For @sethwillits

CMSampleBufferWritingWithTrim.m

- (void)appendEncodedSampleBuffer:(CMSampleBufferRef)encodedSampleBuffer addTrimAtStart:(int)trimDuration fromSource:(id)source
{
    if(!_hasWrittenTrim) {
        GFLog(GFDebug, @"Adding trim to sample buffer from %@", source);
        
        const AudioStreamBasicDescription *asbd = CMAudioFormatDescriptionGetStreamBasicDescription(CMSampleBufferGetFormatDescription(encodedSampleBuffer));
        CMSetAttachment(encodedSampleBuffer, kCMSampleBufferAttachmentKey_TrimDurationAtStart, (id)CFAutorelease(
            CMTimeCopyAsDictionary(
                CMTimeMake(trimDuration, asbd->mSampleRate),
                kCFAllocatorDefault
            )
        ), kCMAttachmentMode_ShouldNotPropagate);
        _hasWrittenTrim = YES;
    }

	NSError *error;
	if(![_writer writeSampleBuffer:encodedSampleBuffer error:&error]) {
		[_delegate audioRecorder:self encounteredPermanentError:error];
		[self stop];
	}
}