Android集成LAME库，实现pcm转mp3 |
您所在的位置：网站首页 › mp3改成tar › Android集成LAME库，实现pcm转mp3 |
Android集成LAME库，实现pcm转mp3
|
一、交叉编译LAME库
LAME是一种非常优秀的MP3编码引擎，在业界，转码成MP3格式的音频文件时，最常用的编码器就是LAME库。 1. 下载LAME库源码https://sourceforge.net/projects/lame/files/lame/ 进入LAME官网下载LAME源码，我选择最新版本：3.100 2. 配置交叉编译环境在编译LAME之前，我们需要先配置交叉编译环境。 Android NDK附带了交叉工具链，具体参考这篇文章：https://developer.android.com/ndk/guides/other_build_systems?hl=zh-cn 我的NDK路径为：/home/lorien/Android/Sdk/ndk/22.1.7171670/toolchains/llvm/prebuilt/linux-x86_64/bin 3. 配置、编译、安装LAME首先我们需要编译使用的一些环境变量： #!/bin/bash export TOOLCHAIN=/home/lorien/Android/Sdk/ndk/22.1.7171670/toolchains/llvm/prebuilt/linux-x86_64 export TARGET=aarch64-linux-android export API=21 export AR=$TOOLCHAIN/bin/llvm-ar export CC=$TOOLCHAIN/bin/$TARGET$API-clang export AS=$CC export CXX=$TOOLCHAIN/bin/$TARGET$API-clang++ export LD=$TOOLCHAIN/bin/ld export RANLIB=$TOOLCHAIN/bin/llvm-ranlib export STRIP=$TOOLCHAIN/bin/llvm-strip export CFLAGS="-fPIC"接下来解压的LAME源码：lame-3.100.tar.gz，解压后进入源码根目录：/lame-3.100 配置： ./configure --host=arm-linux --disable-shared --disable-frontend --enable-static --prefix=/Users/zhanghao43/Desktop/lame/arm64-v8a编译： make clean make -j4安装： make install安装完成后，生成的头文件和库文件，就会在prefix指定的路径下面，即：/Users/zhanghao43/Desktop/lame/arm64-v8a 在生成的文件中，接下来需要使用的文件是： 头文件：/Users/zhanghao43/Desktop/lame/arm64-v8a/include/lame/lame.h库文件：/Users/zhanghao43/Desktop/lame/arm64-v8a/lib/lame/libmp3lame.a至此，LAME库交叉编译完成。 二、创建Android Native项目使用LAME库下面我们使用LAME库创建一个Android Demo项目，完成PCM音频的录制以及PCM文件转MP3的功能 我们需要创建Android Natvie项目。 1. 配置工程我们先把编译LAME库生成的头文件和库文件放到项目中，路径如下图： 接下来，可以写代码了。首先看一下mp3_encoder.h, mp3_encoder.cpp #ifndef LAME_MP3ENCODER_H #define LAME_MP3ENCODER_H #include #include "lame.h" class Mp3Encoder { private: FILE* pcmFile; FILE* mp3File; lame_t lameClient; public: Mp3Encoder(); ~Mp3Encoder(); int Init(const char* pcmFilePath, const char* mp3FilePath, int sampleRate, int channels, int bitRate); void Encode(); void Destroy(); }; #endif //LAME_MP3ENCODER_H #include "mp3_encoder.h" #include "lame.h" Mp3Encoder::Mp3Encoder() { } int Mp3Encoder::Init(const char* pcmFilePath, const char* mp3FilePath, int sampleRate, int channels, int bitRate) { int ret = -1; pcmFile = fopen(pcmFilePath, "rb"); if (pcmFile) { mp3File = fopen(mp3FilePath, "wb"); if (mp3File) { lameClient = lame_init(); // in 采样率 lame_set_in_samplerate(lameClient, sampleRate); // out 采样率 lame_set_out_samplerate(lameClient, sampleRate); lame_set_num_channels(lameClient, channels); lame_set_brate(lameClient, bitRate / 1000); lame_init_params(lameClient); ret = 0; } } return ret; } void Mp3Encoder::Encode() { int bufferSize = 1024 * 256; short *buffer = new short[bufferSize / 2]; short *leftBuffer = new short[bufferSize / 4]; short *rightBuffer = new short[bufferSize / 4]; unsigned char* mp3_buffer = new unsigned char[bufferSize]; size_t readBufferSize = 0; while ((readBufferSize = fread(buffer, 2, bufferSize / 2, pcmFile)) > 0) { for (int i = 0; i leftBuffer[i / 2] = buffer[i]; } else { rightBuffer[i / 2] = buffer[i]; } } size_t wroteSize = lame_encode_buffer(lameClient, (short int *) leftBuffer, (short int *) rightBuffer, (int)(readBufferSize / 2), mp3_buffer, bufferSize); fwrite(mp3_buffer, 1, wroteSize, mp3File); } delete [] buffer; delete [] leftBuffer; delete [] rightBuffer; delete [] mp3_buffer; } void Mp3Encoder::Destroy() { if (pcmFile) { fclose(pcmFile); } if (mp3File) { fclose(mp3File); lame_close(lameClient); } }然后我们看一下native-lib.cpp中的JNI方法： Mp3Encoder *encoder; extern "C" JNIEXPORT jint JNICALL Java_com_baidu_lame_MainActivity_pcmToMp3JNI( JNIEnv *env, jobject, jstring pcm_path, jstring mp3_path, jint sample_rate, jint channel, jint bit_rate) { const char *pcmPath = env->GetStringUTFChars(pcm_path, NULL); const char *mp3Path = env->GetStringUTFChars(mp3_path, NULL); encoder = new Mp3Encoder(); encoder->Init(pcmPath, mp3Path, sample_rate, channel, bit_rate); encoder->Encode(); env->ReleaseStringUTFChars(pcm_path, pcmPath); env->ReleaseStringUTFChars(mp3_path, mp3Path); return 0; } 3. Java代码先贴一下MainAcgtivity的XML文件 MainActivity.kt class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) } external fun stringFromJNI(): String external fun pcmToMp3JNI(pcmPath: String, mp3Path: String, sampleRate: Int, channel: Int, bitRate: Int): Int companion object { init { System.loadLibrary("native-lib") } } private lateinit var audioRecord: AudioRecord private var pcmFilePath: String = "" private var buffersize = 1024 private var isRecord = false /** * 调用Native代码完成PCM文件转成MP3 */ fun pcm2mp3(view: View) { val pcmPath = getPCMFile().absolutePath val mp3Path = getMP3File().absolutePath val sampleRate = 44100 val channel = 2 val bitRate = 64000 val ret = pcmToMp3JNI(pcmPath, mp3Path, sampleRate, channel, bitRate) Toast.makeText(this, "$ret", Toast.LENGTH_SHORT).show() } /** * 开始录制PCM音频文件 */ @SuppressLint("MissingPermission") fun startRecordPcm(view: View) { val frequency = 44100 val channelConfig = AudioFormat.CHANNEL_IN_STEREO val audioEncoding = AudioFormat.ENCODING_PCM_16BIT buffersize = AudioRecord.getMinBufferSize(frequency, channelConfig, audioEncoding) audioRecord = AudioRecord( MediaRecorder.AudioSource.MIC, frequency, channelConfig, audioEncoding, buffersize) pcmFilePath = getPCMFile().absolutePath isRecord = true RecordThread().start() } /** * 结束录制PCM音频文件 */ fun stopRecordPcm(view: View) { isRecord = false } private fun getPCMFile(): File { val root = getExternalFilesDir(null) val csvDir = File(root, "/audio/") if (!csvDir.exists()) { // 创建csv 目录 csvDir.mkdir() } return File(csvDir, "sing.pcm") } private fun getMP3File(): File { val root = getExternalFilesDir(null) val csvDir = File(root, "/audio/") if (!csvDir.exists()) { // 创建csv 目录 csvDir.mkdir() } return File(csvDir, "sing.mp3") } /** * 录制PCM音频线程 */ inner class RecordThread : Thread() { override fun run() { audioRecord.startRecording() var fos: FileOutputStream? = null try { Log.d(TAG, "pcm文件：$pcmFilePath") fos = FileOutputStream(pcmFilePath) val bytes = ByteArray(buffersize) while (isRecord) { audioRecord.read(bytes, 0, bytes.size) fos.write(bytes, 0, bytes.size) fos.flush() } Log.d(TAG, "停止录制") audioRecord.stop() fos.flush() } catch (e: Exception) { Log.d(TAG, "exception: $e") } finally { if (fos != null) { try { fos.close() } catch (e: Exception) { } } } } } }最后，权限： 代码中，没有动态申请权限，APP装上后，需要再到设置页面给APP开下对应权限才能录制音频。 OK，本文到这就结束了，感谢大家阅读。 |
然后，我们修改下CMakeLists.txt，让CMake在编译、链接时，找到LAME头文件和库文件。CMakeLists.txt文件内容如下：【本文地址】
今日新闻 |
推荐新闻 |