Steam Remote Play Big Picture streaming from ultrawide monitors (32:9, 5120×1440) to 16:9 clients produces a cropped 1920×540 stream instead of proper 1920×1080. Root cause: DXGI Desktop Duplication API fails on ultrawide aspect ratios with error "Unable to select DXGI output that matches capture region", forcing fallback to BitBlt which captures the full 5120×1440 desktop. Steam then crops this to 1920×540 to match the client's 16:9 aspect ratio. Configuration settings like and are completely ignored.


Host PC (Streaming FROM):

• Display: Samsung LC49G95T (5120×1440, 32:9 ultrawide)
  
• GPU: NVIDIA GeForce RTX 2080 (Driver 32.0.15.8180)
  
• OS: Windows 11
  
• Steam Client: Latest stable build
  
• Network: Wired Gigabit, cross-VLAN (OPNsense router)

Client (Streaming TO):

• Device: NVIDIA Shield TV (Android 11)
  
• Display: 4K TV (3840×2160)
  
• Steam Link App: Set to 1080p resolution
  
• Network: Wired Gigabit

When streaming Big Picture mode from an ultrawide host to a 16:9 client requesting 1920×1080:

1. Windows desktop should switch to 1920×1080 (per
   ChangeDesktopResolution
   setting)
   
2. Stream should be captured at 1920×1080
   
3. Client should receive full 1920×1080 stream (16:9 aspect ratio)

1. Windows desktop stays at 5120×1440 (resolution switching ignored)
   
2. DXGI Desktop Duplication fails continuously with error:
   CDesktopCaptureDWM: Unable to select DXGI output that matches capture region
3. Steam falls back to BitBlt capture
   
4. BitBlt captures the full 5120×1440 desktop (no resolution override applied)
   
5. Steam crops to 1920×540 to maintain aspect ratio
   
6. Client receives severely cropped stream with top/bottom cut off

1. Set up Steam Remote Play host on PC with ultrawide monitor (32:9 aspect ratio)
   
2. Configure client (Steam Link app) to request 1920×1080
   
3. Enable "Change desktop resolution to match streaming client" in Steam settings
   
4. Add
   ResolutionOverride="1920x1080"
   and
   DesktopResOverrideEnabled="1"
   to localconfig.vdf
   
5. Launch Big Picture mode from the client
   
6. Observe: Stream is cropped to 1920×540 with top/bottom missing

Note: Launching actual games works perfectly - they stream at 1920×1080 using NVFBC capture. Only Big Picture/desktop streaming fails.


File: C:\Program Files (x86)\Steam\userdata\<user-id>\config\localconfig.vdf

Steam GUI Settings:

• Settings → Remote Play → Advanced Host Options → "Change desktop resolution to match streaming client" = ENABLED
  
• Result: Completely ignored - desktop never switches resolution

Continuous DXGI Failure:

Desktop Never Switches Resolution:
(Shows desktop stays at 5120×1440, stream gets cropped to 1920×540)

Successful Game Streaming (for comparison):
(Games use NVFBC and stream perfectly at 1920×1080)

Failed Big Picture Streaming:
(Big Picture uses BitBlt fallback and crops to 1920×540)

1. DXGI Desktop Duplication API incompatibility: The DXGI/DWM capture method fails on 32:9 ultrawide monitors, likely unable to handle non-standard aspect ratios
   
2. BitBlt fallback also broken: When DXGI fails, BitBlt should be the reliable fallback, but it ignores all resolution override settings and captures the raw Windows desktop resolution (5120×1440). Even if DXGI can't work on ultrawides, BitBlt should at least respect
   ResolutionOverride
   and
   ChangeDesktopResolution
   settings to capture at the client's requested resolution.
   
3. Aspect ratio crop as band-aid: Because BitBlt captures 5120×1440, Steam crops it to 1920×540 to maintain 16:9 aspect for the client - this is a symptom, not the root problem
   
4. Configuration settings completely ignored:
   ChangeDesktopResolution
   ,
   ResolutionOverride
   , and
   DisableDesktopDuplication
   settings have no effect on either DXGI or BitBlt
   
5. NVFBC unavailable for desktop: NVFBC only works for game window capture, not desktop/Big Picture streaming. If it were available for desktop, this would bypass both DXGI and BitBlt issues.

Summary: The issue is twofold - DXGI fails on ultrawides AND BitBlt doesn't properly handle resolution overrides. Even accepting that DXGI might not support ultrawide aspect ratios, the BitBlt fallback should still work correctly by respecting the configured resolution settings. It doesn't.


Current working solution:

1. Manually switch Windows display to 1920×1080 before launching Steam Link
   
2. Launch games directly (skip Big Picture) - games use NVFBC and work perfectly

Does NOT work:

• Configuration file settings (all ignored)
  
• GUI "Change desktop resolution" option (ignored)
  
• DisableDesktopDuplication setting (DXGI still attempted)
  
• Custom resolutions via CRU (Steam doesn't use them)

• Unusable Big Picture experience on ultrawide monitors
  
• Affects all 32:9 and possibly 21:9 ultrawide users
  
• Forces manual workarounds or abandoning Big Picture mode
  
• No configuration-based solution available

1. Fix BitBlt to respect resolution settings (highest priority): Even if DXGI can't support ultrawides, BitBlt fallback should honor
   ResolutionOverride
   and
   ChangeDesktopResolution
   settings. BitBlt should capture at the client's requested resolution, not raw desktop resolution.
   
2. OR Fix DXGI Desktop Duplication to support ultrawide/non-standard aspect ratios so it doesn't fail in the first place
   
3. OR Allow NVFBC for desktop capture (currently only used for games) - this would bypass both DXGI and BitBlt issues entirely
   
4. OR At minimum, properly implement
   ChangeDesktopResolution
   to switch Windows resolution before BitBlt captures, so it captures the correct resolution

Note: The most practical fix is #1 - make BitBlt work correctly. It's already the fallback mechanism, so it should handle cases where DXGI fails gracefully by respecting resolution configuration.

• This issue does NOT occur when streaming actual games (they use NVFBC successfully)
  
• Network/bandwidth is not the issue (wired gigabit, working perfectly)
  
• Client configuration is correct (Shield TV app set to 1080p)
  
• Issue is 100% reproducible across all Big Picture streaming sessions
  
• Similar issues likely affect other ultrawide users but may be unreported
  
• BitBlt should be the "it just works" fallback - if the advanced DXGI method fails, BitBlt should still produce correct results by respecting configuration. Currently it doesn't.

Complete available upon request showing:

• Continuous DXGI failure messages
  
• Capture method fallback to BitBlt
  
• Resolution capture/crop details
  
• Successful game streaming vs failed desktop streaming