Preserve media source in transcode URLs

Author: codex

internal/emby/playback.go

@@ -3,7 +3,9 @@ package emby
 import (
 	"encoding/json"
 	"fmt"
+	"net/url"
 	"regexp"
+	"strconv"
 	"strings"
 )
 
@@ -70,16 +72,15 @@ func RewritePlaybackInfoWithReport(body []byte, itemID string, publicURL string,
 		}
 		sourceID, _ := source["Id"].(string)
 		sessionID := SessionID(itemID, sourceID, index)
-		transcodeURL := fmt.Sprintf("/streambridge/transcode/%s/master.m3u8", sessionID)
-		if len(rawQuery) > 0 && rawQuery[0] != "" {
-			transcodeURL += "?" + rawQuery[0]
-		}
-
 		beforeDirectPlay, _ := source["SupportsDirectPlay"].(bool)
 		beforeTranscode, _ := source["SupportsTranscoding"].(bool)
 		beforeDirectStreamURL, _ := source["DirectStreamUrl"].(string)
 		beforeTranscodingURL, _ := source["TranscodingUrl"].(string)
 		sourceReport := sourceReportFromMap(source)
+		transcodeURL := fmt.Sprintf("/streambridge/transcode/%s/master.m3u8", sessionID)
+		if enrichedQuery := transcodeQueryForSource(firstRawQuery(rawQuery), sourceID, sourceReport.AudioStreams); enrichedQuery != "" {
+			transcodeURL += "?" + enrichedQuery
+		}
 		sourceReport.Index = index
 		sourceReport.ID = sourceID
 		sourceReport.SessionID = sessionID
@@ -132,6 +133,27 @@ func RewritePlaybackInfoWithReport(body []byte, itemID string, publicURL string,
 	return out, true, report, nil
 }
 
+func firstRawQuery(rawQuery []string) string {
+	if len(rawQuery) == 0 {
+		return ""
+	}
+	return rawQuery[0]
+}
+
+func transcodeQueryForSource(rawQuery string, sourceID string, audioStreams []AudioStreamReport) string {
+	query, err := url.ParseQuery(rawQuery)
+	if err != nil {
+		return rawQuery
+	}
+	if sourceID != "" && query.Get("MediaSourceId") == "" {
+		query.Set("MediaSourceId", sourceID)
+	}
+	if query.Get("AudioStreamIndex") == "" && len(audioStreams) > 0 {
+		query.Set("AudioStreamIndex", strconv.Itoa(audioStreams[0].Index))
+	}
+	return query.Encode()
+}
+
 func sourceReportFromMap(source map[string]any) SourceReport {
 	report := SourceReport{
 		Name:         stringValue(source, "Name"),

internal/emby/playback_test.go

@@ -57,9 +57,30 @@ func TestRewritePlaybackInfoPreservesQueryString(t *testing.T) {
 	if !changed {
 		t.Fatal("expected rewrite to change response")
 	}
-	if !bytes.Contains(out, []byte(`master.m3u8?X-Emby-Token=abc`)) {
+	if !bytes.Contains(out, []byte(`X-Emby-Token=abc`)) {
 		t.Fatalf("missing query string: %s", out)
 	}
+	if !bytes.Contains(out, []byte(`MediaSourceId=source1`)) {
+		t.Fatalf("missing media source id: %s", out)
+	}
+}
+
+func TestRewritePlaybackInfoAddsSourceParametersWhenClientOmitsThem(t *testing.T) {
+	input := []byte(`{"MediaSources":[{"Id":"source1","SupportsDirectPlay":true,"MediaStreams":[{"Type":"Audio","Index":1,"Codec":"dts"}]}]}`)
+
+	out, changed, err := emby.RewritePlaybackInfo(input, "item123", "http://proxy.local", "AutoOpenLiveStream=false&IsPlayback=false")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !changed {
+		t.Fatal("expected rewrite to change response")
+	}
+	if !bytes.Contains(out, []byte(`MediaSourceId=source1`)) {
+		t.Fatalf("missing media source id: %s", out)
+	}
+	if !bytes.Contains(out, []byte(`AudioStreamIndex=1`)) {
+		t.Fatalf("missing audio stream index: %s", out)
+	}
 }
 
 func TestRewritePlaybackInfoWithReportDescribesSources(t *testing.T) {
@@ -85,7 +106,7 @@ func TestRewritePlaybackInfoWithReportDescribesSources(t *testing.T) {
 	if source.BeforeDirectStreamURL != "/Videos/1/stream" {
 		t.Fatalf("direct stream url = %q", source.BeforeDirectStreamURL)
 	}
-	if source.AfterTranscodingURL != "/streambridge/transcode/item123/master.m3u8" {
+	if source.AfterTranscodingURL != "/streambridge/transcode/item123/master.m3u8?AudioStreamIndex=1&MediaSourceId=source1" {
 		t.Fatalf("after url = %q", source.AfterTranscodingURL)
 	}
 	if source.SessionID != "item123" {