feat(hls): emit blurhash and thumbhash on every NIP-71 video imeta

amethyst/src/main/java/com/vitorpamplona/amethyst/service/uploads/hls/HlsVideoEventBuilder.kt

@@ -54,6 +54,11 @@ data class HlsVideoPublishInput(
     // (gallery thumbnails, previews) have a still to render — the .m3u8 playlist itself is a
     // text manifest that can't be decoded as an image frame.
     val posterUrl: String? = null,
+    // Blurhash + thumbhash derived once from the same poster bitmap. Threaded into every imeta
+    // so receiving clients can render an instant low-res placeholder before the poster JPEG
+    // finishes loading. Per-rendition values would be redundant — the source frame is the same.
+    val blurhash: String? = null,
+    val thumbhash: String? = null,
 )
 
 sealed class HlsVideoEventTemplate {
@@ -96,6 +101,8 @@ object HlsVideoEventBuilder {
                 dimension = masterDimension,
                 alt = input.alt,
                 image = posterImage,
+                blurhash = input.blurhash,
+                thumbhash = input.thumbhash,
             )
 
         val renditionMetas =
@@ -115,6 +122,8 @@ object HlsVideoEventBuilder {
                     size = combinedMetadata?.size?.toInt(),
                     dimension = DimensionTag(summary.width, summary.height),
                     image = posterImage,
+                    blurhash = input.blurhash,
+                    thumbhash = input.thumbhash,
                 )
             }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/video/hls/HlsPublishOrchestrator.kt

@@ -55,6 +55,18 @@ data class HlsPublishRequest(
     val durationSeconds: Int? = null,
 )
 
+/**
+ * Poster JPEG upload result. Carries the public URL plus blurhash/thumbhash derived from the
+ * same poster pixels, so every imeta in the published NIP-71 event can render an instant
+ * low-res placeholder. All three fields share a single source frame; per-rendition variants
+ * would be redundant.
+ */
+data class HlsPosterUpload(
+    val url: String,
+    val blurhash: String? = null,
+    val thumbhash: String? = null,
+)
+
 /**
  * Orchestrates the transcode → upload → build → publish pipeline for a single HLS video publish.
  * Delegates transcoding and segment/media-playlist upload plumbing to the library's
@@ -81,7 +93,7 @@ class HlsPublishOrchestrator(
     // uploader, returning the public URL. Returns null if poster generation isn't possible
     // (unsupported source, decode failure, no readable frame). Failures here must NOT fail
     // the whole publish — the orchestrator catches and continues without a poster.
-    private val uploadPoster: suspend (HlsBlobUploader) -> String? = { _ -> null },
+    private val uploadPoster: suspend (HlsBlobUploader) -> HlsPosterUpload? = { _ -> null },
 ) {
     val state: StateFlow<HlsPublishState> = _state
 
@@ -208,7 +220,7 @@ class HlsPublishOrchestrator(
             // previews) have a still to render. Tolerate failure: skip the poster rather than
             // failing the entire publish, since the user has already paid the cost of the long
             // segment uploads.
-            val posterUrl =
+            val posterResult =
                 try {
                     uploadPoster(uploader)
                 } catch (e: CancellationException) {
@@ -230,7 +242,9 @@ class HlsPublishOrchestrator(
                         description = request.description,
                         durationSeconds = request.durationSeconds,
                         contentWarning = contentWarningOrNull(request),
-                        posterUrl = posterUrl,
+                        posterUrl = posterResult?.url,
+                        blurhash = posterResult?.blurhash,
+                        thumbhash = posterResult?.thumbhash,
                     ),
                 )
             val eventId = signAndPublish(template)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/video/hls/HlsPublishOrchestratorFactory.kt

@@ -28,6 +28,7 @@ import com.davotoula.lightcompressor.hls.HlsContentTypes
 import com.davotoula.lightcompressor.hls.HlsUploadHelper
 import com.vitorpamplona.amethyst.model.Account
 import com.vitorpamplona.amethyst.service.uploads.MediaUploadResult
+import com.vitorpamplona.amethyst.service.uploads.PreviewMetadataCalculator
 import com.vitorpamplona.amethyst.service.uploads.getThumbnail
 import com.vitorpamplona.amethyst.service.uploads.hls.HlsBlobUploader
 import com.vitorpamplona.amethyst.service.uploads.hls.HlsBlobUploaderFactory
@@ -108,8 +109,9 @@ fun createProductionHlsPublishOrchestrator(
     )
 
 /**
- * Extracts a still frame from the source video at [uri], encodes it as JPEG, and uploads it
- * via [uploader]. Returns the public URL on success or null if any step fails (unsupported
+ * Extracts a still frame from the source video at [uri], encodes it as JPEG, computes blurhash +
+ * thumbhash from the same JPEG bytes, and uploads it via [uploader]. Returns an [HlsPosterUpload]
+ * carrying the public URL plus the two hashes on success, or null if any step fails (unsupported
  * source, no readable frame, encode/upload error). The orchestrator treats null as "publish
  * without a poster" — failure here must never abort the publish.
  */
@@ -117,11 +119,24 @@ private suspend fun generateAndUploadPoster(
     context: Context,
     uri: Uri,
     uploader: HlsBlobUploader,
-): String? {
+): HlsPosterUpload? {
     val posterFile = extractPosterToTempFile(context, uri) ?: return null
     return try {
+        // Read once: hash from the same bytes we upload, so the hashes describe the exact
+        // JPEG receiving clients will fetch via the imeta `image` URL.
+        val posterBytes = posterFile.readBytes()
+        val hashes =
+            runCatching {
+                PreviewMetadataCalculator.computeFromBytes(posterBytes, POSTER_CONTENT_TYPE, null)
+            }.onFailure { Log.w(TAG) { "uploadPoster: blurhash/thumbhash compute failed: ${it.message}" } }
+                .getOrNull()
         val result = uploader.upload(posterFile, POSTER_CONTENT_TYPE) { _, _ -> }
-        result.url
+        val url = result.url ?: return null
+        HlsPosterUpload(
+            url = url,
+            blurhash = hashes?.blurhash?.blurhash,
+            thumbhash = hashes?.thumbhash?.thumbhash,
+        )
     } finally {
         if (!posterFile.delete()) {
             Log.w(TAG) { "uploadPoster: failed to delete temp file ${posterFile.absolutePath}" }

amethyst/src/test/java/com/vitorpamplona/amethyst/service/uploads/hls/HlsPublishOrchestratorTest.kt

@@ -30,6 +30,7 @@ import com.davotoula.lightcompressor.hls.Rendition
 import com.vitorpamplona.amethyst.service.uploads.MediaUploadResult
 import com.vitorpamplona.amethyst.ui.actions.mediaServers.ServerName
 import com.vitorpamplona.amethyst.ui.actions.mediaServers.ServerType
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.video.hls.HlsPosterUpload
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.video.hls.HlsPublishOrchestrator
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.video.hls.HlsPublishRequest
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.video.hls.HlsPublishState
@@ -387,7 +388,7 @@ class HlsPublishOrchestratorTest {
                     captured += tpl
                     "event-id"
                 },
-                uploadPoster = { _ -> "https://cdn.test/poster.jpg" },
+                uploadPoster = { _ -> HlsPosterUpload("https://cdn.test/poster.jpg") },
             )
 
         runBlocking { orchestrator.publish(newRequest()) }