MediaCodec的使用(音频编码一)
MediaCodec的使用(音频编码一)准备工作
我们准备一个pcm文件即可，采样率16000，单声道
如果可以使用ffplay如下命令正常播放，那么音频格式是没有问题的。
ffplay -f s16le -ar 16000 -ch_layout mono -i hello.pcm 将文件推送到download目录
adb -s adb-4128230924000237-Nl4jPZ._adb-tls-connect._tcp push hello.pcm /sdcard/Download/Android10+是无法之间操作Download目录的文件的，即使你获取到读写权限。
读写权限的前世今生
android.Manifest.permission.READ_EXTERNAL_STORAGE,
android.Manifest.permission.WRITE_EXTERNAL_STORAGE,这两个已经完全过时了在Android13+
READ_EXTERNAL_STORAGE is deprecated (and is not granted) when targeting Android 13+. If you need to query or interact with MediaStore or media files on the shared storage, you should instead use one or more new storage permissions: READ_MEDIA_IMAGES, READ_MEDIA_VIDEO or READ_MEDIA_AUDIO. Toggle info (Ctrl+F1)Android10+
shared storage 使用MediaStore
但是上面两个还应用于视频、音频、照片
Android13++
上面两个权限完全过时了，视频、音频、照片使用单独的权限
当然国内的魔改手机在Android13+仍有可能使用上面的两个权限
READ_MEDIA_IMAGES, READ_MEDIA_VIDEO or READ_MEDIA_AUDIO我现在这台手机是android11，访问Download目录，所有用不上上面的两个权限。
但是如果是android10以下，还是需要的。
所以将hello.pcm只能通过SAF访问或者MANAGE_EXTERNAL_STORAGE.
SAF
@Composable
internal fun MediaCodecScreen(
navHostController: NavHostController,
snackBarHostState: SnackbarHostState,
) {
val context: Context = LocalContext.current
val coroutineScope: CoroutineScope = rememberCoroutineScope()
val launcher:ManagedActivityResultLauncher, Uri?>= rememberLauncherForActivityResult(
contract = ActivityResultContracts.OpenDocument()
) { uri: Uri? ->
uri?.apply {
Log.i(TAG, "MediaCodecScreen -> uri: $this")
context.contentResolver.openInputStream(this)?.use { inputStream ->
val bytes = ByteArray(1024)
inputStream.read(bytes)
Log.i(TAG, "MediaCodecScreen -> data: ${bytes.joinToString()}")
}
}
}
Column(
modifier = Modifier.fillMaxSize()
) {
Text(
text = "发送信息",
Modifier
.padding(top = 10.dp)
.background(color = Color.Black, shape = RoundedCornerShape10)
.padding(all = 5.dp)
.clickable {
launcher.launch(arrayOf("*/*"))
},
color = Color.White
)
}
}建议在android10+访问shared storage尽量使用MediaStore，如果不使用的话还是很危险的，如果生成一个文件到Download，用户重新卸载安装那你就不能访问这个文件了，会崩溃的，每个app都相当于一个匿名用户，重新安装那你的匿名身份就变更了，当然文件就不能访问了。
当然在android10~android12如果访问视频、音频、照片还是要读写权限的。
还要注意MediaStore相当于是一个数据库，他加快了检索文件的速度。当你使用MeidaStore的时候，不要仅仅是插入一条记录，还有把文件的二进制数据写入到MediaStore.
还有尽量不要使用uri转file，file转uri.不符合现代android的开发。
当然在app的私有目录无论是外部存储还是内部存储都可以使用java 的 File因为他和shared storage没有任何关系。
PCM 编码 MP3
编码函数如下:
internal suspend fun pcmToMp3(
context: Context,
pcmUri: Uri,
mp3Uri: Uri,
): Unit = suspendCancellableCoroutine { continuation ->
val mediaCodecList = MediaCodecList(MediaCodecList.ALL_CODECS)
val mp3Encoders: List<MediaCodecInfo> = mediaCodecList.codecInfos.filter { it.isEncoder }.filter {
it.supportedTypes.contains(element = MediaFormat.MIMETYPE_AUDIO_MPEG)
}
if (mp3Encoders.isEmpty()){
if (continuation.isActive){
continuation.resume(Unit) // 不支持的话可以使用lame软编码
}
return@suspendCancellableCoroutine
}
mp3Encoders.forEach { mediaCodecInfo ->
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
Log.i(TAG, "pcmToAac -> name: ${mediaCodecInfo.name}, canonicalName: ${mediaCodecInfo.canonicalName}, isAlias: ${mediaCodecInfo.isAlias}, isVendor: ${mediaCodecInfo.isVendor}, isHardwareAccelerated: ${mediaCodecInfo.isHardwareAccelerated}, isEncoder: ${mediaCodecInfo.isEncoder}, isSoftwareOnly: ${mediaCodecInfo.isSoftwareOnly}, supportedTypes: ${mediaCodecInfo.supportedTypes.joinToString()}")
} else {
Log.i(TAG, "pcmToAac -> name: ${mediaCodecInfo.name}, isEncoder: ${mediaCodecInfo.isEncoder}, supportedTypes: ${mediaCodecInfo.supportedTypes.joinToString()}")
}
}
val mediaFormat: MediaFormat = MediaFormat.createAudioFormat(MediaFormat.MIMETYPE_AUDIO_MPEG, 16000, 1).apply {
setInteger(MediaFormat.KEY_BIT_RATE, 128000)
}
val mediaCodec: MediaCodec = MediaCodec.createEncoderByType(MediaFormat.MIMETYPE_AUDIO_MPEG)
mediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE)
val pcmInputStream: InputStream = context.contentResolver.openInputStream(pcmUri)!!
val mp3OutputStream: OutputStream = context.contentResolver.openOutputStream(mp3Uri)!!
val bytes = ByteArray(1024 * 8)
mediaCodec.setCallback(object : MediaCodec.Callback(){
override fun onError(
codec: MediaCodec,
e: MediaCodec.CodecException
) {
Log.e(TAG, "onError name: ${codec.name}, thread: ${Thread.currentThread()}, error: ${e.message}", e)
}
override fun onInputBufferAvailable(
codec: MediaCodec,
index: Int
) {
val inputBuffer: ByteBuffer = codec.getInputBuffer(index) ?: return
val size: Int = pcmInputStream.read(bytes, 0, inputBuffer.limit()) // 或许需要去 min(bytes.size, inputBuffer.limit())
Log.i(TAG, "onInputBufferAvailable -> name: ${mediaCodec.name}, index: $index, thread: ${Thread.currentThread()}, size: $size, limit: ${inputBuffer.limit()}, position: ${inputBuffer.position()}")
if (size > 0) {
inputBuffer.put(bytes, 0, size)
codec.queueInputBuffer(index, 0, size, System.nanoTime() / 1000, 0)
} else {
codec.queueInputBuffer(index, 0, 0, System.nanoTime() / 1000, MediaCodec.BUFFER_FLAG_END_OF_STREAM)
}
}
override fun onOutputBufferAvailable(
codec: MediaCodec,
index: Int,
info: MediaCodec.BufferInfo
) {
Log.i(TAG, "onOutputBufferAvailable -> name: ${codec.name}, index: $index, info: ${info.size}, thread: ${Thread.currentThread()}")
val outputBuffer: ByteBuffer = codec.getOutputBuffer(index) ?: return
outputBuffer.get(bytes, 0, info.size)
mp3OutputStream.write(bytes, 0, info.size)
codec.releaseOutputBuffer(index, false)
if (info.flags == MediaCodec.BUFFER_FLAG_END_OF_STREAM){
Log.i(TAG, "onOutputBufferAvailable -> == 编码结束...") // todo
pcmInputStream.close()
mp3OutputStream.close()
if (continuation.isActive){
Log.i(TAG, "pcmToMp3 -> 解码完成 resume before...")
continuation.resume(Unit)
Log.i(TAG, "pcmToMp3 -> 解码完成 resume after...")
}
}
}
override fun onOutputFormatChanged(
codec: MediaCodec,
format: MediaFormat
) {
Log.i(TAG, "onOutputFormatChanged -> name: ${codec.name}, format: ${format.getString(MediaFormat.KEY_MIME)}")
}
})
Log.i(TAG, "pcmToAac -> before start...")
mediaCodec.start()
Log.i(TAG, "pcmToAac -> after start...")
}调用如下
@Composable
internal fun MediaCodecScreen(
navHostController: NavHostController,
snackBarHostState: SnackbarHostState,
) {
val context: Context = LocalContext.current
val coroutineScope: CoroutineScope = rememberCoroutineScope()
val launcher:ManagedActivityResultLauncher, Uri?>= rememberLauncherForActivityResult(
contract = ActivityResultContracts.OpenDocument()
) { uri: Uri? ->
uri?.apply {
Log.i(TAG, "MediaCodecScreen -> uri: $this")
val audioExtractManager = AudioExtractManager()
val contentValues: ContentValues = contentValuesOf(
MediaStore.Audio.Media.DISPLAY_NAME to "hello.mp3",
MediaStore.Audio.Media.MIME_TYPE to MediaFormat.MIMETYPE_AUDIO_MPEG,
MediaStore.Audio.Media.RELATIVE_PATH to Environment.DIRECTORY_MUSIC
)
val mp3Uri: Uri = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
context.contentResolver.insert(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, contentValues)
} else {
FileProvider.getUriForFile(context, "${context.packageName}.provider", File(
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC),
"hello.mp3"
))
} ?: return@apply
Log.i(TAG, "MediaCodecScreen -> mp3Uri: $mp3Uri")
coroutineScope.launch {
Log.i(TAG, "MediaCodecScreen -> before ${Thread.currentThread()}")
audioExtractManager.pcmToMp3(context, this@apply, mp3Uri)
Log.i(TAG, "MediaCodecScreen -> after ${Thread.currentThread()}")
}
}
}
Column(
modifier = Modifier.fillMaxSize()
) {
Text(
text = "开发者",
Modifier
.padding(top = 10.dp)
.background(color = Color.Black, shape = RoundedCornerShape10)
.padding(all = 5.dp)
.clickable {
val intent = Intent(Settings.ACTION_APPLICATION_DEVELOPMENT_SETTINGS)
context.startActivity(intent)
},
color = Color.White
)
Text(
text = "发送信息",
Modifier
.padding(top = 10.dp)
.background(color = Color.Black, shape = RoundedCornerShape10)
.padding(all = 5.dp)
.clickable {
launcher.launch(arrayOf("*/*"))
},
color = Color.White
)
}
}PCM 编码 adts aac
说到adts,它是包含header的aac裸流，在某些设备上是无法正确播放的比如ios.
参考: adts aac
7字节的头
7字节的头其一共7 * 8=56bit位。分为 各占28bit
adts_fixed_header();
adts_variable_header();我们一位一位的看.
adts_fixed_header()
syncword: 前12位是固定的都是1, 代表adts header开始的标识
ID：1bit, MPEG Version: 0 for MPEG-4，1 for MPEG-2
Layer：2bits, always: '00'
protection_absent：1bit, Warning, set to 1 if there is no CRC and 0 if there is CRC
一般是0表示: no CRC
profile：2bits, 表示使用哪个级别的AAC，如01 Low Complexity(LC) -- AAC LC
profile的值等于 Audio Object Type的值减1.
profile = MPEG-4 Audio Object Type - 1
sampling_frequency_index: 4bits, 采样率下标，可以参考上面的链接查看
Private bit, 1bit, 设置为0即可
channel_configuration: 占3bits, 声道数下标，可以参考上面的链接查看
原创性，1bit: 设为1表示音频为原创，设为0则表示非原创。
家用性，1bit：设为1表示音频为家用，设为0则表示非家用。
总共28bit
adts_variable_header
版权标识位（Copyright ID bit）：1bit, 中央注册版权标识符的下一比特位。采用LSB（最低有效位优先）顺序滑动遍历比特串时，将当前比特值填入此字段，到达末尾时循环回到起始位置（环形缓冲区结构）。
版权标识起始位（Copyright ID start）：1bit, 1表示当前帧的版权标识位是起始位，设为0则表示非起始位。
aac_frame_length：13bits, 一个ADTS帧的长度包括ADTS头和AAC原始流。
frame length, this value must include 7 or 9 bytes of header length:
aac_frame_length = (protection_absent == 1 ? 7 : 9) + size(AACFrame)
protection_absent=0时, header length=9bytes
protection_absent=1时, header length=7bytes
adts_buffer_fullness：11bit,
计算公式
max_bit_reservoir = minimum_decoder_input_size - mean_bits_per_RDB; // for CBR
// bit reservoir state/available bits (≥0 and <max_bit_reservoir); for the i-th frame.
bit_reservoir_state = (int)(bit_reservoir_state + mean_framelength - framelength);
// NCC is the number of channels.
adts_buffer_fullness = bit_reservoir_state / (NCC * 32);编码函数如下:
private fun addAdtsHeader(packet: ByteArray, packetLen: Int, sampleRate: Int, channels: Int) {
val profile = 2// AAC LC
val freqIdx = when(sampleRate){
96000 -> 0
88200 -> 1
64000 -> 2
48000 -> 3
44100 -> 4
32000 -> 5
24000 -> 6
22050 -> 7
16000 -> 8
12000 -> 9
11025 -> 10
8000 -> 11
else -> 4 // 默认44100
}
/**
0000 0x00
0001 0x01
0010 0x02
0011 0x03
0100 0x04
0101 0x05
0110 0x06
0111 0x07
1000 0x08
1001 0x09
1010 0x0A
1011 0x0B
1100 0x0C
1101 0x0D
1110 0x0E
1111 0x0F
*/
val chanCfg = channels // CPE = 1, mono = 1
packet = 0xFF.toByte() // 1111 1111 1字节
packet = 0xF9.toByte() // 1111 1001 2字节 id 1 for MPEG-2, layer = 00 protection_absent = 1
// 00 0000 profile 2bits
// 00 freqIdx 4bits
// 0 Private bit
// channel 3 bits 001 右移两位 0
// channel的1位0加上来 // 3字节
packet = ((profile - 1 shl 6) + (freqIdx shl 2) + (chanCfg shr 2)).toByte()
// 0000 0000
// channel 0000 0001 左移6位 01
// 00 0000 channel 处理完成 // 26
//Originality、Home两bit Copyright ID bit, Copyright ID start 2bit 合并到 packetLen，所有其一共17bits
// 0x7FFF
// 0000 0000 0000 000 packetLen 右边移 11 ->
// 0000 0000 0000 0000 0000 00 packetLen 右边移 11 ->
//
packet = (((chanCfg and 3) shl 6) + (packetLen shr 11)).toByte() // 4字节
packet = (packetLen and 0x7FF shr 3).toByte() // 111
// 0 0000 后面即 0xFFC
packet = ((packetLen and 7 shl 5) + 0x1F).toByte() // 0001 1111
// 1111 1100
packet = 0xFC.toByte() // 7字节
}使用案例
internal suspend fun pcmToAac(context: Context, pcmUri: Uri, aacUri: Uri): Unit = suspendCancellableCoroutine { continuation ->
// 编码器
// aac 3gpp audio/amr-wbaudio/flac
// h264
// 解码器 解码器那可就太多了
val mediaCodecList = MediaCodecList(MediaCodecList.ALL_CODECS)
val aacEncoders: List<MediaCodecInfo> = mediaCodecList.codecInfos.filter { it.isEncoder }.filter {
it.supportedTypes.contains(element = MediaFormat.MIMETYPE_AUDIO_AAC)
}
Log.i(TAG, "pcmToAac -> aacEncoders: ${aacEncoders.joinToString { it.name }}")
if (aacEncoders.isEmpty()){
// 不支持硬件解码
Log.i(TAG, "pcmToAac -> 不支持硬件编码...") // 使用软解码
if (continuation.isActive){
continuation.resume(Unit)
}
return@suspendCancellableCoroutine
}
// 可惜 aac 仅支持软解码
Log.i(TAG, "pcmToAac -> 支持硬件编码")
val mediaFormat: MediaFormat = MediaFormat.createAudioFormat(MediaFormat.MIMETYPE_AUDIO_AAC, 16000, 1).apply {
setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC)
setInteger(MediaFormat.KEY_BIT_RATE, 128000)
}
val mediaCodec: MediaCodec = MediaCodec.createEncoderByType(MediaFormat.MIMETYPE_AUDIO_AAC)
mediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE)
val pcmInputStream: InputStream = context.contentResolver.openInputStream(pcmUri)!!
val aacOutputStream: OutputStream = context.contentResolver.openOutputStream(aacUri)!!
val bytes = ByteArray(1024 * 8)
mediaCodec.setCallback(object : MediaCodec.Callback() {
override fun onError(
codec: MediaCodec,
e: MediaCodec.CodecException
) {
Log.e(
TAG,
"onError name: ${codec.name}, thread: ${Thread.currentThread()}, error: ${e.message}",
e
)
}
override fun onInputBufferAvailable(
codec: MediaCodec,
index: Int
) {
Log.i(
TAG,
"onInputBufferAvailable -> name: ${mediaCodec.name}, index: $index, thread: ${Thread.currentThread()}"
)
val inputBuffer: ByteBuffer = codec.getInputBuffer(index) ?: return
val size: Int = pcmInputStream.read(bytes, 0, inputBuffer.limit())
if (size > 0) {
inputBuffer.put(bytes, 0, size)
codec.queueInputBuffer(index, 0, size, System.nanoTime() / 1000, 0)
} else {
codec.queueInputBuffer(
index,
0,
0,
System.nanoTime() / 1000,
MediaCodec.BUFFER_FLAG_END_OF_STREAM
)
}
}
override fun onOutputBufferAvailable(
codec: MediaCodec,
index: Int,
info: MediaCodec.BufferInfo
) {
Log.i(
TAG,
"onOutputBufferAvailable -> name: ${codec.name}, index: $index, info: ${info.size}, thread: ${Thread.currentThread()}"
)
val outputBuffer: ByteBuffer = codec.getOutputBuffer(index) ?: return
val aacData = ByteArray(info.size + 7)
addAdtsHeader(aacData, aacData.size, 16000, 1)
outputBuffer.get(aacData, 7, info.size)
aacOutputStream.write(aacData)
codec.releaseOutputBuffer(index, false)
if (info.flags == MediaCodec.BUFFER_FLAG_END_OF_STREAM) {
Log.i(TAG, "onOutputBufferAvailable -> == 编码结束...") // todo
pcmInputStream.close()
aacOutputStream.close()
if (continuation.isActive) {
Log.i(TAG, "pcmToAac -> 解码完成 resume before...")
continuation.resume(Unit)
Log.i(TAG, "pcmToAac -> 解码完成 resume after...")
}
}
}
override fun onOutputFormatChanged(
codec: MediaCodec,
format: MediaFormat
) {
Log.i(
TAG,
"onOutputFormatChanged -> name: ${codec.name}, format: ${
format.getString(MediaFormat.KEY_MIME)
}"
)
}
})
Log.i(TAG, "pcmToAac -> before start...")
mediaCodec.start()
Log.i(TAG, "pcmToAac -> after start...")
}
@Suppress("SameParameterValue")
private fun addAdtsHeader(packet: ByteArray, packetLen: Int, sampleRate: Int, channels: Int) {
val profile = 2// AAC LC
val freqIdx = when(sampleRate){
96000 -> 0
88200 -> 1
64000 -> 2
48000 -> 3
44100 -> 4
32000 -> 5
24000 -> 6
22050 -> 7
16000 -> 8
12000 -> 9
11025 -> 10
8000 -> 11
else -> 4 // 默认44100
}
/**
0000 0x00
0001 0x01
0010 0x02
0011 0x03
0100 0x04
0101 0x05
0110 0x06
0111 0x07
1000 0x08
1001 0x09
1010 0x0A
1011 0x0B
1100 0x0C
1101 0x0D
1110 0x0E
1111 0x0F
*/
val chanCfg = channels // CPE = 1, mono = 1
packet = 0xFF.toByte() // 1111 1111 1字节
packet = 0xF9.toByte() // 1111 1001 2字节 id 1 for MPEG-2, layer = 00 protection_absent = 1
// 00 0000 profile 2bits
// 00 freqIdx 4bits
// 0 Private bit
// channel 3 bits 001 右移两位 0
// channel的1位0加上来 // 3字节
packet = ((profile - 1 shl 6) + (freqIdx shl 2) + (chanCfg shr 2)).toByte()
// 0000 0000
// channel 0000 0001 左移6位 01
// 00 0000 channel 处理完成 // 26
//Originality、Home两bit Copyright ID bit, Copyright ID start 2bit 合并到 packetLen，所有其一共17bits
// 0x7FFF
// 0000 0000 0000 000 packetLen 右边移 11 ->
// 0000 0000 0000 0000 0000 00 packetLen 右边移 11 ->
//
packet = (((chanCfg and 3) shl 6) + (packetLen shr 11)).toByte() // 4字节
packet = (packetLen and 0x7FF shr 3).toByte() // 111
// 0 0000 后面即 0xFFC
packet = ((packetLen and 7 shl 5) + 0x1F).toByte() // 0001 1111
// 1111 1100
packet = 0xFC.toByte() // 7字节
}
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