player: do actual cap check to see if transcode is required

1 files changed, 66 insertions, 0 deletions

diff --git a/web/script/player/mediacaps.ts b/web/script/player/mediacaps.ts
new file mode 100644
index 0000000..ff143c0
--- /dev/null
+++ b/web/script/player/mediacaps.ts
@@ -0,0 +1,66 @@
+import { SourceTrack, SourceTrackKind } from "./jhls.d.ts";
+
+const cache = new Map<string, boolean>()
+
+// TODO this testing method makes the assumption, that if the codec is supported on its own, it can be
+// TODO     arbitrarly combined with others that are supported. in reality this is true but the spec does not gurantee it.
+
+export async function test_media_capability(track: SourceTrack): Promise<boolean> {
+    const cache_key = `${get_track_kind(track.kind)};${track.codec}`
+    const cached = cache.get(cache_key);
+    if (cached !== undefined) return cached
+    const r = await test_media_capability_inner(track)
+    console.log(`${r ? "positive" : "negative"} media capability test finished for codec=${track.codec}`);
+    cache.set(cache_key, r)
+    return r
+}
+async function test_media_capability_inner(track: SourceTrack) {
+    if (track.kind.subtitles) {
+        return track.codec == "V_TEXT/WEBVTT" // TODO: actually implement it
+    }
+    let res;
+    const codec = MASTROSKA_CODEC_MAP[track.codec]
+    if (!codec) return console.warn(`unknown codec: ${track.codec}`), false
+    if (track.kind.audio) {
+        res = await navigator.mediaCapabilities.decodingInfo({
+            type: "media-source",
+            audio: {
+                contentType: `audio/webm^; codecs=${codec}`,
+                samplerate: track.kind.audio.sample_rate,
+                channels: "" + track.kind.audio.channels,
+                bitrate: 128 * 1000,
+            }
+        })
+    }
+    if (track.kind.video) {
+        res = await navigator.mediaCapabilities.decodingInfo({
+            type: "media-source",
+            video: {
+                contentType: `video/webm; codecs=${codec}`,
+                framerate: track.kind.video.fps || 30,
+                width: track.kind.video.width,
+                height: track.kind.video.height,
+                bitrate: 5 * 1000 * 1000 // TODO we dont know this but we should in the future
+            }
+        })
+    }
+    return res?.supported ?? false
+}
+
+const MASTROSKA_CODEC_MAP: { [key: string]: string } = {
+    "V_VP9": "vp9",
+    "V_VP8": "vp8",
+    "V_AV1": "av1",
+    "V_MPEG4/ISO/AVC": "h264",
+    "V_MPEGH/ISO/HEVC": "h265",
+    "A_OPUS": "opus",
+    "A_VORBIS": "vorbis",
+    "S_TEXT/WEBVTT": "webvtt",
+}
+
+export function get_track_kind(track: SourceTrackKind): "audio" | "video" | "subtitles" {
+    if (track.audio) return "audio"
+    if (track.video) return "video"
+    if (track.subtitles) return "subtitles"
+    throw new Error("invalid track");
+}