0x00 需求
把视频拆成图片，视频文件其实是一帧帧的图片，视频文件信息及结构这里就不再赘述了，网上有很多讲的都比较好的文章，请自行谷歌
0x01 代码实现(AVAssetImageGenerator)
/**
* 把视频文件拆成图片保存在沙盒中
*
* @param fileUrl 本地视频文件URL
* @param fps 拆分时按此帧率进行拆分
* @param completedBlock 所有帧被拆完成后回调
*/
- (void)splitVideo:(NSURL *)fileUrl fps:(float)fps completedBlock:(void(^)())completedBlock {
if (!fileUrl) {
return;
}
NSDictionary *optDict = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:NO] forKey:AVURLAssetPreferPreciseDurationAndTimingKey];
AVURLAsset *avasset = [[AVURLAsset alloc] initWithURL:fileUrl options:optDict];
CMTime cmtime = avasset.duration; //视频时间信息结构体
Float64 durationSeconds = CMTimeGetSeconds(cmtime); //视频总秒数
NSMutableArray *times = [NSMutableArray array];
Float64 totalFrames = durationSeconds * fps; //获得视频总帧数
CMTime timeFrame;
for (int i = 1; i <= totalFrames; i++) {
timeFrame = CMTimeMake(i, fps); //第i帧 帧率
NSValue *timeValue = [NSValue valueWithCMTime:timeFrame];
[times addObject:timeValue];
}
NSLog(@"------- start");
AVAssetImageGenerator *imgGenerator = [[AVAssetImageGenerator alloc] initWithAsset:avasset];
//防止时间出现偏差
imgGenerator.requestedTimeToleranceBefore = kCMTimeZero;
imgGenerator.requestedTimeToleranceAfter = kCMTimeZero;
NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
NSInteger timesCount = [times count];
[imgGenerator generateCGImagesAsynchronouslyForTimes:times completionHandler:^(CMTime requestedTime, CGImageRef _Nullable image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError * _Nullable error) {
printf("current-----: %lld\n", requestedTime.value);
switch (result) {
case AVAssetImageGeneratorCancelled:
NSLog(@"Cancelled");
break;
case AVAssetImageGeneratorFailed:
NSLog(@"Failed");
break;
case AVAssetImageGeneratorSucceeded: {
NSString *filePath = [cachePath stringByAppendingPathComponent:[NSString stringWithFormat:@"/%lld.png",requestedTime.value]];
NSData *imgData = UIImagePNGRepresentation([UIImage imageWithCGImage:image]);
[imgData writeToFile:filePath atomically:YES];
if (requestedTime.value == timesCount) {
NSLog(@"completed");
if (completedBlock) {
completedBlock();
}
}
}
break;
}
}];
}
0x10 获取单帧图片
- (nullable CGImageRef)copyCGImageAtTime:(CMTime)requestedTime actualTime:(nullable CMTime *)actualTime error:(NSError * __nullable * __nullable)outError CF_RETURNS_RETAINED;
requestedTime:要获取的帧时间CMTimeMake(a,b)
0x11 CMTime结构体
/*!
@typedef CMTime
@abstract Rational time value represented as int64/int32.
*/
typedef struct
{
CMTimeValue value; /*! @field value The value of the CMTime. value/timescale = seconds. */
CMTimeScale timescale; /*! @field timescale The timescale of the CMTime. value/timescale = seconds. */
CMTimeFlags flags; /*! @field flags The flags, eg. kCMTimeFlags_Valid, kCMTimeFlags_PositiveInfinity, etc. */
CMTimeEpoch epoch; /*! @field epoch Differentiates between equal timestamps that are actually different because
of looping, multi-item sequencing, etc.
Will be used during comparison: greater epochs happen after lesser ones.
Additions/subtraction is only possible within a single epoch,
however, since epoch length may be unknown/variable. */
} CMTime;
CMTime是专门用于表示视频时间的结构体
value不是指时间
timescale可以理解为帧率
获得秒数：value / timescale = seconds
创建CMTime 用 CMTimeMake(a, b) 当前第a帧，每秒b帧
