2023-04-15：ffmpeg的filter_audio.c的功能是生成一个正弦波音频，然后通过简单的滤镜链，最后输出数据的MD5校验和。请用go语言改写。
答案2023-04-15：
代码见github/moonfdd/ffmpeg-go库。
以下是通过 Go 语言重新实现 ffmpeg 的 filter_audio.c 功能的步骤：
导入必要的依赖包和定义常量和变量。
初始化 FFmpeg 库文件路径。
创建一个音频滤镜图，并将 abuffer、volume 和 aformat 滤镜连接起来。其中，abuffer 滤镜用于获取输入音频采样，volume 滤镜用于调节音频音量，aformat 滤镜用于设置输出音频格式。
创建输出音频流的 AVCodecContext 上下文，并设置相关属性。
使用 avcodec_find_encoder_by_name 函数查找 PCM S16LE 编码器，然后创建编码器的 AVCodec 上下文。
打开编码器并写入头部信息。
循环读取音频帧，将其发送到音频滤镜图进行处理。
从滤镜图中获取输出音频帧，并将其编码为 PCM S16LE 格式。
计算输出音频帧的 MD5 校验和，并将其打印到标准输出上。
释放资源，结束程序运行。
以上就是使用 Go 语言对 filter_audio.c 文件进行重新实现的步骤。
命令如下：
go run ./examples/internalexamples/filter_audio/main.go 1
go代码如下：
package main
import (
"fmt"
"math"
"os"
"strconv"
"unsafe"
"github.com/moonfdd/ffmpeg-go/ffcommon"
"github.com/moonfdd/ffmpeg-go/libavfilter"
"github.com/moonfdd/ffmpeg-go/libavutil"
)
func main0() (ret ffcommon.FInt) {
var md5 *libavutil.AVMD5
var graph *libavfilter.AVFilterGraph
var src, sink *libavfilter.AVFilterContext
var frame *libavutil.AVFrame
var errstr [1024]ffcommon.FUint8T
var duration ffcommon.FFloat
var err, nb_frames, i ffcommon.FInt
if len(os.Args) < 2 {
fmt.Printf("Usage: %s <duration>\n", os.Args[0])
return 1
}
f, err2 := strconv.ParseFloat(os.Args[1], 32)
if err2 != nil {
// handle error
return 1
}
duration = float32(f)
nb_frames = int32(float64(duration) * INPUT_SAMPLERATE / FRAME_SIZE)
if nb_frames <= 0 {
fmt.Printf("Invalid duration: %s\n", os.Args[1])
return 1
}
/* Allocate the frame we will be using to store the data. */
frame = libavutil.AvFrameAlloc()
if frame == nil {
fmt.Printf("Error allocating the frame\n")
return 1
}
md5 = libavutil.AvMd5Alloc()
if md5 == nil {
fmt.Printf("Error allocating the MD5 context\n")
return 1
}
/* Set up the filtergraph. */
err = init_filter_graph(&graph, &src, &sink)
if err < 0 {
fmt.Printf("Unable to init filter graph:")
goto fail
}
/* the main filtering loop */
for i = 0; i < nb_frames; i++ {
// /* get an input frame to be filtered */
err = get_input(frame, i)
if err < 0 {
fmt.Printf("Error generating input frame:")
goto fail
}
/* Send the frame to the input of the filtergraph. */
err = src.AvBuffersrcAddFrame(frame)
if err < 0 {
frame.AvFrameUnref()
fmt.Printf("Error submitting the frame to the filtergraph:")
goto fail
}
/* Get all the filtered output that is available. */
err = sink.AvBuffersinkGetFrame(frame)
for err >= 0 {
/* now do something with our filtered frame */
err = process_output(md5, frame)
if err < 0 {
fmt.Printf("Error processing the filtered frame:")
goto fail
}
frame.AvFrameUnref()
err = sink.AvBuffersinkGetFrame(frame)
}
if err == -libavutil.EAGAIN {
/* Need to feed more frames in. */
continue
} else if err == libavutil.AVERROR_EOF {
/* Nothing more to do, finish. */
break
} else if err < 0 {
/* An error occurred. */
fmt.Printf("Error filtering the data:")
goto fail
}
}
libavfilter.AvfilterGraphFree(&graph)
libavutil.AvFrameFree(&frame)
libavutil.AvFreep(uintptr(unsafe.Pointer(&md5)))
return 0
fail:
libavutil.AvStrerror(err, (*byte)(unsafe.Pointer(&errstr)), uint64(len(errstr)))
fmt.Printf("%s\n", errstr)
return 1
}
const INPUT_SAMPLERATE = 48000
const INPUT_FORMAT = libavutil.AV_SAMPLE_FMT_FLTP
const INPUT_CHANNEL_LAYOUT = libavutil.AV_CH_LAYOUT_5POINT0
const VOLUME_VAL = 0.90
func init_filter_graph(graph **libavfilter.AVFilterGraph, src **libavfilter.AVFilterContext,
sink **libavfilter.AVFilterContext) ffcommon.FInt {
var filter_graph *libavfilter.AVFilterGraph
var abuffer_ctx *libavfilter.AVFilterContext
var abuffer *libavfilter.AVFilter
var volume_ctx *libavfilter.AVFilterContext
var volume *libavfilter.AVFilter
var aformat_ctx *libavfilter.AVFilterContext
var aformat *libavfilter.AVFilter
var abuffersink_ctx *libavfilter.AVFilterContext
var abuffersink *libavfilter.AVFilter
var options_dict *libavutil.AVDictionary
var options_str string
var ch_layout [64]ffcommon.FUint8T
var err ffcommon.FInt
/* Create a new filtergraph, which will contain all the filters. */
filter_graph = libavfilter.AvfilterGraphAlloc()
if filter_graph == nil {
fmt.Printf("Unable to create filter graph.\n")
return libavutil.ENOMEM
}
/* Create the abuffer filter;
* it will be used for feeding the data into the graph. */
abuffer = libavfilter.AvfilterGetByName("abuffer")
if abuffer == nil {
fmt.Printf("Could not find the abuffer filter.\n")
return libavutil.AVERROR_FILTER_NOT_FOUND
}
abuffer_ctx = filter_graph.AvfilterGraphAllocFilter(abuffer, "src")
if abuffer_ctx == nil {
fmt.Printf("Could not allocate the abuffer instance.\n")
return -libavutil.ENOMEM
}
/* Set the filter options through the AVOptions API. */
libavutil.AvGetChannelLayoutString((*byte)(unsafe.Pointer(&ch_layout)), int32(len(ch_layout)), 0, INPUT_CHANNEL_LAYOUT)
libavutil.AvOptSet(uintptr(unsafe.Pointer(abuffer_ctx)), "channel_layout", ffcommon.StringFromPtr(uintptr(unsafe.Pointer(&ch_layout))), libavutil.AV_OPT_SEARCH_CHILDREN)
libavutil.AvOptSet(uintptr(unsafe.Pointer(abuffer_ctx)), "sample_fmt", libavutil.AvGetSampleFmtName(INPUT_FORMAT), libavutil.AV_OPT_SEARCH_CHILDREN)
libavutil.AvOptSetQ(uintptr(unsafe.Pointer(abuffer_ctx)), "time_base", libavutil.AVRational{1, INPUT_SAMPLERATE}, libavutil.AV_OPT_SEARCH_CHILDREN)
libavutil.AvOptSetInt(uintptr(unsafe.Pointer(abuffer_ctx)), "sample_rate", INPUT_SAMPLERATE, libavutil.AV_OPT_SEARCH_CHILDREN)
/* Now initialize the filter; we pass NULL options, since we have already
* set all the options above. */
err = abuffer_ctx.AvfilterInitStr("")
if err < 0 {
fmt.Printf("Could not initialize the abuffer filter.\n")
return err
}
/* Create volume filter. */
volume = libavfilter.AvfilterGetByName("volume")
if volume == nil {
fmt.Printf("Could not find the volume filter.\n")
return libavutil.AVERROR_FILTER_NOT_FOUND
}
volume_ctx = filter_graph.AvfilterGraphAllocFilter(volume, "volume")
if volume_ctx == nil {
fmt.Printf("Could not allocate the volume instance.\n")
return -libavutil.ENOMEM
}
/* A different way of passing the options is as key/value pairs in a
* dictionary. */
libavutil.AvDictSet(&options_dict, "volume", fmt.Sprint(VOLUME_VAL), 0)
err = volume_ctx.AvfilterInitDict(&options_dict)
libavutil.AvDictFree(&options_dict)
if err < 0 {
fmt.Printf("Could not initialize the volume filter.\n")
return err
}
/* Create the aformat filter;
* it ensures that the output is of the format we want. */
aformat = libavfilter.AvfilterGetByName("aformat")
if aformat == nil {
fmt.Printf("Could not find the aformat filter.\n")
return libavutil.AVERROR_FILTER_NOT_FOUND
}
aformat_ctx = filter_graph.AvfilterGraphAllocFilter(aformat, "aformat")
if aformat_ctx == nil {
fmt.Printf("Could not allocate the aformat instance.\n")
return -libavutil.ENOMEM
}
/* A third way of passing the options is in a string of the form
* key1=value1:key2=value2.... */
// snprintf(options_str, sizeof(options_str),
// "sample_fmts=%s:sample_rates=%d:channel_layouts=0x%"PRIx64,
// av_get_sample_fmt_name(AV_SAMPLE_FMT_S16), 44100,
// (uint64_t)AV_CH_LAYOUT_STEREO);
options_str = fmt.Sprintf("sample_fmts=%s:sample_rates=%d:channel_layouts=0x%x",
libavutil.AvGetSampleFmtName(libavutil.AV_SAMPLE_FMT_S16), 44100,
libavutil.AV_CH_LAYOUT_STEREO)
fmt.Println(options_str)
err = aformat_ctx.AvfilterInitStr(options_str)
if err < 0 {
libavutil.AvLog(uintptr(0), libavutil.AV_LOG_ERROR, "Could not initialize the aformat filter.\n")
return err
}
/* Finally create the abuffersink filter;
* it will be used to get the filtered data out of the graph. */
abuffersink = libavfilter.AvfilterGetByName("abuffersink")
if abuffersink == nil {
fmt.Printf("Could not find the abuffersink filter.\n")
return libavutil.AVERROR_FILTER_NOT_FOUND
}
abuffersink_ctx = filter_graph.AvfilterGraphAllocFilter(abuffersink, "sink")
if abuffersink_ctx == nil {
fmt.Printf("Could not allocate the abuffersink instance.\n")
return -libavutil.ENOMEM
}
/* This filter takes no options. */
err = abuffersink_ctx.AvfilterInitStr("")
if err < 0 {
fmt.Printf("Could not initialize the abuffersink instance.\n")
return err
}
/* Connect the filters;
* in this simple case the filters just form a linear chain. */
err = abuffer_ctx.AvfilterLink(0, volume_ctx, 0)
if err >= 0 {
err = volume_ctx.AvfilterLink(0, aformat_ctx, 0)
}
if err >= 0 {
err = aformat_ctx.AvfilterLink(0, abuffersink_ctx, 0)
}
if err < 0 {
fmt.Printf("Error connecting filters\n")
return err
}
/* Configure the graph. */
err = filter_graph.AvfilterGraphConfig(uintptr(0))
if err < 0 {
libavutil.AvLog(uintptr(0), libavutil.AV_LOG_ERROR, "Error configuring the filter graph\n")
return err
}
*graph = filter_graph
*src = abuffer_ctx
*sink = abuffersink_ctx
return 0
}
/* Do something useful with the filtered data: this simple
* example just prints the MD5 checksum of each plane to stdout. */
func process_output(md5 *libavutil.AVMD5, frame *libavutil.AVFrame) ffcommon.FInt {
planar := libavutil.AvSampleFmtIsPlanar(libavutil.AVSampleFormat(frame.Format))
channels := libavutil.AvGetChannelLayoutNbChannels(frame.ChannelLayout)
planes := channels
if planar == 0 {
planes = 1
}
bps := libavutil.AvGetBytesPerSample(libavutil.AVSampleFormat(frame.Format))
plane_size := bps * frame.NbSamples
if planar == 0 {
plane_size = plane_size * channels
}
var i, j ffcommon.FInt
for i = 0; i < planes; i++ {
var checksum [16]ffcommon.FUint8T
md5.AvMd5Init()
ptr := *(*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(frame.ExtendedData)) + uintptr(i*8)))
libavutil.AvMd5Sum((*byte)(unsafe.Pointer(&checksum)), (*byte)(unsafe.Pointer(ptr)), plane_size)
fmt.Printf("plane %d: 0x", i)
for j = 0; j < int32(len(checksum)); j++ {
fmt.Printf("%02X", checksum[j])
}
fmt.Printf("\n")
}
fmt.Printf("\n")
return 0
}
const FRAME_SIZE = 1024
/* Construct a frame of audio data to be filtered;
* this simple example just synthesizes a sine wave. */
func get_input(frame *libavutil.AVFrame, frame_num ffcommon.FInt) ffcommon.FInt {
var err, i, j ffcommon.FInt
// #define FRAME_SIZE 1024
/* Set up the frame properties and allocate the buffer for the data. */
frame.SampleRate = INPUT_SAMPLERATE
frame.Format = INPUT_FORMAT
frame.ChannelLayout = INPUT_CHANNEL_LAYOUT
frame.NbSamples = FRAME_SIZE
frame.Pts = int64(frame_num) * FRAME_SIZE
err = frame.AvFrameGetBuffer(0)
if err < 0 {
return err
}
/* Fill the data for each channel. */
for i = 0; i < 5; i++ {
// float *data = (float*)frame->extended_data[i];
ptr := *(*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(frame.ExtendedData)) + uintptr(i*8)))
data := (*ffcommon.FFloat)(unsafe.Pointer(ptr))
for j = 0; j < frame.NbSamples; j++ {
*(*ffcommon.FFloat)(unsafe.Pointer(uintptr(unsafe.Pointer(data)) + uintptr(4*j))) = float32(math.Sin(2 * libavutil.M_PI * (float64(frame_num + j)) * float64((i+1)/FRAME_SIZE)))
}
}
return 0
}
func main() {
// go run ./examples/internalexamples/filter_audio/main.go 1
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-7.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()
}
