Backchannel notifications

Background

Backchannel notifications are used to signal certain events to mobile client who is connected to the camera. One of the reasons to introduce this signalling mechanism is to allow mobile client to better handle feedback from the camera in terms of refreshing it's UI and to improve UX. Also, it allows camera to send important status information asynchronously so that mobile application can react accordingly.

Backchannel notifications are not HTTP calls, these are TCP packets which are sent on port which is reported as a result of GET /api/<versionNumber>/status method. Typically, every backchannel notification is in the form of JSON object consisting of it's name and actual payload which can be another JSON object. Currently supported backchannel notifications are:

recording_stopped

Description:

Sent when recording has been stopped. Contains information about newly created file name(s), id, time created, size (in bytes), length (in seconds), number of highlights, mode and video's aspect ratio. If multiple videos are recorded within one session, information about every recorded video will be returned in an array of objects.

photo_captured

Description:

Sent when single, continuous or burst photo(s) are captured and after they are written to the SD card. For single photo, payload will contain only one id entry. For photo burst payload will contain list of photo ids captured. For continuous mode, one backchannel message will be sent after every photo is taken and recorded onto SD card.

{
    "recording_started" : {
                            "recording_active":true
                         }
}

recording_stopped

{
    "recording_stopped" : [{
                            "path":"/100TTCAM/MOV_0001.MP4",
                            "id":"3e5bdae0-a097-415e-9f34-e3e031b407da-100-000-001-0001",
                            "created":"2012-03-04T12:05:20Z",
                            "size_bytes":4174913786,
                            "length_secs":1254,
                            "nr_highlights":12,
                            "mode":"normal",
                            "resolution":"1080p",
                            "framerate_fps":60,
                            "aspect_ratio":"16/9"
                         },
                         {
                            "path":"/100TTCAM/MOV_0002.MP4",
                            "id":"a783dae3-b492-1154-cc32-512631b407da-100-000-001-0002",
                            "created":"2012-03-04T11:25:12Z",
                            "size_bytes":74913786,
                            "length_secs":33,
                            "nr_highlights":12,
                            "mode":"normal",
                            "resolution":"1080p",
                            "framerate_fps":60,
                            "aspect_ratio":"16/9"
                         }]
}

photo_captured

{
    "photo_captured" : [{
                            "path":"/100TTCAM/IMG_0001.JPG",
                            "id":"ae03e5bd-7a09-e415-49f3-407dae3e031b-100-001-002-0003",
                            "created":"2012-03-04T12:05:20Z",
                            "size_bytes":2154637,
                            "mode":"normal",
                            "resolution":"16MP",
                            "aspect_ratio":"4/3",
                            "lat_deg":44.715513,
                            "lon_deg":20.632324
                         },
                         {
                            "path":"/100TTCAM/IMG_0002.JPG",
                            "id":"dae03e5b-97a0-5e41-349f-b407dae3e031-100-001-004-0002",
                            "created":"2012-03-04T12:15:40Z",
                            "size_bytes":2857372,
                            "mode":"continuous",
                            "resolution":"8MP",
                            "aspect_ratio":"4/3",
                            "lat_deg":44.715513,
                            "lon_deg":20.632324
                         }]
}

tag_created

{
    "tag_created" : {
                        "id":"3e5bdae0-a097-415e-9f34-e3e031b407da",
                        "offset_secs":8.2,
                        "highlight_offset_secs":3.2,
                        "highlight_length_secs":10.5,
                        "tag_button":true
                    }
}

memory_low

{
    "memory_low" : {
                        "available_bytes":51234
                   }
}

shutting_down

{
    "shutting_down" : {
                        "battery_critical":true
                   }
}

wifi_stopped

{
    "wifi_stopped" : {
                        "wifi_active":false
                   }
}

transcoding_progress

{
    "transcoding_progress" : {
                        "progress_pct":20
                   }
}

viewfinder_started

{
    "viewfinder_started" : {
                        "viewfinder_active":true
                   }
}

viewfinder_stopped

{
    "viewfinder_stopped" : {
                        "viewfinder_active":false
                   }
}

memory_error

{
    "memory_error" : true
}