iphone ios 视频采集AVCaptureSessionPresetHigh/Medium/Low分辨率等参数

做视频capture的时候老是要用到这些参数,记录一下,以下均来自官网

http://developer.apple.com/library/mac/#documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/04_MediaCapture.html#//apple_ref/doc/uid/TP40010188-CH5-SW3
 

Symbol

Resolution

Comments

AVCaptureSessionPresetHigh

High

Highest recording quality.

This varies per device.

AVCaptureSessionPresetMedium

Medium

Suitable for WiFi sharing.

The actual values may change.

AVCaptureSessionPresetLow

Low

Suitable for 3G sharing.

The actual values may change.

AVCaptureSessionPreset640x480

640x480

VGA.

AVCaptureSessionPreset1280x720

1280x720

720p HD.

AVCaptureSessionPresetPhoto

Photo

Full photo resolution.

This is not supported for video output

Preset

iPhone 3G

iPhone 3GS

iPhone 4 (Back)

iPhone 4 (Front)

High

No video

Apple Lossless

640x480

3.5 mbps

1280x720

10.5 mbps

640x480

3.5 mbps

Medium

No video

Apple Lossless

480x360

700 kbps

480x360

700 kbps

480x360

700 kbps

Low

No video

Apple Lossless

192x144

128 kbps

192x144

128 kbps

192x144

128 kbps

640x480

No video

Apple Lossless

640x480

3.5 mbps

640x480

3.5 mbps

640x480

3.5 mbps

1280x720

No video

Apple Lossless

No video

64 kbps AAC

No video

64 kbps AAC

No video

64 kbps AAC

Photo

Not supported for video output

Not supported for video output

Not supported for video output

Not supported for video output

Feature

iPhone 3G

iPhone 3GS

iPhone 4 (Back)

iPhone 4 (Front)

Focus mode

NO

YES

YES

NO

Focus point of interest

NO

YES

YES

NO

Exposure mode

YES

YES

YES

YES

Exposure point of interest

NO

YES

YES

YES

White balance mode

YES

YES

YES

YES

Flash mode

NO

NO

YES

NO

Torch mode

NO

NO

YES

NO

 

Capturing Still Images

You use an AVCaptureStillImageOutput output if you want to capture still images with accompanying metadata. The resolution of the image depends on the preset for the session, as illustrated in this table:

Preset

iPhone 3G

iPhone 3GS

iPhone 4 (Back)

iPhone 4 (Front)

High

400x304

640x480

1280x720

640x480

Medium

400x304

480x360

480x360

480x360

Low

400x304

192x144

192x144

192x144

640x480

N/A

640x480

640x480

640x480

1280x720

N/A

N/A

1280x720

N/A

Photo

1600x1200

2048x1536

2592x1936

640x480

Pixel and Encoding Formats

Different devices support different image formats:

iPhone 3G

iPhone 3GS

iPhone 4

yuvs, 2vuy, BGRA, jpeg

420f, 420v, BGRA, jpeg

420f, 420v, BGRA, jpeg

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