iPhone COM pressed音频格式，将在Windows Media Player播放 [英] iPhone compressed audio formats that will play on Windows Media player

问题描述

我要记录在iPhone上，将播放Windows媒体播放器，不使用非标准codeCS音频;也就是说，不使用codeCS不已经与WMP发货。 （公司要求。）音频已去基地-64到服务器，所以我需要获得音频尺寸尽可能小。即使在录制的8Kb频率，AIFF文件需要极大的相量的空间。我似乎无法找到pssed AIFF格式，WMP会吞下一个COM $ P $。

I have to record audio on an iPhone that will play back on Windows Media Player, using no non-standard codecs; that is, using no codecs that don't already ship with WMP. (Corporate requirement.) The audio has to go base-64 to a server, so I need to get the audio size as small as possible. Even at 8Kb recording frequency, AIFF files take ginormous amounts of space. I can't seem to find a compressed AIFF format that WMP will swallow.

推荐答案

最好的办法是写与ULAW WAV文件或阿劳COM pression（的 mFormatId 你的 AudioStreamBasicDescription 是 kAudioFormatULaw 或 kAudioFormatALaw 。测试以查看哪一个给你最小的文件大小为您的应用程序。

Best bet is to write WAV files with ulaw or alaw compression (the mFormatId of your AudioStreamBasicDescription would be kAudioFormatULaw or kAudioFormatALaw. Test to see which one gives you the smallest file sizes for your application.

下面是一些code设立ExtAudioFile实例来写ULAW：

Here's some code to set up an ExtAudioFile instance to write ulaw:

NSArray * docs = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString * docDir = [docs objectAtIndex:0];	
NSURL * outFile = [NSURL fileURLWithPath:[docDir stringByAppendingPathComponent:@"OutFile.wav"]];
AudioStreamBasicDescription asbd;
bzero(&asbd, sizeof(asbd));
asbd.mSampleRate = 11025; // or whatever
asbd.mFramesPerPacket = 1;
asbd.mChannelsPerFrame = 1;
asbd.mFormatID = kAudioFormatULaw; //or kAudioFormatALaw
ExtAudioFileRef theFile;
err = ExtAudioFileCreateWithURL((CFURLRef)outFile,
						  kAudioFileWAVEType,
						  &asbd,
						  0,
						  kAudioFileFlags_EraseFile,
						  &theFile);

希望有所帮助。

---附加---

下面是修改到code SpeakHere样品拿到ULAW COM pression：

Here are modifications to the SpeakHere sample code to get ulaw compression:

SpeakHereController.mm:116

SpeakHereController.mm:116

recordFilePath = (CFStringRef)[NSTemporaryDirectory() stringByAppendingPathComponent: @"recordedFile.wav"];

SpeakHereController.mm:158

SpeakHereController.mm:158

recorder->startRecord(CFSTR("recordedFile.wav"));

AQRecorder.mm:192

AQRecorder.mm:192

SetupAudioFormat(kAudioFormatULaw);

AQRecorder.mm:215

AQRecorder.mm:215

XThrowIfError(AudioFileCreateWithURL(url, kAudioFileWAVEType, &mRecordFormat, kAudioFileFlags_EraseFile,
									  &mRecordFile), "AudioFileCreateWithURL failed");

这篇关于iPhone COM pressed音频格式，将在Windows Media Player播放的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！