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uniapp/Google Chrome/VideoDownloader.cs

@@ -1,6 +1,7 @@
 using System.Diagnostics;
 using System.Net.Http;
 using System.Text;
+using System.Text.Json;
 using System.Text.RegularExpressions;
 
 namespace WinFormsApp3
@@ -59,6 +60,20 @@ namespace WinFormsApp3
         public static bool IsHlsUrl(string url) =>
             !string.IsNullOrEmpty(url) && Regex.IsMatch(url, @"\.m3u8(\?|#|$)", RegexOptions.IgnoreCase);
 
+        /// <summary>
+        /// 判断是否是 DASH 纯音频轨地址（抖音 .../media-audio-xxx/...）。
+        /// 这种地址单独下载出来没有画面，必须和视频轨合并。
+        /// </summary>
+        public static bool IsDashAudioOnly(string? url) =>
+            !string.IsNullOrEmpty(url) && Regex.IsMatch(url, @"/media-audio[/-]", RegexOptions.IgnoreCase);
+
+        /// <summary>
+        /// 判断是否是 DASH 纯视频轨地址（抖音 .../media-video-xxx/...）。
+        /// 这种地址单独下载出来没有声音，需要配音频轨。
+        /// </summary>
+        public static bool IsDashVideoOnly(string? url) =>
+            !string.IsNullOrEmpty(url) && Regex.IsMatch(url, @"/media-video[/-]", RegexOptions.IgnoreCase);
+
         /// <summary>
         /// 判断是否是 HLS 分片（合并播放列表可用，但单独下载没有意义）。
         /// 只认分片特有的后缀与编号形式，不能拿路径里的 video / seg 字样当依据，
@@ -177,6 +192,105 @@ namespace WinFormsApp3
             return await WriteHlsAsync(client, playlist, filePath, progress, ct);
         }
 
+        /// <summary>
+        /// 下载 DASH 分离的视频轨和音频轨，再用 ffmpeg 合并成单个 mp4。
+        /// 抖音等站点把视频和音频分成两个独立的 mp4 轨道返回，必须合并才能有声有画。
+        /// </summary>
+        public async Task<DownloadResult> DownloadDashPairAsync(string videoUrl, string audioUrl, string filePath, IProgress<DownloadProgress>? progress, CancellationToken ct)
+        {
+            var ffmpeg = FindFfmpeg();
+            if (ffmpeg == null)
+            {
+                throw new NotSupportedException("下载抖音 DASH 分离视频轨需要 ffmpeg 合并音视频，但未找到 ffmpeg.exe。请把 ffmpeg.exe 放到程序目录下。");
+            }
+
+            using var client = CreateClient();
+
+            // 临时文件
+            var tmpDir = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString("N"));
+            Directory.CreateDirectory(tmpDir);
+            var videoTmp = Path.Combine(tmpDir, "video.mp4");
+            var audioTmp = Path.Combine(tmpDir, "audio.mp4");
+
+            try
+            {
+                // 下载视频轨（占总进度 0~50%）
+                progress?.Report(new DownloadProgress("下载视频轨…", 0));
+                await DownloadSingleToFileAsync(client, videoUrl, videoTmp, ct,
+                    p => progress?.Report(new DownloadProgress($"下载视频轨 {FormatSize(p)}", null)));
+                var videoSize = new FileInfo(videoTmp).Length;
+
+                // 下载音频轨（占总进度 50~100%）
+                progress?.Report(new DownloadProgress("下载音频轨…", 0.5));
+                await DownloadSingleToFileAsync(client, audioUrl, audioTmp, ct,
+                    p => progress?.Report(new DownloadProgress($"下载音频轨 {FormatSize(p)}", null)));
+                var audioSize = new FileInfo(audioTmp).Length;
+
+                // 合并
+                progress?.Report(new DownloadProgress("合并音视频…", 0.95));
+                Directory.CreateDirectory(Path.GetDirectoryName(Path.GetFullPath(filePath))!);
+                var ok = await MuxDashAsync(ffmpeg, videoTmp, audioTmp, filePath, ct);
+                if (!ok)
+                    throw new InvalidOperationException("ffmpeg 合并音视频失败");
+
+                var finalSize = new FileInfo(filePath).Length;
+                progress?.Report(new DownloadProgress($"完成 {FormatSize(finalSize)}", 1));
+                return new DownloadResult(filePath, finalSize, true);
+            }
+            finally
+            {
+                try { Directory.Delete(tmpDir, true); } catch { /* 临时目录删不掉不影响结果 */ }
+            }
+        }
+
+        /// <summary>
+        /// 下载单个文件到指定路径（不做 .part 重命名，内部用）。
+        /// </summary>
+        private async Task DownloadSingleToFileAsync(HttpClient client, string url, string filePath, CancellationToken ct, Action<long>? onBytes = null)
+        {
+            using var resp = await GetFollowRedirectAsync(client, url, ct);
+            EnsureVideoResponse(resp);
+
+            await using var input = await resp.Content.ReadAsStreamAsync(ct);
+            await using var output = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None, 1024 * 64, true);
+            var buffer = new byte[1024 * 64];
+            long total = 0;
+            int read;
+            while ((read = await input.ReadAsync(buffer, ct)) > 0)
+            {
+                await output.WriteAsync(buffer.AsMemory(0, read), ct);
+                total += read;
+                onBytes?.Invoke(total);
+            }
+        }
+
+        /// <summary>
+        /// 用 ffmpeg 把 DASH 视频轨和音频轨合并成 mp4（直接 copy 不重编码）。
+        /// </summary>
+        private static async Task<bool> MuxDashAsync(string ffmpeg, string videoFile, string audioFile, string outputFile, CancellationToken ct)
+        {
+            var args = $"-hide_banner -loglevel error -y -i \"{videoFile}\" -i \"{audioFile}\" -c:v copy -c:a aac -strict experimental -movflags +faststart \"{outputFile}\"";
+            var psi = new ProcessStartInfo
+            {
+                FileName = ffmpeg,
+                Arguments = args,
+                UseShellExecute = false,
+                CreateNoWindow = true,
+                RedirectStandardError = true,
+                RedirectStandardOutput = true
+            };
+
+            using var proc = Process.Start(psi);
+            if (proc == null) return false;
+
+            using (ct.Register(() => { try { if (!proc.HasExited) proc.Kill(true); } catch { } }))
+            {
+                await proc.WaitForExitAsync(ct);
+            }
+
+            return proc.ExitCode == 0 && File.Exists(outputFile) && new FileInfo(outputFile).Length > 0;
+        }
+
         private HttpClient CreateClient()
         {
             var client = new HttpClient(new HttpClientHandler { AllowAutoRedirect = false })
@@ -529,13 +643,35 @@ namespace WinFormsApp3
         }
 
         /// <summary>
-        /// 查找 ffmpeg：先看程序目录，再看 PATH。找到就能把 HLS 转成 mp4，找不到则只合并 ts。
+        /// 查找 ffmpeg：顺序为 1) ffmpeg.json 配置文件指定的路径；2) 程序目录 ffmpeg.exe；3) PATH。
+        /// 配置文件格式：{"ffmpegPath": "D:\\NET8\\Exe\\ffmpeg\\bin\\ffmpeg.exe"}
         /// </summary>
         public static string? FindFfmpeg()
         {
+            // 1. 配置文件指定的路径（优先级最高）
+            var configPath = Path.Combine(AppContext.BaseDirectory, "ffmpeg.json");
+            if (File.Exists(configPath))
+            {
+                try
+                {
+                    var json = File.ReadAllText(configPath);
+                    using var doc = JsonDocument.Parse(json);
+                    if (doc.RootElement.TryGetProperty("ffmpegPath", out var prop) &&
+                        prop.ValueKind == JsonValueKind.String)
+                    {
+                        var configured = prop.GetString();
+                        if (!string.IsNullOrWhiteSpace(configured) && File.Exists(configured))
+                            return configured;
+                    }
+                }
+                catch { /* 配置文件损坏就跳过，继续找别的 */ }
+            }
+
+            // 2. 程序目录
             var local = Path.Combine(AppContext.BaseDirectory, "ffmpeg.exe");
             if (File.Exists(local)) return local;
 
+            // 3. PATH
             foreach (var dir in (Environment.GetEnvironmentVariable("PATH") ?? "").Split(Path.PathSeparator))
             {
                 if (string.IsNullOrWhiteSpace(dir)) continue;