优客逸家网站建设,电脑淘宝网页版,生活服务网站开发与设计,南昌建网站做优化公司2023-04-06#xff1a;拥抱Golang#xff0c;优化FFmpeg音频编码器#xff0c;探究encode_audio.c的内部结构。
答案2023-04-06#xff1a;
见moonfdd/ffmpeg-go库。
这段代码是一个示例程序#xff0c;用于将音频 PCM 数据编码为 MP2 格式的音频文件。下面是代码的详细…2023-04-06拥抱Golang优化FFmpeg音频编码器探究encode_audio.c的内部结构。
答案2023-04-06
见moonfdd/ffmpeg-go库。
这段代码是一个示例程序用于将音频 PCM 数据编码为 MP2 格式的音频文件。下面是代码的详细步骤
1.导入 ffmpeg-go 和 os 等 Go 库
2.定义一些变量包括输出文件名、音频编解码器、音频编解码上下文、音频帧、音频数据包等
3.查找 MP2 编码器并分配音频编解码上下文
4.配置音频编解码参数设置音频采样率、通道数、位率等
5.打开音频编解码器
6.创建输出文件
7.开始编码过程并将编码后的音频数据写入输出文件中。
具体地编码过程包括以下几个步骤
1.初始化音频帧
2.将音频 PCM 数据填充到音频帧中
3.发送音频帧到编解码器中进行编码
4.从编解码器中读取编码后的音频数据包
5.将编码后的音频数据包写入输出文件中。
最后释放内存空间并关闭文件和编码器。在该示例程序中我们需要手动设置 FFmpeg 库的路径以便正确加载库文件。
命令如下
go run ./examples/internalexamples/encode_audio/main.go ./out/encode_audio.mp2./lib/ffplay ./out/encode_audio.mp2golang代码如下
package mainimport (fmtmathosunsafegithub.com/moonfdd/ffmpeg-go/ffcommongithub.com/moonfdd/ffmpeg-go/libavcodecgithub.com/moonfdd/ffmpeg-go/libavutil
)func main0() (ret ffcommon.FInt) {var filename stringvar codec *libavcodec.AVCodecvar c *libavcodec.AVCodecContextvar frame *libavutil.AVFramevar pkt *libavcodec.AVPacketvar i, j, k ffcommon.FIntvar f *os.Filevar samples *ffcommon.FUint16Tvar t, tincr ffcommon.FFloatif len(os.Args) 1 {fmt.Printf(Usage: %s output file\n, os.Args[0])return 0}filename os.Args[1]/* find the MP2 encoder */codec libavcodec.AvcodecFindEncoder(libavcodec.AV_CODEC_ID_MP2)if codec nil {fmt.Printf(Codec not found\n)os.Exit(1)}c codec.AvcodecAllocContext3()if c nil {fmt.Printf(Could not allocate audio codec context\n)os.Exit(1)}/* put sample parameters */c.BitRate 64000/* check that the encoder supports s16 pcm input */c.SampleFmt libavutil.AV_SAMPLE_FMT_S16if check_sample_fmt(codec, c.SampleFmt) 0 {fmt.Printf(Encoder does not support sample format %s,libavutil.AvGetSampleFmtName(c.SampleFmt))os.Exit(1)}/* select other audio parameters supported by the encoder */c.SampleRate select_sample_rate(codec)c.ChannelLayout uint64(select_channel_layout(codec))c.Channels libavutil.AvGetChannelLayoutNbChannels(c.ChannelLayout)/* open it */if c.AvcodecOpen2(codec, nil) 0 {fmt.Printf(Could not open codec\n)os.Exit(1)}f, _ os.Create(filename)if f nil {fmt.Printf(Could not open %s\n, filename)os.Exit(1)}/* packet for holding encoded output */pkt libavcodec.AvPacketAlloc()if pkt nil {fmt.Printf(could not allocate the packet\n)os.Exit(1)}/* frame containing input raw audio */frame libavutil.AvFrameAlloc()if frame nil {fmt.Printf(Could not allocate audio frame\n)os.Exit(1)}frame.NbSamples c.FrameSizeframe.Format int32(c.SampleFmt)frame.ChannelLayout c.ChannelLayout/* allocate the data buffers */ret frame.AvFrameGetBuffer(0)if ret 0 {fmt.Printf(Could not allocate audio data buffers\n)os.Exit(1)}/* encode a single tone sound */t 0tincr float32(2 * libavutil.M_PI * 440.0 / float64(c.SampleRate))for i 0; i 200; i {/* make sure the frame is writable -- makes a copy if the encoder* kept a reference internally */ret frame.AvFrameMakeWritable()if ret 0 {os.Exit(1)}samples (*ffcommon.FUint16T)(unsafe.Pointer(frame.Data[0]))for j 0; j c.FrameSize; j {*(*ffcommon.FUint16T)(unsafe.Pointer(uintptr(unsafe.Pointer(samples)) uintptr(2*j*2))) ffcommon.FUint16T(math.Sin(float64(t)) * 10000)for k 1; k c.Channels; k {*(*ffcommon.FUint16T)(unsafe.Pointer(uintptr(unsafe.Pointer(samples)) uintptr((2*jk)*2))) *(*ffcommon.FUint16T)(unsafe.Pointer(uintptr(unsafe.Pointer(samples)) uintptr(2*j*2)))}t tincr}encode(c, frame, pkt, f)}/* flush the encoder */encode(c, nil, pkt, f)f.Close()libavutil.AvFrameFree(frame)libavcodec.AvPacketFree(pkt)libavcodec.AvcodecFreeContext(c)return 0
}/* check that a given sample format is supported by the encoder */
func check_sample_fmt(codec *libavcodec.AVCodec, sample_fmt libavutil.AVSampleFormat) ffcommon.FInt {p : codec.SampleFmtsfor *p ! libavutil.AV_SAMPLE_FMT_NONE {if *p sample_fmt {return 1}p (*libavutil.AVSampleFormat)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) uintptr(8)))}return 0
}/* just pick the highest supported samplerate */
func select_sample_rate(codec *libavcodec.AVCodec) ffcommon.FInt {var p *ffcommon.FIntvar best_samplerate ffcommon.FIntif codec.SupportedSamplerates nil {return 44100}p codec.SupportedSampleratesfor *p ! 0 {if best_samplerate 0 || int32(math.Abs(float64(44100-*p))) int32(math.Abs(float64(44100-best_samplerate))) {best_samplerate *p}p (*int32)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) uintptr(4)))}return best_samplerate
}/* select layout with the highest channel count */
func select_channel_layout(codec *libavcodec.AVCodec) ffcommon.FInt {var p *ffcommon.FUint64Tvar best_ch_layout ffcommon.FUint64Tvar best_nb_channels ffcommon.FIntif codec.ChannelLayouts nil {return libavutil.AV_CH_LAYOUT_STEREO}p codec.ChannelLayoutsfor *p ! 0 {nb_channels : libavutil.AvGetChannelLayoutNbChannels(*p)if nb_channels best_nb_channels {best_ch_layout *pbest_nb_channels nb_channels}p (*uint64)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) uintptr(8)))}return ffcommon.FInt(best_ch_layout)
}func encode(ctx *libavcodec.AVCodecContext, frame *libavutil.AVFrame, pkt *libavcodec.AVPacket, output *os.File) {var ret ffcommon.FInt/* send the frame for encoding */ret ctx.AvcodecSendFrame(frame)if ret 0 {fmt.Printf(Error sending the frame to the encoder\n)os.Exit(1)}/* read all the available output packets (in general there may be any* number of them */for ret 0 {ret ctx.AvcodecReceivePacket(pkt)if ret -libavutil.EAGAIN || ret libavutil.AVERROR_EOF {return} else if ret 0 {fmt.Printf(Error encoding audio frame\n)os.Exit(1)}output.Write(ffcommon.ByteSliceFromByteP(pkt.Data, int(pkt.Size)))pkt.AvPacketUnref()}
}func main() {os.Setenv(Path, os.Getenv(Path);./lib)ffcommon.SetAvutilPath(./lib/avutil-56.dll)ffcommon.SetAvcodecPath(./lib/avcodec-58.dll)ffcommon.SetAvdevicePath(./lib/avdevice-58.dll)ffcommon.SetAvfilterPath(./lib/avfilter-56.dll)ffcommon.SetAvformatPath(./lib/avformat-58.dll)ffcommon.SetAvpostprocPath(./lib/postproc-55.dll)ffcommon.SetAvswresamplePath(./lib/swresample-3.dll)ffcommon.SetAvswscalePath(./lib/swscale-5.dll)genDir : ./out_, err : os.Stat(genDir)if err ! nil {if os.IsNotExist(err) {os.Mkdir(genDir, 0777) // Everyone can read write and execute}}main0()
}
