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PROTOCOL.md

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Amba JSON Protocol

Messages are JSON objects sent back and forth, without any kind of delimiter in between, through a TCP socket. In case of Xiaomi Yi network_message_daemon is running on ports 8787 and 7878. Actual message parsing is happening in libamba_msg_framework.so.1 and libmsgprocess.so.2, and most of the requests are forwarded into uITRON.

Every packet contains msg_id key depicting type of message sent, in most cases being an rpc method identifier. Client packets also need token value, which is handed by MSG_AUTHENTICATE (257) (or AMBA_START_SESSION, following the naming in an android app) call. Messages sent from server to client contain msg_id as mentioned before, and rval, which is a response code. Packets in both directions can contain arbitrary keys when needed, for client-to-server direction param and type are most common.

msg_id 7 (MSG_STATUS) messages can be sent from server to client out-of-order and depict some kind of event.

Known rvals

  • -23 - Invalid msg_id
  • -21 - Value unchanged (config_get)
  • -4 - Session invalid, new token is needed
  • 0 - Success

Known msg_ids

257 - Session start / Authenticate

Returns new token in param field

DEBUG:__main__:>> {'token': 0, 'msg_id': 257}
DEBUG:__main__:<< {u'rval': 0, u'msg_id': 257, u'param': 8}

258 - Session stop

Revokes current token

13 - Battery status

Returns whether device is running off battery or USB adapter, and current battery charge status.

DEBUG:__main__:>> {'token': 8, 'msg_id': 13}
DEBUG:__main__:<< {u'type': u'adapter', u'rval': 0, u'msg_id': 13, u'param': u'86'}
# Camera is running off USB adapter right now, 86% charge

1 - Config get

Returns current config value for key type

DEBUG:__main__:>> {'token': 8, 'msg_id': 1, 'type': 'camera_clock'}
DEBUG:__main__:<< {u'type': u'camera_clock', u'rval': 0, u'msg_id': 1, u'param': u'2016-03-28 02:00:18'}

2 - Config set

Sets config value for key type to param

DEBUG:__main__:>> {'token': 8, 'msg_id': 2, 'type': 'osd_enable', 'param': 'on'}
DEBUG:__main__:<< {u'rval': 0, u'msg_id': 2}

3 - Config get all

Returns all configuration values

DEBUG:__main__:>> {'token': 8, 'msg_id': 3}
DEBUG:__main__:<< {u'rval': 0, u'msg_id': 3, u'param': [{u'camera_clock': u'2016-03-28 02:02:09'}, {u'video_standard': u'NTSC'}, ...]}

4 - Storage format

Formats SD card

5 - Storage usage

Returns current storage usage and size in kilobytes, type request value can be either total (for total storage size), or free (for free storage size)

DEBUG:__main__:>> {'token': 8, 'msg_id': 5, 'type': 'total'}
DEBUG:__main__:<< {u'rval': 0, u'msg_id': 5, u'param': 7774208}

259 - Preview start

Starts preview available on rtmp://ADDRESS/live

DEBUG:__main__:>> {'token': 8, 'msg_id': 259, 'param': 'none_force'}
DEBUG:__main__:<< {u'rval': 0, u'msg_id': 259}

260 - Preview stop

Stops preview

DEBUG:__main__:>> {'token': 8, 'msg_id': 260}
DEBUG:__main__:<< {u'rval': 0, u'msg_id': 260}

513 - Record start

DEBUG:__main__:>> {'token': 8, 'msg_id': 513}
DEBUG:__main__:<< {u'rval': 0, u'msg_id': 513}
DEBUG:__main__:<< {u'msg_id': 7, u'type': u'start_video_record'}

514 - Record stop

DEBUG:__main__:>> {'token': 8, 'msg_id': 514}
DEBUG:__main__:<< {u'rval': 0, u'msg_id': 514}
DEBUG:__main__:<< {u'msg_id': 7, u'type': u'video_record_complete', u'param': u'/tmp/fuse_d/DCIM/101MEDIA/YDXJ0420.mp4'}

769 - Capture photo

Captures photo. Works regardless of current mode, but camera can't be in recording state

DEBUG:__main__:>> {'token': 8, 'msg_id': 769}
DEBUG:__main__:<< {u'msg_id': 7, u'type': u'start_photo_capture', u'param': u'precise quality;off'}
DEBUG:__main__:<< {u'msg_id': 7, u'type': u'precise_capture_data_ready'}
DEBUG:__main__:<< {u'msg_id': 7, u'type': u'photo_taken', u'param': u'/tmp/fuse_d/DCIM/101MEDIA/YDXJ0421.jpg'}
DEBUG:__main__:<< {u'rval': 0, u'msg_id': 514}

More calls can be found in ambarpc.py for now