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iFreeman avatar

Dessin de la forme d'onde avec AVAssetReader

Demandé el 17 de Février, 2011
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J'ai de la lecture de la chanson de la bibliothèque iPod à l'aide de assetUrl (dans le code, il a nommé audioUrl) Je peux jouer de nombreuses façons, je peux le couper, je peux faire quelques mouvement de précession, avec cela, mais... Je ne comprends vraiment pas ce que je vais bien pouvoir faire avec cette CMSampleBufferRef à obtenir des données pour le dessin de la forme d'onde! J'ai besoin d'informations sur les valeurs de crête, comment je peux l'obtenir ceci (peut-être un autre)? 

    AVAssetTrack * songTrack = [audioUrl.tracks objectAtIndex:0];
    AVAssetReaderTrackOutput * output = [[AVAssetReaderTrackOutput alloc] initWithTrack:songTrack outputSettings:nil];
    [reader addOutput:output];
    [output release];

    NSMutableData * fullSongData = [[NSMutableData alloc] init];
    [reader startReading];

    while (reader.status == AVAssetReaderStatusReading){

        AVAssetReaderTrackOutput * trackOutput = 
        (AVAssetReaderTrackOutput *)[reader.outputs objectAtIndex:0];

        CMSampleBufferRef sampleBufferRef = [trackOutput copyNextSampleBuffer];

        if (sampleBufferRef){/* what I gonna do with this? */}

S'il vous plaît aidez-moi!

Demandé el 17 de Février, 2011 par iFreeman

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264voto

unsynchronized avatar
unsynchronized Points 2576

J'étais à la recherche de quelque chose de similaire et a décidé de "lancer mon propre." Je me rends compte que c'est un vieux post, mais au cas où quelqu'un d'autre est à la recherche de cela, voici ma solution. il est relativement rapide et sale et normalise l'image de "pleine échelle". les images qu'il crée sont "large", c'est à dire vous devez les placer dans un UIScrollView ou de gérer l'affichage.

ceci est basé sur certaines réponses données à cette question

Exemple De Sortie

sample waveform

EDIT: j'ai ajouté une version logarithmique de la moyenne et de rendre les méthodes, voir la fin de ce message pour la version alternative et la comparaison de sorties. Personnellement, je préfère l'original de la version linéaire, mais nous avons décidé de le poster, au cas où quelqu'un peut améliorer l'algorithme utilisé.

Vous aurez besoin de ces importations:

#import <MediaPlayer/MediaPlayer.h>
#import <AVFoundation/AVFoundation.h>

Tout d'abord, un générique de la méthode de rendu qui prend un pointeur vers la moyenne de l'échantillon de données,
et renvoie une UIImage. Remarque: ces exemples ne sont pas jouables, des échantillons audio. 

-(UIImage *) audioImageGraph:(SInt16 *) samples
                normalizeMax:(SInt16) normalizeMax
                 sampleCount:(NSInteger) sampleCount 
                channelCount:(NSInteger) channelCount
                 imageHeight:(float) imageHeight {

    CGSize imageSize = CGSizeMake(sampleCount, imageHeight);
    UIGraphicsBeginImageContext(imageSize);
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
    CGContextSetAlpha(context,1.0);
    CGRect rect;
    rect.size = imageSize;
    rect.origin.x = 0;
    rect.origin.y = 0;

    CGColorRef leftcolor = [[UIColor whiteColor] CGColor];
    CGColorRef rightcolor = [[UIColor redColor] CGColor];

    CGContextFillRect(context, rect);

    CGContextSetLineWidth(context, 1.0);

    float halfGraphHeight = (imageHeight / 2) / (float) channelCount ;
    float centerLeft = halfGraphHeight;
    float centerRight = (halfGraphHeight*3) ; 
    float sampleAdjustmentFactor = (imageHeight/ (float) channelCount) / (float) normalizeMax;

    for (NSInteger intSample = 0 ; intSample < sampleCount ; intSample ++ ) {
        SInt16 left = *samples++;
        float pixels = (float) left;
        pixels *= sampleAdjustmentFactor;
        CGContextMoveToPoint(context, intSample, centerLeft-pixels);
        CGContextAddLineToPoint(context, intSample, centerLeft+pixels);
        CGContextSetStrokeColorWithColor(context, leftcolor);
        CGContextStrokePath(context);

        if (channelCount==2) {
            SInt16 right = *samples++;
            float pixels = (float) right;
            pixels *= sampleAdjustmentFactor;
            CGContextMoveToPoint(context, intSample, centerRight - pixels);
            CGContextAddLineToPoint(context, intSample, centerRight + pixels);
            CGContextSetStrokeColorWithColor(context, rightcolor);
            CGContextStrokePath(context); 
        }
    }

    // Create new image
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    // Tidy up
    UIGraphicsEndImageContext();   

    return newImage;
}

Ensuite, une méthode qui prend un AVURLAsset, et renvoie les données d'image au format PNG

- (NSData *) renderPNGAudioPictogramForAsset:(AVURLAsset *)songAsset {

    NSError * error = nil;
    AVAssetReader * reader = [[AVAssetReader alloc] initWithAsset:songAsset error:&error];
    AVAssetTrack * songTrack = [songAsset.tracks objectAtIndex:0];

    NSDictionary* outputSettingsDict = [[NSDictionary alloc] initWithObjectsAndKeys:
                                        [NSNumber numberWithInt:kAudioFormatLinearPCM],AVFormatIDKey,
                                        //     [NSNumber numberWithInt:44100.0],AVSampleRateKey, /*Not Supported*/
                                        //     [NSNumber numberWithInt: 2],AVNumberOfChannelsKey,    /*Not Supported*/
                                        [NSNumber numberWithInt:16],AVLinearPCMBitDepthKey,
                                        [NSNumber numberWithBool:NO],AVLinearPCMIsBigEndianKey,
                                        [NSNumber numberWithBool:NO],AVLinearPCMIsFloatKey,
                                        [NSNumber numberWithBool:NO],AVLinearPCMIsNonInterleaved,
                                        nil];

    AVAssetReaderTrackOutput* output = [[AVAssetReaderTrackOutput alloc] initWithTrack:songTrack outputSettings:outputSettingsDict];

    [reader addOutput:output];
    [output release];

    UInt32 sampleRate,channelCount;

    NSArray* formatDesc = songTrack.formatDescriptions;
    for(unsigned int i = 0; i < [formatDesc count]; ++i) {
        CMAudioFormatDescriptionRef item = (CMAudioFormatDescriptionRef)[formatDesc objectAtIndex:i];
        const AudioStreamBasicDescription* fmtDesc = CMAudioFormatDescriptionGetStreamBasicDescription (item);
        if(fmtDesc ) {

            sampleRate = fmtDesc->mSampleRate;
            channelCount = fmtDesc->mChannelsPerFrame;

            //    NSLog(@"channels:%u, bytes/packet: %u, sampleRate %f",fmtDesc->mChannelsPerFrame, fmtDesc->mBytesPerPacket,fmtDesc->mSampleRate);
        }
    }

    UInt32 bytesPerSample = 2 * channelCount;
    SInt16 normalizeMax = 0;

    NSMutableData * fullSongData = [[NSMutableData alloc] init];
    [reader startReading];

    UInt64 totalBytes = 0;         
    SInt64 totalLeft = 0;
    SInt64 totalRight = 0;
    NSInteger sampleTally = 0;

    NSInteger samplesPerPixel = sampleRate / 50;

    while (reader.status == AVAssetReaderStatusReading){

        AVAssetReaderTrackOutput * trackOutput = (AVAssetReaderTrackOutput *)[reader.outputs objectAtIndex:0];
        CMSampleBufferRef sampleBufferRef = [trackOutput copyNextSampleBuffer];

        if (sampleBufferRef){
            CMBlockBufferRef blockBufferRef = CMSampleBufferGetDataBuffer(sampleBufferRef);

            size_t length = CMBlockBufferGetDataLength(blockBufferRef);
            totalBytes += length;

            NSAutoreleasePool *wader = [[NSAutoreleasePool alloc] init];

            NSMutableData * data = [NSMutableData dataWithLength:length];
            CMBlockBufferCopyDataBytes(blockBufferRef, 0, length, data.mutableBytes);

            SInt16 * samples = (SInt16 *) data.mutableBytes;
            int sampleCount = length / bytesPerSample;
            for (int i = 0; i < sampleCount ; i ++) {

                SInt16 left = *samples++;
                totalLeft  += left;

                SInt16 right;
                if (channelCount==2) {
                    right = *samples++;
                    totalRight += right;
                }

                sampleTally++;

                if (sampleTally > samplesPerPixel) {

                    left  = totalLeft / sampleTally; 

                    SInt16 fix = abs(left);
                    if (fix > normalizeMax) {
                        normalizeMax = fix;
                    }

                    [fullSongData appendBytes:&left length:sizeof(left)];

                    if (channelCount==2) {
                        right = totalRight / sampleTally; 

                        SInt16 fix = abs(right);
                        if (fix > normalizeMax) {
                            normalizeMax = fix;
                        }

                        [fullSongData appendBytes:&right length:sizeof(right)];
                    }

                    totalLeft   = 0;
                    totalRight  = 0;
                    sampleTally = 0;
                }
            }

           [wader drain];

            CMSampleBufferInvalidate(sampleBufferRef);
            CFRelease(sampleBufferRef);
        }
    }

    NSData * finalData = nil;

    if (reader.status == AVAssetReaderStatusFailed || reader.status == AVAssetReaderStatusUnknown){
        // Something went wrong. return nil

        return nil;
    }

    if (reader.status == AVAssetReaderStatusCompleted){

        NSLog(@"rendering output graphics using normalizeMax %d",normalizeMax);

        UIImage *test = [self audioImageGraph:(SInt16 *) 
                         fullSongData.bytes 
                                 normalizeMax:normalizeMax 
                                  sampleCount:fullSongData.length / 4 
                                 channelCount:2
                                  imageHeight:100];

        finalData = imageToData(test);
    }        

    [fullSongData release];
    [reader release];

    return finalData;
}

Options Avancées: Enfin, si vous voulez être en mesure de lire les fichiers audio à l'aide de AVAudioPlayer, vous aurez besoin de cache pour vos applications de bundle dossier cache. Depuis que je faisais cela, j'ai décidé de mettre en cache les données d'image aussi, et enveloppé le tout dans une UIImage catégorie. vous devez inclure ce open source offrant à extraire l'audio, et un peu de code à partir d' ici de traiter de certains arrière-plan filetage caractéristiques.

tout d'abord, certains définit, et un peu de classe générique méthodes pour la gestion des noms de chemin d'accès, etc 

//#define imgExt @"jpg"
//#define imageToData(x) UIImageJPEGRepresentation(x,4)

#define imgExt @"png"
#define imageToData(x) UIImagePNGRepresentation(x)

+ (NSString *) assetCacheFolder  {
    NSArray  *assetFolderRoot = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
    return [NSString stringWithFormat:@"%@/audio", [assetFolderRoot objectAtIndex:0]];
 }

+ (NSString *) cachedAudioPictogramPathForMPMediaItem:(MPMediaItem*) item {
    NSString *assetFolder = [[self class] assetCacheFolder];
    NSNumber * libraryId = [item valueForProperty:MPMediaItemPropertyPersistentID];
    NSString *assetPictogramFilename = [NSString stringWithFormat:@"asset_%@.%@",libraryId,imgExt];
    return [NSString stringWithFormat:@"%@/%@", assetFolder, assetPictogramFilename];
}

+ (NSString *) cachedAudioFilepathForMPMediaItem:(MPMediaItem*) item {
    NSString *assetFolder = [[self class] assetCacheFolder];

    NSURL    * assetURL = [item valueForProperty:MPMediaItemPropertyAssetURL];
    NSNumber * libraryId = [item valueForProperty:MPMediaItemPropertyPersistentID];

    NSString *assetFileExt = [[[assetURL path] lastPathComponent] pathExtension];
    NSString *assetFilename = [NSString stringWithFormat:@"asset_%@.%@",libraryId,assetFileExt];
    return [NSString stringWithFormat:@"%@/%@", assetFolder, assetFilename];
}

+ (NSURL *) cachedAudioURLForMPMediaItem:(MPMediaItem*) item {
    NSString *assetFilepath = [[self class] cachedAudioFilepathForMPMediaItem:item];
    return [NSURL fileURLWithPath:assetFilepath];
}

Maintenant, la méthode init qui ne "l'entreprise" 

- (id) initWithMPMediaItem:(MPMediaItem*) item 
           completionBlock:(void (^)(UIImage* delayedImagePreparation))completionBlock  {

    NSFileManager *fman = [NSFileManager defaultManager];
    NSString *assetPictogramFilepath = [[self class] cachedAudioPictogramPathForMPMediaItem:item];

    if ([fman fileExistsAtPath:assetPictogramFilepath]) {

        NSLog(@"Returning cached waveform pictogram: %@",[assetPictogramFilepath lastPathComponent]);

        self = [self initWithContentsOfFile:assetPictogramFilepath];
        return self;
    }

    NSString *assetFilepath = [[self class] cachedAudioFilepathForMPMediaItem:item];

    NSURL *assetFileURL = [NSURL fileURLWithPath:assetFilepath];

    if ([fman fileExistsAtPath:assetFilepath]) {

        NSLog(@"scanning cached audio data to create UIImage file: %@",[assetFilepath lastPathComponent]);

        [assetFileURL retain];
        [assetPictogramFilepath retain];

        [NSThread MCSM_performBlockInBackground: ^{

            AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:assetFileURL options:nil];
            NSData *waveFormData = [self renderPNGAudioPictogramForAsset:asset]; 

            [waveFormData writeToFile:assetPictogramFilepath atomically:YES];

            [assetFileURL release];
            [assetPictogramFilepath release];

            if (completionBlock) {

                [waveFormData retain];
                [NSThread MCSM_performBlockOnMainThread:^{

                    UIImage *result = [UIImage imageWithData:waveFormData];

                    NSLog(@"returning rendered pictogram on main thread (%d bytes %@ data in UIImage %0.0f x %0.0f pixels)",waveFormData.length,[imgExt uppercaseString],result.size.width,result.size.height);

                    completionBlock(result);

                    [waveFormData release];
                }];
            }
        }];

        return nil;

    } else {

        NSString *assetFolder = [[self class] assetCacheFolder];

        [fman createDirectoryAtPath:assetFolder withIntermediateDirectories:YES attributes:nil error:nil];

        NSLog(@"Preparing to import audio asset data %@",[assetFilepath lastPathComponent]);

        [assetPictogramFilepath retain];
        [assetFileURL retain];

        TSLibraryImport* import = [[TSLibraryImport alloc] init];
        NSURL    * assetURL = [item valueForProperty:MPMediaItemPropertyAssetURL];

         [import importAsset:assetURL toURL:assetFileURL completionBlock:^(TSLibraryImport* import) {
            //check the status and error properties of
            //TSLibraryImport

            if (import.error) {

                NSLog (@"audio data import failed:%@",import.error);

            } else{
                NSLog (@"Creating waveform pictogram file: %@", [assetPictogramFilepath lastPathComponent]);
                AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:assetFileURL options:nil];
                NSData *waveFormData = [self renderPNGAudioPictogramForAsset:asset]; 

                [waveFormData writeToFile:assetPictogramFilepath atomically:YES];

                if (completionBlock) {
                     [waveFormData retain];
                    [NSThread MCSM_performBlockOnMainThread:^{

                        UIImage *result = [UIImage imageWithData:waveFormData];
                        NSLog(@"returning rendered pictogram on main thread (%d bytes %@ data in UIImage %0.0f x %0.0f pixels)",waveFormData.length,[imgExt uppercaseString],result.size.width,result.size.height);

                        completionBlock(result);

                        [waveFormData release];
                    }];
                }
            }

            [assetPictogramFilepath release];
            [assetFileURL release];

        }  ];

        return nil;
    }
}

Un exemple d'appel ce : 

-(void) importMediaItem {

    MPMediaItem* item = [self mediaItem];

    // since we will be needing this for playback, save the url to the cached audio.
    [url release];
    url = [[UIImage cachedAudioURLForMPMediaItem:item] retain];

    [waveFormImage release];

    waveFormImage = [[UIImage alloc ] initWithMPMediaItem:item completionBlock:^(UIImage* delayedImagePreparation){

        waveFormImage = [delayedImagePreparation retain];
        [self displayWaveFormImage];
    }];

    if (waveFormImage) {
        [waveFormImage retain];
        [self displayWaveFormImage];
    }
}

Logarithmique version de la moyenne et de rendre les méthodes de 

#define absX(x) (x<0?0-x:x)
#define minMaxX(x,mn,mx) (x<=mn?mn:(x>=mx?mx:x))
#define noiseFloor (-90.0)
#define decibel(amplitude) (20.0 * log10(absX(amplitude)/32767.0))

-(UIImage *) audioImageLogGraph:(Float32 *) samples
                normalizeMax:(Float32) normalizeMax
                 sampleCount:(NSInteger) sampleCount 
                channelCount:(NSInteger) channelCount
                 imageHeight:(float) imageHeight {

    CGSize imageSize = CGSizeMake(sampleCount, imageHeight);
    UIGraphicsBeginImageContext(imageSize);
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
    CGContextSetAlpha(context,1.0);
    CGRect rect;
    rect.size = imageSize;
    rect.origin.x = 0;
    rect.origin.y = 0;

    CGColorRef leftcolor = [[UIColor whiteColor] CGColor];
    CGColorRef rightcolor = [[UIColor redColor] CGColor];

    CGContextFillRect(context, rect);

    CGContextSetLineWidth(context, 1.0);

    float halfGraphHeight = (imageHeight / 2) / (float) channelCount ;
    float centerLeft = halfGraphHeight;
    float centerRight = (halfGraphHeight*3) ; 
    float sampleAdjustmentFactor = (imageHeight/ (float) channelCount) / (normalizeMax - noiseFloor) / 2;

    for (NSInteger intSample = 0 ; intSample < sampleCount ; intSample ++ ) {
        Float32 left = *samples++;
        float pixels = (left - noiseFloor) * sampleAdjustmentFactor;
        CGContextMoveToPoint(context, intSample, centerLeft-pixels);
        CGContextAddLineToPoint(context, intSample, centerLeft+pixels);
        CGContextSetStrokeColorWithColor(context, leftcolor);
        CGContextStrokePath(context);

        if (channelCount==2) {
            Float32 right = *samples++;
            float pixels = (right - noiseFloor) * sampleAdjustmentFactor;
            CGContextMoveToPoint(context, intSample, centerRight - pixels);
            CGContextAddLineToPoint(context, intSample, centerRight + pixels);
            CGContextSetStrokeColorWithColor(context, rightcolor);
            CGContextStrokePath(context); 
        }
    }

    // Create new image
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    // Tidy up
    UIGraphicsEndImageContext();   

    return newImage;
}

- (NSData *) renderPNGAudioPictogramLogForAsset:(AVURLAsset *)songAsset {

    NSError * error = nil;
    AVAssetReader * reader = [[AVAssetReader alloc] initWithAsset:songAsset error:&error];
    AVAssetTrack * songTrack = [songAsset.tracks objectAtIndex:0];

    NSDictionary* outputSettingsDict = [[NSDictionary alloc] initWithObjectsAndKeys:
                                        [NSNumber numberWithInt:kAudioFormatLinearPCM],AVFormatIDKey,
                                        //     [NSNumber numberWithInt:44100.0],AVSampleRateKey, /*Not Supported*/
                                        //     [NSNumber numberWithInt: 2],AVNumberOfChannelsKey,    /*Not Supported*/

                                        [NSNumber numberWithInt:16],AVLinearPCMBitDepthKey,
                                        [NSNumber numberWithBool:NO],AVLinearPCMIsBigEndianKey,
                                        [NSNumber numberWithBool:NO],AVLinearPCMIsFloatKey,
                                        [NSNumber numberWithBool:NO],AVLinearPCMIsNonInterleaved,
                                        nil];

    AVAssetReaderTrackOutput* output = [[AVAssetReaderTrackOutput alloc] initWithTrack:songTrack outputSettings:outputSettingsDict];

    [reader addOutput:output];
    [output release];

    UInt32 sampleRate,channelCount;

    NSArray* formatDesc = songTrack.formatDescriptions;
    for(unsigned int i = 0; i < [formatDesc count]; ++i) {
        CMAudioFormatDescriptionRef item = (CMAudioFormatDescriptionRef)[formatDesc objectAtIndex:i];
        const AudioStreamBasicDescription* fmtDesc = CMAudioFormatDescriptionGetStreamBasicDescription (item);
        if(fmtDesc ) {

            sampleRate = fmtDesc->mSampleRate;
            channelCount = fmtDesc->mChannelsPerFrame;

            //    NSLog(@"channels:%u, bytes/packet: %u, sampleRate %f",fmtDesc->mChannelsPerFrame, fmtDesc->mBytesPerPacket,fmtDesc->mSampleRate);
        }
    }

    UInt32 bytesPerSample = 2 * channelCount;
    Float32 normalizeMax = noiseFloor;
    NSLog(@"normalizeMax = %f",normalizeMax);
    NSMutableData * fullSongData = [[NSMutableData alloc] init];
    [reader startReading];

    UInt64 totalBytes = 0; 
    Float64 totalLeft = 0;
    Float64 totalRight = 0;
    Float32 sampleTally = 0;

    NSInteger samplesPerPixel = sampleRate / 50;

    while (reader.status == AVAssetReaderStatusReading){

        AVAssetReaderTrackOutput * trackOutput = (AVAssetReaderTrackOutput *)[reader.outputs objectAtIndex:0];
        CMSampleBufferRef sampleBufferRef = [trackOutput copyNextSampleBuffer];

        if (sampleBufferRef){
            CMBlockBufferRef blockBufferRef = CMSampleBufferGetDataBuffer(sampleBufferRef);

            size_t length = CMBlockBufferGetDataLength(blockBufferRef);
            totalBytes += length;

            NSAutoreleasePool *wader = [[NSAutoreleasePool alloc] init];

            NSMutableData * data = [NSMutableData dataWithLength:length];
            CMBlockBufferCopyDataBytes(blockBufferRef, 0, length, data.mutableBytes);

            SInt16 * samples = (SInt16 *) data.mutableBytes;
            int sampleCount = length / bytesPerSample;
            for (int i = 0; i < sampleCount ; i ++) {

                Float32 left = (Float32) *samples++;
                left = decibel(left);
                left = minMaxX(left,noiseFloor,0);
                totalLeft  += left;

                Float32 right;
                if (channelCount==2) {
                    right = (Float32) *samples++;
                    right = decibel(right);
                    right = minMaxX(right,noiseFloor,0);
                    totalRight += right;
                }

                sampleTally++;

                if (sampleTally > samplesPerPixel) {

                    left  = totalLeft / sampleTally; 
                    if (left > normalizeMax) {
                        normalizeMax = left;
                    }

                   // NSLog(@"left average = %f, normalizeMax = %f",left,normalizeMax);

                    [fullSongData appendBytes:&left length:sizeof(left)];

                    if (channelCount==2) {
                        right = totalRight / sampleTally; 

                        if (right > normalizeMax) {
                            normalizeMax = right;
                        }

                        [fullSongData appendBytes:&right length:sizeof(right)];
                    }

                    totalLeft   = 0;
                    totalRight  = 0;
                    sampleTally = 0;
                }
            }

           [wader drain];

            CMSampleBufferInvalidate(sampleBufferRef);
            CFRelease(sampleBufferRef);
        }
    }

    NSData * finalData = nil;

    if (reader.status == AVAssetReaderStatusFailed || reader.status == AVAssetReaderStatusUnknown){
        // Something went wrong. Handle it.
    }

    if (reader.status == AVAssetReaderStatusCompleted){
        // You're done. It worked.

        NSLog(@"rendering output graphics using normalizeMax %f",normalizeMax);

        UIImage *test = [self audioImageLogGraph:(Float32 *) fullSongData.bytes 
                                 normalizeMax:normalizeMax 
                                  sampleCount:fullSongData.length / (sizeof(Float32) * 2) 
                                 channelCount:2
                                  imageHeight:100];

        finalData = imageToData(test);
    }

    [fullSongData release];
    [reader release];

    return finalData;
}

comparaison des sorties

Linear
Linéaire de l'intrigue pour le début de la "Réchauffer" par Acme Swing Société

logarithmic
Logarithmique parcelle de terrain pour le début de "Réchauffer" par Acme Swing Société

Répondu el 12 de Septembre, 2011 par unsynchronized (2576 Points )

5voto

Joel avatar
Joel Points 83

Vous devriez être en mesure d'obtenir un tampon de l'audio à partir de votre sampleBuffRef et puis itérer sur ces valeurs pour construire votre forme d'onde:

CMBlockBufferRef buffer = CMSampleBufferGetDataBuffer( sampleBufferRef );
CMItemCount numSamplesInBuffer = CMSampleBufferGetNumSamples(sampleBufferRef);
AudioBufferList audioBufferList;
CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(
                                                            sampleBufferRef,
                                                            NULL,
                                                            &audioBufferList,
                                                            sizeof(audioBufferList),
                                                            NULL,
                                                            NULL,
                                                                  kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment,
                                                            &buffer
                                                            );

// this copies your audio out to a temp buffer but you should be able to iterate through this buffer instead
SInt32* readBuffer = (SInt32 *)malloc(numSamplesInBuffer * sizeof(SInt32));
memcpy( readBuffer, audioBufferList.mBuffers[0].mData, numSamplesInBuffer*sizeof(SInt32));
Répondu el 22 de Mai, 2011 par Joel (83 Points )

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