iOS MP4解码成yuv和pcm数据

- (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。