From 6b4f12523db46536c750473abdd380763cb0409b Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Thu, 24 Nov 2011 09:55:53 -0300 Subject: [PATCH] [media] v4l spec: document VIDIOC_(TRY_)DECODER_CMD Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- Documentation/DocBook/media/v4l/v4l2.xml | 1 + .../DocBook/media/v4l/vidioc-decoder-cmd.xml | 256 ++++++++++++++++++ .../DocBook/media/v4l/vidioc-encoder-cmd.xml | 9 +- 3 files changed, 262 insertions(+), 4 deletions(-) create mode 100644 Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml diff --git a/Documentation/DocBook/media/v4l/v4l2.xml b/Documentation/DocBook/media/v4l/v4l2.xml index dce3fef15bc9..dcf9e33b695f 100644 --- a/Documentation/DocBook/media/v4l/v4l2.xml +++ b/Documentation/DocBook/media/v4l/v4l2.xml @@ -480,6 +480,7 @@ and discussions on the V4L mailing list. &sub-cropcap; &sub-dbg-g-chip-ident; &sub-dbg-g-register; + &sub-decoder-cmd; &sub-dqevent; &sub-encoder-cmd; &sub-enumaudio; 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 000000000000..466fe27d3ffe --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml @@ -0,0 +1,256 @@ + + + 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 + + + Experimental + + This is an experimental +interface and may change in the future. + + + 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. + + + + + __u32 + 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. + + + + + diff --git a/Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml b/Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml index af7f3f2a36dd..f431b3ba79bd 100644 --- a/Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml +++ b/Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml @@ -74,15 +74,16 @@ only used by the STOP command and contains one bit: If the encoding will continue until the end of the current Group Of Pictures, otherwise it will stop immediately. - A read() call sends a START command to -the encoder if it has not been started yet. After a STOP command, + A read() or &VIDIOC-STREAMON; call sends an implicit +START command to the encoder if it has not been started yet. After a STOP command, read() calls will read the remaining data buffered by the driver. When the buffer is empty, read() will return zero and the next read() call will restart the encoder. - A close() call sends an immediate STOP -to the encoder, and all buffered data is discarded. + A close() or &VIDIOC-STREAMOFF; call of a streaming +file descriptor sends an implicit immediate STOP to the encoder, and all buffered +data is discarded. These ioctls are optional, not all drivers may support them. They were introduced in Linux 2.6.21. -- 2.20.1