本机iPhone音频格式 [英] Native iPhone audio format

问题描述

我目前得到了我的输出音频的iPhone设置为这样的：

I've currently got my output audio on the iPhone setup as this :

AudioStreamBasicDescription audioFormat;

audioFormat.mSampleRate = 48000;

audioFormat.mFormatID   = kAudioFormatLinearPCM;

audioFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;

audioFormat.mFramesPerPacket = 1;

audioFormat.mChannelsPerFrame = 2;

audioFormat.mBitsPerChannel = 16;

audioFormat.mBytesPerPacket = 4;

audioFormat.mBytesPerFrame = 4;

然而，当我通过研究鲨鱼我的表现数字，我看到的功能，如：
SRC_Convert_table_i32_scalar_stereo

需要很长时间公平块。

take a fair chunk of time.

这让我想到 - 什么是iPhone的理想和建议输出格式？需要为设备发挥工作尽可能少的人。

This made me think - what is the ideal and suggested output format for the iPhone? The one that requires as little work for the device to play.

推荐答案

鲨鱼确实与iPhone合作。您可以通过在菜单中选择取样>网络/ iPhone性能分析...让iPhone剖析。

Shark does work with the iPhone. You can enable iPhone profiling by selecting "Sampling > Network/iPhone Profiling..." in the menu.

肯定尝试使用44100 Hz的采样率。随着48000我看到你贴出现在调用堆栈相同的功能 - 使用时，44100在iPhone上的音频单元的规范音频格式非交错无此功能显示出来8.24线性PCM：

Definitely try using a 44100 Hz sampling rate. With 48000 I see the same function that you posted appearing in the callstacks -- no such function shows up when using 44100. The canonical audio format for Audio Units on the iPhone is non-interleaved 8.24 linear PCM:

streamFormat.mFormatID         = kAudioFormatLinearPCM;
streamFormat.mFormatFlags      = 
                  kAudioFormatFlagIsSignedInteger
                | kAudioFormatFlagsNativeEndian
                | kLinearPCMFormatFlagIsNonInterleaved
                | (24 << kLinearPCMFormatFlagsSampleFractionShift);
streamFormat.mSampleRate       = mixing_rate;
streamFormat.mBitsPerChannel   = 32;
streamFormat.mChannelsPerFrame = 2;
streamFormat.mFramesPerPacket  = 1;
streamFormat.mBytesPerFrame    = ( streamFormat.mBitsPerChannel / 8 );
streamFormat.mBytesPerPacket   = streamFormat.mBytesPerFrame *
                                 streamFormat.mFramesPerPacket;

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