Bug 36152
| Summary: | iSight (uvcvideo) VIDIOC_TRY_FMT has side-effects | ||
|---|---|---|---|
| Product: | v4l-dvb | Reporter: | Dave Vasilevsky (dave) |
| Component: | webcam | Assignee: | webcam (v4l-dvb_webcam) |
| Status: | RESOLVED OBSOLETE | ||
| Severity: | normal | CC: | alan, diegoe, filmor, t.matsuu |
| Priority: | P1 | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Kernel Version: | 2.6.38.6 | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
| Attachments: | Test case | ||
I can confirm, your testcase "works" here too: diego:downloads$ ./isight Set 640 x 480 Driver claims 640 x 480, image size 614400 Tried 320 x 240 Driver claims 640 x 480, image size 614400 Actual image size 262144 Actual image size 262371 Actual image size 262145 Actual image size 262144 Actual image size 262803 Actual image size 262144 Actual image size 262144 Actual image size 262463 Actual image size 262144 Actual image size 262144 I first saw this with GNOME's Cheese, where I have to go to preferences and switch back and forth to another video format before I actually see something (640x480 -> 320x240 -> 640x480) GNOME bugzilla btw: https://bugzilla.gnome.org/show_bug.cgi?id=649067 |
Created attachment 59952 [details] Test case The ioctl VIDIOC_TRY_FMT is supposed to modify its argument, and make no changes to the video driver. However, on my MacBook4,1 with the built-in iSight, invoking TRY_FMT causes the video capture output to change mysteriously. The attached test case performs the following steps: 1. Sets the format to UYVY 640 x 480 2. Uses TRY_FMT to check if 320 x 240 would work 3. Verifies that the format is still 640 x 480 4. Captures frames, but they are not of the expected size Output is: Set 640 x 480 Driver claims 640 x 480, image size 614400 Tried 320 x 240 Driver claims 640 x 480, image size 614400 Actual image size 262477 Actual image size 262692 Actual image size 262908 Actual image size 262102 Actual image size 262144 Actual image size 262144 Actual image size 262144 Actual image size 262144 Actual image size 262144 Actual image size 262144 Expected output would have actual size 614400, the same as the driver claims it should be. I have no idea what the ~256k buffer being received actually is, it's not the proper size for 320 x 240 either!