以下是关于我为.mov对.wav对话做了什么的代码：
- (void)mp4ForURL:(NSURL *)videoURL{
// Create the asset url with the video file
AVURLAsset *avAsset = [AVURLAsset URLAssetWithURL:videoURL options:nil];
NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:avAsset];
// Check if video is supported for conversion or not
if ([compatiblePresets containsObject:AVAssetExportPresetMediumQuality])////************************************////
{
//Create Export session
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]initWithAsset:avAsset presetName:AVAssetExportPresetMediumQuality];////************************************////
//Creating temp path to save the converted video
NSString* documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString* myDocumentPath = [documentsDirectory stringByAppendingPathComponent:@"temp.mp4"];
NSURL *url = [[NSURL alloc] initFileURLWithPath:myDocumentPath];
//Check if the file already exists then remove the previous file
if ([[NSFileManager defaultManager]fileExistsAtPath:myDocumentPath])
{
[[NSFileManager defaultManager]removeItemAtPath:myDocumentPath error:nil];
}
exportSession.outputURL = url;
//set the output file format if you want to make it in other file format (ex .3gp)
exportSession.outputFileType = AVFileTypeMPEG4;
exportSession.shouldOptimizeForNetworkUse = YES;
[exportSession exportAsynchronouslyWithCompletionHandler:^{
switch ([exportSession status])
{
case AVAssetExportSessionStatusFailed:
NSLog(@"Export session failed");
break;
case AVAssetExportSessionStatusCancelled:
NSLog(@"Export canceled");
break;
case AVAssetExportSessionStatusCompleted:
{
//Video conversion finished
NSLog(@"Successful!");
[self convertMP4toMP3withFile:myDocumentPath];
}
break;
default:
break;
}
}];
}
else
{
NSLog(@"Video file not supported!");
}
}
-(void)convertMP4toCAFwithFile:(NSString*)dstPath //Converted to Core Audio Format .caf
{
NSURL *dstURL = [NSURL fileURLWithPath:dstPath];
AVMutableComposition* newAudioAsset = [AVMutableComposition composition];
AVMutableCompositionTrack* dstCompositionTrack;
dstCompositionTrack = [newAudioAsset addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
AVAsset* srcAsset = [AVURLAsset URLAssetWithURL:dstURL options:nil];
AVAssetTrack* srcTrack = [[srcAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
CMTimeRange timeRange = srcTrack.timeRange;
NSError* error;
if(NO == [dstCompositionTrack insertTimeRange:timeRange ofTrack:srcTrack atTime:kCMTimeZero error:&error]) {
NSLog(@"track insert failed: %@\n", error);
return;
}
AVAssetExportSession* exportSesh = [[AVAssetExportSession alloc] initWithAsset:newAudioAsset presetName:AVAssetExportPresetPassthrough];
exportSesh.outputFileType = AVFileTypeCoreAudioFormat;
exportSesh.outputURL = dstURL;
[[NSFileManager defaultManager] removeItemAtURL:dstURL error:nil];
[exportSesh exportAsynchronouslyWithCompletionHandler:^{
AVAssetExportSessionStatus status = exportSesh.status;
NSLog(@"exportAsynchronouslyWithCompletionHandler: %li\n", (long)status);
if(AVAssetExportSessionStatusFailed == status) {
NSLog(@"FAILURE: %@\n", exportSesh.error);
} else if(AVAssetExportSessionStatusCompleted == status) {
NSLog(@"SUCCESS!\n");
NSError *error;
//append the name of the file in jpg form
//check if the file exists (completely unnecessary).
NSString *onlyPath = [dstPath stringByDeletingLastPathComponent];
NSInteger randomNumber = arc4random() % 100000;
strDateAndTime = [self getCurrentDateAndTime];
strAudioName = [NSString stringWithFormat:@"%@_%ld_%@.%@", @"Audio", (long)randomNumber, strDateAndTime, @"caf"];
NSString *toPathString = [NSString stringWithFormat:@"%@/%@", onlyPath, strAudioName];
[[NSFileManager defaultManager] moveItemAtPath:dstPath toPath:toPathString error:&error];
//[self uploadAudioOnAWSFromPath:toPathString];
[self convertToWavForFilePath:toPathString];
}
}];
}
- (void)convertToWavForFilePath:(NSString *)cafFilePath
{
// set up an AVAssetReader to read from the iPod Library
// NSString *cafFilePath=[[NSBundle mainBundle]pathForResource:@"test" ofType:@"caf"];
NSURL *assetURL = [NSURL fileURLWithPath:cafFilePath];
AVURLAsset *songAsset = [AVURLAsset URLAssetWithURL:assetURL options:nil];
NSError *assetError = nil;
AVAssetReader *assetReader = [AVAssetReader assetReaderWithAsset:songAsset
error:&assetError];
if (assetError) {
NSLog (@"error: %@", assetError);
return;
}
AVAssetReaderOutput *assetReaderOutput = [AVAssetReaderAudioMixOutput
assetReaderAudioMixOutputWithAudioTracks:songAsset.tracks
audioSettings: nil];
if (! [assetReader canAddOutput: assetReaderOutput]) {
NSLog (@"can't add reader output... die!");
return;
}
[assetReader addOutput: assetReaderOutput];
NSInteger randomNumber = arc4random() % 100000;
_finalAudioName = [NSString stringWithFormat:@"%@_%ld_%@", @"Audio", (long)randomNumber, strDateAndTime];
// NSString *title = @"MyRec";
NSArray *docDirs = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docDir = [docDirs objectAtIndex: 0];
__block NSString *wavFilePath = [[docDir stringByAppendingPathComponent :_finalAudioName]
stringByAppendingPathExtension:@"wav"];
_finalAudioName = [wavFilePath lastPathComponent];
if ([[NSFileManager defaultManager] fileExistsAtPath:wavFilePath])
{
[[NSFileManager defaultManager] removeItemAtPath:wavFilePath error:nil];
}
NSURL *exportURL = [NSURL fileURLWithPath:wavFilePath];
AVAssetWriter *assetWriter = [AVAssetWriter assetWriterWithURL:exportURL
fileType:AVFileTypeWAVE
error:&assetError];
if (assetError)
{
NSLog (@"error: %@", assetError);
return;
}
AudioChannelLayout channelLayout;
memset(&channelLayout, 0, sizeof(AudioChannelLayout));
channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Mono;
NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:kAudioFormatLinearPCM], AVFormatIDKey,
[NSNumber numberWithFloat:44100.0], AVSampleRateKey,
[NSNumber numberWithInt:1], AVNumberOfChannelsKey,
[NSData dataWithBytes:&channelLayout length:sizeof(AudioChannelLayout)], AVChannelLayoutKey,
[NSNumber numberWithInt:16], AVLinearPCMBitDepthKey,
[NSNumber numberWithBool:NO], AVLinearPCMIsNonInterleaved,
[NSNumber numberWithBool:NO], AVLinearPCMIsFloatKey,
[NSNumber numberWithBool:NO], AVLinearPCMIsBigEndianKey,
nil];
AVAssetWriterInput *assetWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio
outputSettings:outputSettings];
if ([assetWriter canAddInput:assetWriterInput])
{
[assetWriter addInput:assetWriterInput];
}
else
{
NSLog (@"can't add asset writer input... die!");
return;
}
assetWriterInput.expectsMediaDataInRealTime = NO;
[assetWriter startWriting];
[assetReader startReading];
AVAssetTrack *soundTrack = [songAsset.tracks objectAtIndex:0];
CMTime startTime = CMTimeMake (0, soundTrack.naturalTimeScale);
[assetWriter startSessionAtSourceTime: startTime];
__block UInt64 convertedByteCount = 0;
dispatch_queue_t mediaInputQueue = dispatch_queue_create("mediaInputQueue", NULL);
[assetWriterInput requestMediaDataWhenReadyOnQueue:mediaInputQueue
usingBlock: ^
{
while (assetWriterInput.readyForMoreMediaData)
{
CMSampleBufferRef nextBuffer = [assetReaderOutput copyNextSampleBuffer];
if (nextBuffer)
{
// append buffer
[assetWriterInput appendSampleBuffer: nextBuffer];
convertedByteCount += CMSampleBufferGetTotalSampleSize (nextBuffer);
CMTime progressTime = CMSampleBufferGetPresentationTimeStamp(nextBuffer);
CMTime sampleDuration = CMSampleBufferGetDuration(nextBuffer);
if (CMTIME_IS_NUMERIC(sampleDuration))
progressTime= CMTimeAdd(progressTime, sampleDuration);
float dProgress= CMTimeGetSeconds(progressTime) / CMTimeGetSeconds(songAsset.duration);
NSLog(@"%f",dProgress);
}
else
{
[assetWriterInput markAsFinished];
[assetReader cancelReading];
[assetWriter finishWritingWithCompletionHandler:^{
[self uploadAudioOnAWSFromPath:wavFilePath];
}];
}
}
}];
}
在上面的代码中，转换后的最终文件是.wav格式，我必须在AWS服务器上发送以从中获取文本，对于文本对话，我们使用Google Speech API，每当我发送从下面转换的文件iOS 11设备（如iOS 9,10），它显示了这个错误： 错误：WAV标头表示格式不受支持。
在将音频文件（.wav）转换为文本格式时，Google语音API会显示以上错误。
以上代码与最新的iOS 11设备完美配合，仅在iOS 11以下（如iOS 9,10）设备无法正常工作。