Fix proxied playlists rendering blank and missing sound

Fixes #928

src/dialogs/renderwidget.cpp

@@ -1299,12 +1299,14 @@ void RenderWidget::prepareRendering(bool delayedRendering, const QString &chapte
         QDomNodeList producers = doc.elementsByTagName(QStringLiteral("producer"));
         QString producerResource;
         QString producerService;
+        QString originalProducerService;
         QString suffix;
         QString prefix;
         for (int n = 0; n < producers.length(); ++n) {
             QDomElement e = producers.item(n).toElement();
             producerResource = Xml::getXmlProperty(e, QStringLiteral("resource"));
             producerService = Xml::getXmlProperty(e, QStringLiteral("mlt_service"));
+            originalProducerService = Xml::getXmlProperty(e, QStringLiteral("kdenlive:original.mlt_service"));
             if (producerResource.isEmpty() || producerService == QLatin1String("color")) {
                 continue;
             }
@@ -1327,6 +1329,10 @@ void RenderWidget::prepareRendering(bool delayedRendering, const QString &chapte
                     producerResource.prepend(root);
                 }
                 if (proxies.contains(producerResource)) {
+                    if (!originalProducerService.isEmpty() && originalProducerService!= producerService) {
+                        // Proxy clips can sometimes use a different mlt service, for example playlists (xml) will use avformat. Fix
+                        Xml::setXmlProperty(e, QStringLiteral("mlt_service"), originalProducerService);
+                    }
                     QString replacementResource = proxies.value(producerResource);
                     Xml::setXmlProperty(e, QStringLiteral("resource"), prefix + replacementResource + suffix);
                     if (producerService == QLatin1String("timewarp")) {

src/jobs/proxyclipjob.cpp

@@ -141,6 +141,10 @@ bool ProxyJob::startJob()
                 continue;
             } else {
                 t.replace(QLatin1Char(' '), QLatin1String("="));
+                if (t == QLatin1String("acodec=copy") && type == ClipType::Playlist) {
+                    // drop this for playlists, otherwise we have no sound in proxies
+                    continue;
+                }
             }
             mltParameters << t;
         }

src/mltcontroller/clipcontroller.cpp

@@ -663,6 +663,10 @@ void ClipController::checkAudioVideo()
         if (orig_service.startsWith(QStringLiteral("avformat")) || (m_masterProducer->get_int("audio_index") + m_masterProducer->get_int("video_index") > 0)) {
             m_hasAudio = m_masterProducer->get_int("audio_index") >= 0;
             m_hasVideo = m_masterProducer->get_int("video_index") >= 0;
+        } else if (orig_service == QStringLiteral("xml")) {
+            // Playlist, assume we have audio and video
+            m_hasAudio = true;
+            m_hasVideo = true;
         } else {
             // Assume image or text producer
             m_hasAudio = false;