[camera_windows] Fixes initializing video preview with latest webcam driver #10303
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Code Review
This pull request addresses an issue with video preview initialization on Windows for certain webcam drivers. The fix involves explicitly querying for video, photo, and audio stream indices instead of relying on predefined constants. A key change is the addition of a call to SetCurrentDeviceMediaType after determining the best media type for preview. These changes are correctly propagated through the photo, preview, and record handlers, and the corresponding tests have been updated. I've identified one potential issue where the search for an audio stream is unconditional, which could cause problems in video-only capture scenarios.
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stuartmorgan-g
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I've left some initial comments. I'm not very familiar with the Media Foundation APIs, so I may be misunderstanding, but the code definitely needs more explanation about what the code is doing and why.
Looking at the comment in the issue, it sounds like this was only tested against a single device; we'll need more justification in terms of docs or examples about this code being correct for more than just the one case.
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| ## 0.2.7 | ||
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| * Fixes initializing video preview with latest webcam driver [#140014](https://github.com/flutter/flutter/issues/140014) |
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This needs a period, per the linked style guide.
| repository: https://github.com/flutter/packages/tree/main/packages/camera/camera_windows | ||
| issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22 | ||
| version: 0.2.6+2 | ||
| version: 0.2.7 |
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0.2.6+3, since this is a bugfix, per Dart conventions for pre-1.0 versioning.
| // for the actual video capture media type. | ||
| // video_source_stream_index: Integer index of the video source stream in | ||
| // MediaFoundation. audio_source_stream_index: Integer index of the audio | ||
| // source stream in MediaFoundation. |
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These need to be formatted the same as the other comments, with separate lines and proper indenting.
| // sample_callback: A pointer to capture engine listener. | ||
| // This is set as sample callback for preview sink. | ||
| // source_stream_index: Integer index of the preview source stream in | ||
| // MediaFoundation. |
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Please update all of these to do consistent indenting.
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Also, the order should match the parameter order.
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| } | ||
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| enum class PlatformStreamCategory { video, photo, audio }; |
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Freestanding internal helpers like enums and functions should be declared at the top of the file in an anonymous namespace.
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| enum class PlatformStreamCategory { video, photo, audio }; | ||
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| HRESULT GetMediaSourceStreamIndex( |
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This needs a declaration comment, per the style guide, explaining what it does and what its overall role is.
| (target_stream_category == PlatformStreamCategory::audio && | ||
| stream_category == MF_CAPTURE_ENGINE_STREAM_CATEGORY_AUDIO)) { | ||
| *source_stream_index = stream_index; | ||
| return S_OK; |
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This is unconditionally returning only the first matching stream; why is that correct? How did you determine that unconditionally using the first stream is never a regression compared to using the preferred stream? That seems counterintuitive.
| if ((target_stream_category == PlatformStreamCategory::video && | ||
| (stream_category == MF_CAPTURE_ENGINE_STREAM_CATEGORY_VIDEO_PREVIEW || | ||
| stream_category == | ||
| MF_CAPTURE_ENGINE_STREAM_CATEGORY_VIDEO_CAPTURE)) || |
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Why are preview and capture streams being treated interchangeably?
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Explanation post: flutter/flutter#140014 (comment)
Resolves #140014.
Pre-Review Checklist
[shared_preferences]pubspec.yamlwith an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under1.CHANGELOG.mdto add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under1.///).If you need help, consider asking for advice on the #hackers-new channel on Discord.
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