
            context.Response.OutputStream.Write(data.ToArray(), 0, data.Count);
            context.Response.Flush();
            
        }

        public bool IsReusable
        {
            get { return false; }
        }

        private void LoadFullAudio(string filePath, bool first, ref List<byte> data)
        {
            bool deleted = first ? true : false;

            using (var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read))
            {
                byte[] buffer = new byte[6];
                while (true)
                {
                    int count = fileStream.Read(buffer, 0, 6);
                    if (count == 0)
                    {
                        return;
                    }
                    if (!deleted)
                    {
                        deleted = true;
                        continue;
                    }

                    for (int i = 0; i < count; i++)
                    {
                        data.Add(buffer[i]);
                    }
                    
                }

            }
        }

    }

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