Add NV21 pixel format support to SDL renderer

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

@@ -9,7 +9,8 @@
 
 const std::vector<int> SdlRenderer::k_SwFormats({
     AV_PIX_FMT_YUV420P,
-    AV_PIX_FMT_NV12
+    AV_PIX_FMT_NV12,
+    AV_PIX_FMT_NV21
 });
 
 SdlRenderer::SdlRenderer()
@@ -285,6 +286,9 @@ void SdlRenderer::renderFrame(AVFrame* frame)
         case AV_PIX_FMT_NV12:
             sdlFormat = SDL_PIXELFORMAT_NV12;
             break;
+        case AV_PIX_FMT_NV21:
+            sdlFormat = SDL_PIXELFORMAT_NV21;
+            break;
         default:
             SDL_assert(false);
             goto Exit;