P6: remote video and audio play through the proxy

- The media proxy streams ranged requests from the origin (passing the range on, never caching), downloads and caches
  whole files otherwise, and serves cached files with range support. A PeerTube video is never fetched whole for one
  viewer, and clients still never contact the remote host.
- PeerTube's fragmented MP4 files inside an HLS entry are read as variants, so HLS-only instances play too.
- A remote Video or Audio post becomes one playable Mastodon attachment: the best MP4 up to 720p that carries both
  sound and picture, with its poster and duration; the card is kept only when nothing is playable.
- nginx: /media/proxy/ with proxy_buffering off and a 600 s read timeout (applied on the box, with a backup).

Checked live: a GoToSocial image through the proxy answers 206 with exactly the asked range when streamed, 200 when
cached, and 206 with the right Content-Range from the cache.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

CLAUDE.md

@@ -212,6 +212,16 @@ cd /var/www/privapub.thepra.dev && sudo -u www-data ASPNETCORE_ENVIRONMENT=Produ
    sibling `media-proxy`, which `/media/files` does not serve.
 3. **A client never contacts a remote server for media:** every remote URL the API returns goes through
    `IMediaProxy.Wrap`, an HMAC-signed `/media/proxy/` URL fetched by `IFederationHttp.GetMedia`.
+4. **The proxy serves three ways:**
+   - **Cached:** a file already cached is served from disk, ranges included.
+   - **Downloaded:** a request without a `Range` is downloaded whole, up to `Media:MaxProxiedBytes`, then cached.
+   - **Streamed:** a ranged request, or anything too big to cache, is streamed from the origin with the range passed on,
+     and never cached. That is how remote video plays.
+
+   nginx has a `/media/proxy/` location with `proxy_buffering off` and a 600 s read timeout for those streams.
+5. **Remote video and audio become one playable attachment** in the Mastodon API (`MastodonMapper.Playable`): the best MP4
+   up to 720p that carries both sound and picture, including PeerTube's fragmented files inside an HLS entry. HLS
+   playlists themselves are not rewritten.
 
 ## Privacy invariants
 

FEDERATION.md

@@ -181,6 +181,7 @@ Posts with a location (shown to nearby users of this server) never leave the ser
 ## Known limitations
 
 - Our own posts carry no custom emoji: emoji are received and shown, not offered.
-- Remote media is fetched through this server's proxy when a local client displays it.
+- Remote media is fetched through this server's proxy when a local client displays it. Video and audio are streamed
+  through it with byte ranges passed on, so a PeerTube file is never fetched whole for one viewer.
 - Collections expose counts, not members.
 - Only `rsa-sha256`-style keys are verified. RFC 9421 signatures are planned.

PrivaPub.Tests/Federation/ObjectShapesTests.cs

@@ -214,6 +214,30 @@ namespace PrivaPub.Tests.Federation
 			Assert.Equal(new DateTime(2026, 9, 30, 12, 0, 0, DateTimeKind.Utc), closed.Poll.ClosedAt);
 		}
 
+		[Fact]
+		public void Finds_playable_files_inside_an_hls_only_peertube_video_and_picks_one_with_sound()
+		{
+			var note = Parse("""
+				{
+					"id": "https://tube.example/videos/watch/2", "type": "Video", "name": "HLS only", "attributedTo": "https://tube.example/accounts/ann",
+					"url": [
+						{ "type": "Link", "mediaType": "text/html", "href": "https://tube.example/w/def" },
+						{ "type": "Link", "mediaType": "application/x-mpegURL", "href": "https://tube.example/master.m3u8", "tag": [
+							{ "type": "Link", "mediaType": "video/mp4", "href": "https://tube.example/1080-fragmented.mp4", "height": 1080,
+								"attachment": [{ "type": "PropertyValue", "name": "ffprobe_codec_type", "value": "video" }, { "type": "PropertyValue", "name": "ffprobe_codec_type", "value": "audio" }] },
+							{ "type": "Link", "mediaType": "video/mp4", "href": "https://tube.example/720-fragmented.mp4", "height": 720,
+								"attachment": [{ "type": "PropertyValue", "name": "ffprobe_codec_type", "value": "video" }] },
+							{ "type": "Link", "mediaType": "video/mp4", "href": "https://tube.example/480-fragmented.mp4", "height": 480,
+								"attachment": [{ "type": "PropertyValue", "name": "ffprobe_codec_type", "value": "video" }, { "type": "PropertyValue", "name": "ffprobe_codec_type", "value": "audio" }] }
+						] }
+					]
+				}
+				""");
+
+			Assert.Equal(3, note.Video.Variants.Count);
+			Assert.Equal("https://tube.example/480-fragmented.mp4", MastodonMapper.BestVideo(note.Video.Variants).Url);
+		}
+
 		[Fact]
 		public void Normalises_hashtags_like_mastodon() =>
 			Assert.Equal("ｆｅｄｉ".Normalize(System.Text.NormalizationForm.FormKC).ToLowerInvariant(), Assert.Single(Parse("""

PrivaPub/Api/Mastodon/Controllers/MediaController.cs

@@ -60,13 +60,38 @@ namespace PrivaPub.Api.Mastodon.Controllers
 		[HttpGet("/media/proxy/{signature}/{encoded}"), AllowAnonymous, ApiExplorerSettings(IgnoreApi = true)]
 		public async Task<IActionResult> Proxy(string signature, string encoded, CancellationToken token)
 		{
-			var (path, contentType) = await _proxy.Fetch(signature, encoded, token);
+			var url = _proxy.Verified(signature, encoded);
-			if (path == default)
+			if (url == default)
 				return NotFound();
 			Response.Headers["X-Content-Type-Options"] = "nosniff";
 			Response.Headers["Content-Security-Policy"] = "default-src 'none'; sandbox";
 			Response.Headers["Cache-Control"] = "public, max-age=604800";
-			return PhysicalFile(path, contentType);
+			if (_proxy.Cached(url) is { Path: not null } cached)
+				return PhysicalFile(cached.Path, cached.ContentType, enableRangeProcessing: true);
+			if (Request.Headers.Range.Count == 0)
+			{
+				var (path, contentType) = await _proxy.Fetch(signature, encoded, token);
+				if (path != default)
+					return PhysicalFile(path, contentType, enableRangeProcessing: true);
+			}
+			return await Stream(url, token);
+		}
+
+		async Task<IActionResult> Stream(string url, CancellationToken token)
+		{
+			var range = System.Net.Http.Headers.RangeHeaderValue.TryParse(Request.Headers.Range.ToString(), out var asked) ? asked : default;
+			using var upstream = await _proxy.Open(url, range, token);
+			if (upstream == default)
+				return NotFound();
+			Response.StatusCode = (int)upstream.StatusCode;
+			Response.ContentType = upstream.Content.Headers.ContentType?.ToString() ?? "application/octet-stream";
+			if (upstream.Content.Headers.ContentLength is { } length)
+				Response.ContentLength = length;
+			if (upstream.Content.Headers.ContentRange is { } contentRange)
+				Response.Headers.ContentRange = contentRange.ToString();
+			Response.Headers.AcceptRanges = "bytes";
+			await upstream.Content.CopyToAsync(Response.Body, token);
+			return new EmptyResult();
 		}
 
 		object View(MediaAttachment attachment) => new

PrivaPub/Api/Mastodon/Mappers/MastodonMapper.cs

@@ -225,7 +225,7 @@ namespace PrivaPub.Api.Mastodon.Mappers
 					SpoilerText = post.SpoilerText ?? (post.HasContentWarning ? post.Title ?? ActivityPubRenderer.ContentWarning : string.Empty),
 					Visibility = Visibility(post.Visibility),
 					Language = post.Language,
-					MediaAttachments = post.Media.Select(Media).ToList(),
+					MediaAttachments = post.Media.Count > 0 ? post.Media.Select(Media).ToList() : Playable(post),
 					Card = Card(post),
 					Poll = Poll(post, viewerId, ownVotes.GetValueOrDefault(post.ID)),
 					Emojis = Emojis(post.Emojis),
@@ -445,11 +445,42 @@ namespace PrivaPub.Api.Mastodon.Mappers
 			Streams = variant.Streams
 		};
 
+		List<MediaAttachment> Playable(PostEntity post)
+		{
+			var (variant, kind, duration) = post.Video is { } video ? (BestVideo(video.Variants), "video", video.DurationSeconds)
+				: post.Audio is { } audio ? (audio.Variants.FirstOrDefault(), "audio", audio.DurationSeconds)
+				: default;
+			if (variant == default)
+				return new List<MediaAttachment>();
+			return new List<MediaAttachment>
+			{
+				Media(new PostMedia
+				{
+					Id = new Guid(System.Security.Cryptography.MD5.HashData(System.Text.Encoding.UTF8.GetBytes(variant.Url))),
+					RemoteURL = variant.Url,
+					ContentType = variant.MediaType ?? kind + "/*",
+					RemotePreviewURL = post.CoverURL,
+					Width = variant.Width,
+					Height = variant.Height,
+					DurationSeconds = duration,
+					Description = post.Title
+				})
+			};
+		}
+
+		public static MediaVariant BestVideo(IReadOnlyCollection<MediaVariant> variants)
+		{
+			var playable = variants.Where(v => v.MediaType?.StartsWith("video/") == true && (v.Streams.Count == 0 || v.Streams.Contains("audio") && v.Streams.Contains("video"))).ToList();
+			return playable.Where(v => v.Height <= 720).OrderByDescending(v => v.Height).FirstOrDefault()
+				?? playable.OrderBy(v => v.Height ?? int.MaxValue).FirstOrDefault();
+		}
+
 		PreviewCard Card(PostEntity post)
 		{
 			if (post.Link is { } link)
 				return Card(link.Href, link.Title ?? post.Title, link.Description ?? (post.Media.Count == 0 ? post.Excerpt : default), link.ImageURL);
-			if (post.IsFederatedCopy && post.ObjectType is "Article" or "Event" or "Video" or "Audio" && post.Url != default && post.Media.Count == 0)
+			if (post.IsFederatedCopy && post.ObjectType is "Article" or "Event" && post.Url != default && post.Media.Count == 0
+				|| post.IsFederatedCopy && post.ObjectType is "Video" or "Audio" && post.Url != default && post.Media.Count == 0 && Playable(post).Count == 0)
 				return Card(post.Url, post.Title, post.Excerpt, post.CoverURL);
 			return default;
 		}

PrivaPub/Domain/Media/MediaProxy.cs

@@ -15,6 +15,9 @@ namespace PrivaPub.Domain.Media
 	{
 		string Wrap(string remoteUrl);
 		Task<(string Path, string ContentType)> Fetch(string signature, string encodedUrl, CancellationToken token);
+		string Verified(string signature, string encodedUrl);
+		(string Path, string ContentType) Cached(string url);
+		Task<HttpResponseMessage> Open(string url, System.Net.Http.Headers.RangeHeaderValue range, CancellationToken token);
 	}
 
 	public class MediaProxy : IMediaProxy
@@ -43,7 +46,7 @@ namespace PrivaPub.Domain.Media
 			return $"{_localActors.BaseAddress}/media/proxy/{Sign(remoteUrl)}/{encoded}";
 		}
 
-		public async Task<(string Path, string ContentType)> Fetch(string signature, string encodedUrl, CancellationToken token)
+		public string Verified(string signature, string encodedUrl)
 		{
 			string url;
 			try
@@ -54,19 +57,38 @@ namespace PrivaPub.Domain.Media
 			{
 				return default;
 			}
-			if (!CryptographicOperations.FixedTimeEquals(Encoding.ASCII.GetBytes(signature ?? string.Empty), Encoding.ASCII.GetBytes(Sign(url))))
+			return CryptographicOperations.FixedTimeEquals(Encoding.ASCII.GetBytes(signature ?? string.Empty), Encoding.ASCII.GetBytes(Sign(url))) ? url : default;
-				return default;
-
-			var name = Convert.ToHexStringLower(SHA256.HashData(Encoding.UTF8.GetBytes(url)));
-			var directory = System.IO.Path.Combine(_media.ProxyRoot, name[..2]);
-			var path = System.IO.Path.Combine(directory, name);
-			var typePath = path + ".type";
-			if (File.Exists(path) && File.Exists(typePath))
-			{
-				File.SetLastWriteTimeUtc(path, DateTime.UtcNow);
-				return (path, await File.ReadAllTextAsync(typePath, token));
 		}
 
+		public (string Path, string ContentType) Cached(string url)
+		{
+			var (path, typePath) = CachePaths(url);
+			if (!File.Exists(path) || !File.Exists(typePath))
+				return default;
+			File.SetLastWriteTimeUtc(path, DateTime.UtcNow);
+			return (path, File.ReadAllText(typePath));
+		}
+
+		public Task<HttpResponseMessage> Open(string url, System.Net.Http.Headers.RangeHeaderValue range, CancellationToken token) =>
+			_http.OpenMedia(url, range, token);
+
+		(string Path, string TypePath) CachePaths(string url)
+		{
+			var name = Convert.ToHexStringLower(SHA256.HashData(Encoding.UTF8.GetBytes(url)));
+			var path = System.IO.Path.Combine(_media.ProxyRoot, name[..2], name);
+			return (path, path + ".type");
+		}
+
+		public async Task<(string Path, string ContentType)> Fetch(string signature, string encodedUrl, CancellationToken token)
+		{
+			var url = Verified(signature, encodedUrl);
+			if (url == default)
+				return default;
+			if (Cached(url) is { Path: not null } cached)
+				return cached;
+			var (path, typePath) = CachePaths(url);
+			var directory = System.IO.Path.GetDirectoryName(path);
+
 			var (bytes, contentType) = await _http.GetMedia(url, _options.CurrentValue.MaxProxiedBytes, token);
 			if (bytes == default)
 				return default;

PrivaPub/Federation/Objects/ObjectShapes.cs

@@ -217,10 +217,13 @@ namespace PrivaPub.Federation.Objects
 			if (Value(note, "type") != "Video")
 				return default;
 			var links = Objects(note["url"]).ToList();
+			var nested = links.Where(l => Value(l, "mediaType")?.Equals("application/x-mpegURL", StringComparison.OrdinalIgnoreCase) == true)
+				.SelectMany(l => Objects(l["tag"]))
+				.ToList();
 			return new VideoDetails
 			{
 				DurationSeconds = Seconds(note["duration"]),
-				Variants = Variants(links, "video/", "audio/"),
+				Variants = Variants(links.Concat(nested).ToList(), "video/", "audio/"),
 				PlaylistURL = links.Where(l => Value(l, "mediaType")?.Equals("application/x-mpegURL", StringComparison.OrdinalIgnoreCase) == true)
 					.Select(l => Value(l, "href")).FirstOrDefault(IsWeb),
 				IsLive = Bool(note, "isLiveBroadcast") == true,

PrivaPub/Infrastructure/Http/FederationHttp.cs

@@ -23,6 +23,7 @@ namespace PrivaPub.Infrastructure.Http
 		Task<FetchedJson> GetJson(string url, string accept, Action<HttpRequestMessage> sign, CancellationToken token);
 		bool FailedTemporarily(string url);
 		Task<(Uri FinalUri, string Html)> GetPage(string url, CancellationToken token);
+		Task<HttpResponseMessage> OpenMedia(string url, System.Net.Http.Headers.RangeHeaderValue range, CancellationToken token);
 		Task<HttpResponseMessage> Send(HttpRequestMessage request, CancellationToken token);
 		Task<(byte[] Bytes, string ContentType)> GetMedia(string url, long maxBytes, CancellationToken token);
 	}
@@ -229,6 +230,46 @@ namespace PrivaPub.Infrastructure.Http
 			}
 		}
 
+		public async Task<HttpResponseMessage> OpenMedia(string url, System.Net.Http.Headers.RangeHeaderValue range, CancellationToken token)
+		{
+			if (!Uri.TryCreate(url, UriKind.Absolute, out var target) || !IsAllowed(target))
+				return default;
+			try
+			{
+				for (var hop = 0; hop <= MaxRedirects; hop++)
+				{
+					using var request = new HttpRequestMessage(HttpMethod.Get, target);
+					request.Headers.Accept.ParseAdd("video/*, audio/*, image/*");
+					request.Headers.Range = range;
+					var response = await _httpClientFactory.CreateClient(ClientName).SendAsync(request, HttpCompletionOption.ResponseHeadersRead, token);
+					if (IsRedirect(response.StatusCode))
+					{
+						var location = response.Headers.Location;
+						response.Dispose();
+						var next = location == default ? default : location.IsAbsoluteUri ? location : new Uri(target, location);
+						if (!IsAllowed(next))
+							return default;
+						target = next;
+						continue;
+					}
+					var mediaType = response.Content.Headers.ContentType?.MediaType?.ToLowerInvariant();
+					if (!response.IsSuccessStatusCode || mediaType == default || mediaType.Contains("svg")
+						|| !(mediaType.StartsWith("video/") || mediaType.StartsWith("audio/") || mediaType.StartsWith("image/") || mediaType == "application/octet-stream"))
+					{
+						response.Dispose();
+						return default;
+					}
+					return response;
+				}
+				return default;
+			}
+			catch (Exception ex) when (ex is HttpRequestException or BlockedDestinationException or OperationCanceledException && !token.IsCancellationRequested)
+			{
+				_logger.LogInformation("Media stream {Url} refused: {Reason}", url, ex.Message);
+				return default;
+			}
+		}
+
 		const int MaxPageBytes = 512 * 1024;
 
 		static async Task<byte[]> ReadPrefix(HttpContent content, int limit, CancellationToken token)

deploy/nginx/privapub.thepra.dev.conf

@@ -48,6 +48,18 @@ server {
 		proxy_read_timeout 300s;
 	}
 
+	location ^~ /media/proxy/ {
+		proxy_buffering    off;
+		proxy_pass         http://127.0.0.1:6970;
+		proxy_http_version 1.1;
+		proxy_set_header   Connection "";
+		proxy_set_header   Host $host;
+		proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
+		proxy_set_header   X-Real-IP $remote_addr;
+		proxy_set_header   X-Forwarded-Proto $scheme;
+		proxy_read_timeout 600s;
+	}
+
 	location / {
 		proxy_pass         http://127.0.0.1:6970;
 		proxy_http_version 1.1;

docs/ROADMAP.md

@@ -465,11 +465,13 @@ it, raw where it doesn't.
   - otherwise the server reads the page (owner decision 1): public posts only, 0–60 s after arrival, cached per address
     for 7 days across the whole server, `Federation:FetchLinkPreviews` to switch it off. Checked live against a
     GoToSocial profile page.
-- **Media:**
+- **Media** (done in v1.14.0 except where noted):
-  - video playback through the proxy (Range requests, HLS playlist rewriting, the poster), with a `video` card;
+  - video playback through the proxy: range requests streamed from the origin, the poster, a playable attachment picked
+    from MP4 or fragmented MP4 files (HLS playlists are not rewritten; not needed while PeerTube publishes the files);
   - audio attachments;
-  - an article reader view;
+  - JPEG/PNG for Pixelfed: uploads were already re-encoded to JPEG, PNG or GIF;
-  - JPEG/PNG renditions kept for Pixelfed.
+  - an article reader view: the data is in `Status.privapub` (title, excerpt, cover, full HTML in `content`); the view
+    itself belongs to the client.
 
 #### P7 Threads, communities and the social graph
 - **Thread backfill:**