967962 - [Camera] Preview size too small in Nexus 4

Status: RESOLVED FIXED

(Firefox OS Graveyard :: Gaia::Camera, defect)

Description

[Diego Marcos [:dmarcos]]

Our algorithm to calculate the best preview size from the list provided by hardware is not returning the best match on Nexus 4.

Steps to reproduce:

1. Open the camera app
2. The selected preview doesn't cover the whole screen.

Expected:

A preview that fills the whole screen

Comment 1

[Diego Marcos [:dmarcos]]

Attachment: Pull Request

Comment 2

[Justin D'Arcangelo [:justindarc]]

If someone with a Nexus 4 can post the values returned from mozCamera.capabilities.previewSizes as well as the dimensions of the display, I can update the unit tests with a better sample of test data.

Comment 3

[Diego Marcos [:dmarcos]]

This is the list I get:

[{"width":1280,"height":720},{"width":800,"height":480},{"width":768,"height":432},{"width":720,"height":480},{"width":640,"height":480},{"width":576,"height":432},{"width":480,"height":320},{"width":384,"height":288},{"width":352,"height":288},{"width":320,"height":240},{"width":240,"height":160},{"width":176,"height":144}]

Comment 4

[Diego Marcos [:dmarcos]]

The viewportSize passed to the selectOptimalPreviewSize function is:

{"width":1180,"height":768}

Comment 5

[Justin D'Arcangelo [:justindarc]]

On other devices, I'm pretty sure that width/height are reversed compared to Nexus 4?

Comment 6

[Diego Marcos [:dmarcos]]

The selected size by the algorithm is:

{"width":720,"height":480}

Comment 7

[Diego Marcos [:dmarcos]]

This is the list returned by hamachi:

[{"height":480,"width":640},{"height":432,"width":576},{"height":320,"width":480},{"height":240,"width":432},{"height":288,"width":384},{"height":288,"width":352},{"height":240,"width":320},{"height":160,"width":240},{"height":144,"width":176}]

width > height

Comment 8

[Justin D'Arcangelo [:justindarc]]

Here's the calculation's internal results for Nexus4:

[{
  "previewSize": {
    "width": 1280,
    "height": 720
  },
  "pw": 1365.3333333333333,
  "ph": 768,
  "scale": 1.0666666666666667,
  "overflow": 142336
}, {
  "previewSize": {
    "width": 800,
    "height": 480
  },
  "pw": 1280,
  "ph": 768,
  "scale": 1.6,
  "overflow": 76800
}, {
  "previewSize": {
    "width": 768,
    "height": 432
  },
  "pw": 1365.3333333333333,
  "ph": 768,
  "scale": 1.7777777777777777,
  "overflow": 142336
}, {
  "previewSize": {
    "width": 720,
    "height": 480
  },
  "pw": 1180,
  "ph": 786.6666666666666,
  "scale": 1.6388888888888888,
  "overflow": 22026.666666666628
}, {
  "previewSize": {
    "width": 640,
    "height": 480
  },
  "pw": 1180,
  "ph": 885,
  "scale": 1.84375,
  "overflow": 138060
}, {
  "previewSize": {
    "width": 576,
    "height": 432
  },
  "pw": 1180,
  "ph": 885,
  "scale": 2.048611111111111,
  "overflow": 138060
}, {
  "previewSize": {
    "width": 480,
    "height": 320
  },
  "pw": 1180,
  "ph": 786.6666666666667,
  "scale": 2.4583333333333335,
  "overflow": 22026.666666666744
}, {
  "previewSize": {
    "width": 384,
    "height": 288
  },
  "pw": 1180,
  "ph": 885,
  "scale": 3.0729166666666665,
  "overflow": 138060
}, {
  "previewSize": {
    "width": 352,
    "height": 288
  },
  "pw": 1180,
  "ph": 965.4545454545454,
  "scale": 3.352272727272727,
  "overflow": 232996.36363636353
}, {
  "previewSize": {
    "width": 320,
    "height": 240
  },
  "pw": 1180,
  "ph": 885,
  "scale": 3.6875,
  "overflow": 138060
}, {
  "previewSize": {
    "width": 240,
    "height": 160
  },
  "pw": 1180,
  "ph": 786.6666666666667,
  "scale": 4.916666666666667,
  "overflow": 22026.666666666744
}, {
  "previewSize": {
    "width": 176,
    "height": 144
  },
  "pw": 1180,
  "ph": 965.4545454545454,
  "scale": 6.704545454545454,
  "overflow": 232996.36363636353
}]

Comment 9

[Justin D'Arcangelo [:justindarc]]

According to what the algorithm is doing, it is technically picking the "correct" size based on the following criteria:

- Smallest overflow (22026.666666666628)
- Scale closest to 1.0 (1.6388888888888888)

Testing with the Nexus4 numbers, however, it is clear that the algorithm needs to compensate for a margin of error with regards to rounding of the overflow number. Based on what the algorithm of CameraUtils.selectOptimalPreviewSize() is supposed to do, we should end up with 3 acceptable sizes:

- 720x480 (Scale: 1.6388888888888888)
- 480x320 (Scale: 2.4583333333333335)
- 240x160 (Scale: 4.916666666666667)

All three of these sizes (when scaled) yield the least amount of overflow (22026.66...). The one that is then picked from these three is the one with the scale that is closest to 1.0 (720x480).

Comment 10

[Justin D'Arcangelo [:justindarc]]

Updated PR to also include updated test data for the CameraUtils unit test. I added real-world preview sizes/viewfinder sizes for Hamachi, Helix and Nexus 4.

Comment 11

[Diego Marcos [:dmarcos]]

Thanks for the thorough testing Justin

Comment 12

[Diego Marcos [:dmarcos]]

Landed in master:

https://github.com/mozilla-b2g/gaia/commit/a1a40a169fcdd5dd995551f0ec0ba2bd7f00ea9b