Avoid slicing for hardware decoders that use SDL as the renderer

app/streaming/video/ffmpeg-renderers/sdlvid.cpp

@@ -127,16 +127,6 @@ bool SdlRenderer::isRenderThreadSupported()
     return true;
 }
 
-int SdlRenderer::getDecoderCapabilities()
-{
-    // Slice up to 4 times for parallel decode, once slice per core
-    int slices = qMin(MAX_SLICES, SDL_GetCPUCount());
-    SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
-                "Encoder configured for %d slices per frame",
-                slices);
-    return CAPABILITY_SLICES_PER_FRAME(slices);
-}
-
 bool SdlRenderer::initialize(PDECODER_PARAMETERS params)
 {
     Uint32 rendererFlags = SDL_RENDERER_ACCELERATED;

app/streaming/video/ffmpeg-renderers/sdlvid.h

@@ -13,7 +13,6 @@ public:
     virtual void renderFrame(AVFrame* frame) override;
     virtual void notifyOverlayUpdated(Overlay::OverlayType) override;
     virtual bool isRenderThreadSupported() override;
-    virtual int getDecoderCapabilities() override;
 
 private:
     void renderOverlay(Overlay::OverlayType type);

app/streaming/video/ffmpeg.cpp

@@ -47,7 +47,18 @@ bool FFmpegVideoDecoder::isHardwareAccelerated()
 
 int FFmpegVideoDecoder::getDecoderCapabilities()
 {
-    return m_BackendRenderer->getDecoderCapabilities();
+    int capabilities = m_BackendRenderer->getDecoderCapabilities();
+
+    if (!isHardwareAccelerated()) {
+        // Slice up to 4 times for parallel CPU decoding, once slice per core
+        int slices = qMin(MAX_SLICES, SDL_GetCPUCount());
+        SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
+                    "Encoder configured for %d slices per frame",
+                    slices);
+        capabilities |= CAPABILITY_SLICES_PER_FRAME(slices);
+    }
+
+    return capabilities;
 }
 
 int FFmpegVideoDecoder::getDecoderColorspace()