2023-10-13 20:52:26 CST W41D5

examples/decode-audio/main.go

@@ -0,0 +1,195 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+
+	ffmpeg "github.com/qrtc/ffmpeg-dev-go"
+)
+
+const (
+	AUDIO_INBUF_SIZE    = 20480
+	AUDIO_REFILL_THRESH = 4096
+)
+
+func getFormatFromSampleFmt(sampleFmt ffmpeg.AvSampleFormat) (string, int32) {
+	sampleFmtEntry := []struct {
+		sampleFmt ffmpeg.AvSampleFormat
+		fmtBe     string
+		fmtLe     string
+	}{
+		{ffmpeg.AV_SAMPLE_FMT_U8, "u8", "u8"},
+		{ffmpeg.AV_SAMPLE_FMT_S16, "s16be", "s16le"},
+		{ffmpeg.AV_SAMPLE_FMT_S32, "s32be", "s32le"},
+		{ffmpeg.AV_SAMPLE_FMT_FLT, "f32be", "f32le"},
+		{ffmpeg.AV_SAMPLE_FMT_DBL, "f64be", "f64le"},
+	}
+
+	for _, entry := range sampleFmtEntry {
+		if sampleFmt == entry.sampleFmt {
+			return ffmpeg.AV_NE(entry.fmtBe, entry.fmtLe), 0
+		}
+	}
+
+	fmt.Fprintf(os.Stderr, "sample format %s is not supported as output format\n",
+		ffmpeg.AvGetSampleFmtName(sampleFmt))
+	return "", -1
+}
+
+func decode(decCtx *ffmpeg.AvCodecContext, pkt *ffmpeg.AvPacket, frame *ffmpeg.AvFrame, outfile *os.File) {
+	// send the packet with the compressed data to the decoder
+	ret := ffmpeg.AvCodecSendPacket(decCtx, pkt)
+	if ret < 0 {
+		fmt.Fprintf(os.Stderr, "Error submitting the packet to the decoder\n")
+		os.Exit(1)
+	}
+
+	// read all the output frames (in general there may be any number of them
+	for ret >= 0 {
+		ret = ffmpeg.AvCodecReceiveFrame(decCtx, frame)
+		if ret == ffmpeg.AVERROR(int32(syscall.EAGAIN)) || ret == ffmpeg.AVERROR_EOF {
+			return
+		} else if ret < 0 {
+			fmt.Fprintf(os.Stderr, "Error during decoding\n")
+			os.Exit(1)
+		}
+		dataSize := ffmpeg.AvGetBytesPerSample(decCtx.GetSampleFmt())
+		if dataSize < 0 {
+			// This should not occur, checking just for paranoia
+			fmt.Fprintf(os.Stderr, "Failed to calculate data size\n")
+			os.Exit(1)
+		}
+		for i := int32(0); i < frame.GetNbSamples(); i++ {
+			for ch := 0; ch < int(decCtx.GetChannels()); ch++ {
+				outfile.Write(ffmpeg.SliceWithOffset(frame.GetDataIdx(ch), dataSize*i, dataSize))
+			}
+		}
+	}
+}
+
+func main() {
+	if len(os.Args) <= 2 {
+		fmt.Fprintf(os.Stdout, "Usage: %s <input file> <output file>\n", os.Args[0])
+		os.Exit(1)
+	}
+	filename := os.Args[1]
+	outfilename := os.Args[2]
+
+	pkt := ffmpeg.AvPacketAlloc()
+
+	codec := ffmpeg.AvCodecFindDecoder(ffmpeg.AV_CODEC_ID_MP2)
+	if codec == nil {
+		fmt.Fprintf(os.Stderr, "Codec not found\n")
+		os.Exit(1)
+	}
+
+	parser := ffmpeg.AvParserInit(codec.GetID())
+	if parser == nil {
+		fmt.Fprintf(os.Stderr, "Parser not found\n")
+		os.Exit(1)
+	}
+
+	avctx := ffmpeg.AvCodecAllocContext3(codec)
+	if avctx == nil {
+		fmt.Fprintf(os.Stderr, "Could not allocate audio codec context\n")
+		os.Exit(1)
+	}
+
+	// open it
+	if ffmpeg.AvCodecOpen2(avctx, codec, nil) < 0 {
+		fmt.Fprintf(os.Stderr, "Could not open codec\n")
+		os.Exit(1)
+	}
+
+	f, err := os.OpenFile(filename, os.O_RDONLY, 0666)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Could not open %s\n", filename)
+		os.Exit(1)
+	}
+	outfile, err := os.OpenFile(outfilename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0755)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Could not open %s\n", outfilename)
+		os.Exit(1)
+	}
+
+	// decode until eof
+	var decodedFrame *ffmpeg.AvFrame
+	inbuf := make([]byte, AUDIO_INBUF_SIZE+ffmpeg.AV_INPUT_BUFFER_PADDING_SIZE)
+	dataOffset := 0
+	dataSize, err := f.Read(inbuf[:AUDIO_INBUF_SIZE])
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n", err.Error())
+		os.Exit(1)
+	}
+
+	for dataSize > 0 {
+		if decodedFrame == nil {
+			if decodedFrame = ffmpeg.AvFrameAlloc(); decodedFrame == nil {
+				fmt.Fprintf(os.Stderr, "Could not allocate audio frame\n")
+				os.Exit(1)
+			}
+		}
+
+		ret := ffmpeg.AvParserParse2(parser, avctx, pkt.GetDataAddr(), pkt.GetSizeAddr(),
+			&inbuf[dataOffset], int32(dataSize),
+			ffmpeg.AV_NOPTS_VALUE, ffmpeg.AV_NOPTS_VALUE, 0)
+		if ret < 0 {
+			fmt.Fprintf(os.Stderr, "Error while parsing\n")
+			os.Exit(1)
+		}
+
+		dataOffset += int(ret)
+		dataSize -= int(ret)
+
+		if pkt.GetSize() > 0 {
+			decode(avctx, pkt, decodedFrame, outfile)
+		}
+
+		if dataSize < AUDIO_REFILL_THRESH {
+			copy(inbuf, inbuf[dataOffset:dataOffset+dataSize])
+			dataOffset = 0
+			length, _ := f.Read(inbuf[dataOffset+dataSize : AUDIO_INBUF_SIZE-dataSize])
+			if length > 0 {
+				dataSize += int(length)
+			}
+		}
+	}
+
+	// flush the decoder
+	pkt.SetData(nil)
+	pkt.SetSize(0)
+	decode(avctx, pkt, decodedFrame, outfile)
+
+	// print output pcm infomations, because there have no metadata of pcm
+	sfmt := avctx.GetSampleFmt()
+
+	if ffmpeg.AvSampleFmtIsPlanar(sfmt) > 0 {
+		packed := ffmpeg.AvGetSampleFmtName(sfmt)
+		if len(packed) == 0 {
+			packed = "?"
+		}
+		fmt.Fprintf(os.Stdout, "Warning: the sample format the decoder produced is planar (%s)."+
+			" This example will output the first channel only.\n", packed)
+		sfmt = ffmpeg.AvGetPackedSampleFmt(sfmt)
+	}
+
+	nChannels := avctx.GetChannels()
+	fmtStr, ret := getFormatFromSampleFmt(sfmt)
+	if ret < 0 {
+		goto end
+	}
+
+	fmt.Fprintf(os.Stdout, "Play the output audio file with the command:\n"+
+		"ffplay -f %s -ac %d -ar %d %s\n",
+		fmtStr, nChannels, avctx.GetSampleRate(), outfilename)
+
+end:
+	f.Close()
+	outfile.Close()
+
+	ffmpeg.AvCodecFreeContext(&avctx)
+	ffmpeg.AvParserClose(parser)
+	ffmpeg.AvFrameFree(&decodedFrame)
+	ffmpeg.AvPacketFree(&pkt)
+}