On Sun, 2010-09-05 at 10:04 +0200, Peter Korsgaard wrote: > >>>>> "Hans" == Hans de Goede <hdegoede@xxxxxxxxxx> writes: > > Hi, > > >> + <entry><constant>V4L2_CID_LEDS</constant></entry> > >> + <entry>integer</entry> > >> + <entry>Switch on or off the LED(s) or illuminator(s) of the device. > >> + The control type and values depend on the driver and may be either > >> + a single boolean (0: off, 1:on) or the index in a menu type.</entry> > >> + </row> > > Hans> I think that using one control for both status leds (which is > Hans> what we are usually talking about) and illuminator(s) is a bad > Hans> idea. I'm fine with standardizing these, but can we please have 2 > Hans> CID's one for status lights and one for the led. Esp, as I can > Hans> easily see us supporting a microscope in the future where the > Hans> microscope itself or other devices with the same bridge will have > Hans> a status led, so then we will need 2 separate controls anyways. > > Why does this need to go through the v4l2 api and not just use the > standard LED (sysfs) api in the first place? It puts a larger burden on the application programmer. Video capture applications are already programmed to provide controls to the user using the V4L2 API for manipulating all aspects of the incoming video image. Using something different for turning on subject illumination would be an exceptional case. The V4L2 control API also allows applications to be written such that they need no apriori knowledge about a video driver's controls, and yet can still present all driver supported controls to the user for manipulation. The VIDIOC_QUERYCTL interface allows applications to discover controls and metadata to build a UI. Two applications that illustrate the point are 'qv4l2' (a Qt control GUI) and 'v4l2-ctl' (a CLI control UI) found here: http://git.linuxtv.org/v4l-utils.git?a=tree;f=utils;h=8d37309cc3b896d11fc77d9f275f82f02ee9c03d;hb=HEAD As an example, here is the output of v4l2-ctl -L for my QX3 microscope: $ v4l2-ctl -d /dev/video1 -L brightness (int) : min=0 max=100 step=1 default=50 value=50 contrast (int) : min=0 max=96 step=8 default=48 value=48 saturation (int) : min=0 max=100 step=1 default=50 value=50 light_frequency_filter (menu) : min=0 max=2 default=1 value=1 0: NoFliker 1: 50 Hz 2: 60 Hz compression_target (menu) : min=0 max=1 default=0 value=0 0: Quality 1: Framerate lamps (menu) : min=0 max=3 default=0 value=0 0: Off 1: Bottom 2: Top 3: Both And here is the output for my PVR-350 TV capture card: $ v4l2-ctl -d /dev/video2 -L User Controls brightness (int) : min=0 max=255 step=1 default=128 value=128 flags=slider contrast (int) : min=0 max=127 step=1 default=64 value=64 flags=slider saturation (int) : min=0 max=127 step=1 default=64 value=64 flags=slider hue (int) : min=-128 max=127 step=1 default=0 value=0 flags=slider volume (int) : min=0 max=65535 step=655 default=58880 value=58880 flags=slider mute (bool) : default=0 value=0 MPEG Encoder Controls stream_type (menu) : min=0 max=5 default=0 value=0 flags=update 0: MPEG-2 Program Stream 2: MPEG-1 System Stream 3: MPEG-2 DVD-compatible Stream 4: MPEG-1 VCD-compatible Stream 5: MPEG-2 SVCD-compatible Stream stream_vbi_format (menu) : min=0 max=1 default=0 value=0 0: No VBI 1: Private packet, IVTV format audio_sampling_frequency (menu) : min=0 max=2 default=1 value=1 0: 44.1 kHz 1: 48 kHz 2: 32 kHz audio_encoding (menu) : min=1 max=1 default=1 value=1 flags=update 1: MPEG-1/2 Layer II audio_layer_ii_bitrate (menu) : min=9 max=13 default=10 value=10 9: 192 kbps 10: 224 kbps 11: 256 kbps 12: 320 kbps 13: 384 kbps audio_stereo_mode (menu) : min=0 max=3 default=0 value=0 flags=update 0: Stereo 1: Joint Stereo 2: Dual 3: Mono audio_stereo_mode_extension (menu) : min=0 max=3 default=0 value=0 flags=inactive 0: Bound 4 1: Bound 8 2: Bound 12 3: Bound 16 audio_emphasis (menu) : min=0 max=2 default=0 value=0 0: No Emphasis 1: 50/15 us 2: CCITT J17 audio_crc (menu) : min=0 max=1 default=0 value=0 0: No CRC 1: 16-bit CRC audio_mute (bool) : default=0 value=0 video_encoding (menu) : min=0 max=1 default=1 value=1 flags=readonly 0: MPEG-1 1: MPEG-2 video_aspect (menu) : min=0 max=3 default=1 value=1 0: 1x1 1: 4x3 2: 16x9 3: 2.21x1 video_b_frames (int) : min=0 max=33 step=1 default=2 value=2 flags=update video_gop_size (int) : min=1 max=34 step=1 default=15 value=15 video_gop_closure (bool) : default=1 value=1 video_bitrate_mode (menu) : min=0 max=1 default=0 value=0 flags=update 0: Variable Bitrate 1: Constant Bitrate video_bitrate (int) : min=0 max=27000000 step=1 default=6000000 value=6000000 video_peak_bitrate (int) : min=0 max=27000000 step=1 default=8000000 value=8000000 video_temporal_decimation (int) : min=0 max=255 step=1 default=0 value=0 video_mute (bool) : default=0 value=0 video_mute_yuv (int) : min=0 max=16777215 step=1 default=32896 value=32896 spatial_filter_mode (menu) : min=0 max=1 default=0 value=0 flags=update 0: Manual 1: Auto spatial_filter (int) : min=0 max=15 step=1 default=0 value=0 flags=slider spatial_luma_filter_type (menu) : min=0 max=4 default=1 value=1 0: Off 1: 1D Horizontal 2: 1D Vertical 3: 2D H/V Separable 4: 2D Symmetric non-separable spatial_chroma_filter_type (menu) : min=0 max=1 default=1 value=1 0: Off 1: 1D Horizontal temporal_filter_mode (menu) : min=0 max=1 default=0 value=0 flags=update 0: Manual 1: Auto temporal_filter (int) : min=0 max=31 step=1 default=8 value=8 flags=slider median_filter_type (menu) : min=0 max=4 default=0 value=0 flags=update 0: Off 1: Horizontal 2: Vertical 3: Horizontal/Vertical 4: Diagonal median_luma_filter_minimum (int) : min=0 max=255 step=1 default=0 value=0 flags=inactive slider median_luma_filter_maximum (int) : min=0 max=255 step=1 default=255 value=255 flags=inactive slider median_chroma_filter_minimum (int) : min=0 max=255 step=1 default=0 value=0 flags=inactive slider median_chroma_filter_maximum (int) : min=0 max=255 step=1 default=255 value=255 flags=inactive slider insert_navigation_packets (bool) : default=0 value=0 v4l2-ctl needed no hardcoded knowledge of what the respective drivers (gspca_cpia1 and ivtv) supported to build a UI. Nor did the v4l2-ctl need to go rummaging about in sysfs to find which control applied to which video device node, because the driver simply tell the app upon request: "here are your options for controlling this device". No guesswork on where the control for this device may be located in sysfs, and no exceptional application code to be written just to toggle an illuminator on and off. Regards, Andy -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
