From 8e4bff4cab0ddac6060645b0715210484d02ff40 Mon Sep 17 00:00:00 2001 From: Yuval Adam <_@yuv.al> Date: Wed, 30 Aug 2017 08:25:59 +0000 Subject: Initial file dump from open source release --- .../DocBook/media/v4l/vidioc-decoder-cmd.xml | 249 +++++++++++++++++++++ 1 file changed, 249 insertions(+) create mode 100644 Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml (limited to 'Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml') diff --git a/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml b/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml new file mode 100644 index 00000000..9215627b --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml @@ -0,0 +1,249 @@ + + + ioctl VIDIOC_DECODER_CMD, VIDIOC_TRY_DECODER_CMD + &manvol; + + + + VIDIOC_DECODER_CMD + VIDIOC_TRY_DECODER_CMD + Execute an decoder command + + + + + + int ioctl + int fd + int request + struct v4l2_decoder_cmd *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_DECODER_CMD, VIDIOC_TRY_DECODER_CMD + + + + argp + + + + + + + + + Description + + These ioctls control an audio/video (usually MPEG-) decoder. +VIDIOC_DECODER_CMD sends a command to the +decoder, VIDIOC_TRY_DECODER_CMD can be used to +try a command without actually executing it. To send a command applications +must initialize all fields of a &v4l2-decoder-cmd; and call +VIDIOC_DECODER_CMD or VIDIOC_TRY_DECODER_CMD +with a pointer to this structure. + + The cmd field must contain the +command code. Some commands use the flags field for +additional information. + + + A write() or &VIDIOC-STREAMON; call sends an implicit +START command to the decoder if it has not been started yet. + + + A close() or &VIDIOC-STREAMOFF; call of a streaming +file descriptor sends an implicit immediate STOP command to the decoder, and all +buffered data is discarded. + + These ioctls are optional, not all drivers may support +them. They were introduced in Linux 3.3. + + + struct <structname>v4l2_decoder_cmd</structname> + + &cs-str; + + + __u32 + cmd + + + The decoder command, see . + + + __u32 + flags + + + Flags to go with the command. If no flags are defined for +this command, drivers and applications must set this field to zero. + + + union + (anonymous) + + + + + + + struct + start + + Structure containing additional data for the +V4L2_DEC_CMD_START command. + + + + + __s32 + speed + Playback speed and direction. The playback speed is defined as +speed/1000 of the normal speed. So 1000 is normal playback. +Negative numbers denote reverse playback, so -1000 does reverse playback at normal +speed. Speeds -1, 0 and 1 have special meanings: speed 0 is shorthand for 1000 +(normal playback). A speed of 1 steps just one frame forward, a speed of -1 steps +just one frame back. + + + + + + __u32 + format + Format restrictions. This field is set by the driver, not the +application. Possible values are V4L2_DEC_START_FMT_NONE if +there are no format restrictions or V4L2_DEC_START_FMT_GOP +if the decoder operates on full GOPs (Group Of Pictures). +This is usually the case for reverse playback: the decoder needs full GOPs, which +it can then play in reverse order. So to implement reverse playback the application +must feed the decoder the last GOP in the video file, then the GOP before that, etc. etc. + + + + + struct + stop + + Structure containing additional data for the +V4L2_DEC_CMD_STOP command. + + + + + __u64 + pts + Stop playback at this pts or immediately +if the playback is already past that timestamp. Leave to 0 if you want to stop after the +last frame was decoded. + + + + + struct + raw + + + + + + + __u32 + data[16] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + +
+ + + Decoder Commands + + &cs-def; + + + V4L2_DEC_CMD_START + 0 + Start the decoder. When the decoder is already +running or paused, this command will just change the playback speed. +That means that calling V4L2_DEC_CMD_START when +the decoder was paused will not resume the decoder. +You have to explicitly call V4L2_DEC_CMD_RESUME for that. +This command has one flag: +V4L2_DEC_CMD_START_MUTE_AUDIO. If set, then audio will +be muted when playing back at a non-standard speed. + + + + V4L2_DEC_CMD_STOP + 1 + Stop the decoder. When the decoder is already stopped, +this command does nothing. This command has two flags: +if V4L2_DEC_CMD_STOP_TO_BLACK is set, then the decoder will +set the picture to black after it stopped decoding. Otherwise the last image will +repeat. If V4L2_DEC_CMD_STOP_IMMEDIATELY is set, then the decoder +stops immediately (ignoring the pts value), otherwise it +will keep decoding until timestamp >= pts or until the last of the pending data from +its internal buffers was decoded. + + + + V4L2_DEC_CMD_PAUSE + 2 + Pause the decoder. When the decoder has not been +started yet, the driver will return an &EPERM;. When the decoder is +already paused, this command does nothing. This command has one flag: +if V4L2_DEC_CMD_PAUSE_TO_BLACK is set, then set the +decoder output to black when paused. + + + + V4L2_DEC_CMD_RESUME + 3 + Resume decoding after a PAUSE command. When the +decoder has not been started yet, the driver will return an &EPERM;. +When the decoder is already running, this command does nothing. No +flags are defined for this command. + + + +
+ + + + + &return-value; + + + + EINVAL + + The cmd field is invalid. + + + + EPERM + + The application sent a PAUSE or RESUME command when +the decoder was not running. + + + + + -- cgit v1.3.1