getting progress information constantly with AVAssetSessionExport - objective-c

Question

I have an issue where I'm using AVAssetSessionExport to do some video conversions.
I've been trying to get the progress information on a UIProgressView but i can't seem to achieve that with this set of code. Could I get suggestions on how I might be able to achieve this?
(look at the commented code, that's how i'm updating the progress bar, but it doesn't work well)
NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:composition];
if ([compatiblePresets containsObject:AVAssetExportPresetHighestQuality]) {
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]
initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:1];
UITableViewCell *cell = (UITableViewCell *)[(UITableView *)self.view cellForRowAtIndexPath:indexPath];
// UIProgressView *prog = [[UIProgressView alloc] initWithProgressViewStyle:UIProgressViewStyleBar];
// [cell.contentView addSubview:prog];
//
exportSession.outputURL = [NSURL fileURLWithPath:[[ShowDAO userDocumentDirectory] stringByAppendingString:exportFilename]];
exportSession.outputFileType = AVFileTypeQuickTimeMovie;
CMTime start = CMTimeMakeWithSeconds(0, 1);
CMTime duration = CMTimeMakeWithSeconds(1000, 1);
CMTimeRange range = CMTimeRangeMake(start, duration);
exportSession.timeRange = range;
[exportSession exportAsynchronouslyWithCompletionHandler:^{
switch ([exportSession status]) {
case AVAssetExportSessionStatusCompleted:
NSLog(#"Export Completed");
[DSBezelActivityView removeViewAnimated:YES];
//delete unused video file
[[NSFileManager defaultManager] removeItemAtPath: [[ShowDAO userDocumentDirectory] stringByAppendingString:videoFilename] error: NULL];
break;
case AVAssetExportSessionStatusFailed:
NSLog(#"Export failed: %#", [[exportSession error] localizedDescription]);
break;
case AVAssetExportSessionStatusCancelled:
NSLog(#"Export cancelled");
break;
default:
break;
}
}];
// while (exportSession.progress <=0.1){
// NSLog(#"prog : %f",exportSession.progress);
// [prog setProgress:exportSession.progress];
//// sleep(1);
// }
[exportSession release];

Answer 1

You're blocking the main thread with the commented code. You should make the exportSession a property of the class you're doing this in. Then I'd suggest having an NSTimer which calls a class method periodically which then updates the progressView until the export session is done. I hope this is clear, if not I can provide some code.

Answer 2

This is what i am doing.
BOOL goOnFlag = YES;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
int count = 0;
while(fabs(avAssetExportSession.progress - 1.0)>0.01&&goOnFlag){
NSLog(#"loading... : %f",avAssetExportSession.progress);
sleep(1);
if(avAssetExportSession.progress==0)
count++;
if(count>8){
[self async_main:^{
[avAssetExportSession cancelExport];
goOnFlag = NO;
NSLog(#"save failed");
}];
}
}
});