| Message ID | 20210606030928.9739-1-laurent.pinchart@ideasonboard.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v5] media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K | expand |
On Sun, 2021-06-06 at 06:09 +0300, Laurent Pinchart wrote: > From: Benjamin Drung <bdrung@posteo.de> > > The Elgato Cam Link 4K HDMI video capture card reports to support three > different pixel formats, where the first format depends on the connected > HDMI device. > > ``` > $ v4l2-ctl -d /dev/video0 --list-formats-ext > ioctl: VIDIOC_ENUM_FMT > Type: Video Capture > > [0]: 'NV12' (Y/CbCr 4:2:0) > Size: Discrete 3840x2160 > Interval: Discrete 0.033s (29.970 fps) > [1]: 'NV12' (Y/CbCr 4:2:0) > Size: Discrete 3840x2160 > Interval: Discrete 0.033s (29.970 fps) > [2]: 'YU12' (Planar YUV 4:2:0) > Size: Discrete 3840x2160 > Interval: Discrete 0.033s (29.970 fps) > ``` > > Changing the pixel format to anything besides the first pixel format > does not work: > > ``` > $ v4l2-ctl -d /dev/video0 --try-fmt-video pixelformat=YU12 > Format Video Capture: > Width/Height : 3840/2160 > Pixel Format : 'NV12' (Y/CbCr 4:2:0) > Field : None > Bytes per Line : 3840 > Size Image : 12441600 > Colorspace : sRGB > Transfer Function : Rec. 709 > YCbCr/HSV Encoding: Rec. 709 > Quantization : Default (maps to Limited Range) > Flags : > ``` > > User space applications like VLC might show an error message on the > terminal in that case: > > ``` > libv4l2: error set_fmt gave us a different result than try_fmt! > ``` > > Depending on the error handling of the user space applications, they > might display a distorted video, because they use the wrong pixel format > for decoding the stream. > > The Elgato Cam Link 4K responds to the USB video probe > VS_PROBE_CONTROL/VS_COMMIT_CONTROL with a malformed data structure: The > second byte contains bFormatIndex (instead of being the second byte of > bmHint). The first byte is always zero. The third byte is always 1. > > The firmware bug was reported to Elgato on 2020-12-01 and it was > forwarded by the support team to the developers as feature request. > There is no firmware update available since then. The latest firmware > for Elgato Cam Link 4K as of 2021-03-23 has MCU 20.02.19 and FPGA 67. > > Therefore correct the malformed data structure for this device. The > change was successfully tested with VLC, OBS, and Chromium using > different pixel formats (YUYV, NV12, YU12), resolutions (3840x2160, > 1920x1080), and frame rates (29.970 and 59.940 fps). > > Cc: stable@vger.kernel.org > Signed-off-by: Benjamin Drung <bdrung@posteo.de> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > --- > Benjamin, could you double-check the adjustments ? I've also updated the > commit messages to not mention a quirk anymore. They are perfect! You also updated the source code comment to not mention a quirk any more. :) > --- > drivers/media/usb/uvc/uvc_video.c | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > index a777b389a66e..e16464606b14 100644 > --- a/drivers/media/usb/uvc/uvc_video.c > +++ b/drivers/media/usb/uvc/uvc_video.c > @@ -127,10 +127,37 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit, > static void uvc_fixup_video_ctrl(struct uvc_streaming *stream, > struct uvc_streaming_control *ctrl) > { > + static const struct usb_device_id elgato_cam_link_4k = { > + USB_DEVICE(0x0fd9, 0x0066) > + }; > struct uvc_format *format = NULL; > struct uvc_frame *frame = NULL; > unsigned int i; > > > > > + /* > + * The response of the Elgato Cam Link 4K is incorrect: The second byte > + * contains bFormatIndex (instead of being the second byte of bmHint). > + * The first byte is always zero. The third byte is always 1. > + * > + * The UVC 1.5 class specification defines the first five bits in the > + * bmHint bitfield. The remaining bits are reserved and should be zero. > + * Therefore a valid bmHint will be less than 32. > + * > + * Latest Elgato Cam Link 4K firmware as of 2021-03-23 needs this fix. > + * MCU: 20.02.19, FPGA: 67 > + */ > + if (usb_match_one_id(stream->dev->intf, &elgato_cam_link_4k) && > + ctrl->bmHint > 255) { > + u8 corrected_format_index = ctrl->bmHint >> 8; > + > + uvc_dbg(stream->dev, VIDEO, > + "Correct USB video probe response from {bmHint: 0x%04x, bFormatIndex: %u} to {bmHint: 0x%04x, bFormatIndex: %u}\n", > + ctrl->bmHint, ctrl->bFormatIndex, > + 1, corrected_format_index); > + ctrl->bmHint = 1; > + ctrl->bFormatIndex = corrected_format_index; > + } > + > for (i = 0; i < stream->nformats; ++i) { > if (stream->format[i].index == ctrl->bFormatIndex) { > format = &stream->format[i];
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c index a777b389a66e..e16464606b14 100644 --- a/drivers/media/usb/uvc/uvc_video.c +++ b/drivers/media/usb/uvc/uvc_video.c @@ -127,10 +127,37 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit, static void uvc_fixup_video_ctrl(struct uvc_streaming *stream, struct uvc_streaming_control *ctrl) { + static const struct usb_device_id elgato_cam_link_4k = { + USB_DEVICE(0x0fd9, 0x0066) + }; struct uvc_format *format = NULL; struct uvc_frame *frame = NULL; unsigned int i; + /* + * The response of the Elgato Cam Link 4K is incorrect: The second byte + * contains bFormatIndex (instead of being the second byte of bmHint). + * The first byte is always zero. The third byte is always 1. + * + * The UVC 1.5 class specification defines the first five bits in the + * bmHint bitfield. The remaining bits are reserved and should be zero. + * Therefore a valid bmHint will be less than 32. + * + * Latest Elgato Cam Link 4K firmware as of 2021-03-23 needs this fix. + * MCU: 20.02.19, FPGA: 67 + */ + if (usb_match_one_id(stream->dev->intf, &elgato_cam_link_4k) && + ctrl->bmHint > 255) { + u8 corrected_format_index = ctrl->bmHint >> 8; + + uvc_dbg(stream->dev, VIDEO, + "Correct USB video probe response from {bmHint: 0x%04x, bFormatIndex: %u} to {bmHint: 0x%04x, bFormatIndex: %u}\n", + ctrl->bmHint, ctrl->bFormatIndex, + 1, corrected_format_index); + ctrl->bmHint = 1; + ctrl->bFormatIndex = corrected_format_index; + } + for (i = 0; i < stream->nformats; ++i) { if (stream->format[i].index == ctrl->bFormatIndex) { format = &stream->format[i];