Add bit stream filter support (#61)

* add bit stream filter support

* bit stream filter is not a class

* add pr suggestions

* add tests for bit stream filter

* create a separated test helper method

* search for first h264 video stream

* add pr suggestions

* remove free since bsfc is taking ownership of it

bit_stream_filter.go

@@ -0,0 +1,35 @@
+package astiav
+
+//#cgo pkg-config: libavcodec
+//#include <libavcodec/bsf.h>
+//#include <stdlib.h>
+import "C"
+import (
+	"unsafe"
+)
+
+// https://github.com/FFmpeg/FFmpeg/blob/release/5.1/libavcodec/bsf.h#L111
+type BitStreamFilter struct {
+	c *C.struct_AVBitStreamFilter
+}
+
+func newBitStreamFilterFromC(c *C.struct_AVBitStreamFilter) *BitStreamFilter {
+	if c == nil {
+		return nil
+	}
+	return &BitStreamFilter{c: c}
+}
+
+func FindBitStreamFilterByName(n string) *BitStreamFilter {
+	cn := C.CString(n)
+	defer C.free(unsafe.Pointer(cn))
+	return newBitStreamFilterFromC(C.av_bsf_get_by_name(cn))
+}
+
+func (bsf *BitStreamFilter) Name() string {
+	return C.GoString(bsf.c.name)
+}
+
+func (bsf *BitStreamFilter) String() string {
+	return bsf.Name()
+}

bit_stream_filter_context.go

@@ -0,0 +1,82 @@
+package astiav
+
+//#cgo pkg-config: libavcodec
+//#include <libavcodec/bsf.h>
+import "C"
+import (
+	"errors"
+	"unsafe"
+)
+
+// https://github.com/FFmpeg/FFmpeg/blob/release/5.1/libavcodec/bsf.h#L68
+type BitStreamFilterContext struct {
+	c *C.struct_AVBSFContext
+}
+
+func newBSFContextFromC(c *C.struct_AVBSFContext) *BitStreamFilterContext {
+	if c == nil {
+		return nil
+	}
+	bsfc := &BitStreamFilterContext{c: c}
+	classers.set(bsfc)
+	return bsfc
+}
+
+var _ Classer = (*BitStreamFilterContext)(nil)
+
+func AllocBitStreamFilterContext(f *BitStreamFilter) (*BitStreamFilterContext, error) {
+	if f == nil {
+		return nil, errors.New("astiav: bit stream filter must not be nil")
+	}
+
+	var bsfc *C.struct_AVBSFContext
+	if err := newError(C.av_bsf_alloc(f.c, &bsfc)); err != nil {
+		return nil, err
+	}
+
+	return newBSFContextFromC(bsfc), nil
+}
+
+func (bsfc *BitStreamFilterContext) Class() *Class {
+	return newClassFromC(unsafe.Pointer(bsfc.c))
+}
+
+func (bsfc *BitStreamFilterContext) Initialize() error {
+	return newError(C.av_bsf_init(bsfc.c))
+}
+
+func (bsfc *BitStreamFilterContext) SendPacket(p *Packet) error {
+	var pc *C.struct_AVPacket
+	if p != nil {
+		pc = p.c
+	}
+	return newError(C.av_bsf_send_packet(bsfc.c, pc))
+}
+
+func (bsfc *BitStreamFilterContext) ReceivePacket(p *Packet) error {
+	if p == nil {
+		return errors.New("astiav: packet must not be nil")
+	}
+	return newError(C.av_bsf_receive_packet(bsfc.c, p.c))
+}
+
+func (bsfc *BitStreamFilterContext) Free() {
+	classers.del(bsfc)
+	C.av_bsf_free(&bsfc.c)
+}
+
+func (bsfc *BitStreamFilterContext) TimeBaseIn() Rational {
+	return newRationalFromC(bsfc.c.time_base_in)
+}
+
+func (bsfc *BitStreamFilterContext) SetTimeBaseIn(r Rational) {
+	bsfc.c.time_base_in = r.c
+}
+
+func (bsfc *BitStreamFilterContext) CodecParametersIn() *CodecParameters {
+	return newCodecParametersFromC(bsfc.c.par_in)
+}
+
+func (bsfc *BitStreamFilterContext) SetCodecParametersIn(cp *CodecParameters) {
+	bsfc.c.par_in = cp.c
+}

bit_stream_filter_context_test.go

@@ -0,0 +1,33 @@
+package astiav
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestBitStreamFilterContext(t *testing.T) {
+	bsf := FindBitStreamFilterByName("null")
+	require.NotNil(t, bsf)
+
+	bsfc, err := AllocBitStreamFilterContext(bsf)
+	require.NotNil(t, bsfc)
+	require.NoError(t, err)
+	defer bsfc.Free()
+
+	cl := bsfc.Class()
+	require.NotNil(t, cl)
+	require.Equal(t, "AVBSFContext", cl.Name())
+
+	bsfc.SetTimeBaseIn(NewRational(15, 1))
+	require.Equal(t, NewRational(15, 1), bsfc.TimeBaseIn())
+
+	cp1 := AllocCodecParameters()
+	require.NotNil(t, cp1)
+	cp1.SetCodecID(CodecIDH264)
+
+	bsfc.SetCodecParametersIn(cp1)
+	require.Equal(t, CodecIDH264, bsfc.CodecParametersIn().CodecID())
+
+	// TODO: add tests for send and receive packet flows
+}

bit_stream_filter_test.go

@@ -0,0 +1,18 @@
+package astiav
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestBitStreamFilter(t *testing.T) {
+	fn := "null"
+	f := FindBitStreamFilterByName(fn)
+	require.NotNil(t, f)
+	require.Equal(t, f.Name(), fn)
+	require.Equal(t, f.String(), fn)
+
+	f = FindBitStreamFilterByName("foobar_non_existing_bsf")
+	require.Nil(t, f)
+}