转载：https://blog.csdn.net/u011270282/article/details/53223055
- (void)startProcessing
{
previousFrameTime = kCMTimeZero;
previousActualFrameTime = CFAbsoluteTimeGetCurrent();
NSDictionary *inputOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES] forKey:AVURLAssetPreferPreciseDurationAndTimingKey];
AVURLAsset *inputAsset = [[AVURLAsset alloc] initWithURL:self.url options:inputOptions];
GPUImageMovie __block *blockSelf = self;
[inputAsset loadValuesAsynchronouslyForKeys:[NSArray arrayWithObject:@"tracks"] completionHandler: ^{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSError *error = nil;
AVKeyValueStatus tracksStatus = [inputAsset statusOfValueForKey:@"tracks" error:&error];
if (tracksStatus != AVKeyValueStatusLoaded)
{
return;
}
blockSelf.asset = inputAsset;
[blockSelf processAsset];
blockSelf = nil;
});
}];
}
- (AVAssetReader*)createAssetReader
{
NSError *error = nil;
AVAssetReader *assetReader = [AVAssetReader assetReaderWithAsset:self.asset error:&error];
NSMutableDictionary *outputSettings = [NSMutableDictionary dictionary];
[outputSettings setObject:@(kCVPixelFormatType_32BGRA) forKey:(id)kCVPixelBufferPixelFormatTypeKey];
// Maybe set alwaysCopiesSampleData to NO on iOS 5.0 for faster video decoding
AVAssetReaderTrackOutput *readerVideoTrackOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:[[self.asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] outputSettings:outputSettings];
readerVideoTrackOutput.alwaysCopiesSampleData = NO;
[assetReader addOutput:readerVideoTrackOutput];
NSArray *audioTracks = [self.asset tracksWithMediaType:AVMediaTypeAudio];
BOOL shouldRecordAudioTrack = (([audioTracks count] > 0) && (self.audioEncodingTarget != nil) );
AVAssetReaderTrackOutput *readerAudioTrackOutput = nil;
if (shouldRecordAudioTrack)
{
[self.audioEncodingTarget setShouldInvalidateAudioSampleWhenDone:YES];
// This might need to be extended to handle movies with more than one audio track
AVAssetTrack* audioTrack = [audioTracks objectAtIndex:0];
NSDictionary *dic = @{AVFormatIDKey :@(kAudioFormatLinearPCM),
AVLinearPCMIsBigEndianKey:@NO,
AVLinearPCMIsFloatKey :@NO,
AVLinearPCMBitDepthKey :@(16)
};
readerAudioTrackOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:audioTrack outputSettings: dic];
readerAudioTrackOutput.alwaysCopiesSampleData = NO;
[assetReader addOutput:readerAudioTrackOutput];
}
return assetReader;
}
- (void)processAsset
{
reader = [self createAssetReader];
AVAssetReaderOutput *readerVideoTrackOutput = nil;
AVAssetReaderOutput *readerAudioTrackOutput = nil;
audioEncodingIsFinished = YES;
for( AVAssetReaderOutput *output in reader.outputs ) {
if( [output.mediaType isEqualToString:AVMediaTypeAudio] ) {
audioEncodingIsFinished = NO;
readerAudioTrackOutput = output;
}
else if( [output.mediaType isEqualToString:AVMediaTypeVideo] ) {
readerVideoTrackOutput = output;
}
}
if ([reader startReading] == NO)
{
NSLog(@"Error reading from file at URL: %@", self.url);
return;
}
__unsafe_unretained GPUImageMovie *weakSelf = self;
while (reader.status == AVAssetReaderStatusReading && (!_shouldRepeat || keepLooping))
{
[weakSelf readNextVideoFrameFromOutput:readerVideoTrackOutput];
if ( (readerAudioTrackOutput) && (!audioEncodingIsFinished) )
{
[weakSelf readNextAudioSampleFromOutput:readerAudioTrackOutput];
}
}
if (reader.status == AVAssetReaderStatusCompleted) {
[reader cancelReading];
if (keepLooping) {
reader = nil;
dispatch_async(dispatch_get_main_queue(), ^{
[self startProcessing];
});
} else {
[weakSelf endProcessing];
}
}
}
- (BOOL)readNextAudioSampleFromOutput:(AVAssetReaderOutput *)readerAudioTrackOutput;
{
if (reader.status == AVAssetReaderStatusReading && ! audioEncodingIsFinished)
{
CMSampleBufferRef audioSampleBufferRef = [readerAudioTrackOutput copyNextSampleBuffer];
if (audioSampleBufferRef)
{
CFRelease(audioSampleBufferRef);
return YES;
}
else
{
}
}
return NO;
}
- (BOOL)readNextVideoFrameFromOutput:(AVAssetReaderOutput *)readerVideoTrackOutput;
{
if (reader.status == AVAssetReaderStatusReading && ! videoEncodingIsFinished)
{
CMSampleBufferRef sampleBufferRef = [readerVideoTrackOutput copyNextSampleBuffer];
if (sampleBufferRef)
{
CFRelease(sampleBufferRef);
return YES;
}
else
{
}
}
return NO;
}
具体可以看看GPUImageMovie，从这里拿出来改一改就可以了，注意设置输出视频和音频格式为自己想要的，比如RGBA、pcm。
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