[Bug 59506] New: IMFMediaEngine video playback fails: no MFT_CATEGORY_VIDEO_PROCESSOR registered for NV12→RGB32 color conversion

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59506

            Bug ID: 59506
           Summary: IMFMediaEngine video playback fails: no
                    MFT_CATEGORY_VIDEO_PROCESSOR registered for NV12→RGB32
                    color conversion
           Product: Wine
           Version: 11.4
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: mfplat
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

IMFMediaEngine video playback fails because no MFT_CATEGORY_VIDEO_PROCESSOR
transform is registered to handle color space conversion (NV12 → RGB32).

On Windows, the Color Converter DSP (CLSID_CColorConvertDMO) handles this. Wine
does not register any equivalent MFT in this category.

== Failure chain (traced with WINEDEBUG=+mf,+mfplat,+mfmediaengine) ==

1. IMFMediaEngine::SetSourceFromByteStream("video.mp4") → OK
2. Source resolver creates media source from byte stream → OK
3. topology_loader_Load runs (real implementation, not a stub despite FIXME
string)
4. MFTEnumEx(MFT_CATEGORY_VIDEO_DECODER, H264) → finds h264_decoder, activates
OK
5. GStreamer pipeline: h264parse → avdec_h264 → videoconvert, all linked
successfully
6. H264 decoder outputs NV12
7. video_frame_sink expects RGB32 (MFVideoFormat_RGB32, GUID
{00000020-0000-0010-8000-00aa00389b71})
8. MFTEnumEx(MFT_CATEGORY_VIDEO_PROCESSOR, NV12→RGB32) → returns 0 results  ←
ROOT CAUSE
9. topology_branch_connect returns 0xc00d5212 (MF_E_TRANSFORM_NOT_POSSIBLE)
10. session_set_topology fails with 0xc00d36b9 (MF_E_TOPO_UNSUPPORTED)
11. MEError 0xc00d3e85 (MF_E_TOPO_CODEC_NOT_FOUND) propagated to application

== Additional stubs ==

IMFMediaEngineEx::SetAutoPlay() and SetLoop() store the flag internally but the
playback engine never consumes it, so video looping does not work.

== Affected application ==

Wallpaper Engine (Steam AppID 431960). Scene wallpapers with embedded video
textures use IMFMediaEngine::SetSourceFromByteStream() to decode .mp4 files as
texture layers. All such wallpapers fail with grey/blank video layers.

== Relevant trace excerpt ==

topology_loader_Load iface ..., input_topology ..., ret_topology ...,
current_topology 0x0 stub!
MFTEnumEx MFT_CATEGORY_VIDEO_DECODER, 0x3f,
{MFMediaType_Video,MFVideoFormat_H264}, ... → found h264_decoder
h264_decoder_create ...
wg_transform_create: input caps video/x-h264, output caps video/x-raw,
format=I420, 1920x1080
gst_pad_link_full: linked avdec_h264-0:src and videoconvert0:sink, successful
MFTEnumEx MFT_CATEGORY_VIDEO_PROCESSOR, 0x3f,
{MFMediaType_Video,MFVideoFormat_NV12}, {MFMediaType_Video,{00000020-...}} → 0
results
topology_branch_connect returning 0xc00d5212
topology_branch_connect returning 0xc00d36b9
session_set_topology failed to load topology ..., hr 0xc00d36b9

== System ==

Wine 11.4 (also reproduced with Valve's wine-staging 10.0 via GE-Proton10-32)
Arch Linux x86_64, kernel 6.19.6
GStreamer 1.22.5, h264 decoders available (avdec_h264, openh264dec, nvh264dec)

== Suggested fix ==

Register a GStreamer-backed MFT_CATEGORY_VIDEO_PROCESSOR that wraps
videoconvert for NV12/I420 → RGB32 conversion. The GStreamer videoconvert
element is already used internally by the decoder pipeline.

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