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perf(camera): MJPEG negotiation before frame reader — camera drives at its best rate

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Slice 10 from today-slices (d1126dd): UVC cameras default MediaFrameReader to their
FIRST media type (YUY2 at crippled fps — C920 720p = 5fps). A 60fps container
then shows a 5-20fps face cam as "every few frames cut out". Fix:
VideoDeviceController.SetMediaStreamPropertiesAsync negotiated to best MJPEG
>=640x360 @>=30fps (<=1280 wide) BEFORE creating the frame reader, with
device-default fallback. Plus a startup.log truth line of the actual agreed media
type so the next diagnosis starts from facts (no more re-deriving the fps).
Build 0 warnings, 289 tests.
This commit is contained in:
Llama Chile Shop
2026-09-05 17:07:24 -07:00
parent 0f059ece33
commit 70db34455f
1 changed files with 48 additions and 0 deletions
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Services/MediaCaptureFrameSource.cs
+48
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@@ -102,6 +102,43 @@ public sealed class MediaCaptureFrameSource : ICameraFrameSource
};
await capture.InitializeAsync(settings);
// MediaFrameReader defaults to the camera's FIRST media type — on UVC webcams
// (Logitech C920 et al.) that is often YUY2 at a crippled rate (720p5!), and a
// real-time 60fps container then shows a 5-20fps face cam as "every few frames
// cut out". OBS's mechanism, available via VideoDeviceController (VideoProfile
// is NOT projected in the 19041 SDK): negotiate the stream property. Pick the
// best MJPEG >=640x360 @>=30fps (largest, fastest), set it BEFORE the frame
// reader is created, fall back to device default on refusal, and log the live
// media type so the next diagnosis starts from facts.
try
{
var controller = capture.VideoDeviceController;
var candidates = controller == null
? new System.Collections.Generic.List<Windows.Media.MediaProperties.VideoEncodingProperties>()
: controller
.GetAvailableMediaStreamProperties(MediaStreamType.VideoPreview)
.OfType<Windows.Media.MediaProperties.VideoEncodingProperties>()
.Where(v => string.Equals(v.Subtype, "MJPG", StringComparison.OrdinalIgnoreCase)
&& v.Width >= 640 && v.Height >= 360
&& v.FrameRate.Denominator > 0
&& v.FrameRate.Numerator / v.FrameRate.Denominator >= 30.0)
.OrderByDescending(v => v.FrameRate.Numerator / (double)Math.Max(1, v.FrameRate.Denominator))
.ThenByDescending(v => (long)v.Width * v.Height)
.ToList();
if (candidates.Count > 0)
{
var pick = candidates
.OrderBy(v => (long)v.Width * v.Height)
.LastOrDefault(v => v.Width <= 1280) ?? candidates[0];
await controller!.SetMediaStreamPropertiesAsync(MediaStreamType.VideoPreview, pick);
}
}
catch (Exception fmtEx)
{
AppLog.Write($"MediaCaptureFrameSource: MJPG negotiation refused ({fmtEx.Message}); " +
"keeping device-default media type");
}
// Post-init resource validation: the capture must actually be bound to
// the device we asked for and must expose a live video controller.
if (!string.Equals(capture.MediaCaptureSettings?.VideoDeviceId, _deviceId,
@@ -147,6 +184,17 @@ public sealed class MediaCaptureFrameSource : ICameraFrameSource
if (reader == null)
throw new InvalidOperationException($"Camera '{_deviceId}' created no frame reader.");
// One-line truth of what the camera actually agreed to (format/size/fps).
try
{
var active = capture.VideoDeviceController?
.GetMediaStreamProperties(colorSource.Info.MediaStreamType);
if (active is Windows.Media.MediaProperties.VideoEncodingProperties vep)
AppLog.Write($"Camera '{_deviceId}' media type: {vep.Subtype} " +
$"{vep.Width}x{vep.Height} @ {vep.FrameRate.Numerator}/{vep.FrameRate.Denominator}fps");
}
catch { /* logging must never kill acquisition */ }
reader.FrameArrived += OnFrameArrived;
var status = await reader.StartAsync();
if (status != MediaFrameReaderStartStatus.Success)