How to check Resolution, bitrate of video in iOS - ios

Question

I'm developing a video compression functionally; my ideas are below:
Getting resolution and bit-rate of video.
Check resolution of video. If it larger 640x480, I will compress this video in half and adjust the bit rate in 1/4 . E.g., if resolution of video is 1920x1080, it will be compressed to 960x540 and 1920x1080 at 4mbps will be compressed to 960x540 at 1mbps.
I have a few questions:
How can get resolution and bit-rate of video in iOS?
If compress 1920x1080 in half to 960x540, the bit-rate will also adaptively adjust, or do I still need to set the bitrate manually? How can do that?
I tried below code to compress video but I don't know it compressed to which resolution:
- (void)convertVideoToLowQuailtyWithInputURL:(NSURL*)inputURL
outputURL:(NSURL*)outputURL
handler:(void (^)(AVAssetExportSession*))handler
{
[[NSFileManager defaultManager] removeItemAtURL:outputURL error:nil];
AVURLAsset *urlAsset = [AVURLAsset URLAssetWithURL:inputURL options:nil];
AVAssetExportSession *session = [[AVAssetExportSession alloc] initWithAsset: urlAsset presetName:AVAssetExportPresetLowQuality];
session.outputURL = outputURL;
session.outputFileType = AVFileTypeQuickTimeMovie;
[session exportAsynchronouslyWithCompletionHandler:^(void)
{
handler(session);
}];
}
Please give me some advice. Thanks in advance.

Answer 1

To get the resolution of the video use this :-
AVAssetTrack *videoTrack = nil;
AVURLAsset *asset = [AVAsset assetWithURL:[NSURL fileURLWithPath:originalVideo]];
NSArray *videoTracks = [asset tracksWithMediaType:AVMediaTypeVideo];
CMFormatDescriptionRef formatDescription = NULL;
NSArray *formatDescriptions = [videoTrack formatDescriptions];
if ([formatDescriptions count] > 0)
formatDescription = (CMFormatDescriptionRef)[formatDescriptions objectAtIndex:0];
if ([videoTracks count] > 0)
videoTrack = [videoTracks objectAtIndex:0];
CGSize trackDimensions = {
.width = 0.0,
.height = 0.0,
};
trackDimensions = [videoTrack naturalSize];
int width = trackDimensions.width;
int height = trackDimensions.height;
NSLog(#"Resolution = %d X %d",width ,height);
you can get the frameRate and bitrate as follows:-
float frameRate = [videoTrack nominalFrameRate];
float bps = [videoTrack estimatedDataRate];
NSLog(#"Frame rate == %f",frameRate);
NSLog(#"bps rate == %f",bps);

Answer 2

Video resolution in Swift:
func resolutionForLocalVideo(url:NSURL) -> CGSize?
{
guard let track = AVAsset(URL: url).tracksWithMediaType(AVMediaTypeVideo).first else { return nil }
let size = CGSizeApplyAffineTransform(track.naturalSize, track.preferredTransform)
return CGSize(width: fabs(size.width), height: fabs(size.height))
}
Solutions without preferredTransform do not return correct values for some videos on the latest devices!

Answer 3

Here is Avt's answer updated and tested for Swift 3:
func resolutionForLocalVideo(url:URL) -> CGSize?
{
guard let track = AVURLAsset(url: url).tracks(withMediaType: AVMediaTypeVideo).first else { return nil }
let size = track.naturalSize.applying(track.preferredTransform)
return CGSize(width: fabs(size.width), height: fabs(size.height))
}