HI Hans, looks good... is there any progress? -- Christian Gmeiner, MSc 2011/6/9 Hans Verkuil <hansverk@xxxxxxxxx>: > RFC: Proposal for a V4L2 decoder API > ------------------------------------ > > This RFC is based on this discussion: > > http://www.mail-archive.com/linux-media@xxxxxxxxxxxxxxx/msg32703.html > > The purpose is to remove the dependency of ivtv to the ioctls in dvb/audio.h > and dvb/video.h. > > The summary of the posting referred to above is: > > - Add two controls to select the audio output channels. > - Add two read-only controls for the PTS and frame count. > - Copy and paste the old VIDEO_(TRY_)COMMAND to VIDIOC_(TRY_)DECODER_CMD. > > So, here is the RFC that does that. I'm going through the items from the > summary in reverse order. > > > 1) Add new VIDIOC_TRY_DECODER_CMD and VIDIOC_DECODER_CMD ioctls. > > These are the decoder counterparts of the VIDIOC_(TRY_)ENCODER_CMD ioctls > that are already in V4L2. > > /* Decoder commands */ > #define V4L2_DEC_CMD_PLAY (0) > #define V4L2_DEC_CMD_STOP (1) > #define V4L2_DEC_CMD_FREEZE (2) > #define V4L2_DEC_CMD_CONTINUE (3) > > /* Flags for V4L2_DEC_CMD_FREEZE */ > #define V4L2_DEC_CMD_FREEZE_TO_BLACK (1 << 0) > > /* Flags for V4L2_DEC_CMD_STOP */ > #define V4L2_DEC_CMD_STOP_TO_BLACK (1 << 0) > #define V4L2_DEC_CMD_STOP_IMMEDIATELY (1 << 1) > > /* Play format requirements (returned by the driver): */ > /* The decoder has no special format requirements */ > #define V4L2_DEC_PLAY_FMT_NONE (0) > /* The decoder requires full GOPs */ > #define V4L2_DEC_PLAY_FMT_GOP (1) > > /* The structure must be zeroed before use by the application > This ensures it can be extended safely in the future. */ > struct v4l2_decoder_cmd { > __u32 cmd; > __u32 flags; > union { > struct { > /* Stop when this PTS is reached */ > __u64 pts; > } stop; > > struct { > /* 0 or 1000 specifies normal speed, > 1 specifies forward single stepping, > -1 specifies backward single stepping, > >1: playback at speed/1000 of the normal speed, > <-1: reverse playback at (-speed/1000) of the normal speed. > */ > __s32 speed; > __u32 format; > } play; > > struct { > __u32 data[16]; > } raw; > }; > }; > > Other than renaming the #defines and struct there are no changes compared to > the current video.h API. I see no reason to change this either. > > > 2) Add read-only controls for the PTS and framecount. > > V4L2_CID_MPEG_STREAM_DEC_PTS - integer64 > > Return the PTS (Presentation Time Stamp) of the currently presented frame. > > V4L2_CID_MPEG_VIDEO_DEC_FRAME - integer > > Return the frame number of the currently presented frame. When the decoder > starts the frame counter is reset to 0. > > > 3) Add two new audio selection controls. > > V4L2_CID_MPEG_AUDIO_DEC_CHANNEL - menu > > Select how to playback stereo audio from a normal audio stream: > > 0 - Auto (playback native format) > 1 - Left (left channel only) > 2 - Right (right channel only) > 3 - Stereo > 4 - Swapped Stereo (I'm not sure whether this should be added. Is this ever > useful?) > > This control relates to its encoder counterpart V4L2_CID_MPEG_AUDIO_MODE for > the non-DUAL modes. > > V4L2_CID_MPEG_AUDIO_DEC_MULTILINGUAL_CHANNEL - menu > > Select how to playback audio from a multilingual audio stream: > > 0 - Auto (either always Left or can be based on some preferred language) > 1 - Left (left channel only) > 2 - Right (right channel only) > 3 - Stereo > 4 - Swapped Stereo (I'm not sure whether this should be added. Is this ever > useful?) > > This control relates to its encoder counterpart V4L2_CID_MPEG_AUDIO_MODE for > the DUAL mode. > > Note that these two controls are specific to the audio layer I/II/III audio > mode setting. They do not support any e.g. AAC decoding. More research will > need to be done to know whether that makes sense or not. > > Regards, > > Hans > -- > 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 > -- 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
