Higher Resolution Output

[piemonte]

Higher Resolution Output

[piemonte]

Hi @imackinn! Thanks for the complements.

So the current video resolution and compression settings are actually very similar to Vine. I have these settings maxed out based on testing across a sampling of devices and device types. You can bump up the resolution and/or reduce the amount of compression, but then you'll encounter situations where the videos drop frames or you create much larger files than you'd want to transfer.

You're not the only one that's asked me about this, so I may expose some enums where folks can pick how much compression they want. It may be good to do once faster hardware is more common, (iPhone 5S and beyond).

If you want to try it on your own, these are the lines you modify to change compression (i've left some of my other settings commented out for reference):

- (BOOL)_setupAssetWriterVideoInput:(CMFormatDescriptionRef)currentFormatDescription
{
    CMVideoDimensions dimensions = CMVideoFormatDescriptionGetDimensions(currentFormatDescription);

    // lower the bitRate, higher the compression, lets compress for 480 x 360 even though we record at 640 x 480
    // 87500, good for 480 x 360
    // 437500, good for 640 x 480
    float bitRate = 87500.0f * 8.0f;
    NSInteger frameInterval = 30;

Video resolution can be adjusted with using other presets:

   // specify video preset
        sessionPreset = AVCaptureSessionPreset640x480;

Hope that helps.

[yury]

// lower the bitRate, higher the compression, lets compress for 480 x 360 even though we record at 640 x 480
// 87500, good for 480 x 360
// 437500, good for 640 x 480

@piemonte , how did you get those numbers? Any specific formula?

[mitchellporter]

@piemonte Would you mind sharing the default settings that were used to create "compression settings similar to Vine" like in your comment?

I've modified all of mine and it's producing extremely high quality video but the file sizes are very large.

[mitchellporter]

For anyone who's curious, here are my current settings for capturing the highest quality video:

vision.cameraMode = PBJCameraModeVideo;
vision.cameraOrientation = PBJCameraOrientationPortrait;
vision.focusMode = PBJFocusModeContinuousAutoFocus;
vision.outputFormat = PBJOutputFormatPreset;
vision.captureSessionPreset = AVCaptureSessionPresetHigh;

The only problem is that a 4 minute video recorded with these settings will be around 100 MB which is ridiculous. I'm uploading these to an AWS S3 bucket and even on wifi the uploads feel pretty slow.

I really need to find a way to reduce the file size but still keep some quality.

Here are some code comments I left myself 3 weeks ago:

// AVCaptureSessionPresetHigh w/ a lower bitrate of PBJVideoBitRate480x360 looks good
// while they are recording, but then when you go to play it, it looks terrible eg. fuzzy
// especially if moving the camera while recording.