NaoAV¶

Introduction¶

The NaoA/V setup is a hack that allows to

• transmit camera images and audio buffers from the Nao robot to a different node
• synchronize audio and video data streams
• store the synchronized audio/video stream in a container file

It consists of several components:

• On the Nao robot
  • rsbvideosender
  • rsbaudiosender
• In a receiver/synchronization/store process on a workstation
  • gst_nao_audio_import
  • gst_nao_video_import

Static View¶

Implementation¶

The implementation uses the GStreamer multimedia framework to synchronize, mux and store the audio and video streams. GStreamer is capable of aligning and synchronizing the audio and video streams which are received via RSB and producing a merged A/V stream that is suitable for writing to a video container file. In order to perform this synchronization, GStreamer makes use of the timestamps which are included in all RSB events.

The abovementioned processing pipeline can be instantiated from the commandline as follows:

gst-launch-0.10                                            \
  audiotestsrc do-timestamp=FALSE                                \
  ! rsb_nao_audio_import pubName="/nao/audio/all"                        \
  ! queue                                            \
  ! "audio/x-raw-int", channels=2, width=16, depth=16, signed=TRUE, rate=48000, endianess=4321    \
  ! audiorate                                            \
  ! mux. videotestsrc do-timestamp=FALSE                            \
  ! rsb_nao_video_import pubName="/nao/vision/top"                        \
  ! queue                                            \
  ! videorate                                            \
  ! 'video/x-raw-yuv,width=320,height=240,framerate=20/1'                    \
  ! mux. avimux name="mux"                                    \
  ! filesink location="/tmp/bla.avi"    

The pipeline uses the following audio and video parameters

Audio:

Parameter	Value
Channels	2 (out of 4 Nao microphones)
Bits per sample	16
Sample rate	48 kHz

Video:

Parameter	Value
Width	320 px
Height	240 px
Frame rate	20 Hz
Colorspace	YUV
Pixel Format	YV12