使用 AVAssetReader 绘制波形
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【中文标题】使用 AVAssetReader 绘制波形【英文标题】：Drawing waveform with AVAssetReader 【发布时间】：2011-06-29 07:12:40 【问题描述】：我使用assetUrl 从iPod 库中读取歌曲（代码名为audioUrl） 我可以以多种方式播放它，我可以剪切它，我可以用它进行一些进动，但是...... 我真的不明白我要用这个 CMSampleBufferRef 做什么来获取绘制波形的数据！我需要有关峰值的信息，我如何才能以这种方式（也许是另一种方式）获得它？
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? */
请帮帮我！
【问题讨论】：
【参考方案1】：我正在寻找类似的东西，并决定“自己动手”。 我意识到这是一个旧帖子，但如果其他人正在寻找这个，这是我的解决方案。它相对快速和肮脏，并将图像标准化为“全尺寸”。 它创建的图像是“宽的”，即您需要将它们放在 UIScrollView 中或以其他方式管理显示。
这是基于给this question的一些答案
样本输出
编辑：我已经添加了平均和渲染方法的对数版本，请参阅此消息的末尾以了解替代版本和比较输出。我个人更喜欢原始的线性版本，但已决定发布它，以防有人可以改进所使用的算法。
您将需要这些导入：
#import <MediaPlayer/MediaPlayer.h>
#import <AVFoundation/AVFoundation.h>
首先，一个通用的渲染方法，它接受一个指向平均样本数据的指针， 并返回一个 UIImage。请注意，这些样本不是可播放的音频样本。
-(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;
接下来，一个接受 AVURLAsset 并返回 PNG 图像数据的方法
- (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;
高级选项： 最后，如果您希望能够使用 AVAudioPlayer 播放音频，则需要缓存 它到您的应用程序的捆绑缓存文件夹。既然我这样做了，我决定缓存图像数据 此外，并将整个事物包装到 UIImage 类别中。您需要包含this open source offering 来提取音频，以及来自here 的一些代码来处理一些后台线程功能。
首先，一些定义，以及一些用于处理路径名等的通用类方法
//#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];
现在是做“生意”的init方法
- (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;
调用这个的一个例子：
-(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];
平均和渲染方法的对数版本
#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;
比较输出
Acme Swing Company 的“Warm It Up”开始的线性图
Acme Swing Company 的“Warm It Up”开始的对数图
【讨论】：
这是一个非常完整且有用的答案。这实际上是一个临界教程，您可以考虑将其放入博客或类似的博客中。如果可以的话，我会投票给你 10 分。 是的，你真的应该写一篇教程或博客文章……还有一个示例项目；） 不知道它有多快，但它确实有效！我不得不添加/修改一些东西，因为你已经硬编码了一些假设，比如 2 声道音频。我还发现以下用于计算 samplesPerPixel 很方便（您分配的方式似乎是任意的？/50 ??） NSTimeInterval duration = (float)songAsset.duration.value/(float)songAsset.duration.timescale; NSLog(@"录制的持续时间：%f sec.", duration); 我还想为视网膜图形更新它，并可能将 UIImage* 方法变为 drawRect: 方法，并能够添加突出显示的区域。感谢您的伟大起点。 AVFoundation 和低级库对于相对缺乏经验的人来说还是有点吓人 谢谢。我已将此作为可可控件的起点，该控件添加了一些其他功能，例如显示播放进度——来源github.com/fulldecent/FDWaveformView【参考方案2】：您应该能够从您的 sampleBuffRef 中获取音频缓冲区，然后遍历这些值以构建您的波形：
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));
【讨论】：
【参考方案3】：另一种使用 Swift 5 和 AVAudioFile 的方法：
///Gets the audio file from an URL, downsaples and draws into the sound layer.
func drawSoundWave(fromURL url:URL, fromPosition:Int64, totalSeconds:UInt32, samplesSecond:CGFloat) throws
print("\(logClassName) Drawing sound from \(url)")
do
waveViewInfo.samplesSeconds = samplesSecond
//Get audio file and format from URL
let audioFile = try AVAudioFile(forReading: url)
waveViewInfo.format = audioFile.processingFormat
audioFile.framePosition = fromPosition * Int64(waveViewInfo.format.sampleRate)
//Getting the buffer
let frameCapacity:UInt32 = totalSeconds * UInt32(waveViewInfo.format.sampleRate)
guard let audioPCMBuffer = AVAudioPCMBuffer(pcmFormat: waveViewInfo.format, frameCapacity: frameCapacity) else throw AppError("Unable to get the AVAudioPCMBuffer")
try audioFile.read(into: audioPCMBuffer, frameCount: frameCapacity)
let audioPCMBufferFloatValues:[Float] = Array(UnsafeBufferPointer(start: audioPCMBuffer.floatChannelData?.pointee,
count: Int(audioPCMBuffer.frameLength)))
waveViewInfo.points = []
waveViewInfo.maxValue = 0
for index in stride(from: 0, to: audioPCMBufferFloatValues.count, by: Int(audioFile.fileFormat.sampleRate) / Int(waveViewInfo.samplesSeconds))
let aSample = CGFloat(audioPCMBufferFloatValues[index])
waveViewInfo.points.append(aSample)
let fix = abs(aSample)
if fix > waveViewInfo.maxValue
waveViewInfo.maxValue = fix
print("\(logClassName) Finished the points - Count = \(waveViewInfo.points.count) / Max = \(waveViewInfo.maxValue)")
populateSoundImageView(with: waveViewInfo)
catch
throw error
///Converts the sound wave in to a UIImage
func populateSoundImageView(with waveViewInfo:WaveViewInfo)
let imageSize:CGSize = CGSize(width: CGFloat(waveViewInfo.points.count),//CGFloat(waveViewInfo.points.count) * waveViewInfo.sampleSpace,
height: frame.height)
let drawingRect = CGRect(origin: .zero, size: imageSize)
UIGraphicsBeginImageContextWithOptions(imageSize, false, 0)
defer
UIGraphicsEndImageContext()
print("\(logClassName) Converting sound view in rect \(drawingRect)")
guard let context:CGContext = UIGraphicsGetCurrentContext() else return
context.setFillColor(waveViewInfo.backgroundColor.cgColor)
context.setAlpha(1.0)
context.fill(drawingRect)
context.setLineWidth(1.0)
// context.setLineWidth(waveViewInfo.lineWidth)
let sampleAdjustFactor = imageSize.height / waveViewInfo.maxValue
for pointIndex in waveViewInfo.points.indices
let pixel = waveViewInfo.points[pointIndex] * sampleAdjustFactor
context.move(to: CGPoint(x: CGFloat(pointIndex), y: middleY - pixel))
context.addLine(to: CGPoint(x: CGFloat(pointIndex), y: middleY + pixel))
context.setStrokeColor(waveViewInfo.strokeColor.cgColor)
context.strokePath()
// for pointIndex in waveViewInfo.points.indices
//
// let pixel = waveViewInfo.points[pointIndex] * sampleAdjustFactor
//
// context.move(to: CGPoint(x: CGFloat(pointIndex) * waveViewInfo.sampleSpace, y: middleY - pixel))
// context.addLine(to: CGPoint(x: CGFloat(pointIndex) * waveViewInfo.sampleSpace, y: middleY + pixel))
//
// context.setStrokeColor(waveViewInfo.strokeColor.cgColor)
// context.strokePath()
//
//
// var xIncrement:CGFloat = 0
// for point in waveViewInfo.points
//
// let normalizedPoint = point * sampleAdjustFactor
//
// context.move(to: CGPoint(x: xIncrement, y: middleY - normalizedPoint))
// context.addLine(to: CGPoint(x: xIncrement, y: middleX + normalizedPoint))
// context.setStrokeColor(waveViewInfo.strokeColor.cgColor)
// context.strokePath()
//
// xIncrement += waveViewInfo.sampleSpace
//
//
guard let soundWaveImage = UIGraphicsGetImageFromCurrentImageContext() else return
soundWaveImageView.image = soundWaveImage
// //In case of handling sample space in for
// updateWidthConstraintValue(soundWaveImage.size.width)
updateWidthConstraintValue(soundWaveImage.size.width * waveViewInfo.sampleSpace)
在哪里
class WaveViewInfo
var format:AVAudioFormat!
var samplesSeconds:CGFloat = 50
var lineWidth:CGFloat = 0.20
var sampleSpace:CGFloat = 0.20
var strokeColor:UIColor = .red
var backgroundColor:UIColor = .clear
var maxValue:CGFloat = 0
var points:[CGFloat] = [CGFloat]()
目前只打印一个声波，但可以扩展。好的部分是您可以按部分打印音轨
【讨论】：
实时音频流怎么样？ 方法不同。您最好的方法是填充数据缓冲区并绘制它，但它是我的客人。【参考方案4】：对上述答案进行一点重构（使用 AVAudioFile）
import AVFoundation
import CoreGraphics
import Foundation
import UIKit
class WaveGenerator
private func readBuffer(_ audioUrl: URL) -> UnsafeBufferPointer<Float>
let file = try! AVAudioFile(forReading: audioUrl)
let audioFormat = file.processingFormat
let audioFrameCount = UInt32(file.length)
guard let buffer = AVAudioPCMBuffer(pcmFormat: audioFormat, frameCapacity: audioFrameCount)
else return UnsafeBufferPointer<Float>(_empty: ())
do
try file.read(into: buffer)
catch
print(error)
// let floatArray = Array(UnsafeBufferPointer(start: buffer.floatChannelData![0], count: Int(buffer.frameLength)))
let floatArray = UnsafeBufferPointer(start: buffer.floatChannelData![0], count: Int(buffer.frameLength))
return floatArray
private func generateWaveImage(
_ samples: UnsafeBufferPointer<Float>,
_ imageSize: CGSize,
_ strokeColor: UIColor,
_ backgroundColor: UIColor
) -> UIImage?
let drawingRect = CGRect(origin: .zero, size: imageSize)
UIGraphicsBeginImageContextWithOptions(imageSize, false, 0)
let middleY = imageSize.height / 2
guard let context: CGContext = UIGraphicsGetCurrentContext() else return nil
context.setFillColor(backgroundColor.cgColor)
context.setAlpha(1.0)
context.fill(drawingRect)
context.setLineWidth(0.25)
let max: CGFloat = CGFloat(samples.max() ?? 0)
let heightNormalizationFactor = imageSize.height / max / 2
let widthNormalizationFactor = imageSize.width / CGFloat(samples.count)
for index in 0 ..< samples.count
let pixel = CGFloat(samples[index]) * heightNormalizationFactor
let x = CGFloat(index) * widthNormalizationFactor
context.move(to: CGPoint(x: x, y: middleY - pixel))
context.addLine(to: CGPoint(x: x, y: middleY + pixel))
context.setStrokeColor(strokeColor.cgColor)
context.strokePath()
guard let soundWaveImage = UIGraphicsGetImageFromCurrentImageContext() else return nil
UIGraphicsEndImageContext()
return soundWaveImage
func generateWaveImage(from audioUrl: URL, in imageSize: CGSize) -> UIImage?
let samples = readBuffer(audioUrl)
let img = generateWaveImage(samples, imageSize, UIColor.blue, UIColor.white)
return img
用法
let url = Bundle.main.url(forResource: "TEST1.mp3", withExtension: "")!
let img = waveGenerator.generateWaveImage(from: url, in: CGSize(width: 600, height: 200))
【讨论】：
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