Request a test frame for MMAL decoder

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

@@ -125,6 +125,13 @@ enum AVPixelFormat MmalRenderer::getPreferredPixelFormat(int videoFormat)
     return AV_PIX_FMT_MMAL;
 }
 
+bool MmalRenderer::needsTestFrame()
+{
+    // We won't be able to decode if the GPU memory is 64 MB or lower,
+    // so we must test before allowing the decoder to be used.
+    return true;
+}
+
 void MmalRenderer::renderFrame(AVFrame* frame)
 {
     MMAL_BUFFER_HEADER_T* buffer = (MMAL_BUFFER_HEADER_T*)frame->data[3];

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

@@ -15,6 +15,7 @@ public:
     virtual bool prepareDecoderContext(AVCodecContext* context) override;
     virtual void renderFrame(AVFrame* frame) override;
     virtual enum AVPixelFormat getPreferredPixelFormat(int videoFormat) override;
+    virtual bool needsTestFrame() override;
 
 private:
     static void InputPortCallback(MMAL_PORT_T* port, MMAL_BUFFER_HEADER_T* buffer);