需要帮助配置ffmpeg解码原始AAC用android ndk

我有一个android应用程序从外部设备获取原始AAC字节，我想解码数据，但我似乎无法让解码器工作，然而ffmpeg似乎对解码包含相同音频数据的mp4文件（用isoviewer验证）工作正常。最近我能够在android上获得这个ffmpeg库来解码来自同一外部设备的视频帧，但音频似乎不起作用。需要帮助配置ffmpeg解码原始AAC用android ndk

这里是ffmpeg的输出文件具有相同的数据：

$ ffmpeg -i Video_2000-01-01_0411.mp4 
ffmpeg version 2.6.1 Copyright (c) 2000-2015 the FFmpeg developers 
    built with Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn) 
    configuration: --prefix=/usr/local/Cellar/ffmpeg/2.6.1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-vda 
    libavutil  54. 20.100/54. 20.100 
    libavcodec  56. 26.100/56. 26.100 
    libavformat 56. 25.101/56. 25.101 
    libavdevice 56. 4.100/56. 4.100 
    libavfilter  5. 11.102/5. 11.102 
    libavresample 2. 1. 0/2. 1. 0 
    libswscale  3. 1.101/3. 1.101 
    libswresample 1. 1.100/1. 1.100 
    libpostproc 53. 3.100/53. 3.100 
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'AXON_Flex_Video_2000-01-01_0411.mp4': 
    Metadata: 
    major_brand  : mp42 
    minor_version : 1 
    compatible_brands: isom3gp43gp5 
    Duration: 00:00:15.73, start: 0.000000, bitrate: 1134 kb/s 
    Stream #0:0(eng): Audio: aac (LC) (mp4a/0x6134706D), 8000 Hz, mono, fltp, 40 kb/s (default) 
    Metadata: 
     handler_name : soun 
    Stream #0:1(eng): Video: mpeg4 (Simple Profile) (mp4v/0x7634706D), yuv420p, 640x480 [SAR 1:1 DAR 4:3], 1087 kb/s, 29.32 fps, 26.58 tbr, 90k tbn, 1k tbc (default) 
    Metadata: 
     handler_name : vide

这是建立和解码音频我的NDK代码：

jint ffmpeg_init(JNIEnv * env, jobject this) { 
    audioCodec = avcodec_find_decoder(AV_CODEC_ID_AAC); 
    if (!audioCodec) { 
     LOGE("audio codec %d not found", AV_CODEC_ID_AAC); 
     return -1; 
    } 

    audioContext = avcodec_alloc_context3(audioCodec); 
    if (!audioContext) { 
     LOGE("Could not allocate codec context"); 
     return -1; 
    } 

    int openRet = avcodec_open2(audioContext, audioCodec, NULL); 
     if (openRet < 0) { 
      LOGE("Could not open codec, error:%d", openRet); 
      return -1; 
     } 

    audioContext->sample_rate = 8000; 
    audioContext->channel_layout = AV_CH_LAYOUT_MONO; 
    audioContext->profile = FF_PROFILE_AAC_LOW; 
    audioContext->bit_rate = 48 * 1024; 
    audioContext->sample_fmt = AV_SAMPLE_FMT_FLTP; 

    // unsigned char extradata[] = {0x15, 0x88}; 
    // audioContext->extradata = extradata; 
    // audioContext->extradata_size = sizeof(extradata); 
    audioFrame = av_frame_alloc(); 
    if (!audioFrame) { 
     LOGE("Could not create audio frame"); 
     return -1; 
    } 
} 


jint ffmpeg_decodeAudio(JNIEnv *env, jobject this, jbyteArray aacData, jbyteArray output, int offset, int len) { 

    LOGI("ffmpeg_decodeAudio()"); 
    char errbuf[128]; 
    AVPacket avpkt = {0}; 
    av_init_packet(&avpkt); 
    LOGI("av_init_packet()"); 
    int error, got_frame;  
    uint8_t* buffer = (uint8_t *) (*env)->GetByteArrayElements(env, aacData,0); 
    uint8_t* copy = av_malloc(len); 
    memcpy(copy, &buffer[offset], len); 
    av_packet_from_data(&avpkt, copy, len); 


    if ((error = avcodec_decode_audio4(audioContext, audioFrame, &got_frame, &avpkt)) < 0) { 
     ffmpeg_log_error(error); 
     av_free_packet(&avpkt); 
     return error; 
    } 
    if (got_frame) { 
     LOGE("Copying audioFrame->extended_data to output jbytearray, linesize[0]:%d", audioFrame->linesize[0]); 
     (*env)->SetByteArrayRegion(env, output, 0, audioFrame->linesize[0], *audioFrame->extended_data); 
    } 

    return 0; 

}

正如你可以看到我已经有了一个init函数来打开解码器并创建上下文，这些工作都很好，没有错误。然而，当我打电话avcodec_decode_audio4我得到一个错误：

FFmpeg的错误：-1094995529，处理输入

时发现无效数据我已经试过各种AVCodecContext属性的组合。我不确定我需要为解码器设置它，但是从在线阅读开始，我只需要设置通道布局和sample_rate（我自己试过）。我也尝试将extradata/extradata_size参数设置为与每个视频设置相匹配的参数：http://wiki.multimedia.cx/index.php?title=MPEG-4_Audio 但是没有运气。

由于我们从中获取数据包的设备发送的数据在开头没有声音（但是是有效的数据包），所以我试图发送这些数据，因为它们肯定应该正确解码。

下面是是沉默的初始音频数据包的一个示例：

010c9eb43f21f90fc87e46fff10a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5dffe214b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4b4bbd1c429696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696969696978

注意，上面示出的数据仅仅是我把在AVPacket数据的十六进制编码，并且它是从外部设备发送到Android应用程序。我的应用程序没有直接访问该文件，所以我需要解码原始帧/样本，因为我得到它们。当我查看isoviewer中的音频轨道数据时，我可以看到音轨的第一个示例与从包含该文件的设备获得的数据相同（因此，外部设备只是将样本的原始数据发送给我）。我相信这些数据可以通过从文件的mdat框中的stco（块偏移量）框开始读取stsz（样本大小）框来获得。

另外，isoviewer示出的esds框为具有以下：

ESDescriptor{esId=0, streamDependenceFlag=0, URLFlag=0, oCRstreamFlag=0, streamPriority=0, URLLength=0, URLString='null', remoteODFlag=0, dependsOnEsId=0, oCREsId=0, decoderConfigDescriptor=DecoderConfigDescriptor{objectTypeIndication=64, streamType=5, upStream=0, bufferSizeDB=513, maxBitRate=32000, avgBitRate=32000, decoderSpecificInfo=null, audioSpecificInfo=AudioSpecificConfig{configBytes=1588, audioObjectType=2 (AAC LC), samplingFrequencyIndex=11 (8000), samplingFrequency=0, channelConfiguration=1, syncExtensionType=0, frameLengthFlag=0, dependsOnCoreCoder=0, coreCoderDelay=0, extensionFlag=0, layerNr=0, numOfSubFrame=0, layer_length=0, aacSectionDataResilienceFlag=false, aacScalefactorDataResilienceFlag=false, aacSpectralDataResilienceFlag=false, extensionFlag3=0}, configDescriptorDeadBytes=, profileLevelIndicationDescriptors=[[]]}, slConfigDescriptor=SLConfigDescriptor{predefined=2}}

和二进制是这样的：

00 00 00 30 65 73 64 73 00 00 00 00 03 80 80 80 
1f 00 00 00 04 80 80 80 14 40 15 00 02 01 00 00 
7d 00 00 00 7d 00 05 80 80 80 02 15 88 06 01 02

来源

2015-08-19 Matt Wolfe

你输入这些函数的数据类型是什么？ 010c ...并没有真正的帮助，它是从分析的m4a文件打包的AAC数据？还是原始的AAC文件块？或者m4a文件块？或者是其他东西？ –

我已更新（最后一段）来解释数据代表什么。 –

@ RonaldS.Bultje我刚刚从这里看到你的评论http://stackoverflow.com/questions/31726738/ffmpeg-native-aac-decoder/31729894#31729894，这让我想知道如果我可以只采取esds箱数据和将其设置为extradata字段。我是设置整个盒子数据还是只设置特定部分？我应该能够对这些数据进行硬编码。 –

我发现的主要问题与上面的代码。当您调用avcodec_open2时，解码器会被初始化。因此，我应该在打开之前先设置上下文字段，如下所示：

jint ffmpeg_init(JNIEnv * env, jobject this) { 
//.... 

audioContext = avcodec_alloc_context3(audioCodec); 

audioContext->sample_rate = 8000; 
audioContext->channel_layout = AV_CH_LAYOUT_MONO; 
audioContext->channels = 1; 
int openRet = avcodec_open2(audioContext, audioCodec, NULL); 
if (openRet < 0) { 
    LOGE("Could not open codec, error:%d", openRet); 
    return -1; 
}

解码器现在正在对音频进行无错解码。

来源

2015-08-20 02:04:30

需要帮助配置ffmpeg解码原始AAC用android ndk

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