add ffmpeg audio decoder and encoder

audio.go

@@ -0,0 +1,177 @@
+package codec
+
+import (
+	// #include "ffmpeg.h"
+	"C"
+	"unsafe"
+	"fmt"
+)
+
+const (
+	S16 = iota+1
+	FLTP
+)
+
+type AudioEncoder struct {
+	ff C.FFCtx
+	SampleRate int
+	BitRate int
+	ChannelCount int
+	SampleFormat int
+	sampleSize int
+}
+
+func (self *AudioEncoder) Setup() (err error) {
+	ff := &self.ff
+
+	switch self.SampleFormat {
+	case S16:
+		ff.codecCtx.sample_fmt = C.AV_SAMPLE_FMT_S16
+		self.sampleSize = 2
+	case FLTP:
+		ff.codecCtx.sample_fmt = C.AV_SAMPLE_FMT_FLTP
+		self.sampleSize = 4
+	default:
+		err = fmt.Errorf("unsupported sample format")
+		return
+	}
+
+	if self.BitRate == 0 {
+		self.BitRate = 50000
+	}
+
+	ff.frame = C.av_frame_alloc()
+	ff.codecCtx.sample_rate = C.int(self.SampleRate)
+	ff.codecCtx.bit_rate = C.int(self.BitRate)
+	ff.codecCtx.channels = C.int(self.ChannelCount)
+	ff.codecCtx.strict_std_compliance = C.FF_COMPLIANCE_EXPERIMENTAL
+	if C.avcodec_open2(ff.codecCtx, ff.codec, nil) != 0 {
+		err = fmt.Errorf("avcodec_open2 failed")
+		return
+	}
+
+	return
+}
+
+func (self *AudioEncoder) Extradata() (data []byte) {
+	data = make([]byte, (int)(self.ff.codecCtx.extradata_size))
+	C.memcpy(
+		unsafe.Pointer(&data[0]),
+		unsafe.Pointer(self.ff.codecCtx.extradata),
+		(C.size_t)(len(data)),
+	)
+	return
+}
+
+func (self *AudioEncoder) Encode(sample []byte, flush bool) (gotPkt bool, pkt []byte, err error) {
+	nbSamples := 1024
+	expectedSize := nbSamples*self.sampleSize*self.ChannelCount
+
+	if len(sample) != expectedSize {
+		err = fmt.Errorf("len(sample) should be %d", expectedSize)
+		return
+	}
+
+	frame := self.ff.frame
+	frame.nb_samples = C.int(nbSamples)
+	for i := 0; i < self.ChannelCount; i++ {
+		frame.data[i] = (*C.uint8_t)(unsafe.Pointer(&sample[i*nbSamples*self.sampleSize]))
+		frame.linesize[i] = C.int(nbSamples*self.sampleSize)
+	}
+	frame.extended_data = &frame.data[0]
+
+	cpkt := C.AVPacket{}
+	cgotpkt := C.int(0)
+	cerr := C.avcodec_encode_audio2(self.ff.codecCtx, &cpkt, frame, &cgotpkt)
+	if cerr < C.int(0) {
+		err = fmt.Errorf("avcodec_encode_audio2 failed: %d", cerr)
+		return
+	}
+
+	if cgotpkt != 0 {
+		gotPkt = true
+		pkt = make([]byte, (int)(cpkt.size))
+		C.memcpy(
+			unsafe.Pointer(&pkt[0]),
+			unsafe.Pointer(cpkt.data),
+			(C.size_t)(len(pkt)),
+		)
+	}
+
+	return
+}
+
+type AudioDecoder struct {
+	ff C.FFCtx
+	Extradata []byte
+}
+
+func (self *AudioDecoder) Setup() (err error) {
+	ff := &self.ff
+
+	ff.frame = C.av_frame_alloc()
+
+	if len(self.Extradata) > 0 {
+		ff.codecCtx.extradata = (*C.uint8_t)(unsafe.Pointer(&self.Extradata[0]))
+		ff.codecCtx.extradata_size = C.int(len(self.Extradata))
+	}
+
+	if C.avcodec_open2(ff.codecCtx, ff.codec, nil) != 0 {
+		err = fmt.Errorf("avcodec_open2 failed")
+		return
+	}
+
+	return
+}
+
+func (self *AudioDecoder) Decode(frame []byte) (gotPkt bool, pkt []byte, err error) {
+	ff := &self.ff
+
+	cpkt := C.AVPacket{
+		data: (*C.uint8_t)(unsafe.Pointer(&frame[0])),
+		size: C.int(len(frame)),
+	}
+	cgotpkt := C.int(0)
+	cerr := C.avcodec_decode_audio4(ff.codecCtx, ff.frame, &cgotpkt, &cpkt);
+	if cerr < C.int(0) {
+		err = fmt.Errorf("avcodec_decode_audio4 failed: %d", cerr)
+		return
+	}
+
+	if cgotpkt != C.int(0) {
+		gotPkt = true
+		pkt = make([]byte, (int)(cpkt.size))
+		C.memcpy(
+			unsafe.Pointer(&pkt[0]),
+			unsafe.Pointer(cpkt.data),
+			(C.size_t)(len(pkt)),
+		)
+	}
+
+	return
+}
+
+func FindAudioEncoderByName(name string) (enc *AudioEncoder) {
+	ff := C.FFCtx{}
+	ff.codec = C.avcodec_find_encoder_by_name(C.CString(name))
+	if ff.codec != nil {
+		ff.codecCtx = C.avcodec_alloc_context3(ff.codec)
+		if ff.codecCtx != nil {
+			return &AudioEncoder{ff: ff}
+		}
+	}
+	return nil
+}
+
+func FindAudioDecoderByName(name string) (dec *AudioDecoder) {
+	ff := C.FFCtx{}
+	ff.codec = C.avcodec_find_decoder_by_name(C.CString(name))
+	if ff.codec != nil {
+		ff.codecCtx = C.avcodec_alloc_context3(ff.codec)
+		if ff.codecCtx != nil {
+			return &AudioDecoder{ff: ff}
+		}
+	}
+	return nil
+}
+

ffmpeg.h

@@ -0,0 +1,14 @@
+
+#include <libavcodec/avcodec.h>
+#include <libavutil/avutil.h>
+#include <string.h>
+
+typedef struct {
+	AVCodec *codec;
+	AVCodecContext *codecCtx;
+	AVFrame *frame;
+} FFCtx;
+
+int FFCtxFindEncoderByName(FFCtx *ff, const char *name);
+int FFCtxFindDecoderByName(FFCtx *ff, const char *name);
+